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1
Connor, Peter. "Computational fluid dynamics modelling of a synchronous electric generator". Thesis, University of Nottingham, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.755815.
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An air-cooled synchronous generator has been studied for its airflow and thermal analysis using Computational Fluid Dynamics (CFD) in conjunction with experimental validation. Due to the temperature dependent resistive losses in the machine’s windings, any improvement in cooling provides a direct reduction in losses and an increase in efficiency. In addition, detailed modelling of machine windage components provide an insight for efficiency savings associated with airflow. A full 3600 CFD generator model has been constructed including all major solid components in conjunction with the air fluid regions. Fluid flow, turbulence, rotation as well as conjugate heat transfer modelling was solved throughout the whole machine. The CFD model has been validated using experimental testing on a newly commissioned rig. Airflow parameters of mass flow rate, torque and local pressures were used to validate the fluid modelling. Thermal measurements of stator temperature, heat flux and calculated heat transfer coefficients were used to validate the conjugate heat transfer modelling of the machine. Temperature distributions throughout all machine components were analysed. These have been explained by detailed analysis of local surface heat transfer coefficients and the associated local air flow structures which determine them. This versatility and detail in the thermal analysis of electrical machines is unique to CFD modelling. The methodology presented in this thesis demonstrates advancement in the scale and complexity for CFD analyses of electrical machines. This level of cooling scrutiny will enable informed design developments for step changes in machine efficiency.
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Danielsson, Christer. "Analysis of Synchronous machine dynamics using a novel equivalent circuit model". Licentiate thesis, Stockholm : Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10510.
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Watson, Eric. "Sun-Synchronous Orbit Slot Architecture Analysis and Development". DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/760.
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Space debris growth and an influx in space traffic will create a need for increased space traffic management. Due to orbital population density and likely future growth, the implementation of a slot architecture to Sun-synchronous orbit is considered in order to mitigate conjunctions among active satellites. This paper furthers work done in Sun-synchronous orbit slot architecture design and focuses on two main aspects. First, an in-depth relative motion analysis of satellites with respect to their assigned slots is presented. Then, a method for developing a slot architecture from a specific set of user defined inputs is derived.
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Diesmann, Markus. "Conditions for stable propagation of synchronous spiking in cortical neural networks single neuron dynamics and network properties /". [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=968772781.
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HAUS, EMANUELE. "DYNAMICS OF AN ELASTIC SATELLITE WITH INTERNAL FRICTION. ASYMPTOTIC STABILITY VS COLLISION OR EXPULSION". Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/172628.
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In this thesis, we study the dynamics of an elastic body, whose shape and position evolve due to the gravitational forces exerted by a pointlike planet whose position is fixed in space.
The first result of this thesis is that, if any internal deformation of the body dissipates some energy, then the dynamics of the system has only three possible final behaviors: (i) the satellite is expelled to infinity, (ii) the satellite falls on the planet, (iii) the satellite is captured in a synchronous orbit. By item (iii) we mean that the shape of the body reaches a final configuration, that a principal axis of inertia is directed towards the attracting planet and that the center of mass of the satellite moves on a circle of constant radius.
Secondly, we study the stability of the synchronous orbit. Restricting to the quadrupole approximation and assuming that the body is very rigid, we prove that such an orbit is (locally) asymtotically stable, both in the case of a triaxial satellite and in the case of a satellite with spherical symmetry. Some additional results on the dynamics of the body close to the synchronous orbit and some new kinematical results are also present in the thesis.
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Le, Luong Huong Thao. "Optimal Design of Modular High Performance Brushless Wound Rotor Synchronous Machine for embedded systems". Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0111/document.
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Cette thèse est dédiée à la conception optimale de la machine synchrone à rotor bobiné modulaire sans balais pour les systèmes embarqués. Cette machine est basée sur une structure POKIPOKITM développée par Mitsubishi Electric Coopération avec les convertisseurs de puissance intégrée pour augmenter la capacité de tolérance aux défauts. L'analyse électromagnétique est utilisée pour étudier les différentes machines synchrones à rotor bobiné et donc, pour sélectionner la structure qui offre la meilleure tolérance aux défauts et les performances les plus élevées. D’abord, le choix des nombres de phases, d’encoches et de pôles est un point critique. Ensuite, quelques machines sont analysées et comparées selon les critères tels que la densité de couple, le rendement, l'ondulation de couple. La machine avec 7 phases, 7 encoches et 6 pôles est alors choisie. Cette machine est ensuite comparée à la machine synchrone à aimant permanent monté en surface. Le résultat démontre que la machine synchrone à rotor bobiné modulaire sans balais possède le potentiel de remplacer la machine synchrone à aimant permanent dans notre application parce qu’elle présente des performances similaires avec une capacité de tolérance aux défauts élevée. Dans un second temps, une fois la structure 7phases/7encoches/6pôles choisie, cette machine est optimisée en utilisant NOMAD (qui est un logiciel d'optimisation de boîte noire) afin de minimiser le volume externe sous les contraintes électromagnétiques, thermiques et mécaniques. Comme ce problème d'optimisation est extrêmement difficile à résoudre, quelques relaxations ont été effectuées pour tester les différents algorithmes d'optimisation : fmincon (de Matlab) et NOMAD. Nous remarquons que NOMAD est plus efficace que fmincon pour trouver des solutions à ce problème de conception où certaines contraintes sont calculées par des simulations numériques (ANSYS Maxwell ; code éléments finis). En utilisant la méthode NOMAD basée sur l’algorithme Mesh Adaptive Direct Search, nous obtenons des résultats optimaux qui satisfont toutes les contraintes proposées. Il est nécessaire de valider ce design optimisé en vérifiant toutes les contraintes par des simulations électromagnétiques et thermiques en 3D. Les résultats montrent que le couple moyen obtenu par la simulation en 3D est inférieur à la valeur souhaitée. Par conséquent, en augmentant la longueur de la machine, une nouvelle machine corrigée est ainsi obtenue. Nous observons que les pertes de fer obtenues en 3D sont plus élevées qu'en 2D en raison du flux de fuite dans la tête de bobinage. En prenant les valeurs des pertes analysées par la simulation en 3D, la température de surface de la nouvelle machine analysée par la méthode Computational Fluid Dynamics est plus élevée que celle calculée dans l’optimisation. Enfin, un prototype de machine est construit et quelques tests expérimentaux est réalisés. Le résultat montre que la force électromotrice à vide a une forme d'onde similaire par rapport à la prédiction numérique en 3D et la différence de couple statique maximum entre les tests expérimentaux et les simulations par éléments finis en 3D est faibleThis thesis is dedicated to the design and the optimization of modular brushless wound rotor synchronous machine for embedded systems. This machine is constructed based on POKIPOKITM structure with integrated drive electronics. Finite element analysis based optimization becomes more popular in the field of electrical machine design because analytical equations are not easily formalized for the machines which have complicate structures. Using electromagnetic analysis to comparatively study different modular brushless wound rotor synchronous machines and therefore, to select the structure which offers the best fault tolerant capability and the highest output performances. Firstly, the fundamental winding factor calculated by using the method based on voltage phasors is considered as a significant criterion in order to select the numbers of phases, stator slots and poles. After that, 2D finite element numerical simulations are carried out for a set of 15 machines to analyze their performances. The simulation results are then compared to find an appropriate machine according to torque density, torque ripple and machine efficiency. The 7phase/7-slot/6-pole machine is chosen and compared with a reference design surfacemounted permanent magnet synchronous machine in order to evaluate the interesting performance features of the wound rotor synchronous machine. In the second design stage, this machine is optimized by using derivative-free optimization. The objective is to minimize external volume under electromagnetic, thermal and mechanical constraints. Given that an accurate finite element analysis for machine performance takes a long time. Moreover, considering that the average torque can be obtained by simulating the model with only four rotor positions instead of one electric period, optimization strategy is proposed to reduce computational time and therefore, obtain a fast convergence ability by defining relaxed problems which enable minimizing the external volume of the machine under only several constraints such as average torque, torque ripple and copper losses. By testing relaxed problems, two different optimization methods (NOMAD and fmincon) are compared in order to select an appropriate method for our optimization problem. Using NOMAD method based on Mesh Adaptive Direct Search, we achieve optimal results which satisfy all of the constraints proposed. In the third design stage, all constraints are validated by 3D electromagnetic and thermal simulations using finite element and computational fluid dynamics methods. The 3D results show that the average torque obtained is lower than the desired value. By increasing the length of the machine, a new corrected machine is thus obtained. It can be observed that the iron losses obtained in 3D are higher than that in 2D due to the leakage flux in the end-winding. Then, the machine temperature is analyzed by using ANSYS Fluent. Note that the surface temperature is higher than that calculated in the optimization and the coil temperature is 8.48°C higher than the desired value (105°C). However, some dissipation by the shaft and the bearings of the machine are expected to reduce the machine temperature. Finally, a machine prototype is built and some experimental tests are carried out. The results show that the electromotive force has a similar waveform compared to 3D prediction and the difference of the measured and predicted maximum static torques is small
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Roman, Jan. "Řízení lineární pohonů HIWIN". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231280.
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The diploma thesis deals with three phase linear synchronous electric motors mounted on linear drive, its system of sensors and control. The analysis of working principle and classification of linear motor was done in the beginning part; analysis of the drives sensors system was made in the following chapter. The thesis also deals with the driver from the automation point of view, its tuning and behavior according to high dynamics and precise positioning. The last chapter discusses the issue of controlling two linear drives. Whole thesis was realized on a borrowed linear motor with driver from HIWIN corp.
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Veprauskas, Amy y J. M. Cushing. "A juvenile–adult population model: climate change, cannibalism, reproductive synchrony, and strong Allee effects". TAYLOR & FRANCIS LTD, 2016. http://hdl.handle.net/10150/623279.
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We study a discrete time, structured population dynamic model that is motivated by recent field observations concerning certain life history strategies of colonial- nesting gulls, specifically the glaucouswinged gull ( Larus glaucescens). The model focuses on mechanisms hypothesized to play key roles in a population's response to degraded environment resources, namely, increased cannibalism and adjustments in reproductive timing. We explore the dynamic consequences of these mechanics using a juvenile- adult structure model. Mathematically, the model is unusual in that it involves a high co- dimension bifurcation at R0 = 1 which, in turn, leads to a dynamic dichotomy between equilibrium states and synchronized oscillatory states. We give diagnostic criteria that determine which dynamic is stable. We also explore strong Allee effects caused by positive feedback mechanisms in the model and the possible consequence that a cannibalistic population can survive when a non- cannibalistic population cannot.
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Carvalho, Marcelo Moreira de. "Análise da influência de diferentes tipos de cargas no desempenho da proteção anti-ilhamento de geradores distribuídos". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-10102014-103332/.
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A conexão de geradores distribuídos nas redes de subtransmissão e de distribuição de energia elétrica se mostra cada vez mais crescente devido aos inúmeros benefícios técnicos e econômicos alcançados com essa tecnologia. No entanto, há importantes implicações técnicas que precisam ser analisadas antes que um gerador distribuído seja conectado em paralelo ao sistema elétrico. Um aspecto a ser analisado, e que é comum entre as concessionárias de energia elétrica é a adequação da proteção anti-ilhamento, a qual tem a função de detectar essa condição e, automaticamente, desconectar os geradores distribuídos, dentro de um tempo pré-determinado, e assim mantê-los até que o fornecimento de energia seja restabelecido. Neste contexto, este trabalho analisará o desempenho dos relés de proteção anti-ilhamento em face de diferentes tipos de cargas que acabam afetando o tempo de detecção do ilhamento. Com isso, pretende-se obter subsídios para que os ajustes desses relés sejam calculados de forma eficiente. Os relés estudados são o relé de sub/sobrefrequência e o relé de taxa de variação da frequência, e o gerador distribuído é do tipo síncrono equipado com controle de tensão. As análises mostraram que no instante em que ocorre um ilhamento os fatores que mais influenciam no desempenho dos relés de proteção anti-ilhamento são as condições de carga e geração, tempo de detecção estabelecido, tipo do relé adotado, ajuste do mesmo e modelo de carga utilizado.The connection of distributed generators to power subtransmission and distribution networks has been increasing recently due to the technical and economic benefits that such technology can provide. However, there are important technical issues that need to be carefully analyzed before a distributed generator is connected to electrical systems. One issue to be analyzed, which is common sense among utility companies, is the anti-islanding protection, whose main goal is to detect unintentional islanding and, automatically, disconnect the distributed generators within a required time-interval. In this context, this work will analyze the performance of anti-islanding protection relays in face of different load types. With this study, one intend to get support for adjusting these relays efficiently. The relays studied in this work are the under/over frequency and the rate of change of frequency relays, and the distributed generator is a synchronous machine equipped with an automatic voltage regulator. The analyzes showed that the moment a islanding occurs the most important factors influencing the performance of relays anti-islanding protection are the conditions of load and generation, detection time set, type and relay setting adopted and load model.
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Poole, M. J. "Synchronous concurrent algorithms and dynamical systems". Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638547.
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A synchronous concurrent algorithm (SCA) is an algorithm that is described as a network of interconnected processors or modules, whose computation and communication are synchronised by a global clock. The concept of an SCA was originally introduced to model parallel deterministic computer systems, and as a neutral basis for formally reasoning about their structure, operation and correctness. The mathematical theory of SCAs is based on the theory of primitive recursive functions over many-sorted stream algebras. Examples of SCAs studied thus far include conventional digital hardware, systolic arrays and signal processing algorithms. In addition, many models of physical and biological systems have been identified as SCAs. These include cellular automata (CAs), coupled map lattices (CMLs), neural networks (NNs), and numerical approximations to partial differential equations (PDEs) and coupled ordinary differential equations (CODEs). The study of these spatially-extensive dynamical systems may be unified and enriched by the application of a wide range of mathematical tools from the theory of SCAs in particular, and from theoretical computer science in general. The first aim of this thesis is to integrate fully two of these classes, CAs and CMLs, into the formal computational framework of SCAs. We demonstrate the application of SCA theory of these dynamical systems, and present detailed SCA case studies of CA and CML models of wave propagation in excitable media and electrical signals in heart muscle. Our other primary objective is to provide practical software tools for the computer simulation, analysis and automatic testing of SCAs. We define formally a collection of new SCA programming languages, known as Caress II, in which parallelism is represented by the multiple or concurrent assignment. Caress II is designed to facilitate the representation of networks, tasks specifications and automatic testing procedures that are defined over arbitrary stream algebras.
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Huang, Ming-Hui. "Dynamic characteristics of slender suspension footbridges". Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16450/1/Ming-Hui_Huang_Thesis.pdf.
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Due to the emergence of new materials and advanced engineering technology, slender footbridges are increasingly becoming popular to satisfy the modern transportation needs and the aesthetical requirements of society. These structures however are always "lively" with low stiffness, low mass, low damping and low natural frequencies. As a consequence, they are prone to vibration induced by human activities and can suffer severe vibration serviceability problems, particularly in the lateral direction. This phenomenon has been evidenced by the excessive lateral vibration of many footbridges worldwide such as the Millennium Bridge in London and the T-Bridge in Japan. Unfortunately, present bridge design codes worldwide do not provide sufficient guidelines and information to address such vibrations problems and to ensure safety and serviceability due to the lack of knowledge on the dynamic performance of such slender vibration sensitive bridge structures.
A conceptual study has been carried out to comprehensively investigate the dynamic characteristics of slender suspension footbridges under human-induced dynamic loads and a footbridge model in full size with pre-tensioned reverse profiled cables in the vertical and horizontal planes has been proposed for this purpose. A similar physical suspension bridge model was designed and constructed in the laboratory, and experimental testings have been carried out to calibrate the computer simulations. The synchronous excitation induced by walking has been modelled as crowd walking dynamic loads which consist of dynamic vertical force, dynamic lateral force and static vertical force. The dynamic behaviour under synchronous excitation is simulated by resonant vibration at the pacing rate which coincides with a natural frequency of the footbridge structure. Two structural analysis software packages, Microstran and SAP2000 have been employed in the extensive numerical analysis.
Research results show that the structural stiffness and vibration properties of suspension footbridges with pre-tensioned reverse profiled cables can be adjusted by choosing different structural parameters such as cable sag, cable section and pretensions in the reverse profiled cables. Slender suspension footbridges always have four main kinds of vibration modes: lateral, torsional, vertical and longitudinal modes. The lateral and torsional modes are often combined together and become two kinds of coupled modes: coupled lateral-torsional modes and coupled torsionallateral modes. Such kind of slender footbridges also have different dynamic performance in the lateral and vertical directions, and damping has only a small effect on the lateral vibration but significant effect on the vertical one.
The fundamental coupled lateral-torsional mode and vertical mode are easily excited when crowd walking dynamic loads are distributed on full bridge deck. When the crowd walking dynamic loads are distributed eccentrically on half width of the deck, the fundamental coupled torsional-lateral mode can be excited and large lateral deflection can be induced. Higher order vertical modes and coupled lateral-torsional modes can also be excited by groups of walking pedestrians under certain conditions.
It is found that the coupling coefficient introduced in this thesis to describe the coupling of a coupled mode, is an important factor which has significant effect on the lateral dynamic performance of slender suspension footbridges. The coupling coefficient, however, is influenced by many structural parameters such as cable configuration, cable section, cable sag, bridge span and pre-tensions, etc. In general, a large dynamic amplification factor is expected when the fundamental mode of a footbridge structure is the coupled lateral-torsional mode with a small coupling coefficient.
The research findings of this thesis are useful in understanding the complex dynamic behaviour of slender and vibration sensitive suspension footbridges under humaninduced dynamic loads. They are also helpful in developing design guidance and techniques to improve the dynamic performance of such slender vibration sensitive footbridges and similar structures and hence to ensure their safety and serviceability.
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Huang, Ming-Hui. "Dynamic characteristics of slender suspension footbridges". Queensland University of Technology, 2006. http://eprints.qut.edu.au/16450/.
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Due to the emergence of new materials and advanced engineering technology, slender footbridges are increasingly becoming popular to satisfy the modern transportation needs and the aesthetical requirements of society. These structures however are always "lively" with low stiffness, low mass, low damping and low natural frequencies. As a consequence, they are prone to vibration induced by human activities and can suffer severe vibration serviceability problems, particularly in the lateral direction. This phenomenon has been evidenced by the excessive lateral vibration of many footbridges worldwide such as the Millennium Bridge in London and the T-Bridge in Japan. Unfortunately, present bridge design codes worldwide do not provide sufficient guidelines and information to address such vibrations problems and to ensure safety and serviceability due to the lack of knowledge on the dynamic performance of such slender vibration sensitive bridge structures. A conceptual study has been carried out to comprehensively investigate the dynamic characteristics of slender suspension footbridges under human-induced dynamic loads and a footbridge model in full size with pre-tensioned reverse profiled cables in the vertical and horizontal planes has been proposed for this purpose. A similar physical suspension bridge model was designed and constructed in the laboratory, and experimental testings have been carried out to calibrate the computer simulations. The synchronous excitation induced by walking has been modelled as crowd walking dynamic loads which consist of dynamic vertical force, dynamic lateral force and static vertical force. The dynamic behaviour under synchronous excitation is simulated by resonant vibration at the pacing rate which coincides with a natural frequency of the footbridge structure. Two structural analysis software packages, Microstran and SAP2000 have been employed in the extensive numerical analysis. Research results show that the structural stiffness and vibration properties of suspension footbridges with pre-tensioned reverse profiled cables can be adjusted by choosing different structural parameters such as cable sag, cable section and pretensions in the reverse profiled cables. Slender suspension footbridges always have four main kinds of vibration modes: lateral, torsional, vertical and longitudinal modes. The lateral and torsional modes are often combined together and become two kinds of coupled modes: coupled lateral-torsional modes and coupled torsionallateral modes. Such kind of slender footbridges also have different dynamic performance in the lateral and vertical directions, and damping has only a small effect on the lateral vibration but significant effect on the vertical one. The fundamental coupled lateral-torsional mode and vertical mode are easily excited when crowd walking dynamic loads are distributed on full bridge deck. When the crowd walking dynamic loads are distributed eccentrically on half width of the deck, the fundamental coupled torsional-lateral mode can be excited and large lateral deflection can be induced. Higher order vertical modes and coupled lateral-torsional modes can also be excited by groups of walking pedestrians under certain conditions. It is found that the coupling coefficient introduced in this thesis to describe the coupling of a coupled mode, is an important factor which has significant effect on the lateral dynamic performance of slender suspension footbridges. The coupling coefficient, however, is influenced by many structural parameters such as cable configuration, cable section, cable sag, bridge span and pre-tensions, etc. In general, a large dynamic amplification factor is expected when the fundamental mode of a footbridge structure is the coupled lateral-torsional mode with a small coupling coefficient. The research findings of this thesis are useful in understanding the complex dynamic behaviour of slender and vibration sensitive suspension footbridges under humaninduced dynamic loads. They are also helpful in developing design guidance and techniques to improve the dynamic performance of such slender vibration sensitive footbridges and similar structures and hence to ensure their safety and serviceability.
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Nategh, Shafigh. "Thermal Analysis and Management of High-Performance Electrical Machines". Doctoral thesis, KTH, Elektrisk energiomvandling, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122695.
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This thesis deals with thermal management aspects of electric machinery used in high-performance applications with particular focus put on electric machines designed for hybrid electric vehicle applications. In the first part of this thesis, new thermal models of liquid (water and oil) cooled electric machines are proposed. The proposed thermal models are based on a combination of lumped parameter (LP) and numerical methods. As a first case study, a permanent-magnet assisted synchronous reluctance machine (PMaSRM) equipped with a housing water jacket is considered. Particular focus is put on the stator winding and a thermal model is proposed that divides the stator slot into a number of elliptical copper and impregna- tion layers. Additionally, an analysis, using results from a proposed simplified thermal finite element (FE) model representing only a single slot of the sta- tor and its corresponding end winding, is presented in which the number of layers and the proper connection between the parts of the LP thermal model representing the end winding and the active part of winding are determined. The approach is attractive due to its simplicity and the fact that it closely models the actual temperature distribution for common slot geometries. An oil-cooled induction machine where the oil is in direct contact with the stator laminations is also considered. Here, a multi-segment structure is proposed that divides the stator, winding and cooling system into a number of an- gular segments. Thereby, the circumferential temperature variation due to the nonuniform distribution of the coolant in the cooling channels can be predicted. In the second part of this thesis, the thermal impact of using different winding impregnation and steel lamination materials is studied. Conven- tional varnish, epoxy and a silicone based thermally conductive impregnation material are investigated and the resulting temperature distributions in three small induction machines are compared. The thermal impact of using different steel lamination materials is investigated by simulations using the developed thermal model of the water cooled PMaSRM. The differences in alloy con- tents and steel lamination thickness are studied separately and a comparison between the produced iron losses and the resulting hot-spot temperatures is presented. Finally, FE-based approaches for estimating the induced magnet eddycurrent losses in the rotor of the considered PMaSRM are reviewed and compared in the form of a case study based on simulations. A simplified three-dimensional FE model and an analytical model, both combined with time-domain 2D FE analysis, are shown to predict the induced eddy current losses with a relatively good accuracy compared to a complete 3D FE based model. Hence, the two simplified approaches are promising which motivates a possible future experimental verification.QC 20130528
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LEITE, ARMANDO GONCALVES. "STATIC AND DYNAMIC SIMULATION OF VOLTAGE CONTROL BY GENERATOR AND SYNCHRONOUS COMPENSATOR". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=12362@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROO tema abordado neste trabalho é a observação e análise, em regime permanente e dinâmico, da ocorrência de um fenômeno que já foi observado em condições reais de operação do sistema elétrico brasileiro, que é a relação oposta entre a tensão de excitação de geradores e compensadores síncronos e a tensão controlada. Nessas situações, a capacidade nominal de um gerador / compensador síncrono, por exemplo, não seria útil para manter a tensão controlada. Em virtude da relação oposta, um aumento na excitação da máquina abaixaria a tensão controlada. O controle automático continuaria agindo, abaixando ainda mais a tensão. Este mecanismo pode levar o sistema ao colapso. A abordagem do problema baseou-se na verificação do comportamento do gerador / compensador como dispositivo de controle de tensão, em regime permanente e dinâmico, ante as diversas situações normais de um sistema elétrico, tais como variações do valor da tensão de referência (tensão controlada) e de carga. A análise em regime permanente utilizou um algoritmo de fluxo de carga, enquanto a análise em regime dinâmico utilizou a simulação no domínio do tempo. A real existência do fenômeno foi comprovada através de várias destas análises, mostrando inclusive a mudança da região de operação em algumas delas. Em outros casos, os resultados da análise em regime permanente não coincidiram com os da análise em regime dinâmico.
The aim of this work is to investigate, in steady state and dynamic performance, the phenomenon of the opposite relationship, already observed at real operation conditions of the Brazilian Electric System, between generators and synchronous compensators excitation voltage and the controlled one. In these situations, the generator / synchronous compensator nominal capacity, for example, would not be useful to keep the voltage controlled. Due the opposite relationship, an increase in the excitation voltage would reduce the controlled voltage. The automatic control would keep acting and reducing more the voltage. This mechanism can lead the system to the collapse. The study of this problem was based in the generator / compensator behavior as a control voltage device, in steady- state and dynamic performance, front of several operation situations of electric power system, like reference voltage (controlled voltage) variation and load changing. The steady state analysis used a load flow algorithm, while the time domain simulation was utilized for the dynamic performance analysis. The real existence of the phenomenon was verified through these analyses, emphasizing the operation region changing in some of them. In other cases, the analyses results in the steady-state were different of the dynamic performance results.
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Devarakonda, SaiPrasanth. "Particle Swarm Optimization". University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1335827032.
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Ramachandran, Bhaskar. "Dynamic operation of sensorless dead-time optimization in digitally controlled synchronous buck converters". Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447688.
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Queriaud, Celia. "Dynamiques d'interventions des ergonomes dans le champ du maintien dans l'emploi de salariés malades chroniques". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0332/document.
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Le maintien dans l'emploi d'un salarié malade chronique est une situation de hautecomplexité par des implications professionnelles, juridiques, sociales et relatives à la sphèreprivée, concernant une multitude d'acteurs communiquant de façon plus ou moins efficace.L'ergonome consultant est sollicité ponctuellement pour agir sur cet objet multidimensionnelavec de multiples contingences, impliquant des contraintes de temps, des contretemps etdes imprévus. Dans cette recherche, le processus "maintien dans l'emploi" est modélisé autravers des cadres temporels (fenêtre d'intervention ergonomique et épisode "InterventionMaintien dans l'Emploi") et des temporalités (histoires longues du salarié et de l'entreprise)impliqués. A l'aide de trois grandes méthodes d'analyse (autoanalyse d'interventions,simulations d'interventions et suivis-observations d'autres ergonomes), il est possible decaractériser le pilotage efficace et subtil des dimensions temporelles, mis en oeuvre parl'ergonome dans ce contexte d'intervention précis. Ce pilotage implique une certainedynamique d'intervention alternant des processus de compréhensions et d'actions.L'ergonome agit ici et maintenant mais dépasse aussi le cadre contraint de sa fenêtred’intervention. Il cherche à avoir prise sur chacune de ces dimensions temporelles, par unprocessus actif de construction de sa représentation. Pour pérenniser au mieux le maintiendans l'emploi du salarié concerné, il va tenter de réduire, voire de prévenir les dyschroniesentre ces dimensions temporelles, et de promouvoir entre elles des articulations efficientesKeeping a chronically ill person at work is a highly complex situation, considering itsimplications in professional, legal, and social implications as well as those related to theprivate sphere. These situations involve a multitude of stakeholders who communicate inmore or less efficient ways. Consultants in ergonomics are occasionally called on to act uponthis multidimensional object that is subject to many contingencies that involve timeconstraints, delays, and unforeseen events. In this research work, we have modelled theprocess of “maintaining in employment” based on the time frames (the window of ergonomicintervention and the episode of “intervention for maintaining in employment”) and the timelapses (the long-term histories of the employee and of the company) involved. Using threemain methods of analysis (self-analysis of interventions, simulations of interventions andobservations of other ergonomists), we were able to characterize the effective and subtlemanagement of temporal aspects by the ergonomist operating within this specific context ofintervention. This management implies specific dynamics of intervention, alternatingprocesses of understanding and action. Ergonomists act in the “here and now”, but also gobeyond the constrained framework of their window of intervention. They aim to gain controlover each of these temporal dimensions, through a process of active construction of theirrepresentations. In order to maintain the workers involved in sustained employment in thebest possible way, they will attempt to reduce, or even prevent the dyschronies betweenthese different dimensions, and to promote constructive connections between them
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De, Kock Hugo Werner. "Dynamic control of the permanent magnet assisted reluctance synchronous machine with constant current angle". Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2062.
Texto completoResumen
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006.This thesis is about the dynamic control of a permanent magnet assisted reluctance synchronous machine (PMA RSM). The PMA RSM in this thesis is a 110 kW traction machine and is ideal for the use in electrical rail vehicles. An application of the dynamic control of the PMA RSM in electrical rail vehicles is to reduce wheel slip. The mathematical model of the PMA RSM is derived and explained in physical terms. Two methods of current control for the PMA RSM are investigated, namely constant field current control (CFCC) and constant current angle control (CCAC). It is shown that CCAC is more appropriate for the PMA RSM. A current controller for the PMA RSM that guarantees stability is derived and given as an analytic formula. This current controller can be used for any method of current control, i.e. CFCC or CCAC. An accurate simulation model for the PMA RSM is obtained using results from finite element analysis (FEA). The accurate model is used in a simulation to verify CCAC. A normal proportional integral speed controller for the PMA RSM is designed and the design is also verified by simulation. Practical implementation of the current and speed controllers is considered along with a general description of the entire drive system. The operation of the resolver (for position measurement) is given in detail. Important safety measures and the design of the electronic circuitry to give protection are shown. Practical results concerning current and speed control are then shown. To improve the dynamic performance of the PMA RSM, a load torque observer with compensation current feedback is investigated. Two observer structures are considered, namely the reduced state observer and the full state observer. The derivation of the full state observer and the detail designs of the observer elements are given. The accurate simulation model of the PMA RSM is used to verify the operation of the observer structures and to evaluate the dynamic performance. Both observer structures are implemented practically and practical results are shown. One method of position sensorless control, namely the high frequency voltage injection method, is discussed in terms of the PMA RSM. This work is additional to the thesis but it is shown, because it raises some interesting questions regarding the dynamic control of the PMA RSM.
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Veprauskas, Amy. "On the dynamic dichotomy between positive equilibria and synchronous 2-cycles in matrix population models". Thesis, The University of Arizona, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10124871.
Texto completoResumen
For matrix population models with nonnegative, irreducible and primitive inherent projection matrices, the stability of the branch of positive equilibria that bifurcates from the extinction equilibrium as the dominant eigenvalue of the inherent projection matrix increases through one is determined by the direction of bifurcation. However, if the inherent projection matrix is imprimitive this bifurcation becomes more complicated. This is the result of the simultaneous departure of multiple eigenvalues from the unit complex circle. Matrix models with imprimitive projection matrices commonly appear in models of semelparous species, which are characterized by one reproductive event that is often followed by death.
Due to the imprimitivity of the projection matrix, semelparous Leslie models exhibit two contrasting dynamics, either equilibria in which all age classes are present or synchronized cycles in which age classes are separated temporally. The two-stage semelparous Leslie model has index of imprimitivity two, meaning that two eigenvalues simultaneously leave the unit circle when the dominant eigenvalue increases past one. This model exhibits a dynamic dichotomy in which the two steady states have opposite stability properties.
We show that this dynamic dichotomy is a general feature of synchrony models which are characterized by the simultaneous creation of a branch of positive equilibria and a branch of synchronous 2-cycles when the extinction equilibrium destabilizes (Chapter 3). A synchrony model must, necessarily, have index of imprimitivity two but is not limited to models of semelparous species. We provide a specific example of a synchrony model for an iteroparous species which is motivated by observations of a cannibalistic gull population (Chapter 2). We also extend the study of the synchrony model to a Darwinian model which couples population dynamics with the dynamics of a suite of evolving phenotypic traits (Chapter 4). For the evolutionary synchrony model, we show that the dynamic dichotomy occurs provided that fitness, as measured by the spectral radius, is maximized. In addition, we examine the dynamic dichotomy for semelparous species in a continuous-time setting (Chapter 5).
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Gao, Feng. "Interior Permanent Magnet Synchronous Motor Demagnetization Fault Modeling and Analysis by Using Dynamic Phasors Model". Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27473.
Texto completoResumen
Interior permanent magnet synchronous motor (IPMSM) has been widely used in hybrid electric vehicles (HEVs) since the high power density and efficiency. However, the primary drawback of IPMSM is the demagnetization phenomenon caused by the permanent magnets. Modeling of the demagnetization fault are important in developing and designing a protection system for the traction on HEVs, thus, an efficient and accurate IPMSM model for demagnetization fault simulation is necessary. By using the conventional dq0 IPMSM model, the current indicators of demagnetization fault are affected by noise which will cause inaccuracy of the simulation. For this reason, a dynamic phasors model of IPMSM is presented in this thesis. In this thesis, firstly, the dynamic phasors model of IPMSM is verified by using small-signal transient analysis for its stability. Secondly, the time-domain transient simulations of positive sequence currents are shown and compared to the conventional dq0 model with demagnetization fault.
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Munukuntla, Sowmya. "Sensitivity Analysis of Synchronous Generators for Real-Time Simulation". ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2172.
Texto completoResumen
The purpose of this thesis is to validate generator models for dynamic studies of power systems using PSS/E (Power System Simulator for Engineering), EMTP (ElectroMagnetic Transient Program), and Hypersim. To thoroughly evaluate the behavior of a power system in the three specified software packages, it is necessary to have an accurate model for the power system, especially the generator which is of interest. The effect of generator modeling on system response under normal conditions and under faulted conditions is investigated in this work. A methodology based on sensitivity analysis of generator model parameters is proposed aiming to homogenize the behavior of the same power system that is modeled in three software packages. Standard IEEE 14-Bus system is used as a test case for this investigation. Necessary changes in the exciter parameters are made using the proposed methodology so that the system behaves identical across all three software platforms.
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Bahrami, Abdorrahim. "Modelling and Verifying Dynamic Properties of Neuronal Networks in Coq". Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42643.
Texto completoResumen
Since the mid-1990s, formal verification has become increasingly important because it can provide guarantees that a software system is free of bugs and working correctly based on a provided model. Verification of biological and medical systems is a promising application of formal verification. Human neural networks have recently been emulated and studied as a biological system. Some recent research has been done on modelling some crucial neuronal circuits and using model
checking techniques to verify their temporal properties. In large case studies, model checkers often cannot prove the given property at the desired level of generality. In this thesis, we provide a model using the Coq proof assistant and prove some properties concerning the dynamic behavior of some basic neuronal structures. Understanding the behavior of these modules is crucial because they constitute the elementary building blocks of bigger neuronal circuits. By using a proof assistant,
we guarantee that the properties are true in the general case, that is, true for any input values, any length of input, and any amount of time. In this thesis, we define a model of human neural networks. We verify some properties of this model starting with properties of neurons. Neurons are the smallest unit in a human neuronal network. In the next step, we prove properties about
functional structures of human neural networks which are called archetypes. Archetypes consist of two or more neurons connected in a suitable way. They are known for displaying some particular classes of behaviours, and their compositions govern several important functions such as walking, breathing, etc. The next step is verifying properties about structures that couple different archetypes to perform more complicated actions. We prove a property about one of these kinds of
compositions. With such a model, there is the potential to detect inactive regions of the human brain and to treat mental disorders. Furthermore, our approach can be generalized to the verification of other kinds of networks, such as regulatory, metabolic, or environmental networks.
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Herculano-Houzel, Suzana. "Modulation of neuronal synchronous oscillations : dynamic variation with level of cortical activation and long-term use-dependent modification". Paris 6, 1999. http://www.theses.fr/1999PA066610.
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Jayam, Prabhakar Aditya. "Application of STATCOM for improved dynamic performance of wind farms in a power grid". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Jayam_Prabhakar_09007dcc804f7428.pdf.
Texto completoResumen
Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 12, 2008) Includes bibliographical references (p. 64-66).
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Mitchell-Colgan, Elliott James. "Improved Dynamical Analysis Tools for DFIG Wind Farms via Traditional and Koopman Linearizations". Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/94134.
Texto completoResumen
The electric power system is designed to economically and reliably transmit electricity to homes, industry, and businesses. The economic impact of the electric grid was demonstrated by the 2003 blackout's visible impact in the graph of the yearly gross domestic product of the Unites States. However, because the number of customers is so large and economies of scale are leveraged to keep electricity prices low, utilities are strongly interconnected.
Performing comprehensive engineering analyses to ensure reliable operation is still impossible. Instead, heuristics and safety factors are incorporated into planning processes to continually meet demand in a way that complies with Federal regulations. As evidenced by the infrequency of blackouts in the United States, the sophisticated planning processes have up to date been relatively successful.
However, the power system is constantly changing. Electrical generators based on renewable energies are a beneficial addition to the grid, but these and other technological changes like high-voltage power electronic converters also come with their own challenges. These systems as currently employed tend to have a different impact on the reliability of operation than traditional fossil fuel based generators. As the system changes, so do the engineering analyses required to ensure reliable operation.
In particular, the wind energy conversion systems (WECS) negatively impact the response of the grid to disturbances in certain ways due to inherent challenges harnessing the wind as an energy sources. These negative impacts (and the advent of powerful personal computing) require an increase in the sophistication of power system models.
Thus, there are competing challenges: the scale of the power system necessitates computationally efficient modeling, but the complexity of analysis required to maintain reliable operation is also increasing. The primary aim of this study is to develop models and methods for more detailed yet computationally manageable simulation. To this aim, higher order linearizations and the properties of linear systems (graph theory and linear algebra) are exploited.
More specifically, this document contains three studies. In the short term planning and situational awareness context, a method is proposed to quickly check credible outages of important grid equipment. This methodology enables the inspection of a wider breadth of system conditions to ameliorate the negative impacts of the unpredictability of the wind. A linear model in the traditional sense is also developed to model any arbitrary number of wind turbines in a wind farm. This enables industry players to study the impacts wind turbine interaction on the dynamic stability of the grid in response to small disturbances. Finally, a wind farm is modeled as a large matrix to model even nonlinear behavior of wind farms. This helps industry players analyze the impact of large disturbances on the grid.Doctor of Philosophy
The electric power system is designed to economically and reliably transmit electricity to homes, industry, and businesses. The economic impact of the electric grid was demonstrated by the 2003 blackout’s visible impact in the graph of the yearly gross domestic product of the United States. However, because the number of customers is so large and economies of scale are leveraged to keep electricity prices low, utilities are strongly interconnected. Performing comprehensive engineering analyses to ensure reliable operation is still impossible. Instead, heuristics and safety factors are incorporated into planning processes to continually meet demand in a way that complies with Federal regulations. As evidenced by the infrequency of blackouts in the United States, the sophisticated planning processes have up to date been relatively successful. However, the power system is constantly changing. Electrical generators based on renewable energies are a beneficial addition to the grid, but these and other technological changes like high-voltage power electronic converters also come with their own challenges. These systems as currently employed tend to have a different impact on the reliability of operation than traditional fossil fuel based generators. As the system changes, so do the engineering analyses required to ensure reliable operation. In particular, the wind energy conversion systems (WECS) negatively impact the response of the grid to disturbances in certain ways due to inherent challenges harnessing the wind as an energy sources. These negative impacts (and the advent of powerful personal computing) require an increase in the sophistication of power system models. Thus, there are competing challenges: the scale of the power system necessitates computationally efficient modeling, but the complexity of analysis required to maintain reliable operation is also increasing. The primary aim of this study is to develop models and methods for more detailed yet computationally manageable simulation. To this aim, higher order linearizations and the properties of linear systems (graph theory and linear algebra) are exploited. More specifically, this document contains three studies. In the short term planning and situational awareness context, a method is proposed to quickly check credible outages of important grid equipment. This methodology enables the inspection of a wider breadth of system conditions to ameliorate the negative impacts of the unpredictability of the wind. A linear model in the traditional sense is also developed to model any arbitrary number of wind turbines in a wind farm. This enables industry players to study the impacts wind turbine interaction on the dynamic stability of the grid in response to small disturbances. Finally, a wind farm is modeled as a large matrix to model even nonlinear behavior of wind farms. This helps industry players analyze the impact of large disturbances on the grid.
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Mitchell-Colgan, Elliott. "Improved Dynamical Analysis Tools for DFIG Wind Farms via Traditional and Koopman Linearizations". Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/94134.
Texto completoResumen
The electric power system is designed to economically and reliably transmit electricity to homes, industry, and businesses. The economic impact of the electric grid was demonstrated by the 2003 blackout's visible impact in the graph of the yearly gross domestic product of the Unites States. However, because the number of customers is so large and economies of scale are leveraged to keep electricity prices low, utilities are strongly interconnected.
Performing comprehensive engineering analyses to ensure reliable operation is still impossible. Instead, heuristics and safety factors are incorporated into planning processes to continually meet demand in a way that complies with Federal regulations. As evidenced by the infrequency of blackouts in the United States, the sophisticated planning processes have up to date been relatively successful.
However, the power system is constantly changing. Electrical generators based on renewable energies are a beneficial addition to the grid, but these and other technological changes like high-voltage power electronic converters also come with their own challenges. These systems as currently employed tend to have a different impact on the reliability of operation than traditional fossil fuel based generators. As the system changes, so do the engineering analyses required to ensure reliable operation.
In particular, the wind energy conversion systems (WECS) negatively impact the response of the grid to disturbances in certain ways due to inherent challenges harnessing the wind as an energy sources. These negative impacts (and the advent of powerful personal computing) require an increase in the sophistication of power system models.
Thus, there are competing challenges: the scale of the power system necessitates computationally efficient modeling, but the complexity of analysis required to maintain reliable operation is also increasing. The primary aim of this study is to develop models and methods for more detailed yet computationally manageable simulation. To this aim, higher order linearizations and the properties of linear systems (graph theory and linear algebra) are exploited.
More specifically, this document contains three studies. In the short term planning and situational awareness context, a method is proposed to quickly check credible outages of important grid equipment. This methodology enables the inspection of a wider breadth of system conditions to ameliorate the negative impacts of the unpredictability of the wind. A linear model in the traditional sense is also developed to model any arbitrary number of wind turbines in a wind farm. This enables industry players to study the impacts wind turbine interaction on the dynamic stability of the grid in response to small disturbances. Finally, a wind farm is modeled as a large matrix to model even nonlinear behavior of wind farms. This helps industry players analyze the impact of large disturbances on the grid.Doctor of Philosophy
The electric power system is designed to economically and reliably transmit electricity to homes, industry, and businesses. The economic impact of the electric grid was demonstrated by the 2003 blackout’s visible impact in the graph of the yearly gross domestic product of the United States. However, because the number of customers is so large and economies of scale are leveraged to keep electricity prices low, utilities are strongly interconnected. Performing comprehensive engineering analyses to ensure reliable operation is still impossible. Instead, heuristics and safety factors are incorporated into planning processes to continually meet demand in a way that complies with Federal regulations. As evidenced by the infrequency of blackouts in the United States, the sophisticated planning processes have up to date been relatively successful. However, the power system is constantly changing. Electrical generators based on renewable energies are a beneficial addition to the grid, but these and other technological changes like high-voltage power electronic converters also come with their own challenges. These systems as currently employed tend to have a different impact on the reliability of operation than traditional fossil fuel based generators. As the system changes, so do the engineering analyses required to ensure reliable operation. In particular, the wind energy conversion systems (WECS) negatively impact the response of the grid to disturbances in certain ways due to inherent challenges harnessing the wind as an energy sources. These negative impacts (and the advent of powerful personal computing) require an increase in the sophistication of power system models. Thus, there are competing challenges: the scale of the power system necessitates computationally efficient modeling, but the complexity of analysis required to maintain reliable operation is also increasing. The primary aim of this study is to develop models and methods for more detailed yet computationally manageable simulation. To this aim, higher order linearizations and the properties of linear systems (graph theory and linear algebra) are exploited. More specifically, this document contains three studies. In the short term planning and situational awareness context, a method is proposed to quickly check credible outages of important grid equipment. This methodology enables the inspection of a wider breadth of system conditions to ameliorate the negative impacts of the unpredictability of the wind. A linear model in the traditional sense is also developed to model any arbitrary number of wind turbines in a wind farm. This enables industry players to study the impacts wind turbine interaction on the dynamic stability of the grid in response to small disturbances. Finally, a wind farm is modeled as a large matrix to model even nonlinear behavior of wind farms. This helps industry players analyze the impact of large disturbances on the grid.
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Arsoy, Aysen. "Electromagnetic Transient and Dynamic Modeling and Simulation of a StatCom-SMES Compensator in Power Systems". Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27225.
Texto completoResumen
Electromagnetic transient and dynamic modeling and simulation studies are presented for a StatCom-SMES compensator in power systems. The transient study aims to better understand the transient process and interaction between a high power/high voltage SMES coil and its power electronics interface, dc-dc chopper. The chopper is used to attach the SMES coil to a StatCom. Following the transient study, the integration of a StatCom with SMES was explored to demonstrate the effectiveness of the combined compensator in damping power oscillations. The transient simulation package PSCAD/EMTDC has been used to perform the integrated modeling and simulation studies.
A state of the art review of SMES technology was conducted. Its applications in power systems were discussed chronologically. The cost effective and feasible applications of this technology were identified. Incorporation of a SMES coil into an existing StatCom controller is one of the feasible applications, which can provide improved StatCom operation, and therefore much more flexible and controllable power system operation.
The SMES coil with the following unique design characteristics of 50MW (96 MW peak), 100 MJ, 24 kV interface has been used in this study. As a consequence of the high power/ high voltage interface, special care needs to be taken with overvoltages that can stress the insulation of the coil. This requires an investigation of transient overvoltages through a detailed modeling of SMES and its power electronics interface. The electrical model for the SMES coil was developed based on geometrical dimensions of the coil. The interaction between the SMES coil and its power electronics interface (dc-dc chopper for the integration to StatCom) was modeled and simulated to identify transient overvoltages. Transient suppression schemes were developed to reduce these overvoltages. Among these are MOV implementation, surge capacitors, different configurations of the dc-dc chopper.
The integration of the SMES coil to a StatCom controller was developed, and its dynamic behavior in damping oscillations following a three-phase fault was investigated through a number of simulation case studies. The results showed that the addition of energy storage to a StatCom controller can improve the StatCom-alone operation and can possibly reduce the MVA rating requirement for the StatCom operating alone. The effective location selection of a StatCom-SMES controller in a generic power system is also discussed.Ph. D.
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Marchenko, Vadim. "On orbital stability of synchronous solutions of some singularly perturbed dynamical systems of relaxation-type oscillators with excitatory coupling /". The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486398528556623.
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Svetlík, Martin. "Dynamický model synchronního stroje s využitím magnetických ekvivalentních obvodů". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219176.
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The thesis focuses on constructing dynamic model - synchronous generator with using magnetic equivalent circuit diagrams. The model construction is based on knowledge of geometric parameters, magnetic characteristic of used material and fyzical deployment of vindings placed in stator slots. Computed reults are compared with results optained from model created with finite element method.
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Chrobák, Petr. "Dynamický model a odbuzení bezkartáčového synchronního generátoru". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-219904.
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This master thesis is focused on the synchronous generator mathematical model analysis. Based on the analysis are compiled mathematical models of main generator and exciter cooperating in brushless synchronous generator excitation system. Mathematical models of both machines are based on system of differential equations and their validity is verified in Matlab-Simulink. The master thesis is devided into three main parts. First part is focused on the derivation of differential equations to describe the behavior of electrical quantities of machines. In the second part are compiled and simulated mathematical models of both synchronous machines in Matlab-Simulink. The correctness of models are verified by approximate analytical calculations of selected steady and dynamic states. The last part is focused on design and simulation of concept for main generator rapid field winding deexcitation in brushless synchronous genereator excitation system.
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Kopička, Marek. "Dynamické modely výrobních modulů". Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-446740.
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The dissertation thesis deals with the design of the concept and implementation of models of electrical power system elements with regard to the potential of the use of computer programs – simulations. The solution of the thesis focuses on the compliance simulations of power-generating modules according to RfG (Requirements for Generators), as a document which setting out the requirements for the connection of power-generating facilities and also focuses on the issue of smart grids and MAS (Multi-Agent Systems) respectively. The framework of the thesis is thus defined by the area of requirements for power-generating modules according to legislative requirements (not only RfG, but also related standards incl. DSC (Distribution System Code), CSN EN 50438 and CSN EN 50549), requirements for agent functionalities and power-generating module abilities to operate in synchronous and island operation, including transitions between them, the process of synchronization (phasing) and communication between the individual elements of the power system.
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Huang, Renke. "Seamless design of energy management systems". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53518.
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The contributions of the research are (a) an infrastructure of data acquisition systems that provides the necessary information for an automated EMS system enabling autonomous distributed state estimation, model validation, simplified protection, and seamless integration of other EMS applications, (b) an object-oriented, interoperable, and unified component model that can be seamlessly integrated with a variety of applications of the EMS, (c) a distributed dynamic state estimator (DDSE) based on the proposed data acquisition system and the object-oriented, interoperable, and unified component model, (d) a physically-based synchronous machine model, which is expressed in terms of the actual self and mutual inductances of the synchronous machine windings as a function of rotor position, for the purpose of synchronous machine parameters identification, and (e) a robust and highly efficient algorithm for the optimal power flow (OPF) problem, one of the most important applications of the EMS, based on the validated states and models of the power system provided by the proposed DDSE.
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Ladjavardi, Marjan. "Improving small signal stability of power systems in the presence of harmonics". Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/511.
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This thesis investigates the impact of harmonics as a power quality issue on the dynamic behaviour of the power systems. The effectiveness of the power system stabilizers in distorted conditions is also investigated. This thesis consists of three parts as follows:The first part focuses on the operation of the power system under distorted conditions. The conventional model of a synchronous generator in the dq-frame of reference is modified to include the impact of time and space harmonics. To do this, the synchronous generator is first modelled in the harmonic domain. This model helps in calculating the additional parts of the generator fundamental components due to the harmonics. Then the Park transformation is used for calculating the modified fundamental components of the synchronous generator in dq axes. The modified generator rotor angle due to the presence of harmonics is calculated and the impact of damper windings under the influence of harmonics is investigated. This model is used to study the small-signal stability of a distorted Single Machine Infinite Bus (SMIB) system. The eigenvalue analysis method is employed and the system state space equations are calculated by linearizing the differential equations around the operating point using an analytical method. The simulation results are presented for a distorted SMIB system under the influence of different harmonic levels. The impact of damper windings and also harmonics phase angles are also investigated.In the second part of the thesis, the effectiveness of the power system damping controllers under distorted conditions is studied. This investigation is done based on a distorted SMIB system installed with a Static Synchronous Series Compensator (SSSC). In the first step, the system state space equations are derived. A Power Oscillation Damping (POD) controller with a conventional structure is installed on the SSSC to improve the system dynamic behaviour. A genetic-fuzzy algorithm is proposed for tuning the POD parameters. This method along with the observability matrix is employed to design a POD controller under sinusoidal and distorted conditions. The impact of harmonics on the effectiveness of the POD controller under distorted conditions is investigated.In the last part, the steady state and dynamic operation of an actual distributed generation system under sinusoidal and distorted conditions are studied. A decoupled harmonic power flow program is employed for steady state analysis. The nonlinear loads are modelled as decoupled harmonic current sources and the nonlinear model of synchronous generator in harmonic domain is used to calculate the injected current harmonics. For the system dynamic stability study, the power system toolbox with the modified model of the synchronous generator is used. The system eigenvalues are calculated and the effectiveness of the installed Power System Stabilisers (PSS) is investigated under sinusoidal and distorted conditions. Simulation results show that in order to guarantee the effectiveness of a PSS in distorted conditions, it is necessary to consider the harmonics in tuning its parameters.
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Passos, Sébastien. "Dynamique des systèmes d'entraînement par courroie synchrone intégrant des poulies à profils innovants". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI049.
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Dans le domaine automobile, l’utilisation de poulies ayant un profil primitif non circulaire (NC) est devenue chose courante pour la conception des façades de distribution par courroie synchrone des moteurs à combustion interne. Pour des paramètres de conception bien choisis (forme, calage angulaire), ces poulies innovantes permettent à priori de réduire l’impact vibratoire des sources d’excitation angulaire affectant la façade. La phénoménologie associée aux poulies NC s’avère toutefois complexe et difficile à prédire par le calcul. Le dimensionnement des façades équipées de ces dispositifs s’avère délicat mais primordial. Dans ce contexte, un modèle numérique adapté à la simulation de la dynamique angulaire des façades de distribution intégrant des poulies NC a été proposé. Ce modèle est fondé sur une approche discrète (0D/1D) inspirée de modèles classiquement utilisés pour l’étude des transmissions intégrant uniquement des poulies circulaires. La courroie est associée à un solide élastique 1D uniforme en prise sur l’enveloppe de solides 2D indéformables représentant les poulies. L’interaction poulie-courroie est concentrée aux points de tangence localisés aux frontières des brins de courroies. En ces points, s'exercent les efforts de tension résultant de l’élongation des brins. Le mouvement des points tangence, engendré par les poulies NC, est pris en compte par l’emploi d’une formulation originale pour le calcul de l'élongation des brins. Cette formulation est obtenue par l’application d’un bilan de matière opéré sur la courroie via une méthode Lagrangienne-Eulérienne. En parallèle de la Modélisation, des travaux expérimentaux ont permis d’analyser l’impact d’une poulie bilobée sur la dynamique angulaire d’une façade de distribution (moteur à 4 cylindres). Le dispositif expérimental utilisé a été spécialement développé dans le cadre de cette thèse. Son instrumentation permet une analyse complète du comportement en dynamique angulaire de la façade. Des comparaisons calculs/essais ont finalement permis de valider le modèle numérique proposéIn response to ever-stricter requirements for internal combustion engine efficiency, noise and reliability, car manufacturers now commonly design Timing belt drives comprising innovative pulleys with non-circular (NC) profiles. For well-chosen design parameters (profile shape, angular phasing), the use of a NC pulley can considerably improve the vibratory performances of a timing belt transmission. Nevertheless, designing efficiently a belt transmission including NC pulleys remains hard to accomplish. To achieve this, it is important to clearly understand and identify the impact of such pulleys on the dynamic behaviour of Timing belt drives. In this context, a numerical model able to simulate the angular dynamics of Timing belt drives comprising NC pulleys has been developed. The model is based on a discrete approach (0D/1D), similar to the models of transmissions with circular pulleys only. The belt is modelled as a 1D linear elastic material (wire) and the pulley are considered as rigid bodies represented by rotary inertias. Rotations of the driven pulleys are the degrees of freedom of the discrete system. The pulley rotation is actuated by the effect of the belt span tensions applied at the belt/pulley seating/unseating points. In the case of a NC pulley, these points are mobile and their motion has to be tracked rigorously. To achieve this, a novel formulation has been written by establishing a feed-in/out balance on the belt spans using a Lagrangian-Eulerian method. In parallel to the numerical developments, experimentations have been performed for analysing the impact of an oval pulley on Timing belt drive angular dynamics (4 cylinder engine). The experimental test rig has been fully developed during this thesis. It is equipped with numerous sensors that enable a complete analysis of belt transmission angular dynamics. Finally, comparative analyses have shown a quite good agreement between experiments and simulations
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Marada, Ondřej. "Analýza kostry synchronního generátoru". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229522.
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The thesis is focused on the examination of the utility of a synchronous generator of a small hydroelectric power station in the case of a change of working position of the machine. The utility will be measured on the basis of the examination of deformations and state of stress of the frame of the generator for the present running (with vertical axis of rotation of the generator) and subsequently for modified running (with horizontal axis of rotation). This will be accomplished partly on the static shell model by finite element method and consequently on the simplified dynamic model.
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Katariya, Ashish Santosh. "Dynamic modeling and feedback control with mode-shifting of a two-mode electrically variable transmission". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45825.
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This thesis develops dynamic models for the two-mode FWD EVT, develops a control system based on those models that is capable of meeting driver torque demands and performing synchronous mode shifts between different EVT modes while also accommodating preferred engine operating points. The two-input two-output transmission controller proposed herein incorporates motor-generator dynamics, is based on a general state-space integral control structure, and has feedback gains determined using linear quadratic regulator (LQR) optimization.
Dynamic modeling of the vehicle is categorized as dynamic modeling of the mechanical and electrical subsystems where the mechanical subsystem consists of the planetary gear sets, the transmission and the engine whereas the electrical subsystem consists of the motor-generator units and the battery pack. A discussion of load torque is also considered as part of the mechanical subsystem. With the help of these derived dynamic models, a distinction is made between dynamic output torque and steady-state output torque.
The overall control system consisting of multiple subsystems such as the human driver, power management unit (PMU), friction brakes, combustion engine, transmission control unit (TCU) and motor-generator units is designed. The logic for synchronous mode shifts between different EVT modes is also detailed as part of the control system design. Finally, the thesis presents results for responses in individual operating modes, EVT mode shifting and a full UDDS drive cycle simulation.
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Majdič, Petr. "Deformačně napěťová analýza synchronního generátoru". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-230608.
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This master thesis deals with an impact of particular static and dynamic forces and temperature strain on horizontal synchronous generator. In connection with this, a stress distribution in construction and an assessment of security to terminal state of flexibility and weariness is being solved together with finding the most critical places on horizontal synchronous generator.
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Kalantari, Shahram. "Improving spoken term detection using complementary information". Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/90074/1/Shahram_Kalantari_Thesis.pdf.
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This research has made contributions to the area of spoken term detection (STD), defined as the process of finding all occurrences of a specified search term in a large collection of speech segments. The use of visual information in the form of lip movements of the speaker in addition to audio and the use of topic of the speech segments, and the expected frequency of words in the target speech domain, are proposed. By using these complementary information, improvement in the performance of STD has been achieved which enables efficient search of key words in large collection of multimedia documents.
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Sagha, Hossein. "Development of innovative robust stability enhancement algorithms for distribution systems containing distributed generators". Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/91052/1/Hossein_Sagha_Thesis.pdf.
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This project was a step forward in improving the voltage profile of traditional low voltage distribution networks with high photovoltaic generation or high peak demand. As a practical and economical solution, the developed methods use a Dynamic Voltage Restorer or DVR, which is a series voltage compensator, for continuous and communication-less power quality enhancement. The placement of DVR in the network is optimised in order to minimise its power rating and cost. In addition, new approaches were developed for grid synchronisation and control of DVR which are integrated with the voltage quality improvement algorithm for stable operation.
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Grézaud, Romain. "Commande de composants grand gap dans un convertisseur de puisance synchrone sans diodes". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT107/document.
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Les composants de puissance grand gap présentent d'ores et déjà des caractéristiques statiques et dynamiques supérieures à leurs homologues en silicium. Mais ces composants d'un nouvel ordre s'accompagnent de différences susceptibles de modifier le fonctionnement de la cellule de commutation. Les travaux qui furent menés au cours de cette thèse se sont intéressés aux composants grand gap et à leur commande au sein d'un convertisseur de puissance synchrone robuste, haut rendement et haute densité de puissance. En particulier deux points critiques ont été identifiés et étudiés. Le premier est la grande sensibilité des composants grand gap aux composants parasites. Le second est l'absence de diode parasite interne entre le drain et la source de nombreux transistors grand gap. Pour répondre aux exigences de ces nouveaux composants et en tirer le meilleur profit, nous proposons des solutions innovantes, robustes, efficaces et directement intégrables aux circuits de commande. Des circuits de commande entièrement intégrés ont ainsi été conçus spécifiquement pour les composants grand gap. Ceux-ci permettent entre autres le contrôle précis des formes de commutation par l'adaptation de l'impédance de grille, et l'amélioration de l'efficacité énergétique et de la robustesse d'un convertisseur de puissance à base de composants grand sans diodes par une gestion dynamique et locale de temps morts très courtsWide band gap devices already demonstrate static and dynamic performances better than silicon transistors. Compared to conventional silicon devices these new wide band gap transistors have some different characteristics that may affect power converter operations. The work presented in this PhD manuscript deals with a specific gate drive circuit for a robust, high power density and high efficiency wide band gap devices-based power converter. Two critical points have been especially studied. The first point is the higher sensitivity of wide band gap transistors to parasitic components. The second point is the lack of parasitic body diode between drain and source of HEMT GaN and JFET SiC. In order to drive these new power devices in the best way we propose innovative, robust and efficient solutions. Fully integrated gate drive circuits have been specifically developed for wide band gap devices. An adaptive output impedance gate driver provides an accurate control of wide band gap device switching waveforms directly on its gate side. Another gate drive circuit improves efficiency and reliability of diode-less wide band gap devices-based power converters thanks to an auto-adaptive and local dead-time management
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Li, Li. "Etude et mise au point d'une nouvelle famille d'alterno-démarreur pour véhicules hybrides et électriques". Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00639305.
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Les travaux de cette thèse portent sur une nouvelle structure de machine à double excitation (MSDE) pour l'application des véhicules hybrides et électriques. Ce type de machine, ayant deux sources d'excitation, bénéficie un degré de liberté supplémentaire et un contrôle facile sur le flux. Grâce à ce degré de liberté, la machine peut être dimensionnée de manière que son meilleur rendement coïncide avec la zone de fonctionnement la plus sollicitée de la machine. Cette nouvelle structure a fait l'objet principal de ce mémoire. Le fonctionnement de la MSDE est présenté dans les deux premiers chapitres. La machine est dimensionnée suivant un cahier des charges pour véhicule hybride. La validation expérimentale a confirmé le bon fonctionnement de la structure et montré son intérêt. Une autre problématique dans le dimensionnement de la machine est l'aspect thermique car les machines sont devenues de plus en plus compactes et puissantes. Une estimation correcte des pertes est indispensable pour évaluer correctement les performances de la machine. C'est la raison pour laquelle on a décidé de consacrer une partie de cette thèse à la modélisation des pertes fer, dont l'estimation n'est pas évidente.
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Malik, Naveed ur Rehman. "Modelling, Analysis, and Control Aspects of a Rotating Power Electronic Brushless Doubly-Fed Induction Generator". Doctoral thesis, KTH, Elektrisk energiomvandling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174349.
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This thesis deals with the modeling, analysis and control of a novel brushlessgenerator for wind power application. The generator is named as rotatingpower electronic brushless doubly-fed induction machine/generator (RPEBDFIM/G). A great advantage of the RPE-BDFIG is that the slip power recoveryis realized in a brushless manner. This is achieved by introducing an additionalmachine termed as exciter together with the rotating power electronicconverters, which are mounted on the shaft of a DFIG. It is shown that theexciter recovers the slip power in a mechanical manner, and delivers it backto the grid. As a result, slip rings and carbon brushes can be eliminated,increasing the robustness of the system, and reducing the maintenance costsand down-time of the turbine. To begin with, the dynamic model of the RPE-BDFIG is developed andanalyzed. Using the dynamic model, the working principle of the generatoris understood and its operation explained. The analysis is carried out atspeeds, ±20% around the synchronous speed of the generator. Moreover, thedynamics of the generator due to external load-torque disturbances are investigated.Additionally, the steady-state model is also derived and analyzed forthe machine, when operating in motor mode. As a next step, the closed-loop control of the generator is considered indetail. The power and speed control of the two machines of the generator andthe dc-link voltage control is designed using internal model control (IMC)principles. It is found that it is possible to maintain the stability of thegenerator against load-torque disturbances from the turbine and the exciter,at the same time maintain a constant dc-link voltage of the rotor converter.The closed-loop control is also implemented and the operation of the generatorwith the control theory is confirmed through experiments.In the third part of the thesis, the impact of grid faults on the behaviourof the generator is investigated. The operation of the generator and its responseis studied during symmetrical and unsymmetrical faults. An approachto successful ride through of the symmetrical faults is presented, using passiveresistive network (PRN). Moreover, in order to limit the electrical and mechanicaloscillations in the generator during unsymmetrical faults, the dualvector control (DVC) is implemented. It is found that DVC to a certain extentcan be used to safeguard the converter against large oscillations in rotorcurrents. Finally, for completeness of the thesis, a preliminary physical design ofthe rotating power electronic converter has been done in a finite elementsoftware called ANSYS. The thermal footprint and the cooling capability,with estimates of the heatsink and fan sizes, are presented. Besides, another variant of a rotating electronic induction machine whichis based on the Lindmark concept and operating in a single-fed mode is also investigated. It’s steady-state model is developed and verified through experiments.QC 20151006
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Abbas, Khaled. "Effet de traitements thermiques sur les propriétés fonctionnelles de fromages traditionnels : le cas des pâtes persillées". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00724803.
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Les ventes des fromages AOP subissent un affaiblissement. L'utilisation de ces fromages sous forme d'ingrédient représente une alternative intéressante à la dégustation et permettrait de maintenir une activité durable aux producteurs de ces fromages. L'objectif de ce travail est d'explorer les potentialités de 4 catégories de fromages à pâte persillée AOP du Massif-Central à être utilisés comme ingrédient à chaud pour répondre à des propriétés telles que " fondant, nappant, filant, gratinant". Les fonctionnalités recherchées pour ce type d'usage ont été prospectées à l'aide de méthodes physico-chimiques et instrumentales classiques mais également à l'aide de méthodes spectrales et sensorielles afin d'enrichir les observations de la macro et microstructure fromagère et de la perception du consommateur. Dans un premier temps, les caractéristiques physicochimiques, rhéologiques et sensorielles à froid et certaines propriétés à chaud ont été décrites pour les 4 catégories de fromages. Ces premiers résultats ont permis de cataloguer les fromages selon des caractéristiques essentiellement liées à l'organisation matricielle des composants tels que les protéines, les matières grasses, les minéraux. L'analyse sensorielle a permis de décrire précisément certaines propriétés à froid qui ne sont pas mises en évidence par d'autres analyses. Les pâtes persillées ont une grande hétérogénéité de pâte due à la présence de" veines " de moisissures. La seconde partie est une étude sur la capacité de la SFS en tant que méthode d'étude de la micro structure, à prédire la diversité de composition de ces fromages. Malgré la forte hétérogénéité des fromages, la SFS permet une " empreinte " identifiable des fromages et prédit certains mais pas la totalité des paramètres physicochimiques. L'évolution de la macro et microstructure de ces fromages au cours du chauffage et du refroidissement a ensuite été étudiée par SFS et par test de compression dynamique. Ces méthodes décrivent bien la fonte de la matière grasse et de la matrice fromagère. Elles sont corrélées entre elles et démontrent une relation entre la structure moléculaire et les propriétés rhéologiques de ces fromages. Une étude comparative des propriétés sensorielles des fromages a été menée à froid et après chauffage. Les attributs décrivent des caractéristiques de texture différentes entre les 2 conditions. Cette démarche a permis de bien différencier les 4 catégories de fromages et de mettre en évidence certains attributs de qualité ou de défaut pour une utilisation à chaud. En conclusion, ces 4 catégories de fromages à pâte persillée ont des potentialités à être utilisées comme ingrédient pour usage à chaud. L'analyse sensorielle a caractérisé les perceptions des consommateurs vis à vis de ces fromages chauffés et ainsi aider à préciser leurs fonctionnalités. Les analyses rhéologiques et spectrales ont apporté des explications liées à ce traitement au niveau de la macro et microstructure de la matrice fromagère.
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Tan, Jiak-San. "Flexibility in MLVR-VSC back-to-back link". Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1119.
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This thesis describes the flexible voltage control of a multi-level-voltage-reinjection voltage source converter. The main purposes are to achieve reactive power generation flexibility when applied for HVdc transmission systems, reduce dynamic voltage balancing for direct series connected switches and an improvement of high power converter efficiency and reliability. Waveform shapes and the impact on ac harmonics caused by the modulation process are studied in detail. A configuration is proposed embracing concepts of multi level, soft-switching and harmonic cancellation. For the configuration, the firing sequence, waveform analysis, steady-state and dynamic performances and close-loop control strategies are presented. In order not to severely compromise the original advantages of the converter, the modulated waveforms are proposed based on the restrictions imposed mathematically by the harmonic cancellation concept and practically by the synthesis circuit complexity and high switching losses. The harmonic impact on the ac power system prompted by the modulation process is studied from idealistic and practical aspects. The circuit topology being proposed in this thesis is developed from a 12-pulse bridge and a converter used classically for inverting power from separated dc sources. Switching functions are deduced and current paths through the converter are analysed. Safe and steady-state operating regions of the converter are studied in phasor diagrams to facilitate the design of simple controllers for active power transfer and reactive power generations. An investigation into the application of this topology to the back-to-back VSC HVdc interconnection is preformed via EMTDC simulations.
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Spiker, Meredith Anne. "Development of an Efficient Design Method for Non-synchronous Vibrations". Diss., 2008. http://hdl.handle.net/10161/585.
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Diesmann, Markus [Verfasser]. "Conditions for stable propagation of synchronous spiking in cortical neural networks : single neuron dynamics and network properties / von Markus Diesmann". 2002. http://d-nb.info/968772781/34.
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Jacquier, Vanessa. "Metastability for serial and parallel dynamics". Doctoral thesis, 2022. http://hdl.handle.net/2158/1274534.
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Metastability is an ubiquitous phenomenon in nature. It appears in a plethora of diverse fields including physics, chemistry, biology, computer science, climatology and economics. Metastability is best described as a dynamical phenomenon that occurs when a system is close to a first order phase transition. After changing some thermodynamic parameters, the system remains for a considerable (random) time in the old phase, the metastable state, before suddenly making a transition to the new phase, the stable state. In other words, on a short time scale, the system behaves as if it was in equilibrium, while, on a long time scale, it moves between different regions of the state space. At low temperature, this motion is preceded by the appearance of a critical mesoscopic configuration of the system via a spontaneous fluctuation or some external perturbation. Thus, when the system is initiated in the metastable phase, it starts its long transition towards the stable phase. In particular, it must overcome an energy barrier to reach the stable state starting from the metastable state. Formally, an Hamiltonian or energy function and the associated dynamics characterized the detailed evolution of the system. Moreover, it is possible to define an equilibrium measure based on the Hamiltonian, for example the Gibbs measure. If the dynamics satisfies the detailed balance condition, then it is reversible with respect to this equilibrium measure.
There are three interesting questions that are typically investigated in metastability. The first is the study of the transition time from the set of metastable states to the set of the stable states, i.e., the time necessary to arrive at the equilibrium phase. The second issue is the identification of the so-called critical configurations that the system creates in order to reach equilibrium. The third question concerns the study of the typical paths that the system follows with high probability during the transition from the metastable state to the stable state.
The thesis is organized in five chapters. In the first two chapters, we present the different approaches and results on asynchronous (serial) and synchronous (parallel) dynamics, in Chapters 2 and 3 respectively. In particular, at the end of the third chapter, we present one of the novelties of this work: an estimate of the mixing time and of the spectral gap, and the computation of the prefactor for the mean transition time also in the case of a series of degenerate metastable states. Next, we study three models evolving under different dynamics. In Chapter 4, we examine the Ising model on the hexagonal lattice with a serial non-conservative dynamics, Glauber dynamics. In particular, we prove some model-dependent results that together with the results of Chapter 2 yield the desired metastability theorems. Indeed, we identify the metastable states proving the recurrence property and computing the maximal stability level. In addition to this, we give a geometrical description of the critical configurations and we show how these are related to polyiamonds. The characterization of the shape of the critical configurations allows us to estimate the mean transition time via potential-theoretic approach. In Chapter 5.1, we describe a particular Probabilistic Cellular Automata model to represent the metastable
behavior of a system subject to parallel dynamics. In particular, using our model-independent results at the end of Chapter 3, we show the behavior of the mixing time and the spectral gap, and we find a rigorous estimate of the expected hitting time. In addition, we identify the metastable states proving recurrence property and classifying the configurations according their stability level. Finally, in Chapter 6, we study the Blume-Capel model evolving under a serial conservative dynamics, the Kawasaki dynamics. These results are still quite heuristic since this is an ongoing project. We present an heuristic study of the phase-diagram and we explain the behavior of the system showing which should be the stable and the metastable states. We suggest an idea based on the crucial role of the boundary to estimate the stability level, to prove the recurrence property and to show the asymptotic behavior of transition time.
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Wu, Chih-Feng y 吳志豐. "Feeddback Linearization for Dynamic Response Analysis of Synchronous Machines". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/67108244066948409245.
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碩士國立海洋大學
電子工程學系
82
Most physical systems has nonlinearity in natural. In the discussion of nonlinear system, the system is often linearized at the equilibrium point to obtain a linear system which is used as an approximation to the original system to avoid the difficulity of dealing with nonlinear systems. However, there are still some defferences bwtween the linearized system and the original system. The method to be studied is the feedback linearization method which is not the same as the conventional linearization method. The feedback linearization transforms the original nonlinear system into an equivalent linear system via coordinate transfor- mation and stste feedback. In comparision with the conventional linearization method which is just an approximation method, the feedback linearization method is an exact linearization method and thus linear system theory can then be readily applied. In the thesis, the method of feedback linearization is dis- cussed and applied to the dynamic responsive analysis of a single-machine-infinitive-bus power system. First, the applicabi- lity of feedback linearization is analyzed. Then the related pro- blems of dynamic stability and control of the system will be studied under fault conditions on buses and transmission lines. The results reveal that by using the feedback linearization we can derive for the original system an exact linear equivalent model from which precise analysis results can be obtained.
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RAN, LI-RONG y 冉立榮. "Survey on dynamic characteristic of salient pole synchronous motor". Thesis, 1989. http://ndltd.ncl.edu.tw/handle/64773144166894270041.
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Chih-hui, Hsu y 徐誌輝. "Dynamic Modeling and Control of a Permanent Magnet Synchronous Motor". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/08203828231992917000.
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碩士國立臺灣科技大學
自動化及控制研究所
92
A comprehensive comparison was made for the various motors operating under different conditions from the previousresearch, and the PMSM (Permanent magnet synchronous motor) was observed to possess the inherent advantages of high efficiency and power factor. As a result, the speed control of the PMSM has been the subject of study by many contemporary researchers. In the first half of this thesis, an analysis is performed on the vector control scheme in the synchronously rotating reference frame that is used for controlling the PMSM. Then the modern control theories are used to design a faster response plant and change shapes of input to eliminate oscillation of the corresponding system. The second half of the thesis is devoted to applying intelligent control theories such as fuzzy and fuzzy sliding-mode control to design the closed loop system of PMSM. After using the Matlab/ Simulink software to perform the simulation under the PMSM, a response comparison of the fuzzy controller and fuzzy sliding-mode controller is made for the speed in the closed loop of PMSM. The simulation results verify that the fuzzy sliding-mode controller gives reasonably better performance in the aspects of faster settling time, smooth response curve and prevention of overshoot, as compared to the fuzzy controller.