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Meuwissen, R. H. G. "Waar controle en controleur elkaar ontmoeten." Maastricht : Maastricht : Universiteit Maastricht, Faculteit der Economische Wetenschappen en Bedrijfskunde ; University Library, Maastricht University [Host], 2005. http://arno.unimaas.nl/show.cgi?fid=12761.
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Buyukkeles, Umit. "Improved Torque And Speed Control Performance In A Vector-controlled Pwm-vsi Fed Surface-mounted Pmsm Drive With Conventional P-i Controllers." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614294/index.pdf.
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In this thesis, high performance torque and speed control for a surface-mounted permanent magnet synchronous machine (PMSM) is designed, simulated and implemented. A three-phase two-level pulse width modulation voltage-source inverter (PWM-VSI) with power MOSFETs is used to feed the PMSM.
The study has three objectives. The first is to compensate the voltage disturbance caused by nonideal characteristics of the voltage-source inverter (VSI). The second is to decouple the coupled variables in the synchronous reference frame model of the PMSM. The last is to design a load torque estimator in order to increase the disturbance rejection capability of the speed control. The angular acceleration required for load torque estimation is extracted through a Kalman filter from noisy velocity measurements.
Proposed methods for improved torque and speed control performance are verified through simulations and experimental tests. The drive system is modeled in Matlab/Simulink, and control algorithms are developed based on this model. The experimental drive system comprises a three-phase VSI and a 385 W surface-mounted PMSM. Control algorithms developed in the study have been implemented in a digital signal processor (DSP) board and tested comprehensively. With the use of the proposed methods, a considerable improvement of torque and speed control performance has been achieved.
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Du, Plooy Jon-Pierre. "Development of a converter-fed reluctance synchronous generator wind turbine controller." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97015.
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Thesis (MEng)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The growing contribution of wind energy to utility grids has sparked interest in small-scale wind turbines and thus a growing global cumulative installed capacity. Small-scale wind turbines find use in the saving of cost of electricity or for the carbon footprint reduction of small farms and small-holdings, as well as the electrification of rural communities. A goal of any wind turbine is to produce power at as low of a cost per unit energy as possible. Thus, a generator with a high power density and high efficiency is essential. The reluctance synchronous machine (RSM) is a strong competitor in this regard. Additionally, the RSM is a robust brushless topology that has good properties of manufacturability. However, studies published on the use of RSMs as generators in wind turbines is limited. This study serves to explore the performance and controllability of an RSM as a generator in a small-scale 9:2 kW wind turbine. For maximum power capture, it is desirable to have a wind turbine vary its rotor speed. However, there is a limit to the power that the generator may produce and so techniques are employed to reduce the captured power when operating above the rated wind speed. A turbine controller is developed that employs a speed-controlled maximum power point tracking (MPPT) technique for maximum power capture and soft-stalling of the blades to reduce power capture at excessive wind speeds. The RSM is modelled along with a turbine simulation model, complete with a wind source generator, to evaluate the performance of the system. Speed-controlled MPPT is known to sacrifice torque smoothness for fast tracking performance. To mitigate these harsh effects on the drivetrain, the speed reference of the generator is filtered to provide an average response to the optimal speed reference. This is shown to reduce the frequent and excessive speed, torque, and electrical power variations though optimal performance is not possible. However, any reduction on drivetrain fatigue that will maximise operation time of the turbine is considered an important gain. The RSM proves to have qualities that are applicable to wind turbine applications with its high efficiency, good manufacturability properties, low cost, and high robustness. Its higher power density over induction machines is also favourable though power electronics are required for optimal operation of the machine.
AFRIKAANSE OPSOMMING: Die groeiende bydrae van wind energie te nut roosters het aanleiding gegee tot belangstelling in kleinskaalse wind turbines en dus 'n groeiende w^ereldwye kumulatiewe geïnstalleerde kapasiteit. Kleinskaalse wind turbines vind ook gebruik in die besparing van koste van elektrisiteit, of vir die koolstofvoetspoor vermindering van klein plase en klein-hoewes, sowel as die elektrifisering van landelike gemeenskappe. Een van die doelwitte van enige wind turbine is om krag te produseer teen so laag van 'n koste per eenheid energie as moontlik. Dus, 'n kragopwekker met 'n hoë krag digtheid en hoë doeltreffendheid is noodsaaklik. Die reluktansie sinchroonmajien (RSM) is 'n sterk mededinger in hierdie verband. Daarbenewens is die RSM 'n robuuste borsellose topologie wat goeie eienskappe van vervaardigbaarheid het. Maar studies oor die gebruik van RSMs as kragopwekkers gepubliseer in die wind turbines is beperk. Hierdie studie dien om die prestasie te ondersoek en die beheerbaarheid van 'n RSM as 'n a kragopwekker in 'n klein-skaal 9:2 kW wind turbine te verken. Vir maksimum krag vang is dit wenslik dat die wind turbine sy rotor spoed wissel. Maar daar is 'n beperking op die krag wat die kragopwekker kan produseer en daarom work tegnieke gebruik om die gevange krag te verminder wanneer daar bo die gegradeerde wind spoed gewerk word. 'n Turbine beheerder word ontwikkel wat werk om 'n spoedbeheer maksimum kragpunt dop tegniek vir maksimum krag vang en die sagtestaking van die lemme krag vang deur oormatige wind spoed te verminder. Die RSM is gemodeleer saam met 'n turbine simulasie model kompleet met 'n wind bron kragopwekker om die prestasie van die stelsel te evalueer. Spoedbeheerde maksimum kragpunt dop is bekend om wringkrag gladheid vir 'n vinnige dop prestasie te offer. Om hierdie harde gevolge op die kragoorbringstelsel te versag is die spoed verwysing van die kragopwekker gefiltreer om 'n gemiddelde reaksie op die optimale spoed verwysing te verskaf. Dit word getoon om gereelde en hoë spoed, wringkrag en elektriese krag variases te verminder al is optimale prestasie nie moontlik nie. Enige afname van aandrystelsel moegheid wat operasie tyd van die turbine maksimeer word beskou as 'n belangrike gewin. Die RSM bewys eienskappe wat van toepassing is op die turbine aansoeke na aanleiding met sy hoë doeltreffendheid, goeie vervaardigbaarheid eienskappe, lae koste end ' hoë robuustheid. Sy hoër krag digtheid oor induksiemasjien is ook gunstig al is drywingselektronika nodig vir optimale werking van die masjien.
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Zelaya, de la Parra H. "Microprocessor-controlled cycloconverter for excitation of a doubly-fed induction generator." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376697.
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Chaves, Juan Sebastián Solís. "Controle preditivo generalizado com horizonte deslizante e controle direto de potência deadbeat aplicados em sistemas eólicos baseados no gerador de indução de rotor bobinado." reponame:Repositório Institucional da UFABC, 2017.
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Orientador: Prof. Dr. Alfeu J. Sguarezi FilhoTese (doutorado) - Universidade Federal do ABC. Programa de Pós-Graduação em Energia, 2017.
Nesta pesquisa são propostos dois novos algoritmos de controle, operando a velocidade variável e robustos às variações nos parâmetros para um sistema eólico baseado no gerador de indução duplamente alimentado, cuja aplicação é realizada em condições normais de operação. Os controladores propostos são nomeados de Controle Direto de Potência (CDP) Deadbeat e do Controle Preditivo Generalizado com Horizonte Deslizante (CPG¿hd). O primeiro possui duas malhas de controle: uma para o desacoplamento do fluxo do estator e o controle das potências e a outra para o controle da corrente, essa malha é chamada de Deadbeat. O CDP calcula o vetor de tensão fornecido ao rotor a fim de garantir que a potência ativa e reativa atinjam seus valores de referência desejados. A dependência do algoritmo a parâmetros que tenham que ser sintonizados por meio de procedimentos heurísticos é nula quando é comparado com o controle Proporcional¿Integral ou Controle PI, sendo preciso somente calcular o coeficiente Gc. O segundo controlador, calcula os preditores para a corrente do rotor usando um horizonte de predição definido e assim obter as novas tensões do rotor que devem ser injetadas no sistema para controlar as potências ativa e reativa do estator com base nas equações do gerador. O CPG¿hd precisa de um parâmetro para sua sintonização chamado fator de peso do controlador, esse parâmetro faz parte da função de custo quadrática que deve ser minimizada, para obter um valor ótimo das tensões do rotor. Testes são feitos usando Matlab¿Simulink para os dois controladores operando sob condições normais de operação, ou seja: teste a velocidade fixa e teste a velocidade variável do rotor. Os mesmos testes são repetidos por meio de um protótipo de escala pequena disponível no LEPS . A dependência dos dois algoritmos às variações dos parâmetros foi também investigada, assim como a influência dos erros na estimativa desses parâmetros, obtendo-se um desempenho superior do controlador preditivo generalizado CPG¿hd sobre o CDP Deadbeat.
In this research two new control algorithms for a wind power system based on the Double Fed Induction Generator (DFIG) are proposed. The wind energy system is operating under normal conditions i.e. fixed rotor speed, variable rotor speed and under variations in DFIG parameters. The proposed controllers are named Direct Power Control (DPC) Deadbeat and Long¿range Generalized Predictive Control (GPC¿dq). The DPC calculates the sup- plied voltage vector to the rotor to ensure that the active and reactive power reaches their desired reference values. The algorithm dependence on parameters that have to be tuned by means of heuristic procedures is zero when its compared with the Proportional¿Integral (PI) Control, being necessary only estimate the Gc coeficient. The second controller evalu- ates the DFIG predictive rotor currents, using a defined long-range prediction horizon and thus obtain the new rotor voltages that have to be injected to controlling the active and reactive stator powers. The GPC¿dq needs a parameter for been tuned, this is called as a weighting factor and is a part of the quadratic cost function that has to be minimized, to obtain an optimal value of the rotor voltages. Tests are done using Matlab¿Simulink for the two controllers operating under normal operating conditions, ie: a fixed speed test and a variable rotor speed test. The same tests are repeated using a small scale prototype avai- lable in the LEPS. The dependence of the two algorithms on the parameter variations was also investigated, as well as the influence of the errors in the estimation of these parame- ters, obtaining a superior performance for the long¿range generalized predictive controller over the other one.
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Boris, Jakovljević. "Optimalno i suboptimalno podešavanje parametara robusnih linearnih regulatora necelog reda." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=94916&source=NDLTD&language=en.
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Rad je posvećen robusnom upravljanju sistemima čiji je linearni regulator i/ili dinamika necelog reda, kao i upravljačkim problemima gde regulator necelog reda u sebi poseduje i linearnu i nelinearnu dinamiku, a koji upravlja procesima čija dinamika može i linearna i nelinearna.The thesys is dedicated to robust control systems problems with linearcontrollers and/or process dynamics of noninteger order, as well as controlissues with combination of linear and nonlinear controllers of nonintegerorder that control either linear or nonlinear systems.
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Micael, Karlberg. "Soft sensor application on lactate controlled fed-batch cultivation for monoclonal antibody production." Thesis, Linköpings universitet, Teknisk biologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-117179.
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Monoclonal antibody producing cells are of great interest and used frequently in the field of biomedical research, diagnostics and therapy with increasing need for better systems to more efficiently produce antibodies at a lower costs. In this project three fed-batch cultivations of hybridoma cells (HB-8696) were cultured in a stirred tank reactor with the use of a soft sensor to monitor the lactate concentration and as well as a dielectric probe for biomass measurements. In addition, a protocol for growing the inoculum was also successfully produced and a previous batch cultivation was also analyzed which gave crucial information about stoichiometrically relation in the feed medium which was used in the fed-batch cultivations. The BioSenz Analyzer was used for on-line lactate concentration monitoring and was later used to control the feed profile to avoid overflow metabolism in two of the three fed-batch cultivations. However, nothing conclusive could be said about the lactate controller as of yet which needs further research.
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Dòria, Cerezo Arnau. "Modeling, Simulation and Control of Doubly-Fed Induction Machine Controlled by Back-to-Back converter." Doctoral thesis, Universitat Politècnica de Catalunya, 2006. http://hdl.handle.net/10803/5945.
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Aquesta Tesi estudia el control d'un sistema complex, un sistema d'emmagatzement d'energia cinètica, incloent les seves especificacions de control, modelat, disseny de controladors, simulacions, muntatge i validació experimental.Primerament, s'estudia l'interconnexió i control dels sistemes electromecànics. Es presenta el formalisme Hamiltonià (PCHS) en general, i després particularitzant en els sistemes electromecànics, inclòs els sistemes d'estructura variable (VSS).
L'IDA-PBC (Interconnection and damping assignment-passivity based control) és una tècnica de control basat en els PCHS. En aquesta Tesi s'estudien el problemes que apareixen en controlar, per IDA-PBC, sortides de grau relatiu u quan el paràmetres nominals del controlador són incerts. Per evitar-los es proposa introduir una acció integral que pot ésser interpretada dins l'estructura Hamiltoniana.
En aquesta Tesi també es presenten dues modificacions que permeten millorar el rang d'aplicacions de la tècnica IDA-PBC. Primer, es demostra que el fet de descomposar la tècnica de l'IDA-PBC en deformar la funció d'energia i una injecció de fregament, redueix el conjunt de sistemes que es poden estabilitzar mitjançant aquest mètode. Per evitar aquest problema, es proposa fer simultàniament els dos passos donant lloc a l'anomenat SIDA-PBC. Per altre costat, el mètode IDA-PBC requereix el coneixement de la funció energia (o Hamiltonià). Això representa un problema perquè, en general, el punt d'equilibri depèn de paràmetres incerts. En aquest treball es desenvolupa una metodologia per seleccionar l'estructura Hamiltoniana que redueix aquesta dependència dels paràmetres. Aquesta tècnica permet millorar la robustesa dels les sortides d'ordre relatiu superior a u.
El sistema d'emmagatzement d'energia cinètica consisteix en una màquina d'inducció doblament alimentada (DFIM) amb un volant d'inèrcia, controlada pel rotor per un convertidor de potència back-to-back (B2B). L'objectiu és gestionar el flux d'energia entre la DFIM i una càrrega local connectada a la xarxa, commutant entre diferents punts de funcionament. Per això es planteja una gestió de l'energia, basada en la velocitat òptima de la DFIM.
Pel què fa al control de la DFIM, es proposa un nou esquema de control que ofereix importants avantatges, i que és considerablement més senzill que el mètode clàssic, el vector control. Aquest nou controlador permet una fàcil descomposició de les potències activa i reactiva de l'estator, i el seu control a través de les tensions de rotor. Aquest disseny s'obté aplicant el procediment que millora la robustesa de l'IDA-PBC.
S'han estudiat d'altres controladors, com el vector control clàssic. També a partir de la tècnica IDA-PBC, on l'equació en derivades parcials que apareix en aplicar el mètode es pot resoldre fixant l'energia en llaç tancat, i afegint nous termes a la matriu d'interconnexió. Per obtenir un controlador definit globalment s'afegeix un terme de fregament depenent dels estats, que desacobla la part elèctrica i mecànica del sistema. Finalment, també es prova que mitjançant el SIDA-PBC es pot modelar l'energia total (elèctrica i mecànica) de la DFIM. Tots aquest controladors han estat simulats i comparats. El controlador robust IDA-PBC s'ha validat experimentalment amb uns resultats satisfactoris.
A la Tesi també es presenta un controlador que permet el flux bidireccional de potència pel B2B. L'estudi de la dinàmica zero adverteix que les tècniques de control estàndard no garanties en l'estabilitat en ambdós direccions, i per això s'utilitza un controlador IDA-PBC. Pel disseny s'utilitza un model basat en GSSA (generalized state space averaging), on es descomposa i es trunca el sistema per determinades freqüències, i que permet expresar els objectius de control (tensió constant al bus de contínua i factor de potència unitari) com un problema de regulació. Les simulacions i els resultats experimentals validen, tant la llei de control, com les simplificacions efectuades.
Els controladors proposats i validats experimentalment són usats, finalment, per implementar la gestió de potència del sistema d'emmegatzement d'energia cinètica. Els resultats confirmen el bon comportament del sistema i dels controladors IDA-PBC proposats.
This Thesis studies a complex multidomain system, the Flywheel Energy Storage System, including the control objectives specification, modeling, control design, simulation, experimental setup assembling and experimental validation stages.
The port interconnection and control of electromechanical systems is studied. The port Hamiltonian formalism is presented in general, and particularized for generalized electromechanical systems, including variable structure systems (VSS).
Interconnection and damping assignment-passivity based control (IDA-PBC) is a well known technique for port Hamiltonian systems (PCHS). In this Thesis we point out the kind of problems that can appear in the closed-loop structure obtained by IDA-PBC methods
for relative degree one outputs, when nominal values are used in a system with uncertain parameters. To correct this, we introduce an integral control, which can be cast into the Hamiltonian framework.
This Thesis also presents two new approaches which improve the range of applicability of the IDA-PBC technique.
First, we show that the standard two-stage procedure used in IDA-PBC consisting of splitting the control action into the sum of energy-shaping and damping injection terms is not without loss of generality, and effectively reduces the set of systems that can be stabilized with IDA-PBC. To overcome this problem we suggest to carry out simultaneously both stages and refer to this variation of the method as SIDA-PBC.
Secondly, we present an improvement of the IDA-PBC technique. The IDA-PBC method requires the knowledge of the full energy (or Hamiltonian) function. This is a problem because, in general, the equilibrium point which is to be regulated depends on uncertain parameters. We show how select the target port-Hamiltonian structure so that this dependence is reduced. This new approach allows to improve the robustness for higher relative degree outputs.
The Flywheel Energy Storage System consists of a doubly-fed induction machine (DFIM), controlled through the rotor voltage by a power electronics subsystem (a back-to-back AC/AC converter (B2B)), and coupled to flywheel. The control objective is to optimally regulate the power flow between the DFIM and a local load connected to the grid, and this is achieved by commuting between different steady-state regimes. A police management based on the optimal speed for the DFIM is proposed.
In this Thesis we propose a new control scheme for the DFIM that offers significant advantages, and is considerably simpler, than the classical vector control method. This controller allows an easy decomposition of the active and reactive powers on the stator side and their regulation, acting on the rotor voltage, via stator current control. This design was obtained applying the new robust IDA-PBC procedure.
Other controllers are also designed along the dissertation. The classical vector control is studied. We also apply the classic IDA-PBC technique. It is shown that the partial differential equation that appears in this method can be circumvented by fixing the desired closed-loop total energy and adding new terms to the interconnection structure. Furthermore, to obtain a globally defined control law we introduce a state--dependent damping term that has the nice interpretation of effectively decoupling the electrical and mechanical parts of the system. This results in a globally convergent controller parameterized by two degrees of freedom. Finally, we also prove that with SIDA-PBC we can shape the total energy of the full (electrical and mechanical) dynamics of the DFIM. These different controllers (vector control, IDA-PBC, SIDA-PBC and robust IDA-PBC) are simulated and compared. The IDA-PBC robust controller is also experimentally tested and shown to work satisfactorily.
A controller able to achieve bidirectional power flow for the B2B converter is presented. Standard techniques cannot be used since it is shown that no single output yields a stable zero dynamics for power flowing both ways. The controller is computed using standard IDA-PBC techniques for a suitable generalized state space averaging truncation of the system, which transforms the control objectives, namely constant output voltage dc-bus and unity input power factor, into a regulation problem. Simulation and experimental results for the full system confirm the correctness of the simplifications introduced to obtain the controller.
The proposed and tested controllers for the DFIM and the B2B are used to implement the power management policy. These results show a good performance of the flywheel energy storage system and also validate the IDA-PBC technique, with the proposed improvements.
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Pimentel, Guilherme Araujo. "Controle robusto por realimentação linearizante parcial de bioreatores em modo de operação "FED-BATCH"." Pontifícia Universidade Católica do Rio Grande do Sul, 2010. http://hdl.handle.net/10923/3149.
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Previous issue date: 2010This dissertation aims to use a general model to describe the growth of both bacteria Escherichia Coli as yeast Saccharomyces Cerevisiae in a bioreactor on fed-batch mode. In general, to maximize the production of biomass (microorganisms) by controlling the substrate (food) injected into the bioreactor. By the principle of bottle-neck, the maximum yield is obtained when the substrate level is maintained at a certain critical value which depends on biological variables of the process (which vary in time) and certain parameters with high degree of uncertainty. An alternative approach is the control of the by-product (acetate in the case of E. Coli or ethanol in the case of S. Cervisiae ) which should be maintained at levels close to zero and thus entire substrate is used in the production of biomass. Through the nonlinear model of the dynamic growth of the microorganism, it is proposed in this dissertation a robust control law based on the idea partial feedback linearization, in order to avoid measure a large number of biological variables di cult instrumentation. To improve the dynamic performance of the system, is also proposed a mechanism for online estimation and parametric adaptation of the reaction rate of glucose oxidation. Using the description of nonlinearities with the quasi-LPV approach and the formulation of stability conditions through linear matrix inequalities (LMIs), is designed a free linear dynamic, yield of feedback linearization, to ensure the robust stability (related to nonlinearities not canceled and parametric variations)in closed loop and also a certain performance. To verify the behavior of the proposed methodology are conducted several tests on simulations using the platform Matlab=Simulinkr, where is possible to study the behavior of the proposed strategy with regard to jobs available in the literature.
Esta dissertação apresenta um modelo geral que descreve a dinâmica do crescimento tanto da bactéria Escherichia Coli quanto da levedura Saccharomyces Cerevisiae quando produzidas em bioreatores operando no modo descontínuo com alimentação controlada (fed-batch). Em geral, procura-se maximizar a produção da biomassa (microorganismos) através do controle do substrato (alimento) injetado ao bioreator. Pelo princípio do bottle-neck, a máxima produtividade é obtida quando o nível de substrato é mantido em um determinado valor crítico que depende de variáveis biológicas do processo (que variam ao longo do tempo) e de certos parâmetros com elevado grau de incerteza. Uma alternativa a esta abordagem é através do controle do produto secundário (acetato no caso da E. Coli ou etanol no caso da S. Cervisiae) o qual deve ser mantido em níveis próximos a zero e desta forma todo o substrato é utilizado na produção de biomassa. A partir do modelo não linear da dinâmica de crescimento do microorganismo, propõe-se nesta dissertação uma lei de controle robusta baseada na ideia de realimentação linearizante parcial com o objetivo de evitar a medição de um elevado número de variáveis biológicas de difícil instrumentação. Para melhorar o desempenho dinâmico do sistema, também é proposto um mecanismo de adaptação paramétrica para a estimação online da taxa de reação da oxidação da glicose. Utilizando a descrição das não linearidades através da abordagem quasi-LPV e a formulação das condições de estabilidade por desigualdades matriciais lineares (LMIs), projeta-se a dinâmica linear livre, resultante da realimentação linearizante, de maneira a garantir a estabilidade robusta (em relação a não linearidades não canceladas e variações paramétricas) em malha fechada e também um certo desempenho. Para verificar o comportamento da metodologia proposta são realizados vários testes em simulações utilizando a plataforma Matlab=Simulinkr, onde estuda-se o comportamento da estratégia proposta em relação a trabalhos disponíveis na literatura especializada.
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Royakkers, Cornelia Henrica Maria. "De controle over de politie in Engeland en Wales." [Deventer] : Maastricht : Gouda Quint ; University Library, Maastricht University [Host], 1997. http://arno.unimaas.nl/show.cgi?fid=5785.
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Buijink, Willem Frederik Jan. "Empirical financial accounting research compliance with regulation, distributional properties of financial ratios and demand for external auditing /." Maastricht : Maastricht : Universitaire Pers Maastricht ; University Library, Maastricht University [Host], 1992. http://arno.unimaas.nl/show.cgi?fid=8263.
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Nepomuceno, Leonardo. "Modelos de otimização equivalente para minimização de perdas atraves de FPO Newton." [s.n.], 1997. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260629.
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Orientador: Anesio dos Santos JuniorTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Os estudos de otimização "on-line" realizados nos centros de controle têm apresentado algumas deficiências, apontadas na literatura, que têm limitado suas aplicações práticas na operação dos sistemas de potência. O presente trabalho enfoca uma destas deficiências, qual seja, a representação das áreas externas (modelos de equivalentes externos) durante estudos com ferramentas de otimização reativa através de um Fluxo de Carga Ótimo tipo Newton. Tradicionalmente, os modelos de equivalentes externos e as ferramentas de otimização foram desenvolvidos separadamente. Este trabalho enfoca o uso de ferramentas de otimização reativa acopladas a modelos de representação de áreas não observáveis, propondo e discutindo conceitos envolvidos. Para isso, inicialmente alguns modelos equivalentes clássicos, utilizados nos estudos de Análise de Segurança Estática, são reavaliados no contexto dos estudos de otimização. Para a avaliação dos modelos equivalentes em estudos de otimização é proposta uma Metodologia de Análise. Dadas as deficiências apresentadas pelos modelos clássicos, é proposto um enfoque de otimização para modelos equivalentes de representação das áreas externas. Os modelos são formulados como problemas de otimização com as áreas externas representadas de forma explícita (sem redução). A representação das áreas externas é feita conjuntamente com o modelo da otimização da parte interna do sistema através de um problema denominado Fluxo de Carga Ótimo Equivalente (FCOE) ...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital
Abstract: On-line optimization studies performed on control centers present some deficiencies, pointed-out in literature, limiting the scope of their practical aplications in power system operation. This work focuses on one of such deficiencies: the representation of external are as (external equivalent models) during studies with reactive optimization tools such as a Newton Optimal Power Flow. External equivalent models and optimization tools have been traditionaly developed separately. This work focuses on the use of reactive optimization tools coupled to models representing external non-observable areas, proposing and discussing related concepts. For such a purpose, some classical equivalent models are evaluated in the context of optimization studies. An Analysis Methodology is proposed to evaluate equivalent models in optimization studies. Given the deficiencies presented by classical models, an optimization approach to equivalent models is proposed. The models are formulated as optimization problems having the external area represented explicitly (with no reduction). The representation of such external models is obtained simultaneously with internal optimization solution, through a problem named Equivalent Optimal Power Flow (FCOE). Hybrid models, sinthetyzing the Extended Ward models and the FCOE tool in an unifying approach are analised. Three alternative ways of coupling (boundary matching) Hybrid models to the internal system are proposed ...Note: The complete abstract is available with the full electronic digital thesis or dissertations
Doutorado
Doutor em Engenharia Elétrica
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Galdino, Rodrigo Almeida. "Estratégia de controle para um processo de flotação por ar dissolvido (FAD) de separação àgua-óleo." Universidade Católica de Pernambuco, 2017. http://tede2.unicap.br:8080/handle/tede/960.
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The state of Pernambuco is becoming increasingly industrialized and diversified array, with projects in the areas of petroleum refining, petrochemical, steel, shipbuilding and offshore industry, automotive, and electrical equipment. In the current global context, where one strives for environmental preservation, the major challenge faced by these large developments has been to ensure the quality and continuous development of its processes without compromising local environmental quality. Therefore it is of paramount importance to reduce the amount and / or improve the quality of wastewater generated by various industries and their production processes. The systems of dissolved air flotation (DAF) are more compact than alternative systems in water-oil separation, and they allow the recovery of raw materials in the treatment of these industrial effluents. In this sense, the goal of this project is to develop an effective strategy for automation and process control for a type of FAD, in the treatment of oily waters. The findings demonstrate that it is possible to maintain the level of the fluid at a reference value established by the operator using the software program LabVIEW through the application of classic proportional integral derivative controllers. Using this control tool, the efficiency of water-oil separation in the pilot flotation chamber prototype was increased to nearly 98%.
O estado de Pernambuco está se tornando cada vez mais industrializado e com matriz diversificada, com empreendimentos nas áreas de refino de petróleo, petroquímica, siderurgia, indústria naval e offshore, automobilística, e de equipamentos para energia elétrica. No contexto mundial atual, onde se prima pela preservação ambiental, o grande desafio enfrentado por esses grandes empreendimentos tem sido garantir a qualidade e o desenvolvimento contínuo de seus processos, sem comprometer a qualidade ambiental local. Portanto é de suma importância reduzir a quantidade e/ou melhorar a qualidade dos efluentes gerados pelos mais diversos setores industriais e seus respectivos processos de produção. Os sistemas de flotação por ar dissolvido (FAD) são mais compactos que os sistemas alternativos na separação água-óleo, além de possibilitarem a recuperação de matéria-prima no tratamento desses efluentes industriais. Neste sentido, o objetivo deste projeto é desenvolver uma estratégia eficiente de automação e controle de nível para um processo do tipo FAD, no tratamento de águas oleosas. Os resultados obtidos demonstram que a partir da aplicação de técnicas de controladores clássicos PID, foi possível manter o nível do líquido em um valor de referência estabelecido pelo usuário a partir do software LabVIEW. Com a adoção da referida ferramenta de controle, a eficiência de separação água-óleo na câmara de flotação do protótipo piloto ficou próximo a 98 %, validando a estratégia de controle adotada.
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Pimentel, Guilherme Araujo. "Controle robusto por realimenta??o linearizante parcial de bioreatores em modo de opera??o "FED-BATCH"." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2010. http://tede2.pucrs.br/tede2/handle/tede/3032.
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Previous issue date: 2010-10-01Esta disserta??o apresenta um modelo geral que descreve a din?mica do crescimento tanto da bact?ria Escherichia Coli quanto da levedura Saccharomyces Cerevisiae quando produzidas em bioreatores operando no modo descont?nuo com alimenta??o controlada (fed-batch). Em geral, procura-se maximizar a produ??o da biomassa (microorganismos) atrav?s do controle do substrato (alimento) injetado ao bioreator. Pelo princ?pio do bottle-neck, a m?xima produtividade ? obtida quando o n?vel de substrato ? mantido em um determinado valor cr?tico que depende de vari?veis biol?gicas do processo (que variam ao longo do tempo) e de certos par?metros com elevado grau de incerteza. Uma alternativa a esta abordagem ? atrav?s do controle do produto secund?rio (acetato no caso da E. Coli ou etanol no caso da S.Cervisiae) o qual deve ser mantido em n?veis pr?ximos a zero e desta forma todo o substrato ? utilizado na produ??o de biomassa. A partir do modelo n?o linear da din?mica de crescimento do microorganismo, prop?e-se nesta disserta??o uma lei de controle robusta baseada na ideia de realimenta??o linearizante parcial com o objetivo de evitar a medi??o de um elevado n?mero de vari?veis biol?gicas de dif?cil instrumenta??o. Para melhorar o desempenho din?mico do sistema, tamb?m ? proposto um mecanismo de adapta??o param?trica para a estima??o online da taxa de rea??o da oxida??o da glicose. Utilizando a descri??o das n?o linearidades atrav?s da abordagem quasi-LPV e a formula??o das condi??es de estabilidade por desigualdades matriciais lineares (LMIs), projeta-se a din?mica linear livre, resultante da realimenta??o linearizante, de maneira a garantir a estabilidade robusta (em rela??o a n?o linearidades n?o canceladas e varia??es param?tricas) em malha fechada e tamb?m um certo desempenho. Para verificar o comportamento da metodologia proposta s?o realizados v?rios testes em simula??es utilizando a plataforma Matlab=Simulinkr, onde estuda-se o comportamento da estrat?gia proposta em rela??o a trabalhos dispon?veis na literatura especializada.
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Raban, Moegammad Shukri. "Rapid versus slow rate advancement of feeds for enterally fed extremely low birth weight infants < 1000g: randomised controlled trial." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13973.
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Background The timeous achievement of full enteral nutrition in a preterm infant is a critical prerequisite for optimal growth, neurodevelopment and long-term wellbeing. However, the optimal enteral feeding regimen for preterm infants has not been established, and wide variations occur in practice. The debate on the most appropriate feeding strategy is nuanced by studies suggesting that early introduction of enteral feeds and the rapid advancement of enteral feeds may increase the risk of feeding intolerance and may be involved in the pathogenesis of necrotising enterocolitis (NEC). Objective 1. To review randomised controlled trials (RCT); examining the effect that the rate of advancement of enteral feeds has on the incidence of; NEC, mortality, growth, health care utilisation and other morbidities in very low birth weight (VLBW) and extremely low birth weight (ELBW) infants. 2. To establish the safety and efficacy of commencing enteral breast milk feeds at 24 ml/kg/day on the day of birth and advancing enteral breast milk feeds at 36 ml/kg/day, in infants weighing ≤ 1000 g.
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Verhey, L. F. M. "De zwoegers uit het vooronder over ambtelijke taakuitoefening, ministeriële verantwoordelijkheid en parlementaire controle /." Deventer : Maastricht : W.E.J. Tjeenk Willink ; University Library, Maastricht University [Host], 2001. http://arno.unimaas.nl/show.cgi?fid=12691.
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Kuijl, J. G. "De HBO-fraude, een terugblik op de Commissie Rekenschap." Maastricht : Maastricht : Universiteit Maastricht ; University Library, Maastricht University [Host], 2005. http://arno.unimaas.nl/show.cgi?fid=12773.
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Gogas, Kyriakos. "Design of a robust speed and position sensorless decoupled P-Q controlled doubly-fed induction generator for variable-speed wind energy applications." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99762.
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Wind energy is a relatively young but rapidly expanding industry. In order for wind generation to be cost effective, it must produce energy at a minimum cost per dollar of investment. Performance characteristics such as power output versus wind speed must be optimized in order to compete with other energy sources. Also, if the utility uses wind power for a part of its generation, the output power of these turbines must have the same high quality and reliability when it enters the utility grid. The ability to vary operating speed is important in wind generation because it allows for an optimization of the transfer of power from the wind to the turbine shaft. Doubly-fed induction generators (DFIG) are an interesting solution for variable-speed systems with limited variable speed range, and are typically used in wind energy conversion systems.The objectives of this thesis are to implement a decoupled P-Q control of a DFIG that does not rely on mechanical sensors and to design a speed and position sensorless algorithm that is robust to variations of the values of the machine parameters. The sensorless DFIG control algorithm presented in this thesis is based on a modified phasedlock loop with an improved positioning algorithm. With the measured stator voltages, stator and rotor currents, the speed and position of the DFIG are estimated. The speed is estimated independent of machine parameters, which results in a significant improvement in speed control robustness to parameter variations. In addition, the algorithm avoids using differentiation, which significantly improves its immunity to noise and does not require the measurement of the rotor voltages. Also, it is shown that the positioning algorithm has an improved operation in generator mode. Although the accuracy of the positioning algorithm is depended on machine parameters; it is shown with the designed controller that the P-Q decoupled control is robust to changes of machine parameters. Theoretical and simulation results are validated on an experimental setup.
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Ávila, Manuel Ricardo Vargas. "Modelagem dinâmica e controle de um gerador tipo DFIG em redes de distribuição." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/114469.
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Neste momento o Brasil possui uma das mais renováveis matrizes energéticas do mundo, mas o desafio de reduzir os níveis de emissão, permitir o crescimento econômico e atender a aproximadamente um milhão de pessoas sem energia elétrica no pais, requer a pesquisa e o desenvolvimento de novas tecnologias que possibilitem a utilização de fontes limpas e sustentáveis de energia, como é a energia eólica. A energia eólica é considerada, entre as alternativas renováveis existentes, a mais viável no mercado de energia, devido à baixa relação custo/benefício de exploração, tendo apresentado um crescimento exponencial ao longo dos anos. Os principais sistema eólicos classificam-se de acordo com sua operação em dois tipos: sistemas com operação a velocidade fixa e sistemas com operação a velocidade variável. Durante muitos anos a liderança do mercado foi para os geradores que operam a velocidade fixa, sendo a máquina mais usada o gerador de indução de rotor em gaiola (SCIG). A partir do ano 2000, a supremacia no mercado passou a ser para o gerador de velocidade variável. Hoje, tem-se dois tipos de geradores amplamente utilizados em sistemas eólicos que operam a velocidade variável: o gerador síncrono e o gerador de indução com rotor bobinado. Neste trabalho será estudada uma das máquinas que operam a velocidade variável e utilizam geradores de indução com rotor bobinado: o gerador de indução duplamente alimentado (DFIG). Sua importância é principalmente o controle independente da potência ativa e da potência reativa fornecida para a rede elétrica, e à operação com máxima eficiência na conversão de energia. Neste contexto, este trabalho apresenta uma análise comparativa de um sistema de geração utilizando máquinas do tipo DFIG com quatro estratégias de controle: controle da potência ativa e da tensão nos terminais da máquina, controle da potência reativa e da tensão nos terminais da máquina, controle da velocidade de rotação e da tensão nos terminais da máquina, controle da potência ativa e da potência reativa fornecidas pela máquina ao sistema. Esta análise é feita comparando o comportamento do sistema quando sujeito a diversas situações, tais como: variações da demanda de potência da carga elétrica, variações do torque mecânico e ocorrência de uma falta trifásica. O desempenho de sistemas de geração eólica com SCIG também é incluído nesta análise para ilustrar de maneira quantitativa os ganhos obtidos com o uso do DFIG. Os resultados obtidos ilustram as virtudes de cada uma das diferentes possibilidades de modos de operação do DFIG em um sistema de distribuição e permitem uma melhor compreensão da vantagem do desempenho do DFIG em relação à utilização do SCIG.At present Brazil has one of the most renewable energy matrices in the world, but the challenge of reducing emission levels, allowing the economic growth, and helping about 1 million people without electric energy in the country, requires research and development of new technologies that enable the use of clean and sustainable energy sources, such as wind power. Wind energy is considered among the existing renewable alternatives the more viable in the energy market, due to the low cost / benefit ratio of exploitation, having experienced exponential growth over the years. The wind system are classified according to their operation into two types: operating systems with fixed speed and systems with variable speed operation. For many years the leadership in the market was for fixed speed generator, being the most used machine, the induction generator rotor cage (SCIG). From 2000, the leadership in the market was for variable speed wind turbine. Today, there are two types of wind generators widely used in systems that operate at variable speed: synchronous generator and generator with wound rotor induction. In this work we will study one of the machines that operate at variable speed and use induction generators with wound rotor: the doubly-fed induction generator (DFIG). Its importance is mainly the independent control of active power and reactive power supplied to the grid, and operating at maximum efficiency in energy conversion. In this context, this work presents a comparative analysis of a generation system using DFIG type machines with four control strategies: control of active power and voltage at the terminals of the machine, control of reactive power and voltage at the machine terminals, control the rotational speed and tension in the machine terminals, control of active power and reactive power supplied by the machine. This analysis is done by comparing the behavior of the system when subjected to various situations, such as variations in power demand of electric load, changes in the mechanical torque and the occurrence of a three-phase fault. The performance of wind power generation systems with SCIG is also included in this analysis to illustrate quantitatively the gains obtained using DFIG. The results illustrate the virtues of each of the different possible operating modes of the DFIG in a distribution system and allow a better understanding of the performance advantage of the machine DFIG over the use of the machine SCIG.
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Franco, Rodrigo. "Controle direto de potência deadbeat para o gerador de indução com dupla alimentação operando durante afundamento de tensão aplicado à geração eólica." reponame:Repositório Institucional da UFABC, 2014.
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Orientador: Prof. Dr. Alfeu Joãozinho Sguarezi FilhoDissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2014.
A energia eólica tem seu interesse aumentado nos últimos anos como uma das mais importantes fontes de energia renováveis devido a sua característica ecologicamente correta. Um dos componentes principais do sistema de geração eólica é o aerogerador, que deve ser capaz de operar com velocidade variável do vento e deve estar conectado à rede elétrica mesmo com a presença de distúrbios elétricos, como afundamento de tensão. Este trabalho apresenta uma proposta de controlador direto de potência do tipo deadbeat para o Gerador de Indução com Dupla Alimentação (GIDA), onde tem-se seu estator conectado diretamente à rede elétrica e o seu rotor, conectado à rede elétrica com o emprego de um conversor bidirecional. O controlador proposto é projetado a partir do modelo matemático dinâmico discreto do GIDA para trabalhar durante a ocorrência de afundamentos de tensão sem o emprego de crowbar e sem danificar a máquina de indução. O GIDA e o controlador direto de potência deadbeat foram simulados com o emprego do pagote Simulink® do Matlab® e os resultados desta simulação são apresentados nesta dissertação, incluindo a operação do GIDA durante afundamento de tensão trifásico equilibrado. Para comprovar a capacidade de operação durante afundamento de tensão, foram realizados testes em bancada com o controlador direto de potência proposto e os resultados experimentais apresentados validam a correta operação do controlador direto de potência deadbeat na condição de falha da rede.
Wind energy is gaining interest in the last years as one of the most important renewable sources of energy due to its ecofriendly nature. One of the main components of the wind energy system is the wind generator, which must be able to work with variable wind speed and have to be connected directly to the grid even during faults, like symmetrical sag. This work presents a proposal of a direct power control deadbeat for Doubly-Fed Induction Generator (DFIG), where its stator is connected directly to the grid and its rotor is connected to the grid trough a bidirectional converter. The proposed controller is designed using the mathematical discretized dynamic model of DFIG, with the goal to withstand its operation during sag with no crowbar and avoiding damage to the induction machine. The DFIG and the direct power controller deadbeat were simulated using the suite Simulink® from Matlab® and the results are presented in this work, including the DFIG operation during symmetrical sag. For assuring the performance of the controller during sag, practical results with the proposed direct power controlled were performed using a test bench and the final results validate the correct design of the proposed deadbeat direct power controller.
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Jacomini, Rogério Vani. "Controle sensorless do gerador de indução duplamente alimentado operando com afundamentos de tensão." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260708.
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Orientador: Edson BimTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: O resumo poderá ser visualizado no texto completo da tese digital
Abstract: The abstract is available with the full electronic document
Doutorado
Energia Eletrica
Doutor em Engenharia Elétrica
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Segnini, Helio Henrique de Agostini. "Controle do fluxo de potencia da maquina de indução duplamente alimentada." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261743.
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Orientador: Edson BimDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: O objetivo deste trabalho é estudar o modelo da máquina de indução duplamente alimentada no sistema de referência síncrono, bem como controlar seu fluxo de potências através de orientação de fluxo. São analisadas as orientações de fluxo de estator, de entreferro e de rotor em várias operações: compensador de reativos, gerador e motor, com fator de potência indutivo, capacitivo e unitário, nas faixas de velocidade subsíncrona, síncrona e supersíncrona
Abstract: The purpose of this work is to study the Doubly Fed Induction Machine modeling at the synchronous reference frame, as well as to control its power flux by flux oriented control The stator, rotor and air gap flux orientations with the machine operating as reactive compensator, generator and drive, with lag power factor, lead power factor and unity power factor at subsynchronous, synchronous and supersynchronous speeds are analyzed.
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica
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Ukkonen, K. (Kaisa). "Improvement of recombinant protein production in shaken cultures:focus on aeration and enzyme-controlled glucose feeding." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526203621.
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Abstract Efficient production of biologically functional recombinant proteins is a cornerstone of modern biotechnological research. Laboratory-scale protein production is most commonly accomplished in simple shaking bioreactors such as shake flasks. However, productivity of these cultures is often severely limited by low biomass yield and non-optimal growth conditions regarding medium composition, pH and oxygen supply. In many cases, poor culture performance can constitute a major research bottleneck. This study aims to improve recombinant protein production in shaking Escherichia coli cultures by use of enzyme-controlled, fed-batch-like glucose feeding in a rich medium, and by investigating the effects of culture aeration on different aspects of protein production. The results show that the enzymatic fed-batch medium can provide higher cell densities, volumetric protein yields and, in some cases, improved product solubility or activity compared to traditionally used media. While these improvements could be obtained in ordinary shaking vessels, the results also demonstrate that cultivation in shake flasks with elevated aeration capacity can further improve cell density and volumetric productivity in the fed-batch medium. However, enhanced aeration may also have an adverse effect on the expression of certain proteins such as Fab antibody fragments. Maximum volumetric Fab yield was achieved under reduced aeration rates, and lower oxygen availability also contributed to substantially increased accumulation of periplasmically produced Fab fragments into extracellular medium. Hence modification of aeration conditions and medium composition can be used to control periplasmic/extracellular product localization as outlined in this study. Moreover, high aeration was detrimental to expression in a glycerol-based lactose autoinduction medium, but this strict dependency on aeration level could be mitigated and robustness of expression improved by an autoinduction medium based on the enzymatic glucose feeding as the supporting carbon source instead of glycerol. The results of this study can be utilized to improve volumetric productivity, protein solubility and control of product localization in small-scale protein production, as well as to facilitate robust and efficient high-throughput protein expression for such applications as structural and functional characterizationTiivistelmä Biologisesti aktiivisten vierasproteiinien tehokas tuottaminen on yksi bioteknologisen tutkimuksen kulmakivistä. Laboratoriomittakaavan proteiinituotto toteutetaan yleisimmin yksinkertaisissa ravistelubioreaktoreissa, kuten ravistelupulloissa. Näiden viljelmien tuottavuutta rajoittaa kuitenkin usein biomassan matala saanto sekä epäoptimaaliset olosuhteet kasvualustan koostumuksen, pH:n ja hapen suhteen. Monissa tapauksissa viljelmän heikko tuottavuus muodostaa tutkimukselle merkittävän pullonkaulan. Tämän tutkimuksen tavoite on parantaa vierasproteiinien tuottoa Escherichia coli –ravisteluviljelmissä hyödyntäen entsymaattisesti kontrolloitua, panossyöttökasvatusta jäljittelevää glukoosisyöttöä rikkaassa kasvualustassa, sekä selvittää ilmastuksen vaikutusta proteiinituoton eri osatekijöihin. Tulosten mukaan glukoosisyöttöön perustuva kasvualusta mahdollistaa korkeamman solutiheyden sekä proteiinituoton verrattuna tavallisimmin käytettyihin kasvualustoihin. Joissain tapauksissa myös proteiinin liukoisuus tai aktiivisuus voi parantua. Vaikka nämä edut pystyttiin saavuttamaan myös tavanomaisissa ravistelupulloissa, voidaan panossyöttökasvualustan solutiheyttä ja tuottoa tilavuutta kohti edelleen lisätä käyttämällä korkeamman ilmastustehokkuuden ravistelupulloja. Toisaalta tehostetun ilmastuksen havaittiin olevan mahdollisesti haitallista tiettyjen proteiinien, kuten Fab-vasta-ainefragmenttien, tuotolle. Fab-fragmenttien maksimaalinen tuotto saavutettiin ilmastustehokkuutta laskemalla. Lisäksi matalampi hapen saatavuus edisti periplasmaan ohjattujen Fab-fragmenttien kerääntymistä solunulkoiseen kasvualustaan. Näin ollen ilmastusolosuhteita ja kasvualustan koostumusta muokkaamalla voidaan vaikuttaa tuotteen lopulliseen sijoittumiseen. Korkean ilmastustehokkuuden havaittiin myös olevan haitallista proteiinituotolle glyserolipohjaisessa autoinduktiokasvualustassa. Tätä riippuvuutta ilmastuksen tasosta pystyttiin vähentämään ja autoinduktion luotettavuutta parantamaan käyttämällä kasvualustaa jossa hiililähteenä toimii glyserolin sijaan entsymaattinen glukoosisyöttö. Tutkimuksen tuloksia hyödyntäen voidaan parantaa vierasproteiinien saantoa, liukoisuutta ja periplasmisen/solunulkoisen kerääntymisen säätelyä, sekä mahdollistaa luotettava ja tehokas proteiinituotto viljelmien suurta lukumäärää vaativiin sovelluksiin, kuten proteiinien rakenteen ja toiminnan tutkimukseen
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Silva, Kleber Freire da. "Controle e integração de centrais eólicas à rede elétrica com geradores de indução duplamente alimentados." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-18042006-182933/.
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Esta Tese trata do controle e integração de centrais eólicas à rede elétrica interligada, utilizando-se geradores de indução duplamente alimentados (GIDE). O objetivo principal da Tese foi desenvolver estratégias de controle discreto para o sistema de geração eólica, de forma a reduzir os impactos na qualidade da energia gerada, em função dos diversos regimes e transitórios de vento, que podem ocorrer no sítio eólico. Para o projeto do sistema de controle dos geradores foi adotada a técnica do controle vetorial, de forma a desacoplar o controle do fluxo das potências ativa e reativa entre o gerador e a rede elétrica. Visando caracterizar os diversos modos de operação do GIDE, com velocidades acima e abaixo da síncrona, foi desenvolvido um estudo de regime permanente do gerador, obtendo-se os limites de correntes, tensões e demais grandezas elétricas e mecânicas, para uma determinada faixa de velocidade. As principais estratégias de controle atualmente utilizadas pelos fabricantes de turbinas eólicas foram analisadas, destacando-se os aspectos da eficiência energética do conjunto turbina-gerador e da qualidade da energia. O projeto das malhas de controle dos conversores estáticos conectados ao circuito do rotor foi desenvolvido utilizando a técnica de controle discreto, propondo-se as estratégias de controle e o conjunto de especificações para definição dos ganhos dos controladores, objetivando reduzir os impactos na qualidade da energia gerada. Foi analisada a influência da modelagem da turbina com eixos elásticos e eixos rígidos, no comportamento das variáveis controladas. Buscando reduzir os harmônicos de ordem elevada da corrente do gerador, devido à modulação por largura de pulso (PWM) dos conversores estáticos, foi proposta uma estratégia de projeto de filtro passivo LCL, instalado no circuito do rotor. Um programa de simulação no ambiente Matlab/Simulinkâ foi desenvolvido, para análise da interligação de um parque eólico, representado por uma turbina equivalente, ao sistema elétrico de potência reduzido, permitindo estudos de regime permanente e transitório. Com este programa, um estudo de caso foi realizado, avaliando-se o controle e a integração de uma usina eólica de 192MW, conectada na rede básica do sistema interligado nacional, na tensão 230kV. Os resultados obtidos mostram as contribuições, das estratégias de controle propostas, para melhorar o comportamento das tensões do sistema elétrico quando da ocorrência de transitórios de ventos na usina.This Thesis presents the control and integration of wind farms to the interconnected power grid, using doubly fed induction generators (DFIG). The main objective of the present Thesis was to develop discrete control strategies for the wind generation system, with the goal to reduce the wind variations impacts in the grid power quality. The design technique selected for the generators control system was the vector control technique, which allows independent control of active and reactive power flow between the generator and the grid. In order to characterize the diverse operation modes of the DFIG, below and above the synchronous speed, a generator steady-state study was developed, getting the current and voltage limits and the others electric and mechanical safe limits variables, for one determined speed range. The main control strategies currently used by the wind turbines manufacturers were analyzed, highlighting the aspects of the turbine-generator energy efficiency and the power quality. The control loops design of the static converters was developed using the discrete control technique. It was elaborated the control strategies and also the basic specifications used to define the controllers gains, with the key target to reduce the impacts in the grid power quality caused by the wind variations. Other aspect covered by this work was the influence of the turbine modeling, with rigid shafts and with shafts of a relatively low stiffness, in the control system performance. In a way to reduce high order harmonics in the generator current, caused by the pulse width modulation (PWM) of the static converters, it was proposed a design strategy of a passive LCL filter, installed in the rotor circuit. A simulation program was developed, using the Matlab/SimulinkÔ platform, to analyze the interconnection of a wind farm, represented by a equivalent turbine, to the reduced power electrical system, allowing steady-state and transient studies. With this simulation program, a case study was developed evaluating the control and integration of a 192MW wind farm, connected to 230kV voltage level of the national interconnected power system. The main results reached by this work showed the contributions of the control strategies proposed to improve the electrical system voltages behavior, when wind variations occur in the wind farm.
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Jacomini, Rogério Vani. "Controle do fluxo de potencia do gerador de indução duplamente alimentado funcionando na velocidade subsincrona." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258914.
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Orientador: Edson BimDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Esta tese trata da implementação do controle do fluxo de potência de um gerador de indução duplamente alimentado conectado ao barramento infinito. A orientação de fluxo do estator é utilizada, pois permite o controle, de forma independente, das potências ativa e reativa do estator, por meio das componentes de eixo direto e em quadratura da corrente de rotor. Na verdade, se for considerada a resistência de estator, o modelo apresentará um pequeno acoplamento. A estratégia de controle do GIDA foi implementada no DSP TMS320F2812. São apresentados resultados de simulação e experimentais para o gerador de 2,25kW, 220 V, 60 Hz. O gerador foi acionado por um motor de indução acoplado diretamente ao seu eixo. Operando com velocidades subsíncronas e com cargas indutiva, capacitiva e resistiva, resultados de simulação computacional e experimental relevantes são apresentados para validar a proposta.
Abstract: This thesis presents the results about an impIementation of an active and reactive power controI of a doubIy fed induction generator. The stator flux orientation allows the independent contraI of active and reactive power of stator connected to infinity bus. ln fact, if the resistance of stator is not negIected, the stator flux orientation will be coupIed. The controI technique was implemented by using of DSP TMS320F2812, therefore simuIation and experiments results are presented in further notes to vaIidate the proposaI. The generator was drivi:q.g for a squirreI cage induction motor directIy coupIed to tlÍe primary rator axis. The operation was based on sub synchronous speed and with inductive, capacitive and resistive Ioads.
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica
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Santana, Marcelo Patrício de. "Controle vetorial aplicado à redução das ondulações do torque eletromagnético no gerador de indução duplamente alimentado em sistemas eólicos." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-31012018-155034/.
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Este trabalho apresenta um sistema de controle com o objetivo de atenuar as ondulações do torque eletromagnético considerando os harmônicos de quinta, sétima, décima primeira e décima terceira ordem da tensão do estator do Gerador de Indução Duplamente Alimentado (GIDA). Dessa maneira, propõe-se a utilização de controladores proporcional-integrativo vetoriais juntamente com um sistema de identificação dos componentes harmônicos da corrente do estator empregando a transformada discreta de Fourier. O trabalho aborda a influência dos harmônicos de quinta, sétima, décima primeira e décima terceira ordem da tensão do estator nos harmônicos da corrente do estator, nas ondulações do torque eletromagnético e nas potências ativa e reativa do estator. Resultados de simulação avaliam o controlador proposto em condições adversas: variações paramétricas e da frequência da rede, além da influência de atrasos na corrente do estator. Finalmente, resultados experimentais validam o sistema proposto.This work presents a vector controller with the objective of reducing the electromagnetic torque and the active and reactive powers of the stator by means of control of the harmonics of the stator current in harmonic conditions of fifth, seventh, eleventh and thirteenth order of the stator voltage. The objective of the work is to propose a controller that uses two techniques already consolidated in the literature, proportional-integrative and discrete Fourier transform, besides being robust the main disadvantages of the existing harmonic controllers in the literature that are dependencies of the parameters of the machine and the Frequency of the network beyond the influence of the stator current delays on the harmonic controller. First, the influence of the fifth, seventh, eleventh, eleventh and thirteenth order harmonics of the stator voltage on the harmonics of the stator current and on the undulations of the electromagnetic torque and the active and reactive powers of the stator are studied. Next, simulation results evaluate the proposed controller under adverse conditions: parametric variations and the frequency of the network, besides the influence of stator current delays. Finally, experimental results validate the controller under conditions that the controller reference is nonzero.
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Nakata, Bruno Hideki. "Análise do controle de aerogeradores de indução duplamente alimentados e do perfil de tensão em redes de subtransmissão." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-12032018-094014/.
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Com o aumento da penetração da energia eólica nos sistemas de potência, critérios cada vez mais rigorosos vem sendo estabelecidos ao longo do tempo para a conexão e operação das plantas eólicas nas redes elétricas. A evolução das tecnologias empregadas em turbinas possibilitou o atendimento a esses critérios, passando do conceito dinamarquês de turbinas de velocidade fixa para turbinas de velocidade variável, que possibilitam melhor aproveitamento da energia disponível nos ventos e maior capacidade de controle das grandezas envolvidas. Neste trabalho, foram analisados diferentes tipos de controle de um gerador de indução duplamente alimentado (DFIG) e a influência dessa máquina nos níveis de tensão de uma rede de subtransmissão à qual está conectada. Os resultados mostram que os tipos de controles indicados para a operação da planta eólica podem variar sensivelmente de acordo com o carregamento e a velocidade do vento em um determinado momento. O crescimento de carga esperado da rede também pode influenciar na estratégia de controle da planta.With the increased penetration of wind energy in electrical power systems, increasingly stringent grid codes have been stablished over time for the connection and operation of wind power plants. The evolution of the technologies applied in wind turbines allowed meeting these criteria, moving from the Danish concept of fixed-speed turbines to variable-speed wind turbines, which enable better use of the available wind power and greater control of the variables involved. This study analyzes different control strategies of a doubly-fed induction generation (DFIG) and the influence of this machine in the voltage profile of a subtransmission system to which it is connected. The results show that the types of control suitable for the operation of the wind power plant may vary considerably according to the load and the wind speed at a given time. The expected load growth of the network can also influence in power plant control strategy.
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Tabares, Harrison García. "Controle direto de torque aplicado em aerogeradores que empregam o gerador de indução com rotor bobinado." reponame:Repositório Institucional da UFABC, 2014.
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Orientador: Dr. Alfeu J. Sguarezi FilhoDissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2014.
Devido as preocupações com a redu¸c¿ao do uso dos recursos f'osseis e das emiss¿oes de CO2 ocasionadas pelos mesmos, o interesse no uso de energias renov 'aveis aumentou, sendo uma destas fontes a energia e'olica. O Gerador de Indu¸c¿ao de Rotor Bobinado (GIRB) tem demonstrado ser uma ferramenta capaz de otimizar o uso da energia e'olica, dada a sua alta efici¿encia, rentabilidade e robustez mec¿anica, ainda assim 'e necess'ario superar os numerosos desafios que est¿ao presentes nesta tecnologia, tais como qualidade da pot¿encia, estabilidade da rede, entre outros. O objetivo desta pesquisa se concentra no estudo de t'ecnicas de controle de pot¿encia fornecida pelo GIRB aplicado a sistemas de gera¸c¿ao e'olica. No presente caso, o sistema de gera¸c¿ao 'e composto por um GIRB com seu estator conectado diretamente 'a rede e seu rotor 'e conectado 'a rede atrav'es de um conversor bidirecional. Prop¿oe-se estudar o m'etodo de controle direto de torque (CDT) com emprego de controladores PI e por modos deslizantes (SMC) mais PI. O controle direto de torque 'e uma t'ecnica de alto desempenho din¿amico e possibilita o controle independente do torque e fluxo do gerador o que possibilitar'a o controle das pot¿encias ativa e reativa do GIRB. Da mesma forma, 'e estudado o conversor para o processamento da energia gerada. As simula¸c¿oes baseadas em modelos matem'aticos destes m'etodos de controle foram revistos, analisados e comparados com as simula¸c¿oes de textos de refer¿encia. Resultados experimentais obtidos em uma bancada validaram o prot'otipo proposto.
Due to concerns about reducing the use of fossil resources and the CO2 emissions caused by them, interest in the use of renewable energy increased, one of these sources is wind energy. The Wound Rotor Induction Generator (WRIG) has been proved to be a tool to optimize the use of wind energy, given its high efficiency, profitability and mechanical robustness, it is still necessary to overcome the many challenges that are present in this technology, such as power quality, grid stability, among others. This research focuses on the study of control techniques for power supply by WRIG applied to wind generation systems. In this case, the generation system consists of a stator WRIG is connected directly to the electrical network and its rotor too, but via a bidirectional converter. It is proposed to study the method of direct torque control (DTC) with the use of PI and sliding mode controllers (SMC) more PI. The direct torque control is a technique of high dynamic performance and enables independent control of torque and flux generator, which will enable the control of active and reactive power ofWRIG. Likewise, it is studied the converter for processing the generated power. The simulations based on mathematical models of these control methods were reviewed , analyzed and compared with simulations of reference texts . Experimental results obtained on a bench validated the proposed prototype.
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Santana, Marcelo Patrício de. "Estratégias para identificação de faltas externas e controle do gerador de indução duplamente alimentado." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-26092012-093155/.
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O presente trabalho desenvolve uma topologia de controle para o gerador de indução duplamente alimentado (GIDA) em condições normais e em condições de falta monofásica. O sistema de controle é dividido em três partes principais: sistema de identificação de faltas, controle em condições normais e controle em condições de falta monofásica. A primeira parte, o sistema de identificação (SI) de faltas, é responsável pela seleção da topologia de controle da máquina. O SI é composto por uma combinação entre redes neurais artificiais (RNA) e a Fast Fourier Transform (FFT). As RNA são responsáveis pela identificação do estado atual da rede, se possui falta ou não. Os dados de entrada das RNA são as correntes de linha do estator que passam por um pré-processamento por meio da FFT. Alguns conteúdos harmônicos de saída da FFT irrelevantes no processo de identificação são eliminados por um método similar ao Principal Components Analysis (PCA). A segunda parte do trabalho é o controle em condições normais, sendo ativado quando o SI aponta a ausência de faltas. A topologia de controle vetorial é utilizada nesta condição para manter a tensão e frequência constante com a velocidade mecânica do eixo variável. A última parte do trabalho é o controle em condições adversas, que é ativado quando o SI detecta uma falta monofásica. A topologia de controle nesta condição utiliza as transformações ortogonais para reduzir o fluxo concatenado no enrolamento do estator com falta. A utilização deste novo controle reduz a corrente do estator quando comparado com o controle vetorial em condições de falta, sendo que a tensão do estator nas fases sem falta é mantida dentro de uma faixa de operação. O trabalho possui resultados de simulação das três principais partes do sistema de controle. Primeiramente, resultados do controle vetorial de tensão e frequência do GIDA sob condições de velocidade do eixo variável e cortes de carga são apresentados. Logo após, apresenta-se os resultados do SI na identificação de faltas monofásicas na fase B e o seu comportamento sob condições adversas como desequilíbrio de carga e cortes de cargas. Finalmente, alguns resultados do controle em condições de falta sobre uma falta fase-neutro na fase B são apresentados.This paper presents a control topology for doubly fed induction generator (DFIG) in normal and single fault conditions. The control system is divided into three main parts: fault identification system, control in normal condition and control in single fault conditions. In the first part, the system of identification (SI) is responsible for selecting the topology of the control. The SI is composed by a combination of artificial neural networks (ANN) and Fast Fourier Transform (FFT). The ANN is responsible for identifying the current state of the grid, if has fault or not. The inputs of the ANN are stator currents line through of a pre-processing by means of FFT. Some harmonic contents are irrelevant in the identification process and they are eliminated by a method similar to Principal Components Analysis (PCA). The second part of the paper is the control under normal conditions, activated when the SI indicates the absence of faults. The topology of vector control in this condition is used to maintain the voltage and frequency constant, where the speed of the mechanical axis variable. The last part of the work is the control in adverse conditions, which is activated when the SI detects a singlephase fault. The control topology in this condition uses the orthogonal transformations to reduce the mutual flux in the stator winding with fault. The use of this new control reduces the stator current as compared to vector control in fault conditions, and the stator voltage in the stages without fault is maintained within an operating range. The paper has simulation results of three main parts of the control system. First, the results of the vector control voltage and frequency of DFIG under conditions of variable shaft speed and load sections are provided. Soon after, the results of the SI in identifying faults in the phase B under conditions such as load imbalance and cutting loads are shown. Finally, some results of control in fault condition in the phase B are shown.
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Osório, Carlos Mario Rocha. "Controle das potências do aerogerador de indução com rotor bobinado com emprego de lógica fuzzy durante afundamentos de tensão." reponame:Repositório Institucional da UFABC, 2015.
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Orientador: Prof. Dr. Alfeu Joãozinho Sguarezi FilhoDissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2015.
This research project presents the active and reactive power control of the Doubly Fed Induction Generator (DFIG) employing fuzzy logic for a wind power generation system, the proposed controller is a Fuzzy Logic Controller Takagi Sugeno type (TS FLC) which determines the rotor voltage by the rules base dened by a linear combination of the membership sets of the rotor current error, that reduces the complexity of the structure and consequently a lower computational cost and its easy to implement on a experimental set compared to other controllers such as Fuzzy Mamdani type. System control is accomplished using Stator Flux Field Oriented Control with Space Vector Modulation and computer simulation using mathematical models implemented in Matlab/Simulink. The results indicates that the FLC TS could be an interesting alternative to conventional controllers in the power control of the DFIG during normal operation conditions and under balanced voltage sags conditions.
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Murari, André Luiz de Lacerda Ferreira. "Regulador quadrático linear ponderado com otimização por enxame de partículas modificado aplicado a geradores de indução com rotor bobinado." reponame:Repositório Institucional da UFABC, 2018.
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Orientador: Prof. Dr. Alfeu Joãzinho Sguarezi FilhoCoorientador: Prof. Dr. José Alberto Torrico Altuna
Tese (doutorado) - Universidade Federal do ABC. Programa de Pós-Graduação em Energia, Santo André, 2018.
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Murari, André Luiz de Lacerda Ferreira. "Proposta de projeto de ganhos de controladores PI empregados no controle de geradores de indução com rotor bobinado aplicados a sistemas eólicos." reponame:Repositório Institucional da UFABC, 2015.
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Orientador: Prof. Dr. Alfeu Joãozinho Sguarezi FilhoDissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2015.
Inicialmente, este trabalho apresenta aspectos de viabilidade e técnicos para a construção de sistemas de geração eólicos. Nele é disposto uma breve literatura de alguns dos conversores elétricos utilizados para diferentes tipos de geradores. Por fim, este trabalho propõe um método de ajuste de ganhos dos controladores proporcionais-integrais através do emprego do método por compensação de polos da função de transferência do sistema em malha fechada, para o conversor do lado do rotor, com objetivo de garantir controle estável do fluxo das potências ativa e reativa de estator do GIRB. Também, serão apresentadas as malhas de controle do conversor conectado à rede elétrica. Resultados obtidos através de simulação computacional deste sistema de controle são apresentados para validar a proposta.
This work includes feasibility and technical aspects for the construction of wind generation systems. In it, there is disposed a brief literature some electrical converters used for different types of generators. It also presents a design method for the gains of the proportional-integral controllers used in power vector control of DFIG connected to the grid in wind power generation systems where GIRB is connected directly to the power grid and its rotor through a converter called "back to back". The rotor controllers will be adjusted with the use of the method for compensating poles of the system's transfer function in closed loop. Also, the converter control loops connected to the grid will be displayed. Results from computer simulation of this control system are presented to validate the proposal.
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Loures, Daniele Rebouças Santana. "Enzimas fibrolíticas e emurchecimento no controle de perdas da ensilagem e na digestão de nutrientes em bovinos alimentados com rações contendo silagem de capim Tanzânia." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/11/11139/tde-16072004-155623/.
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Este trabalho teve por objetivo avaliar o efeito de enzimas fibrolíticas na degradação da parede celular do volumoso, quando aplicadas antes da ensilagem e no momento da alimentação do animal. No experimento I analisou-se o efeito do emurchecimento, da redução do tamanho de partículas e da adição de enzimas fibrolíticas (associadas ou não ao inoculante bacteriano Lactobacillus plantarum) na fermentação e nas perdas do processo de ensilagem de capim Tanzânia (Panicum maximum, Jacq. cv. Tanzânia). A forragem foi cortada aos 45 dias de crescimento vegetativo e armazenada em silos experimentais (50 L) durante 136 dias. Durante o período de armazenamento o efluente foi coletado e quantificado no 1o, 2o, 7o, 14o, 21o, 60o, 90o e 136o dias. A redução do tamanho de partícula não influenciou as perdas totais, embora o tamanho menor tenha contribuído para garantir maior estabilidade aeróbia da silagem. A taxa de recuperação e as perdas de MS por efluente e gases foram de 72, 5 e 23% nas silagens não-emurchecidas e de 80, 0 e 21% nas silagens emurchecidas, respectivamente. A adição de enzimas fibrolíticas associadas ou não ao inoculante bacteriano promoveu redução da fração fibrosa (FDN, FDA, celulose, hemicelulose), sendo esta redução mais acentuada nas silagens emurchecidas. Contudo, não houve aumento da digestibilidade in vitro da MS com adição de enzimas fibrolíticas. Foram observados os valores médios de DBO (11.289 mg L 1), DQO (36.279 mg L 1) e DQO/DBO (3,35) no efluente das silagens contendo umidade original; o maior período de armazenamento aumentou significativamente o potencial poluidor do efluente. O experimento II teve por objetivo avaliar o efeito do conteúdo de matéria seca da forragem e o uso de enzimas fibrolíticas aplicadas durante a ensilagem de capim Tanzânia ou após a abertura do silo. Os tratamentos foram confeccionados da seguinte forma: A - forragem emurchecida sem aplicação de enzimas; B não-emurchecida sem aplicação de enzimas; C - emurchecida com enzimas (2 L t -1 de massa verde); D não-emurchecida com enzimas; e E não-emurchecida com enzimas (10 L t -1 de massa verde), após a abertura do silo. Cinco novilhos da raça Nelore foram distribuídos ao acaso em delineamento do tipo Quadrado Latino 5 x 5. Os parâmetros de cinética de passagem de sólidos (2,23% hora-1) e de líquidos (4,83% hora-1) foram similares para os tratamentos avaliados. O comportamento ingestivo dos animais não foi alterado com a elevação da concentração de MS da silagem, sendo observados os seguintes tempos (minutos dia-1) e taxas (min kg MSI-1) de ingestão de MS (247 e 24), de ruminação (426 e 43) e de mastigação (673 e 67), respectivamente. As médias das concentrações totais dos ácidos graxos voláteis (109,62 mM) e de nitrogênio amoniacal (5,6 mg dL-1), do fluido ruminal, não foram alteradas pelos tratamentos aplicados. Diante dessas observações, pode-se concluir que o emurchecimento da forragem e o uso de aditivo enzimático não resultaram em alterações significativas no comportamento ingestivo, nos parâmetros ruminais e na digestibilidade de nutrientes em animais.The present trial aimed to evaluate the effect of fibrolytic enzymes on forage cell wall degradation, when applied either during the ensiling process or just before the animal feeding. The experiment I analyzed the effects of wilting (wet vs wilted), particle size reduction (small vs large) and the addition of fibrolytic enzymes (alone vs combined with Lactobacillus plantarum) on the fermentation and ensiling losses of Tanzania grass (Panicum maximum, Jacq. cv. Tanzania). Forage was harvested and cut at 45-day vegetative re-growth period and stored in experimental plastic silos (50 L) during 136 days. During the storage period, the effluent flow was collected and measured at days 1, 2, 7, 14, 21, 60, 90 and 136. Total silage losses were not affected by particle size reduction, even though the smallest particle size promoted better aerobic stability of the silage. The rate of silage DM recovery, effluent and gases losses were 72, 5 e 23 % for wet and 80, 0 e 21% for wilted silages, respectively. The addition of fibrolytic enzymes exclusively or combined with Lactobacillus plantarum led to decreased concentrations of NDF, ADF, cellulose and hemicellulose mainly on wilted silages, however, no benefit was observed in the in vitro DM digestibility. Mean values for BOD (11.289 mg L 1), COD (36.279 mg L 1), and the ratio COD/BOD (3.35) were observed on the effluent of wet silages, which increased the potential of environmental pollution with the longer silage storage period. The experiment II aimed to study the effects of forage wilting or fibrolytic enzymes addition to the Tanzania grass silages. Treatments consisted of: A - wilted forage without enzymes; B - fresh forage without enzymes; C - wilted forage with enzymes at ensiling (2 L t-1 wet forage); D - fresh forage with enzymes at ensiling; E - enzymes applied onto silage (10 L t-1 wet silage) 30 minutes before feeding (direct-fed). Five ruminally cannulated Nellore beef steers were randomly assigned to a 5 x 5 Latin square design. The ruminal passage rate of solid (2.23 % hour 1) and liquid (4.83 % hour 1) phases were similar for all treatments. The animal ingestive behavior measured as total time (minutes day-1) and rate (minutes DM kg-1) was not changed across silages DM concentration, averaging DM eating (247; 24), DM ruminating (426; 43) and DM chewing (673; 67), respectively. The molar concentration (109.62 mM) of total volatile fatty acids (VFA) and ammonia-N (5.6 mg dL-1) observed in ruminal fluid were similar across silages diets. According to the results it may be concluded that wilting Tanzania grass or the application of fibrolytic enzymes did not improve significantly either the animal ingestive behavior, ruminal parameters or the nutrient digestibilty.
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Cheng, Chin-Min. "Leaching of coal combustion products field and laboratory studies /." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1133195856.
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Amêndola, Cesar Augusto Moreira. "Contribuição ao estudo de aerogeradores de velocidade e passo variáveis com gerador duplamente alimentado e sistema de controle difuso." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-06122007-142431/.
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A captação eficaz da energia eólica ocorre por meio de turbinas de três pás com ângulo de passo e velocidade de rotação ajustáveis, sendo o ajuste do ângulo de passo utilizado para limitar a captação de energia na ocorrência de ventos muito fortes e o ajuste da velocidade de rotação utilizado para maximizar a captação da energia cinética dos ventos fracos. Neste regime de operação, o gerador deve converter a energia mecânica de entrada, caracterizada por velocidade de rotação e conjugado variáveis, em energia elétrica de saída nos padrões da rede elétrica a que estão conectados, caracterizada por tensão de valor eficaz e freqüência constantes. No presente trabalho, a conversão eletromecânica de energia é realizada por um gerador de indução duplamente alimentado, excitado pelos enrolamentos rotóricos por meio de um conversor eletrônico. O comportamento estocástico dos ventos e as não linearidades significativas da turbina eólica e do gerador motivaram a utilização de controladores difusos, elaborados de acordo com a seguinte metodologia: a base de regras foi estabelecida a partir dos princípios físicos e da dinâmica desejada para o sistema em malha fechada; as funções de pertinência de entrada foram distribuídas de maneira a garantir uma maior sensibilidade nas regiões próximas ao valor de referência; a distribuição das funções de pertinência de saída proporciona um aumento significativo da intensidade da ação de controle conforme a saída do sistema se afaste do valor de referência; e, a sintonia fina foi feita pelo dimensionamento dos universos de discurso de maneira a garantir a estabilidade do sistema em malha fechada e a dinâmica desejada para a variável controlada. Os resultados das simulações computacionais de variações em degrau nos valores de referência, tanto da velocidade de rotação quanto da potência reativa, demonstram dinâmica estável, sem overshoot ou erro de regime permanente. Destaca-se que, em relação ao estado-da-arte, o controlador difuso da velocidade de rotação proporciona uma dinâmica semelhante, mas com uma ação de controle desprovida de transitórios e picos 65% menores e o controlador difuso de potência reativa impõe uma resposta 64% mais rápida. Os resultados de simulações computacionais de regimes reais de ventos ilustram as atuações do sistema de controle, no ângulo de passo e na velocidade de rotação da turbina, para proporcionar ao aerogerador uma operação suave e estável sob diversos regimes de vento, desde os mais fracos até os mais intensos e turbulentos.The efficient capture of aeolic-energy occurs by means of three blades turbines with adjustable pitch-angle and angular-speed. The pitch-angle adjustment is utilized to limit the aeolic-energy capture when occur very strong winds and, the angular speed adjustment is utilized to maximize the capture of kinetic energy of weak winds. In this mode of operation the generator must convert the input mechanical energy, which is characterized by variable angular speed and variable torque, in the output electrical energy that must obey the standards of the electrical network with constant RMS-voltage and frequency, where the aeolic-generator is connected. In this work the electromechanical energy conversion is done by one double-fed induction generator excited by means of an electronic converter applied to the rotor winding. The air masses complex dynamics, the wind regime stochastic nature, and the turbine and generator non-linear behavior motivated the use of the fuzzy controllers, elaborated in agreement with the following methodology: the rule base was established from the system\'s physical principles and from the desired closed loop dynamics; the input membership functions was distributed so that ensure a bigger sensibility in the regions near the reference value; the output membership functions distribution provide a control action significant increase as the systems output move away from the reference value; and, the fine tuning was made via scaling universes of discourse. The computer simulation\'s results of the, rotational speed and reactive power, reference values step, demonstrated stable dynamics, without overshoot or steady state error. It is emphasize that, in relation to state-of-art, the fuzzy speed controller provide similar dynamic, but with a control action without transients and peaks 65% smaller and the fuzzy reactive power controller impose a 64% faster response. Some computer simulations of the wind real regime show the pitch-angle and turbine angular speed reactions so that to supply the wind generator with a soft and stable operation, from the weak winds up to the most strong and turbulent winds.
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Rocha, Marco Aurélio. "Modelagem e controle de gerador de indução duplamente alimentado para estudo de sistema de geração eólica." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153628.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Esta dissertação apresenta a análise, modelagem e controle vetorial de um sistema de geração eólica tendo um gerador de indução duplamente alimentado como máquina primária e equipado com um conversor back-to-back para gerenciamento da potência entregue ou absorvida da rede elétrica, independentemente do tipo de carga instalada, por meio de compensação de reativos e filtragem ativa das correntes da rede. Para atingir este objetivo, a modelagem do sistema, bem como o projeto dos controladores foram desenvolvidos no ambiente de simulação Matlab®/Simulink®, em que o controle do conversor do lado do rotor realiza a regulação do torque e o controle de potência ativa e reativa, enquanto que o controle do conversor do lado da rede tem a função de manter a tensão do link-CC constante e produzir fator de potência unitário, compensando reativos oriundos do sistema de geração eólica e da carga instalada e atuando como um filtro ativo de potência, melhorando o índice de distorção harmônica da corrente da rede. Além disso, controladores proporcionais-ressonantes foram utilizados a fim de mitigar harmônicos gerados pelo conversor atuando no modo retificador. Também foi realizado o controle do ângulo de passo das pás da turbina, com a finalidade de obter a máxima potência para qualquer velocidade do vento. Os resultados obtidos permitiram avaliar o desempenho dos controladores, de modo que o fator de potência foi mantido unitário para variações abruptas de carga. Tem-se compensação harmônica para cargas não-lineares sendo extraída e gerada a máxima potência oriunda do vento.
This dissertation presents the analysis, modeling and vector control of a wind power system with a doubly-fed induction generator as a primary machine and equipped whit a back-to-back converter to manage power delivered to or absorbed from the grid, independently of the installed load type, through reactive compensation and active filtering of grid currents. To achieve this goal, the system modelling and the controller design was developed in the Matlab®/Simulink® software, where the rotor-side converter control regulates torque and control active and reactive power. The grid-side converter control has the function of maintaining the DC link voltage constant and produce unit power factor, compensating reactive power from the wind generation system and the installed load and acting as an active power filter, which improves the total harmonic distortion of the grid current. In addition, proportional-resonant controller was used to mitigate harmonics generated by the converter acting in the rectifier mode. The pitch angle controller also was made in order to obtain the maximum power for any wind speed. The results obtained allowed to evaluate the performance of the controllers, so that the power factor was unit for abrupt loads variation, there was harmonic compensation for nonlinear loads and the maximum power from the wind was extracted and generated.
CNPq: 13.2999/2016-1
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Pinto, Vandilberto Pereira. "Controladores Robustos LQG/LTR com AÃÃo Integral Aplicados ao Controle de Geradores EÃlicos Interligados ao Sistema de DistribuiÃÃo de Energia ElÃtrica Baseados em MÃquinas de InduÃÃo Duplamente Alimentada." reponame:Repositório Institucional da UFC, 2012. http://www.repositorio.ufc.br/handle/riufc/2499.
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PINTO, W. F.Controladores robustos LQG/LTR com ação integral aplicados ao controle de geradores eólicos interligados ao sistema de distribuição de energia elétrica baseados em máquina de indução duplamente alimentada. 2012. 149 f. Tese (Doutorado em Engenharia Elétrica) - Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2012.Submitted by Marlene Sousa (mmarlene@ufc.br) on 2012-04-17T18:55:24Z No. of bitstreams: 1 2012_tese_vppinto.pdf: 4748816 bytes, checksum: 5ed094d97b04c5a274f84f921d09abf5 (MD5)
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It is proposed in this thesis a LQG/LTR robust controller (Linear Quadratic Gaussian with Loop Transfer Recovery) with integral action (LQG/LTRI) in a new application for gain tuning for the rotor side converter and grid side converter in a wind energy conversion system (WECS) with Doubly-Fed Induction Generator(DFIG). The proposed control method assures the robustness with respect to the tracking error rejection, insensitivity to parameter variations and permits that measurement and modeling errors are incorporated in the project. Robustness and performance tests were performed for variations of machine internal parameters and speed. Simulation and experimental results, obtained from a laboratory prototype that uses a 2 kW machine are presented to validate and demonstrate the robustness and performance of the proposed controller through the comparison with the proportional and integral (PI) controller employed in a wind energy conversion system with DFIG.
Na presente tese, propõe-se um controlador robusto LQG/LTR (Linear Quadratic Gaussian with Loop Transfer Recovery) com ação integral (LQG/LTRI) em uma nova aplicação para o ajuste dos controladores do conversor do lado da máquina e do conversor do lado rede elétrica em um sistema de conversão eólica utilizando um gerador de indução duplamente alimentado (Doubly-Fed Induction Generator - DFIG). A metodologia de controle proposta assegura a robustez em relação à rejeição do erro de rastreamento, insensibilidade a variações paramétricas, além de permitir que erros de medida e modelagem sejam incorporados no projeto. Testes de robustez e desempenho foram realizados para variações dos parâmetros internos da máquina e variações de referência de velocidade. Resultados de simulação e experimentais, obtidos em um protótipo de laboratório com uma máquina de 2kW são apresentados para validar e demonstrar o bom desempenho e robustez do controlador proposto comparado com os controladores clássicos Proporcional- Integral (PI) em um sistema de geração eólica com máquinas DFIG.
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Honda, Daniel Wanderley. "Controlador adaptativo por posicionamento de p?los e estrutura vari?vel aplicado ao controle de geradores e?licos baseados em m?quina de indu??o duplamente alimentada." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15481.
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Previous issue date: 2013-09-13Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
In the last decade, the renewable energy sources have present a major propulsion in the world due to several factors: political, environmental, financial and others. Within this context, we have in particular the energy obtained through wind, wind energy - that has highlighted with rapid growth in recent years, including in Brazil, mostly in the Northeast, due to it s benefit-cost between the clean energies. In this context, we propose to compare the variable structure adaptive pole placement control (VS-APPC) with a traditional control technique proportional integral controller (PI), applied to set the control of machine side in a conversion system using a wind generator based on Double-Fed Induction Generator (DFIG). Robustness and performance tests were carried out to the uncertainties of the internal parameters of the machine and variations of speed reference.
As fontes de energia renov?veis t?m, na ?ltima d?cada, ganho uma grande propuls?o em todo o mundo devido aos mais diversos fatores: pol?ticos, ambientais, financeiros, entre outros. Dentro deste universo, temos, em especial, a energia obtida atrav?s do vento, energia e?lica - que tem se destacado com um crescimento vertiginoso nos ?ltimos anos, inclusive no Brasil, principalmente na regi?o Nordeste, devido ao seu custo-benef?cio entre as energias "limpas". Neste cen?rio, prop?e-se a compara??o do controlador por posicionamento de polos e estrutura vari?vel (VS-APPC) com o controlador proporcional integral (PI) aplicados em um sistema de convers?o de energia e?lica que utiliza um gerador de indu??o duplamente alimentado (Double-Fed Induction Generator- DFIG). Testes de robustez e desempenho foram realizados com incertezas nos par?metros da m?quina e varia??es de refer?ncia de velocidade
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Maia, Roberta de Assis. "Screening de uma bibliotecade expressãode cDNA de cerebelo de rato usando-se como sonda o anticorpo anti-KM+ e expressão de drebinas em displasia cortical focal IIB (DCF IIB) associada com epilepsia de difícil controle medicamentoso." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/17/17140/tde-13052010-153055/.
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p83 é uma proteína com massa molecular aparente de 83 kDa, supostamente ainda não descrita, específica de sistema nervoso, e desenvolvimento regulada. p83 interage fortemente com laminina, Tau, tubulina e heat shock protein 90. p83 foi inicialmente detectada por imunohistoquímica e western blot usando-se um anticorpo anti-lectina KM+ purificado por afinidade. Sua purificação a partir de cérebro de rato está em progresso. Identificar o envolvimento de p83 em processos do Sistema Nervoso Central humano é um passo necessário em direção à compreensão de sua função biológica. Uma biblioteca de expressão de cDNA de cerebelo de rato (Lambda ZAP II, Stratagene) foi submetida ao screening, usando-se um anticorpo específico para isolar o cDNA de p83. O anticorpo anti-KM+ foi pré-adsorvido contra proteínas de E. coli XL1 Blue MRF, antes de ser usado no screening. As membranas foram reveladas por imunodetecção cromogênica (fosfatase alcalina e NBT/BCIP). A análise de todos os clones Lambda ZAP II foi feita por excisão in vivo do fagomídeo pBluescript, subclonagem em E. coli XL1 Blue MRF, purificação do DNA plasmidial e digestão com Eco RI. A seqüência correspondente ao clone isolado foi analisada usando-se ferramentas e bancos de dados do NCBI. A seqüência nucleotídica mostrou identidade com as isoformas A e E de drebrina. As isoformas A e E de drebrina foram detectadas em adulto e embrião, respectivamente. Drebrina A é uma proteína sistema nervoso-específica, desenvolvimento regulada e associa-se com F-actina. Embora drebrina e p83 compartilhem propriedades em comum, nossos dados de western blot indicaram que parecem não se tratar da mesma proteína. Nós investigamos a expressão de drebrina em Displasia Cortical Focal tipo IIB, comparando com córtex normal. As secções de tecido foram coradas com hematoxilina-eosina e prata (Bielchowsky). Secções foram processadas por imunohistoquímica usando-se os anticorpos anti-drebrina M2F6 e o DAS2, e recuperação antigênica. A detecção foi feita usando-se um anticorpo biotinilado, e DAB como cromógeno. Os tecidos displásicos (13 casos) foram obtidos cirurgicamente de tecidos exibindo epilepsia droga-resistente. Os controles foram obtidos de necrópsia de 15 pacientes sem história prévia de doenças neurológicas ou alterações patológicas. Nossos resultados sugerem uma associação entre drebrina e DCF IIB, um distúrbio do desenvolvimento cortical.p83 is 83 kDa protein supposedly not yet described, nervous system specific, and developmentally regulated. p83 strongly interacts with laminin, Tau, tubulin and heat shock protein 90. It was initially detected by immunohistochemistry and western blot using an affinity-purified anti-lectin KM+ antibody. Its purification from rat brain is in progress. Identifying the involvement of p83 in human Central Nervous System processes is a required step towards understanding its biological roles. A premade cDNA rat cerebellum expression library (Lambda ZAP II, Stratagene) has been screened, using a specific antibody to isolate p83 cDNA. Anti-KM+ antibody was pre-adsorbed against E. coli XL1 Blue MRF proteins, before using in screening. Membranes were revealed by cromogenic immunodetection (alcaline fostase and NBT/BCIP). The analysis of all positive Lambda ZAP II clones was carried out by in vivo excision of pBluescript, subcloning in E. coli XL1 Blue MRF, plasmidial DNA purification and Eco RI digestion. The sequence corresponding to the clone isolated was analyzed using the NCBI tools and database. The nucleotide sequence showed identity with drebrin A and E isoforms. Drebrin A and E isoforms were detected in adults and embryos. Drebrin A is a neuron-specific, development-regulated F-actin-binding protein. It participates in growth cone extension and dendritic spine formation. Although have same drebrin and p83 properties in common, they not seem to be the same protein. We have investigated the expression of drebrin in Focal Cortical Dysplasia type IIB (FCD IIB) as compared to normal cortex. Tissue sections were stained with hematoxylin-eosin and silver (Bielchowsky). Sections were processed for immunohistochemistry using anti-drebrin antibodies M2F6 and DAS2, and an antigen retrieval technique. Detection was carried out using a biotinylated antibody, using DAB as chromogen. Dysplastic tissues (13 cases) were obtained at surgery for drug-resistant epilepsy. Controls were obtained at autopsy from 15 patients without history of neurological disorder and gross pathological changes. A specific drebrin labeling in dysplastic tissue was more intense than in controls. Indeed, most control cases exhibited at most a slightly higher staining than the background. Balloon, clear and undetermined cells, and giant, dysmorphic neurons, showed a conspicuous labeling by anti-drebrin. These cells showed a thin rim labeling of the nuclear membrane, and a finely punctate nuclear labeling. In contrast, a coarse nuclear, but a faint cytoplasm labeling was observed in autopsy cases. Our data suggest an association between Drebrin expression and the FCD IIB, a disturbance of cortical development.
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Costa, João Marcos Nacif da. "Avaliação dos resultados da Instrução Normativa nº 50/2008 (MAPA) na melhoria da purificação das vacinas contra a febre aftosa comercializadas no Brasil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/179730.
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A febre aftosa é causada por um vírus do gênero Aphtovirus, cujas proteínas não estruturais (PNE) estão relacionadas diretamente a replicação viral e são comuns a todos os sorotipos e, portanto, são mais adequadas à pesquisa de anticorpos contra este vírus. Métodos de diagnóstico capazes de diferenciar animais infectados de vacinados aliados ao uso de vacinas purificadas quanto à PNE são imprescindíveis na estratégia para comprovação de ausência de transmissão viral. Através da Instrução Normativa nº 50/2008, o Brasil passou a realizar o controle oficial da pureza nas vacinas contra a febre aftosa. O objetivo deste trabalho foi avaliar se as chances de encontrar bovinos reativos aos testes sorológicos serão maiores antes da implantação do controle oficial, tanto nos resultados do controle oficial das vacinas, quanto nos inquéritos. Para isto, foram utilizados modelos de regressão logística com efeitos aleatórios, interações e controle de possíveis confundidores. Os resultados demonstraram que no realizado em laboratório oficial em 1016 partidas de vacinas, observou-se que a chance de ocorrência de resultados reativos antes da implantação da norma utilizando o método de triagem ELISA 3ABC NCPanaftosa foi 2,86 (IC95%,1,92-4,14) vezes a chance de ocorrência nos testes de vacina feitos após a norma, utilizando-se o mesmo método de triagem. Já a chance de resultados reativos antes da norma, utilizando-se o método NCPanaftosa, foi 19,70 (IC 95%,8,55- 45,37) vezes a chance de ocorrência após a norma com o uso do método PrioCHECK como triagem Já, a partir da comparação entre inquéritos soroepidemiológicos, foi possível observar que antes da implantação da IN50/2008 a chance de ocorrência de resultados reativos em bovinos que receberam uma dose de vacina foi 2,22 (IC 95%, 1,22-4,06) vezes a chance da ocorrência em bovinos não vacinados. Já, a chance de ocorrência de resultados reativos em bovinos que receberam duas ou três vacinas foi 5,94 (IC 95%, 3,25-10,87) vezes a de bovinos não vacinados. Nas estimativas modeladas para os inquéritos soroepidemiológicos realizados após a implantação da norma, independentemente do método de triagem utilizado, não houve associação significativa entre diferentes doses de vacinas e a ocorrência de animais reativos. Os resultados obtidos sugerem que há uma associação do controle oficial com a melhoria da produção de vacinas no que diz respeito a purificação do antígeno, assim como, indicam que a melhoria na pureza está associada à diminuição na chance de ocorrência de bovinos reativos em inquéritos soroepidemiológicos, ou seja, redução nos falso-positivos a campo.Foot and mouth disease (FMD) is a highly contagious disease caused by an Aphtovirus. Non-structural proteins (NSP) of this virus are directly related to viral replication and are common to all serotypes. Therefore, are more suitable for antibodies-based serological diagnosis. Diagnostic methods capable of differentiating infected from vaccinated animals (DIVA) are important surveillance tools; however, strategies should be in step with the development of vaccines. Since January 2009, the Brazilian government has been conducting an official control to evaluate NSP purity in vaccines production through the Normative Instruction No. 50 from 2008. This paper evaluates the situation of the vaccines produced in Brazil regarding NSP purification based on the results of the official control carried out by MAPA, as well as the adequacy of the surveillance system based on seroepidemiological surveys. Logistic regression with random effects, interactions and control for potential confounders were the chosen models. For the data obtained from the control of vaccines carried out in the official laboratory, the model estimated that the chance of occurrence of seroreactive results before the application of the official control using the 3ABC NCPanaftosa ELISA as screening method was 2.86 (95% CI, 1.92-4.14) times the chance of occurrence in the vaccine tests made after the standard, using the same method. The chance of seroreactive results before the official control, using the NCPanaftosa method as screening, was 19.70 (95% CI, 8.55 to 45.37) times the chance of occurrence after the official control with the use of the PrioCHECK method Comparing the seroepidemiological surveys results, the model indicated that, before the official control of vaccine purity, the chance of occurrence of reactive results in cattle receiving a single dose of vaccine was 2.22 (95% CI, 1.22 -4.06) times the chance of occurrence in unvaccinated animals. Furthermore, the chance of occurrence of reactive results in animals receiving two or three vaccines was 5.94 (95% CI, 3.25-10.87) times that of unvaccinated animals. Despite that, there was no significant difference in the estimates of the odds ratio between different doses of vaccines regardless of the screening method used for the seroepidemiological surveys performed after the official control of vaccines purity,. The present study suggests that there is an association of the implementation of Normative Instruction No. 50 from 2008 with the improvement of the NSP purity of vaccines, as well as indicates that this improvement is associated with a decrease in chance of occurrence of reactive animals in seroepidemiological surveys, i.e., reduction of false-positives in field monitoring.
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Ferreira, Liliam Rosalves. "Análise da relação valor de estoque e valor da empresa na indústria petrolífera." Pontifícia Universidade Católica de São Paulo, 2006. https://tede2.pucsp.br/handle/handle/1184.
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Previous issue date: 2006-10-05Inventories are an important component of companies assets in agriculture, mining, manufacturing and commerce sectors where they have a representative weight in the company valuation. The last decade was marked by important advances in inventories management, especially with Information Technology evolution. The oil industry has very peculiar challenges in inventories management due to a extensive global supply chain, with uncertainties about supply, pressures from ecologists, strong political issues and with great commodity prices variation verified during the last years. The subject has an increasing importance particularly regarding the market oil situation and with the general business environment that registers merger and acquisitions movements between companies which demands a necessary evaluation of the involved companies´ value. This work investigates the relationship between inventories´ value and companies´ value in order to identify whether or not a proper inventory management is related to company valuation by market value and also by Deducted Cash Flow (DCF). To develop this work, we carried and evaluated a quantitative research regarding performance data from 35 oil companies.. These companies are from different sizes and regions of the planet. The finding results indicate that the market does not penalize the oil companies inefficient inventories management., but the market gives a small award for the efficient companies. This award is larger than the one verified in previous studies with a wider range of activity sectors. For DCF valuation there is a small penalty for inefficient companies, however there is an excellent award for efficient companies. Considering other performance factors regarded in this study as control variables, efficient companies showed better general financial performance than the inefficient ones
Os estoques correspondem a uma parcela importante dos ativos de empresas dos setores de agricultura, mineração, indústria e comércio tendo assim peso representativo na avaliação da empresa. A última década foi marcada por avanços importantes na gestão dos estoques, especialmente com a evolução da Tecnologia da Informação. O setor do petróleo tem desafios muito peculiares na gestão dos estoques devido à extensão global da cadeia produtiva, às incertezas quanto ao fornecimento, às pressões de ecologistas, às fortes questões políticas associadas e à grande variação de preços da commodity verificada nos últimos anos. O tema possui importância crescente diante da situação do mercado de petróleo em particular e do ambiente empresarial como um topo, com movimentações de fusões e aquisições entre empresas que demandam uma avaliação precisa do valor das empresas envolvidas. Esta dissertação investiga as relações entre valor de estoque e valor da empresa identificando se uma boa gestão de estoques está relacionada com uma valorização da empresa do ponto de vista do valor de mercado e também da análise por Fluxo de Caixa Descontado (FCD). Para está avaliação é feito uma pesquisa quantitativa com dados do setor de petróleo e dados de desempenho de 35 empresas do setor, de diferentes portes e de diversas regiões do planeta. Os resultados encontrados indicam que o mercado não penaliza as empresas do setor petrolífero com gestão ineficiente de estoques, mas concede um pequeno prêmio para as empresas com gestão eficiente, maior que o prêmio verificado em estudos anteriores para uma gama maior de setores de atividade. Para avaliação com a metodologia FCD, existe uma pequena penalização para as empresas ineficientes, mas existe uma forte e relevante premiação para as empresas eficientes. Na dependência também com outros fatores tratados como variável de controle, as empresas eficientes mostraram melhor desempenho geral nos índices contábeis analisados
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Ngo, Van Quang Binh. "Algorithmes de conception de lois de commande prédictives pour les systèmes de production d’énergie." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC031/document.
Full textAbstract:
Cette thèse vise à élaborer de nouvelles stratégies de commande basées sur la commande prédictive pour le système de génération d’énergie éolienne. La topologie des systèmes de production éolienne basées sur le Générateur Asynchrone à Double Alimentation (GADA) qui convient à des plateformes de génération dans la gamme de puissance de 1.5 à 6 MW est abordée. Du point de vue technologique, le convertisseur à trois niveaux et clampé par le neutre (3L-NPC) est considéré comme une bonne solution pour une puissance élevée en raison de ses avantages: capacité à réduire la distorsion harmonique de la tension de sortie et du courant, et augmentation de la capacité du convertisseur grâce à une tension réduite appliquée à chaque semi-conducteur de puissance. Une description détaillée de la commande prédictive à ensemble de commande fini (FCS-MPC) avec un horizon de prédiction de deux pas est présentée pour deux boucles de régulation: celle liée au convertisseur connecté au réseau et celle du convertisseur connecté au GADA. Le principe de la commande repose sur l’utilisation d’un modèle de prédiction permettant de prédire le comportement du système pour chaque état de commutation du convertisseur. La minimisation d’une fonction de coût appropriée prédéfinie permet d’obtenir la commutation optimale à appliquer au convertisseur. La thèse étudie premièrement les problèmes liées à la compensation du temps de calcul de la commande et au choix et aux pondérations de la fonction de coût. Ensuite, le problème de stabilité de la commande FCS-MPC est abordé en considérant une fonction de Lyapunov dans la minimisation de la fonction de coût. Finalement, une étude sur la compensation des effets des temps morts du convertisseur est présentéeThis thesis aims to elaborate new control strategies based on Model Predictive control for wind energy generation system. We addressed the topology of doubly fed induction generator (DFIG) based wind generation systems which is suitable for generation platform power in the range in 1.5-6 MW. Furthermore, from the technological point of view, the three-level neutral-point clamped (3L-NPC) inverter configuration is considered a good solution for high power due to its advantages: capability to reduce the harmonic distortion of the output voltage and current, and increase the capacity of the converter thanks to a decreased voltage applied to each power semiconductor.In this thesis, we presented a detailed description of finite control set model predictive control (FCS-MPC) with two step horizon for two control schemes: grid and DFIG connected 3L-NPC inverter. The principle of the proposed control scheme is to use system model to predict the behaviour of the system for every switching states of the inverter. Then, the optimal switching state that minimizes an appropriate predefined cost function is selected and applied directly to the inverter.The study of issues such as delay compensation, computational burden and selection of weighting factor are also addressed in this thesis. In addition, the stability problem of FCS-MPC is solved by considering the control Lyapunov function in the design procedure. The latter study is focused on the compensation of dead-time effect of power converter
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DEVRA, SANGEETA. "IMPLEMENTATION OF PID AND FPD+I CONTROLLER ON NON-LINEAR SYSTEMS." Thesis, 2013. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16127.
Full textAbstract:
Since Fuzzy controllers are nonlinear, it is more difficult to set the controller gains compared to Proportional-Integral-Derivative (PID) controller. The idea is to start with a tuned conventional PID controller, replace it with an equivalent fuzzy controller. In contrast, a PID controller is a simple, linear combination of three signals: P action proportional to error, the I-action proportional to the integral of the error and the D-action proportional to the time derivative of error. This introduces a systematic tuning procedure for fuzzy PID type controllers and study of higher order systems based on Fuzzy controller This comprises of level control of a surge tank level system and inverted pendulum’s angular position as well as cart position using fuzzy PD+I controller with effect of different membership function on the system control as well as comparison with conventional PID Controller has been carved out. Different type of membership functions like Bell, Pi, Gaussian and Psigmoid are used in the fuzzy PD+I control of the system. The stability of the system has also been discussed upon using phase plot. The simulation results have been obtained using MATLAB.
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ARYA, YOGENDRA. "SOME STUDIES ON AUTOMATIC GENERATION CONTROL OF MULTI-AREA INTERCONNECTED RESTRUCTURED POWER SYSTEMS." Thesis, 2017. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16145.
Full textAbstract:
The prime objective of automatic generation control (AGC) is to adjust the active
power generation in response to variable power demands and hence to maintain
scheduled system frequency and scheduled tie-line power flows with neighboring
control areas at desired tolerance values. A sizeable fall in frequency might badly
affect the timing of electric clocks, magnetizing currents in transformers/induction
motors, constant speed of AC motors, continuous operation of processes and
synchronous operation of various units in power system. Additionally, power system
may face a serious instability problem at substantial drop in the frequency. In steady
state, automatically these variations must be zero. Enhanced power system stability is
achieved with the proper design of supplementary controller adopted in an AGC
system. However, continuous growth in size and complexity, stochastically changing
power demands, system modeling errors, alterations in electric power system
structures and variations in the system parameters over the time has turned AGC task
into a challenging one. Consequently, conventional control strategies may be
incompetent to handle such unpredictable variations in an AGC system. Hence, the
researchers over the world are trying to propose several novel control strategies that
fuse knowledge, techniques and methodologies from varied sources to tackle AGC
problem of power system effectively. The literature survey indicates that several
researchers, to tackle AGC issue in restructured system, have presented various types
of controllers optimized using various conventional and intelligent soft computing
techniques. The literature survey also unveils that the performance of AGC system
depends chiefly on the sort of intelligent technique exploited and structure of the
controller. Hence, the goal of the present study is to propose different types of new
vi
supplementary controller structures for various types of restructured as well as
traditional power systems.
The presented work is divided into ten chapters. Chapter 1 deals with the
introduction of AGC topic in deregulated environment. Chapter 2 presents a critical
review of AGC schemes in restructured power system. Chapter 3 stresses on the
modeling of traditional and restructured power systems under the study. The main
simulation work starts from Chapter 4.
In Chapter 4, the study is firstly conducted on a proposed restructured two-area
multi-source hydrothermal and hydrothermal gas power systems interconnected via
AC and AC/DC parallel tie-lines. Modern optimal control theory based optimal PI
structured controllers are designed with full state vector feedback control strategy
employing performance index minimization criterion. From the results obtained in the
study, it is substantiated that the use of AC/DC parallel links as an area
interconnection shows enrichment in the dynamic performance of the system in terms
of less oscillations, settling time and peak overshoots/undershoots in the deviation in
frequency and tie-line power responses. Eigenvalue study confirmed the positive
effect of AC/DC parallel links on the system dynamic performance and stability. It is
also observed that the multi-source hydrothermal system shows inferior performance
in comparison to the single-source thermal system due the presence of hydro source in
each area of the multi-source hydrothermal system due to the non-minimum phase
characteristics of hydro turbines.
The full state feedback optimal PI controllers work well and are very much robust
but in realistic environments, the measurement of all states is not feasible all the time.
Hence, next, in Chapter 5, some modern methods are adopted to conduct the study. In
first attempt, a modified fuzzy PI (FPI) controller optimized using genetic algorithm
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(GA) is proposed for different electric power system models such as traditional two
area non-reheat thermal, reheat thermal, multi-source hydrothermal and restructured
two-area reheat thermal systems. In traditional two-area multi-source hydrothermal
system, each control area owns two generating units, one non-reheat thermal and one
mechanical governor based hydro power plant. However, in restructured two-area
single-source system, each control area owns two single reheat thermal generating
units. Firstly, a FPI-1 controller is designed with nominal range of membership
functions (mfs) and GA tuned output scaling factors. Secondly, to test the impact of
alteration in horizontal range of mfs of FPI-1, it is further optimized to get FPI-2
controller. The results of FPI-1 and 2 controllers are compared and the results due to
later controller are found to be superior. Yet, FPI controllers are designed only for a
traditional two-area non-reheat thermal system; they are successfully applied on other
system under studies. The performance of FPI controllers is found significantly
superior in terms of lesser numerical values of settling times (STs), peak undershoots
(PUs) and various performance indices (PIs) compared to conventional controllers
based on optimal, GA, gravitational search algorithm (GSA), bacterial foraging
optimization algorithm (BFOA), hybrid BFOA-particle swarm optimization (hBFOA
PSO) and hybrid firefly algorithm-pattern search (hFA-PS) techniques.
Next, in Chapter 6, BFOA optimized fuzzy PI (FPI) and fuzzy PID (FPID)
controllers are proposed for traditional two-area non-reheat thermal, reheat thermal,
multi-source hydrothermal and restructured multi-source hydrothermal power
systems. BFOA is used to simultaneously tune the input and output scaling factors of
FPI/FPID controller keeping mfs and fuzzy rules invariant. It is observed that FPI
controller shows superior results in terms of lesser values of STs/PUs/PIs compared to
PI controller based on recently reported techniques like GA/PSO/BFOA/hBFOA
viii
PSO/hFA-PS/FA/artificial bee colony (ABC) and FPI controller tuned using PS/PSO
algorithms for the same system design.
Further, a fractional order PID (FOPID) structured controller is suggested for AGC
problem solution of power systems in Chapter 7. The parameters of FOPID controller
are optimized exploiting BFOA. At first, a traditional two-area multi-source
hydrothermal system is considered and the advantage of FOPID is established over
PI/PID controller optimized using hFA-PS and PID controller optimized using grey
wolf optimization (GWO) techniques. To show the effectiveness of the method, the
approach is further extended to restructured two-area multi-source hydrothermal and
thermal gas systems. The analysis of the simulation results discloses the efficacy of
FOPID controller over BFOA/differential evolution (DE)/GA optimized PID
controller. Then, the study is extended to a restructured three-area multi-source
hydrothermal power system.
In the next step of the study, a maiden attempt is made to propose a fractional
order fuzzy PID (FOFPID) controller for traditional two-area multi-source
hydrothermal, restructured two-area multi-source hydrothermal, restructured two-area
multi-source thermal gas and restructured three-area multi-source hydrothermal AGC
systems in Chapter 8. The parameters of FOFPID controller are also tuned utilizing
BFOA. The critical analysis of the obtained results revealed the worth of FOFPID
controller over FOPID controller in terms of less numerical value of STs, PUs and
PIs. It is also experienced that FOFPID controller satisfies the AGC requirements in
different power transactions taking place under deregulated environment more
fruitfully than FOPID controller.
In Chapter 9, FOFPID controller is implemented in AGC of restructured three
area multi-source hydrothermal system considering appropriate generation rate
ix
constraint (GRC), deadzone (DZ), boiler dynamics (BD) and time delay (TD).
However, controller is optimized for linear system it works robustly in the presence of
GRC/DZ/BD/TD physical constraints; though in the presence of GRC/DZ/BD/TD the
system performance degraded drastically in comparison to the linear or the system
with GRC only. Further, investigations clearly reveal that the controller is found to
perform well when the system is subjected to higher degree of uncontracted load
demands and simultaneous occurrence of uncontracted load demands. Thus, controller
parameters obtained for the linear system are robust enough and need not be retuned
for the system having appropriate GRC or GRC/DZ/BD/TD or wide changes in the
size and location of contract violations. Thus, BFOA tuned FOFPID controller and
other controllers proposed in the previous chapters may be options to supply reliable
power with quality to the consumers.
Finally, Chapter 10 presents an overview of the contributions made in the current
thesis. Few suggestions are also given to extend the research in the future.
45
Dey, Anubrata. "Investigations on Online Boundary Variation Techniques for Nearly Constant Switching Frequency Hysteresis Current PWM Controller for Multi-Level Inverter Fed IM Drives." Thesis, 2012. http://etd.iisc.ac.in/handle/2005/3161.
Full textAbstract:
In DC to AC power conversion, voltage source inverters (VSI) based current controllers are usually preferred for today’s high performance AC drive which requires excellent dynamic and steady state performances at different transient and load conditions, with the additional advantages like inherent short circuit and over current protection. Out of different types of current controllers, hysteresis controllers are widely used due to their simplicity and ability to meet the requirements for a high performance AC drives. But the conventional hysteresis controllers suffers from wide variation of PWM switching frequency, overshoot in current errors, sub-harmonic components in the current waveform and non-optimum switching at different operating point of the drive system. To mitigate these problems, particularly to control the switching frequency variation, which is the root cause of all other problems, several methodologies like ramp comparison based controller, predictive current controller, etc. were proposed in the literature. But amplitude and phase offset error in the ramp comparison based controllers and complexities involved in the predictive controllers have limited the use of these controllers. Moreover, these type of controllers, which uses three separate and independently controlled tolerance band (sinusoidal type or adaptive) to control the 3-phase currents, shows limited dynamic responses and they are not simple to implement. To tackle the problem of controlling 3-phase currents simultaneously, space vector based hysteresis current controller is very effective as it combines the current errors of all the three phases as a single entity called current error space vector. It has a single controller’s logic with a hysteresis boundary for controlling this current error space vector. Several papers on space vector based hysteresis controllers for 2-level inverter with constant switching frequency have been published, but the application of the constant switching frequency based hysteresis current controllers for multi¬level inverter fed drive system, has not been addressed properly. Use of multi-level inverter in modern high performance drive for medium and high voltage levels is more prominent because of multi-level’s inherent advantages like good power quality, good electromagnetic compatibility (EMC), better DC link voltage utilization, reduced device voltage rating, so on. Even though some of the earlier works describe three-level space vector based hysteresis current controller techniques, they are specific to the particular level of inverters and does not demonstrate constant switching frequency of operation. This thesis proposes a novel approach where nearly constant switching frequency based hysteresis controller can be implemented for any general n-level inverter and it is also independent of inverter topology. In this work, varying parabolic boundary is used as the hysteresis current error boundary for controlling the current in a multi-level space vector structure. The computation of the parabolic boundary is accomplished offline and all the necessary boundary parameters at different operating points are stored in the look-up tables. The varying parabolic boundary for the multi-level space vector structure depends on the sampled reference phase voltage values which are estimated from stator current error information and then using the equivalent circuit model of induction motors. Here, a mapping technique is adopted to bring down all the three phase references to the inner- most carrier region, which results in mapping any outer triangular structure where tip of the voltage space vector is located, to one of the sectors of the inner most hexagon of the multi-level space vector structure. In this way, the required mapped sector information is easily found out to fix the correct orientation of the parabolic boundary in the space vector plane. This mapping technique simplifies the controller’s logic similar to that of a 2-level inverter. For online identification of the inverter switching voltage vectors constructing the present outer triangle of the multi-level space vector structure, the proposed controller utilizes the sampled phase voltage references. This identification technique is novel and also generic for any n-level inverter structure. This controller is having all the advantages of a space vector based hysteresis current controller and that of a multi-level inverter apart from having a nearly constant switching frequency spectrum similar to that of a voltage controlled space vector PWM (VC-SVPWM).
Using the proposed controller, simulation study of a five-level inverter fed induction motor (IM) drive scheme, was carried out using Matlab-Simulink. Simulation study showed that the switching frequency variations in a fundamental cycle and over the entire speed range of the linear modulation region, is similar to that of a VC-SVPWM based multi-level VSI. The proposed hysteresis controller is experimentally verified on a 7.5 kW IM vector control drive fed with a five-level VSI. The proposed current error space vector based hysteresis controller providing nearly constant switching frequency is implemented on a TI TMS320LF2812 DSP and Xilinx XC3S200FT256 FPGA based platform. The three-phase reference currents are generated depending on the frequency command and the controller is tested with the drive for the entire operating speed range of the machine in forward and reverse directions. Steady state and quick transient results of the proposed drive are presented in this thesis.
This thesis also proposes another type of hysteresis controller, firstly for 2-level inverter and then for general n-level multi-level inverter, which eliminates the parabolic boundary and replaces it with a boundary which is computed online and does not use any look up table for boundary selection. The current error boundary for the proposed hysteresis controller is computed online in a very simple way, using the information of estimated fundamental stator voltages along α and β axes of space vector plane. The method adopted for the proposed controller to compute the boundary does not involve any complicated computations and it selects the optimal vector for switching when current error space vector crosses the boundary. This way adjacent voltage vector switching similar to VC-SVPWM can be ensured. For 2-level inverter, it precisely determines the sector, in which reference voltage vector is present. In multi-level inverter, this controller also finds out the mapped sector information using the same mapping techniques as explained in the first part of this thesis. In both 2-level and multi-level inverter, the proposed controller does not use any look up table for finding individual voltage vector switching times from the estimated voltage references. These switching times are used for the computation of hysteresis boundary for individual vectors. Thus the hysteresis boundary for individual vectors is exactly calculated and the boundary is similar to that of VC-SVPWM scheme for the respective levels of inverter. In the present scheme, the phase voltage harmonic spectrum is very close to that of a constant switching frequency VC-SVPWM inverter. In this thesis, at first, the proposed on line boundary computation scheme is implemented for a 2-level inverter based controller for the initial study, so that it can be executed as fast as 10 µs in a DSP platform, which is required for accurate current control. Then the same algorithm of 2-level inverter is extended for multi-level inverter with the additional logic for online identification of nearest switching voltage vectors (also used in the parabolic boundary case) for the present sampling interval. Previously mentioned mapping technique for multi-level inverter, is also implemented here to bring down the phase voltage references to the inner-most carrier region to realize the multi-level current control strategy equivalent to that of a 2-level inverter PWM current control.
Simulation study to verify the steady state as well as transient performance of the proposed controller for both 2-level as well as five-level VSI fed IM drive is carried out using Simulink tool box of MATLAB Simulation Software. The proposed hysteresis controllers are experimentally verified on a 7.5 kW IM vector control drive fed with a two-level VSI and five-level VSI separately. The proposed current error space vector based hysteresis controller providing nearly constant switching frequency profile for phase voltage is implemented on the TI TMS320LF2812 DSP and Xilinx XC3S200FT256 FPGA based platform. The three-phase reference currents are generated depending on the frequency command and the proposed hysteresis controllers are tested with drive for the entire operating speed range of the machine in forward and reverse directions. Steady state and transient results of the proposed drive are also presented for different operating conditions, through the simulation study followed by experimental verifications. Even though the simulation and experimental verifications are done on a 5-level inverter to explain the proposed hysteresis controller, it can be easily implemented for any general n-level inverter, as described in this thesis.
46
Dey, Anubrata. "Investigations on Online Boundary Variation Techniques for Nearly Constant Switching Frequency Hysteresis Current PWM Controller for Multi-Level Inverter Fed IM Drives." Thesis, 2012. http://hdl.handle.net/2005/3161.
Full textAbstract:
In DC to AC power conversion, voltage source inverters (VSI) based current controllers are usually preferred for today’s high performance AC drive which requires excellent dynamic and steady state performances at different transient and load conditions, with the additional advantages like inherent short circuit and over current protection. Out of different types of current controllers, hysteresis controllers are widely used due to their simplicity and ability to meet the requirements for a high performance AC drives. But the conventional hysteresis controllers suffers from wide variation of PWM switching frequency, overshoot in current errors, sub-harmonic components in the current waveform and non-optimum switching at different operating point of the drive system. To mitigate these problems, particularly to control the switching frequency variation, which is the root cause of all other problems, several methodologies like ramp comparison based controller, predictive current controller, etc. were proposed in the literature. But amplitude and phase offset error in the ramp comparison based controllers and complexities involved in the predictive controllers have limited the use of these controllers. Moreover, these type of controllers, which uses three separate and independently controlled tolerance band (sinusoidal type or adaptive) to control the 3-phase currents, shows limited dynamic responses and they are not simple to implement. To tackle the problem of controlling 3-phase currents simultaneously, space vector based hysteresis current controller is very effective as it combines the current errors of all the three phases as a single entity called current error space vector. It has a single controller’s logic with a hysteresis boundary for controlling this current error space vector. Several papers on space vector based hysteresis controllers for 2-level inverter with constant switching frequency have been published, but the application of the constant switching frequency based hysteresis current controllers for multi¬level inverter fed drive system, has not been addressed properly. Use of multi-level inverter in modern high performance drive for medium and high voltage levels is more prominent because of multi-level’s inherent advantages like good power quality, good electromagnetic compatibility (EMC), better DC link voltage utilization, reduced device voltage rating, so on. Even though some of the earlier works describe three-level space vector based hysteresis current controller techniques, they are specific to the particular level of inverters and does not demonstrate constant switching frequency of operation. This thesis proposes a novel approach where nearly constant switching frequency based hysteresis controller can be implemented for any general n-level inverter and it is also independent of inverter topology. In this work, varying parabolic boundary is used as the hysteresis current error boundary for controlling the current in a multi-level space vector structure. The computation of the parabolic boundary is accomplished offline and all the necessary boundary parameters at different operating points are stored in the look-up tables. The varying parabolic boundary for the multi-level space vector structure depends on the sampled reference phase voltage values which are estimated from stator current error information and then using the equivalent circuit model of induction motors. Here, a mapping technique is adopted to bring down all the three phase references to the inner- most carrier region, which results in mapping any outer triangular structure where tip of the voltage space vector is located, to one of the sectors of the inner most hexagon of the multi-level space vector structure. In this way, the required mapped sector information is easily found out to fix the correct orientation of the parabolic boundary in the space vector plane. This mapping technique simplifies the controller’s logic similar to that of a 2-level inverter. For online identification of the inverter switching voltage vectors constructing the present outer triangle of the multi-level space vector structure, the proposed controller utilizes the sampled phase voltage references. This identification technique is novel and also generic for any n-level inverter structure. This controller is having all the advantages of a space vector based hysteresis current controller and that of a multi-level inverter apart from having a nearly constant switching frequency spectrum similar to that of a voltage controlled space vector PWM (VC-SVPWM).
Using the proposed controller, simulation study of a five-level inverter fed induction motor (IM) drive scheme, was carried out using Matlab-Simulink. Simulation study showed that the switching frequency variations in a fundamental cycle and over the entire speed range of the linear modulation region, is similar to that of a VC-SVPWM based multi-level VSI. The proposed hysteresis controller is experimentally verified on a 7.5 kW IM vector control drive fed with a five-level VSI. The proposed current error space vector based hysteresis controller providing nearly constant switching frequency is implemented on a TI TMS320LF2812 DSP and Xilinx XC3S200FT256 FPGA based platform. The three-phase reference currents are generated depending on the frequency command and the controller is tested with the drive for the entire operating speed range of the machine in forward and reverse directions. Steady state and quick transient results of the proposed drive are presented in this thesis.
This thesis also proposes another type of hysteresis controller, firstly for 2-level inverter and then for general n-level multi-level inverter, which eliminates the parabolic boundary and replaces it with a boundary which is computed online and does not use any look up table for boundary selection. The current error boundary for the proposed hysteresis controller is computed online in a very simple way, using the information of estimated fundamental stator voltages along α and β axes of space vector plane. The method adopted for the proposed controller to compute the boundary does not involve any complicated computations and it selects the optimal vector for switching when current error space vector crosses the boundary. This way adjacent voltage vector switching similar to VC-SVPWM can be ensured. For 2-level inverter, it precisely determines the sector, in which reference voltage vector is present. In multi-level inverter, this controller also finds out the mapped sector information using the same mapping techniques as explained in the first part of this thesis. In both 2-level and multi-level inverter, the proposed controller does not use any look up table for finding individual voltage vector switching times from the estimated voltage references. These switching times are used for the computation of hysteresis boundary for individual vectors. Thus the hysteresis boundary for individual vectors is exactly calculated and the boundary is similar to that of VC-SVPWM scheme for the respective levels of inverter. In the present scheme, the phase voltage harmonic spectrum is very close to that of a constant switching frequency VC-SVPWM inverter. In this thesis, at first, the proposed on line boundary computation scheme is implemented for a 2-level inverter based controller for the initial study, so that it can be executed as fast as 10 µs in a DSP platform, which is required for accurate current control. Then the same algorithm of 2-level inverter is extended for multi-level inverter with the additional logic for online identification of nearest switching voltage vectors (also used in the parabolic boundary case) for the present sampling interval. Previously mentioned mapping technique for multi-level inverter, is also implemented here to bring down the phase voltage references to the inner-most carrier region to realize the multi-level current control strategy equivalent to that of a 2-level inverter PWM current control.
Simulation study to verify the steady state as well as transient performance of the proposed controller for both 2-level as well as five-level VSI fed IM drive is carried out using Simulink tool box of MATLAB Simulation Software. The proposed hysteresis controllers are experimentally verified on a 7.5 kW IM vector control drive fed with a two-level VSI and five-level VSI separately. The proposed current error space vector based hysteresis controller providing nearly constant switching frequency profile for phase voltage is implemented on the TI TMS320LF2812 DSP and Xilinx XC3S200FT256 FPGA based platform. The three-phase reference currents are generated depending on the frequency command and the proposed hysteresis controllers are tested with drive for the entire operating speed range of the machine in forward and reverse directions. Steady state and transient results of the proposed drive are also presented for different operating conditions, through the simulation study followed by experimental verifications. Even though the simulation and experimental verifications are done on a 5-level inverter to explain the proposed hysteresis controller, it can be easily implemented for any general n-level inverter, as described in this thesis.
47
Yang, Wu Chang, and 楊武璋. "Implementation of a Vector Controlled Doubly-Fed Induction Generator." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/61589300932318481571.
Full text
48
Kuo, Ping-Hsun, and 郭秉勳. "Design of Fuzzy Controllers for Doubly Fed Induction Generators." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/34741931967764402169.
Full textAbstract:
碩士國立臺灣大學
電機工程學研究所
104
This thesis presents power mode control strategy with a Fuzzy proportional-integral(PI) controller in the rotor side converter of the doubly fed induction generator (DFIG). The proposed technique is employed to control the active and reactive power of wind turbine to the grid and reduces the overcurrent during the grid fault. The DFIG is operated at maximum power tracking mode in the steady state, and keeps operating at this mode to deliver power as much as possible during fault. However, it causes overcurrent problem in this operation. In this work, the mathematical model of the power controller is developed by theoretical analysis for DFIG and employed to determine proper gain for the Fuzzy PI controller such that DFIG has fast response and good stability. Moreover, DFIG under power mode control delivers not only active power but also reactive power to boost the system voltage. The MATLAB/Simulink® software is employed to develop the grid-connected DFIG model and evaluate the effectiveness of Fuzzy PI controller. The simulation results show that the Fuzzy PI controller enhances the dynamic performance and the rotor transient overcurrent can be suppressed during fault initiation. Moreover, DFIG under power mode control is able to decrease the steady-state rotor current during faulted period. Therefore, the rotor side converter can be protected by employing the Fuzzy PI controller for the DFIG operated under power control mode during the fault. Low voltage ride through capability of the DFIG can be enhanced by the proposed fuzzy PI controller.
49
CAI, PING-HE, and 蔡平和. "A study on the current-controlled voltage-fed inverters." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/69968642360562808972.
Full text
50
Lin, Bo-Nian, and 林柏年. "Microgrid Frequency Improvement Using a Model Predictive Controller for Doubly Fed Induction Generator." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/9j7z9z.
Full textAbstract:
碩士國立臺灣大學
電機工程學研究所
106
Design of a model predictive auxiliary frequency controller and maximum power tracking compensator for a doubly-fed induction generator (DFIG) in a microgrid is investigated in this thesis. When there’s frequency change in a microgrid, the conventional approach is to rely on the inertia control, primary control, and secondary control of synchronous generators to stabilize the system frequency. With the increasing need of green energy, some of the traditional synchronous generators are replaced by wind turbine generators. If the wind turbine generators are not provided with auxiliary frequency controller mechanism, satisfactory frequency response can not be achieved. Therefore, the wind turbines must be designed with the auxiliary frequency controller in order to improve system frequency response. In a doubly-fed induction generator (DFIG), the auxiliary frequency controller is usually installed on the rotor side converter (RSC) and frequency regulation is achieved through a droop control signal which is proportional to frequency deviation and the torque reference command of the RSC is modulated through this droop control input. In previous works, the gain of the auxiliary frequency controller was fixed. However, a fixed-gain auxiliary frequency controller is not able to provide satisfactory frequency response when there is a change in generator parameter or wind speed. Moreover, underfrequency load shedding must be enforced when the frequency deviation exceeds the preset value. In the present work, a model predictive auxiliary frequency controller is designed for the DFIG in order to improve frequency response in a microgrid. The plant predictive model will change when there is a change in generator parameter or wind speed. As a result, better frequency response can be achieved with the adaptive control provided by the proposed model predictive auxiliary frequency controller. Furthermore, underfrequency load shedding can be avoided with the implementation of state variable (frequency) constraint in the model predictive auxiliary frequency controller. When there is a change in system frequency, the auxiliary frequency controller of the wind turbines would provide the needed active power to the system timely. In the dynamic process, the rotating speed of the wind turbine would decrease. As a result, the maximum power tracking control and frequency compensation are affected. Therefore, the investigation of maximum power tracking compensator is required. The research results show that, with maximum power tracking compensator, the frequency response in the dynamic process can be improved. In order to demonstrate the effectiveness of the proposed model predictive auxiliary frequency controller and maximum power tracking compensator, MATLAB/Simulink dynamic simulation are performed on a microgrid in central Taiwan which comprises conventional synchronous generators and off-shore wind farms.