Dissertations / Theses: 'Energy distortion'

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Bihun, Oksana Chicone Carmen Charles. "Approximate isometries and distortion energy functionals." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6129.

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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 11, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Professor Carmen Chicone. Vita. Includes bibliographical references.

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VERDEROSA, ANTONELLA. "Density and Energy Distortion in an Oscillator Chain." Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2679565.

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The work in this thesis is focused on the thermodynamic properties of microscopic systems in low dimen- sions which are characterized by some peculiar features. In particular we try to understand how the density and the energy of the particles in an oscillator chain can change due to the presence of non equilibrium conditions. This kind of system has been studied widely and deeply: here we choose a different approach and we deal with the problem in a different way. More precisely, instead of considering the dynamics of the chain and its interaction with the reservoirs, we focus on the heat flux that travels through the chain by adding a distorsion to the Hamiltonian that describes the oscillator chain. The chain has fixed edges and equal masses for all particles and it is defined in a phase space of 2N dimensions, with N the number of particles. The work is divided into two part: in the first one we consider for the system a harmonic potential. It is known in literature that not only numerical but also exact analytical solutions already exist in this case. Indeed we use the harmonic chain as a check, to understand if our results are in agreement with the known ones and hence if our model can be consistent. To do this we try to extrapolate the properties of this physical system by computing some basic observables that characterize the chain. We start in Chapter 3 with the analytical computation for a 2-particle system: the quantities taken into account are the kinetic temperature, the variance of the space variables, the average position of the particles and the average of the distance between two particles. We prove for these observables exact solutions exist for this model but only under some constraints on the parameter space. We then study the same observables numerically in Chapter 4 for a 50-particle system by running some Monte Carlo simulations: the results were quite promising: the qualitative behavior of all the quantities considered prove to be similar to the ones known in literature. We consider also the temperature profile to check if the relation hv i 2 i = β 1 < x i+1 − x i > +β 2 still holds for this model: indeed the relation still stands for our model with β 1 = 1 and β 2 having a quadratic dependence on γ. In the second part of the thesis, a new potential is considered: precisely, a α-FPU potential. In this case exact analitycal solutions do not exist yet and hence in Chapter 5 we try to investigate if with this model it is possible to overcome this problem, by computing the same observables as in Chapter 3. this task is indeed not successful, even if some approximated solutions can be obtained by considering a restricted phase space. In Chapter 6 we then run the numerical simulations for the 50-particle system for three different values of k 3 , the coupling constant of the cubic term in the FPU-potential, to understand how the system is changing as we slowly move away from the harmonic case. For k 3 = 0.001 it is straightforward to notice that the behavior is similar to the harmonic case for all variables, while for k 3 = 0.002 and k 3 = 0.003 the trend prove to be more irregular: this is due to a lack of statistics since a higher number of samples is needed in the Monte Carlo simulations for higher values of k 3 . Still, the dependence of these quantities on the non equilibrium conditions, for all the three values is the same as in the harmonic case with the momentum and the variance increasing with the intensity of the distorsion. Finally we study again the temperature profile for the different values of k 3 to comapare the results with the harmonic case: we can see that also the dependence of β 2 on γ is the same, with β 1 = 1 and β 2 with a quadratic dependence on γ and increasing as we move away from the harmonic case.

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Goh, William Man-Yeki. "Complex distortion of energy spectrum in computable representations of scattering amplitudes /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487584612164897.

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Negumbo, Rosalia. "Analysis for electrical energy and overall efficiency in distribution networks with harmonic distortion." Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/1103.

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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009
Traditionally, harmonics are ignored in overall efficiency and energy usage studies. However, in the modern era, power systems contain levels of harmonics which can no longer be ignored by engineers, planners, energy conservationists and economists. The directions of power flows have to be considered when harmonics are present in the power network. A methodology and new formulae for individual and overall efficiency and energy usage is developed at each frequency (f1, h and H) and forms the main contribution to research in this field. Two case studies were conducted; a measurement based laboratory experiment set-up and a simulated case study. In the set-up, measurements of current, voltage and power at different points in the network for the 1st, 5th and 7th frequencies were taken. Current and voltage results were used for hand calculations to prove the measured power flows and directions. The measurements were taken with a Fluke 345 three-phase harmonic power quality analyzer. For the simulated case study, a network was investigated using the DIgSILENT and SuperHarm software packages. Their results were compared and it was found that DIgSILENT is the preferred package for power results. It was found that the total harmonic distortion limit for voltage in the simulated network exceeded an acceptable level. The harmonic mitigation solution chosen was to design a passive filter to decrease the distortion by shifting the resonance point of the network. The method to design the passive filter and its impact on efficiency and energy usage is included in the thesis. Unique power flow direction diagrams are developed as part of the methodology and form an essential step in the derivation of the new formulae. Efficiencies, power losses and energy usage at individual and combined frequencies were determined. Results showed the negative effects of harmonics on overall efficiency, energy usage and power losses of the system. The methodology and new formulae developed was found to be effective and their application is recommended for use by industry.

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Larsson, Anders. "On high-frequency distortion in low-voltage power systems." Doctoral thesis, Luleå tekniska universitet, Energivetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26658.

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Power quality is a subject that has received a lot of attention during the last 10 to 20 years, both in industry and in academia. Power quality concerns interaction between the power grid and its customers and between the power grid and equipment connected to it, reflected in voltages and currents. Research and other developments in this area have to a great extent concentrated on relatively slow and low-frequency phenomena, with the main emphasis being on voltage dips (reductions in voltage magnitude with duration between about 50 ms and several seconds) and low-frequency harmonics (waveform distortion by frequency components up to about 2 kHz). These phenomena are reasonably well understood and several standards cover the area. For higher-frequency phenomena, above 2 kHz, there is no such general understanding, nor is there anything close to a complete set of standards covering this area. Modern energy efficient equipment connected to the grid, like fluorescent lamps but also solar panels, often uses switching technology, with switching frequencies that can range from a couple of kHz up to several hundreds of kHz. The grid is also used for communication of e.g. meter readings, system controls etc. This so-called power-line communication is using the same frequency range. The main frequency range of interest for this thesis has been the range from 2 to 150 kHz. There are two completely different measurement methods covering this frequency range: time-domain based and frequency-domain based. Time domain based measurements are used throughout the thesis. This gives an opportunity to choose between different analysing tools where among others the joint time-frequency domain has shown to be a useful tool for describing waveform distortion in our frequency range of interest. The majority of the measurements presented in this thesis have been directed towards fluorescent light powered by high frequency ballasts. This type of load has been, due to stringent harmonic limits, one of the first to use a more advanced switching technology called active power factor correction. This technique is also getting more frequently used in other small-power equipment, like computers. Installations of lights in stores etc. normally contain a large number of ballast connected together and the interaction is of importance, for example for setting emission and immunity standards. The measurements on ballasts presented in this work have shown that distortion in the frequency rage 2-150 kHz comes in three types: narrowband distortion; wideband distortion; and recurrent oscillations. The recurrent oscillations are a new type of powerquality disturbance that had not been recognized as such before. The measurements further have shown that the three types of distortion spread in a completely different way from the individual devices to the grid. This knowledge is essential for the setting of emission requirements on energy-efficient equipment.
Godkänd; 2011; 20110216 (andlar); DISPUTATION Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Anders Larsson Ämnesområde: Energiteknik/Energy Engineering Avhandling: On High-Frequency Distortion in Low-Voltage Power Systems Opponent: Adj. professor Lars Gertmar, Institutionen för industriell elektroteknik och automation, Lunds universitet Ordförande: Professor Math Bollen, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Onsdag den 23 mars 2011, kl 10.00 Plats: Hörsal A, Campus Skellefteå, Luleå tekniska universitet

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Cho, Jang Rae. "Residual stresses and distortion during the high energy power beam processing of titanium alloys." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/251875.

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Cheng, Wenye. "Embedded system design and power-rate-distortion optimization for video encoding under energy constraints." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5050.

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Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 3, 2008) Includes bibliographical references.

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Larsson, Anders. "High frequency distortion in power grids due to electronic equipment." Licentiate thesis, Luleå : Luleå tekniska universitet/Tillämpad fysik, maskin- och materialteknik/Energiteknik, 2006. http://epubl.ltu.se/1402-1757/2006/63/LTU-LIC-0663-SE.pdf.

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Skolthanarat, Siriya. "The Modeling and Control of a Wind Farm and Grid Interconnection in a multi-machine system." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28920.

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This dissertation focuses on the modeling and control of WECS (Wind Energy Conversion System) in a multi-machine system. As one of the fastest growing renewable energy resources, the trend of wind energy changes to variable speed wind turbines. The concept of the variable speed is based on the variable speed according to the instantaneous wind speed of wind turbines. Since the utility grid requires the stable frequency and magnitude voltages, there must be grid interconnection of the wind farm and the utility grid. The grid interconnection must support the concept of the variable speed wind turbines. Since each wind turbine locates in a different location in a wind site, it receives the different wind speed. Hence the grid interconnection must convert the variable frequency and magnitude output voltages of the wind turbines to a synchronous frequency and magnitude voltages associated to the grid. With the new technologies of power semiconductor devices, the power converter can operate with high voltage, high current, and high switching frequency. This results in a higher power capacity of a wind farm. Nonetheless, the power converters generate harmonic distortions to the utility grid. The harmonic distortions components in the voltages and currents of the grid degrade the power quality. This results in the damage of electrical components in the power system such as capacitor banks, inductors, protection devices, etc. The harmonic distortions can be reduced with the technology of the multi-level inverter. It is required that the wind energy provides the real and reactive power control for frequency and voltage stability. In order to achieve the power control, the modeling and control of the power electronic grid interconnection is presented in this dissertation. The grid interconnection is modeled with linearization techniques. The models in frequency domain in the form of transfer functions are used to design the compensators in the control system. The model is considered as a SISO (Single Input Single Output) system to design the compensators in SISO tool of MATLAB. The selected control system is current control that can control the real and reactive powers independently. Furthermore, since the grid interconnection is modeled separately for each sub-system, the control system is verified with integration of the sub-systems. The grid interconnection is modeled in Simulink and simulated in the PSCAD. In reality, the power system is comprised of multi-machines. They affect the power system stability, reliability, and quality. The dynamic modeling of an aggregated wind farm with synchronous generator and grid interconnection in a multi-machine system is presented. The test system is a 10-bus system with three generators and three loads. The dynamic modeling involves the power flow calculations that determine the equilibrium points of the system. The system is modeled with differential equations of wind turbines, synchronous generators, and grid interconnection. The system is modeled in the time domain in state space form. The system characteristics can be determined by poles or eigen values obtained from the characteristic equations. Since the system is MIMO (Multi Input Multi Output) system, the optimal control theory is used to reduce the deviation of system behaviors during disturbances. The LQR (Linear Quadratic Regulator) is utilized to control the system with eigen value assignment method. Simulation results in Simulink are illustrated.
Ph. D.

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Hareer, Rahila Wardak. "Seismic response of building façade system with energy absorbing connections." Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16537/1/Rahila_Hareer_Thesis.pdf.

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Facades are popular in modern buildings and are made of different materials such as pre-cast concrete, glass, aluminium, granite or marble and steel. During recent times seismic activity in densely populated areas has resulted in damage and a consequent loss of life. There were many types of building failure, including failure of building facade systems. Facade systems are highly vulnerable and fail more frequently than the buildings themselves with significant devastating effects. During an earthquake building frames suffer large interstorey drifts, causing racking of the building facade systems. The facade systems may not be able to cater for such large deformations and this can result in either functional or total failure at the facade connections or damage by pounding (impact) with adjacent facade panels. Façade failure and collapse can cause serious damage to buildings and injury to people in the vicinity. Moreover, facade represent between 10- 20 % or more of the total building cost depending on the size and importance of the facility and facade material (Facades1980). Considering the cost and safety issues, the importance of a well designed facade system on a building needs to be emphasised. In modern buildings, energy absorbing passive damping devices are very commonly used for energy absorption in order to manage the vibration response of multistorey buildings in an earthquake event. A number of manufactured dampers such as Viscoelastic and viscous, friction and yielding dampers are available. These dampers use a range of materials and designs in order to achieve diverse levels of damping and stiffness. This thesis is an investigation of the seismic behaviour of building facade systems and studies the effects of facade and connection properties on this response. The objectives with energy absorbing connections of the study are to determine and control facade distortions and to establish the required connection properties. Finite Element techniques have been used for modelling and analysis of the building frame, facade and connections. Time history analyses under earthquake loadings were carried out to determine the system response in terms of inter-storey drifts, facade distortions, differential displacement between facades and frames and the axial force in horizontal connections. Connection properties with respect to stiffness and energy absorption capability (or damping) have been modelled and varied to obtain the desired response. Findings illustrate the influence of these connection properties on system response and show that it is possible to control facade distortions to within acceptable limits. They also demonstrate that energy absorbing connections are able to reduce inter-storey drifts and mitigate the detrimental seismic effects on the entire building facade system.

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Hareer, Rahila Wardak. "Seismic response of building façade system with energy absorbing connections." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16537/.

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Facades are popular in modern buildings and are made of different materials such as pre-cast concrete, glass, aluminium, granite or marble and steel. During recent times seismic activity in densely populated areas has resulted in damage and a consequent loss of life. There were many types of building failure, including failure of building facade systems. Facade systems are highly vulnerable and fail more frequently than the buildings themselves with significant devastating effects. During an earthquake building frames suffer large interstorey drifts, causing racking of the building facade systems. The facade systems may not be able to cater for such large deformations and this can result in either functional or total failure at the facade connections or damage by pounding (impact) with adjacent facade panels. Façade failure and collapse can cause serious damage to buildings and injury to people in the vicinity. Moreover, facade represent between 10- 20 % or more of the total building cost depending on the size and importance of the facility and facade material (Facades1980). Considering the cost and safety issues, the importance of a well designed facade system on a building needs to be emphasised. In modern buildings, energy absorbing passive damping devices are very commonly used for energy absorption in order to manage the vibration response of multistorey buildings in an earthquake event. A number of manufactured dampers such as Viscoelastic and viscous, friction and yielding dampers are available. These dampers use a range of materials and designs in order to achieve diverse levels of damping and stiffness. This thesis is an investigation of the seismic behaviour of building facade systems and studies the effects of facade and connection properties on this response. The objectives with energy absorbing connections of the study are to determine and control facade distortions and to establish the required connection properties. Finite Element techniques have been used for modelling and analysis of the building frame, facade and connections. Time history analyses under earthquake loadings were carried out to determine the system response in terms of inter-storey drifts, facade distortions, differential displacement between facades and frames and the axial force in horizontal connections. Connection properties with respect to stiffness and energy absorption capability (or damping) have been modelled and varied to obtain the desired response. Findings illustrate the influence of these connection properties on system response and show that it is possible to control facade distortions to within acceptable limits. They also demonstrate that energy absorbing connections are able to reduce inter-storey drifts and mitigate the detrimental seismic effects on the entire building facade system.

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Musoni, Nkusi Emmanuel. "Analysis of the effect of renewable generation on the power quality of the grid, modelling and analysis of harmonic and voltage distortion." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2805.

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Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018.
As the electric energy demand grows, there is a significant increase in the penetration of renewable generation (RG) in the existing electrical grid network. Interconnecting of renewable generation technologies to an existing distribution system has proven to provide various benefits such as meeting the growing load demand and its contribution to energy system decarbonisation, long-term energy security and expansion of energy access to new energy consumers in the developing urban and rural areas. However, the aim of this thesis is to conduct a study on the impacts of renewable generation on the power quality of electrical grid. Therefore, this work aims at assessing the potential effects of Distributed Generation (DG) on the operation of electric power system by modelling of harmonics and voltage distortion. With different types of renewable generation available at present, it is believed that some designs contribute significantly to electrical network’s Power Quality (PQ). After the analysis of harmonic currents (chapter 6 and 7 of this thesis) introduced by renewable generation technologies, their negative impact on the power quality of the grid is seen to be apparent at point of connection (POC) but only within controlled limits. Analytical method for modeling of harmonic interactions between the grid and aggregated distributed generation technologies are investigated using DIgSILENT Power Factory software and the results obtained are discussed.

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Al, Abed Isrà. "Measurement System at Large Bandwidth for Quality Evaluation of Electric Energy up to 150 kHz." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

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Nowadays, Power Quality monitoring is an essential service many utilities perform for their industrial and other key commercial customers. Monitoring power quality has become specifically more effective in recent years due to the advent of the technology and software. Not only can a monitoring system provide information such as quality of the power and the causes of power system disturbances, but it is also able to identify problem conditions throughout the system prior they cause widespread customer complaints, equipment malfunctions, and even equipment failures. Power Quality problems are not necessarily limited to the utility power system. Many surveys have shown that most problems are localized within customer facilities. Essential requirements for a successful monitoring system include extensive data processing capabilities, easily understood reporting, and universal sharing of information.

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Machado, Luís Fernando Moreira. "Aspectos harmônicos na geração eólica." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-04082017-160108/.

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A utilização da energia eólica é ainda recente no setor elétrico e, por isso, apresenta inúmeros desafios na operação e integração dessa nova tecnologia com o sistema elétrico. Desta forma, este trabalho aborda o impacto da injeção de correntes harmônicas que as Centrais de Geração Eólica geram no Sistema Interligado Nacional. Inicialmente, aborda-se a fundamentação teórica e o conceito básico da energia eólica, principalmente em relação ao panorama desta fonte renovável no Brasil e no mundo e, de uma forma sucinta, aborda-se também sobre o aspecto tecnológico dos aerogeradores. Outro aspecto relevante deste trabalho, é o levantamento do estado da arte sobre os conceitos e cálculos das distorções harmônicas, bem como sobre o processo de integração das novas Centrais de Geração Eólica à rede básica. O principal resultado obtido neste trabalho, é o estudo de sensibilidade da distorção harmônica de tensão, no ponto de acoplamento da Central à rede básica de transmissão, frente à variação topológica da rede coletora da Central de Geração Eólica. Para tal estudo, foi modelada uma Central de Geração Eólica e aplicadas as metodologias estudadas no estado da arte. Os resultados obtidos do estudo de sensibilidade, é de grande interesse para os operadores da rede e transmissão de energia elétrica, bem como às geradoras de energia eólica.
The use of wind energy is still recent in the electric sector and, therefore, presents numerous challenges in the operation and integration of this new technology with the electric system. In this way, this work approaches the impact of the injection of harmonic currents generated by the Wind Generation Plants in the National Interconnected System. Initially, it addresses the theoretical basis and the basic concept of wind energy, mainly in relation to the panorama of this renewable source in Brazil and in the world and, briefly, it also addresses the technological aspect of wind turbines. Another relevant aspect of this work is the state of the art survey on the concepts and calculations of harmonic distortions, as well as on the integration process of the new Wind Generation Plants into the basic grid. The main result obtained in this work is the sensitivity study of the harmonic distortion of voltage at the coupling point of the Central to the basic transmission network, in front of the topological variation of the collecting network of the Wind Generation Plant. For such study, a Wind Generation Plant was modeled and the methodologies studied in the state of the art were applied. The results obtained from the sensitivity study, is of great interest to the network operators and transmission of electricity, as well as to wind power generators.

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Moussa, Hassan. "Contribution to the Decentralized Energy Management of Autonomous AC-Microgrid." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0161/document.

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Cette thèse porte sur des micro-réseaux AC isolées qui permettent l’intégration des ressources énergétiques distribuées (DER) pouvant fournir leur énergie d'alimentation existante de manière contrôlée pour assurer le bon fonctionnement global du système. L'interconnexion d'un DER à une micro-réseau s'effectue habituellement en utilisant un convertisseur d'interface distribué (DIC) (i.e. un bloc d'interface d'électronique de puissance générale) qui est constitué d’un module de convertisseur à l'entrée de la source, un onduleur de tension (VSI), un module d'interfaçage de sortie, et le module de commande. Dans cette thèse on réalise plusieurs lois de commande basées sur des méthodes décentralisées. L'accent principal est mis sur les fonctions "Droop" qui ont la tâche de maintenir un équilibre de distribution d'énergie entre les différentes sources énergétiques connectées à la micro-réseau. L'objectif est d'assurer la stabilité du système et d’améliorer les performances dynamiques en partageant la puissance entre les différents générateurs d’électricité distribués (DGs) en fonction de leur puissance nominale. Le développement d'une analyse de stabilité en boucle fermée s’avère utile pour étudier la dynamique du système afin d'obtenir une réponse transitoire souhaitée qui permet d'identifier les paramètres de contrôle de boucle appropriés. L'amélioration de la qualité d’énergie des micro-réseaux est également un objectif de cette thèse. La réduction des distorsions harmoniques de la tension de sortie en présence de charges linéaires et non linéaires est prise en compte dans nos travaux. D'autres aspects seront étudiés sur la façon de traiter les charges constantes connectées au réseau et les grandes perturbations qu’ils produisent. Cela donne lieu à d'autres études de recherche portant sur la stabilité grand signal des micro-réseaux
This thesis deals with islanded AC microgrid that allows any integration of Distributed Energy Resources (DERs) that may provide their existing supply energy in a controlled manner to insure overall system functioning. The interconnection of a DER to a microgrid is done usually by using a Distributed Interface Converter (DIC), a general power electronics interface block, which consists of a source input converter module, a Voltage Source Inverter module (VSI), an output interface module, and the controller module. The thesis realizes several control laws based on decentralized methods. The major focus is on the Droop functions that are responsible for providing a power distribution balance between different Energy Resources connected to a microgrid. The aim is to insure system stability and better dynamic performance when sharing the power between different DGs as function to their nominal power. Developing a closed loop stability analysis is useful for studying system dynamics in order to obtain a desired transient response that allows identifying the proper loop control parameters. Power Quality enhancement in microgrids is also a purpose of this research. The reduction of harmonic distortions of the output voltage when supplying linear and non-linear loads are taken in consideration in this thesis. Further aspects will be studied about how to deal with constant power loads connected to the grid and the large perturbations exerted. This results to further research studies that deal with large-signal stability of microgrids

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Ruckdaschel, James David. "Harmonic Analysis of a Static VAR Compensated Mixed Load System." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/82.

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As power electronic based controllers and loads become more prevalent in power systems, there is a growing concern about how the harmonics generated by these controllers and loads affect the power quality of the system. One widely used power electronic based load is the Variable Frequency Drive (VFDs) used to vary the speed of an induction motor; whereas a common example of a power electronic based controller used in power systems is the Static VAR Compensator (SVC) for improving a system’s power factor. In this thesis, the harmonic content and overall performance of a system including both a VFD and a SVC will be studied and analyzed. Specifically, the cases of no compensation, static capacitor compensation, and power electronic based static VAR compensation are examined. A small-scale model of a system for study was constructed in lab. Several cases were then performed and tested to simulate a system which contained both fixed and power electronic based harmonic generating loads. The performance of each case was determined by total harmonic current and voltage distortions, true power factor, and RMS current levels at different points in the system.

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Lemes, Marcelo Inácio. "Comparação técnico-econômica entre equipamentos mitigadores de harmônicos e compensadores de energia reativa." Universidade Federal de Uberlândia, 2010. https://repositorio.ufu.br/handle/123456789/14442.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Soothing Equipment of harmonics and compensating reactive power have been widely discussed and applied successfully in recent years in the most varied industrial and commercial installations, encouraged by eliminating the fine for low power factor and by problems arising out of the significant increase in nonlinear loads connected to these electrical systems. Currently, various types of equipment that do the dual function of reducing harmonic content and power factor correction are applied using simulation techniques and well-known studies (through programmes computational load flow and flow harmonics) to ensure the most appropriate field response. In this sense, the proposed work is to show a technical-economical comparison between the equipment most frequently used as a solution of power factor and problems with harmonics, being them: Bank capacitors, passive harmonic filter detuned, passive harmonic filter tuned active harmonic filter, and harmonic hybrid filter. Evaluates the performance of each of these equipment mentioned above, where the following technical aspects will be assessed: voltage, current effective, total harmonic distortion of voltage (DTT), total harmonic distortion of current (DTI), active power, reactive, apparent, harmonic distortion and power factor. Simulations with the application of all types of equipment cited, power factor correction and filtering of harmonics, provide results with their respective implementation costs. Finally, the results obtained will be presented by monitoring in the field of the main electrical magnitudes in analysis, the solution adopted in the light of better cost x benefit and the performance of equipment installed for the desired by the company consumer goals.
Equipamentos mitigadores de harmônicos e compensadores de energia reativa têm sido bastante discutidos e aplicados nos últimos anos com sucesso nas mais variadas instalações comerciais e industriais, fomentados pela eliminação da tarifação por baixo fator de potência e por problemas advindos do aumento significativo de cargas não lineares conectadas a estes sistemas elétricos. Atualmente, diversos tipos de equipamentos que fazem à dupla função de redução do conteúdo harmônico e correção do fator de potência são aplicados, utilizando técnicas de simulação e estudos bem conhecidos (através de programas computacionais de fluxo de carga e fluxo harmônicos) visando garantir a resposta em campo mais adequada. Neste sentido, o trabalho proposto tem por objetivo mostrar uma comparação técnico-econômica entre os equipamentos mais utilizados como solução do fator de potência e de problemas com harmônicos, sendo eles: banco de capacitores, filtro harmônico passivo dessintonizado, filtro harmônico passivo sintonizado, filtro harmônico ativo e filtro harmônico híbrido. Será avaliado o desempenho destes equipamentos através dos seguintes aspectos técnicos: tensão eficaz, corrente eficaz, distorção harmônica total de tensão (DTT), distorção harmônica total de corrente (DTI), potência ativa, reativa, aparente, distorção harmônica e fator de potência. As simulações com a aplicação de todos os tipos de equipamentos citados, de correção do fator de potência e filtragem de harmônicos, proporcionarão resultados com seus respectivos custos de aplicação. Finalmente, serão apresentados os resultados obtidos através do monitoramento em campo das principais grandezas elétricas em análise, da solução adotada em função de uma melhor relação custo x benefício, bem como do desempenho dos equipamentos instalados, para os objetivos desejados pela empresa consumidora.
Mestre em Ciências

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18

Sparks, Taylor David. "Oxide Thermoelectrics: The Role of Crystal Structure on Thermopower in Strongly Correlated Spinels." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10243.

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This dissertation reports on the synthesis, structural and thermal characterization and electrical and thermal transport properties of a variety of strongly correlated spinels. General structure property relationships for electrical and thermal transport are discussed. However, the relationship between thermopower and features of the crystal structure such as spin, crystal field, anti-site disorder, and structural distortions are explored in depth. The experimental findings are reported in the context of improving existing oxide thermoelectric materials, screening for new materials or using thermopower as a unique characterization tool to determine the cation distribution in spinels. The need for improved n-type oxide thermoelectric materials has led researchers to consider mixed valence \((+3/+4)\) manganese oxides. Contrary to previous findings we report herein that the \(LiMn_2O_4\) compound reaches the relatively large n-type thermopower of \(-73 \mu V/K\) which is three times larger than the value observed in other manganese oxides, \(-25 \mu V/K\). The cause of this increase in thermopower is shown to be the absence of a Jahn-Teller distortion on the \(Mn^{3+}\) ions in \(LiMn_2O_4\). By avoiding this structural distortion the orbital degeneracy is doubled and the Koshibae et al.’s modified Heikes formula predicts a thermopower of \(-79 \mu V/K\) in good agreement with the experiment. Altering the \(Mn^{3+/4+}\) ratio via aliovalent doping did not affect the thermopower and is a second evidence of universal charge transport first reported by Kobayashi et al. The role of anti-site disorder was further examined in \(Fe_xMn_{1-x}NiCrO_4\) x=0, ½, ¾, 1 spinels but the effect on thermopower was inconclusive due to the presence of impurity phases. Next, the thermopower as a function of temperature in \(Co_3O_4\) was investigated as a means whereby the Wu and Mason’s 30 year old model for using thermopower to calculate cation distribution in spinels could be revisited. We report evidence that Wu and Mason’s original model using the standard Heikes formula and considering octahedral sites alone leads to a stoichiometrically inconsistent result at high temperatures. Alternate models are evaluated considering Koshibae et al.’s modified Heikes formula and accounting for tetrahedral site contributions. Furthermore, the effect of a possible spin state transition is considered.
Engineering and Applied Sciences

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19

Seixas, Mafalda Maria Morais. "Conversão eólica offshore ligada à rede elétrica: modelação e simulação." Doctoral thesis, Universidade de Évora, 2015. http://hdl.handle.net/10174/16084.

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A tese incide sobre a modelação e simulação de um sistema de conversão de energia eólica offshore com ligação à rede elétrica por transmissão de energia elétrica estudada quer em corrente alternada quer em corrente contínua, no contexto atual de reestruturação do setor elétrico, e integrando a dinâmica relevante. Além da transmissão de energia elétrica, o sistema é constituído por uma plataforma flutuante semissubmersível; uma turbina eólica de velocidade variável; um sistema de transmissão de energia mecânica cuja dinâmica é descrita respetivamente por uma, duas, três ou cinco massas girantes; um gerador síncrono com excitação assegurada por meio de ímanes permanentes; um conversor eletrónico de energia, descrito respetivamente por um conversor de dois níveis ou por um conversor multinível na configuração de díodos de ligação múltipla de três, de quatro, de cinco ou de p níveis. O controlo do sistema utiliza o modo de deslizamento associado com a modulação PWM por vetores espaciais e controladores PI, ditos de clássicos, ou controladores PI de ordem fracionária. Os comportamentos que advêm do facto da energia eólica ser uma fonte de energia variável, com intermitência, assim como, os de eventuais falhas de funcionamento dos dispositivos que controlam o sistema são estudados na tese, recorrendo a simulações computacionais. As contribuições fundamentais envolvem a modelação do conversor de p níveis, as correntes nos bancos de condensadores associadas aos níveis de tensão e a estratégia de controlo do conversor multinível para a selecção do vetor de tensão. As simulações computacionais permitem concluir sobre o desempenho favorável do sistema e simultaneamente fornecem informação quantificada sobre o comportamento das grandezas mecânicas e elétricas, permitindo quer em fase de projeto, quer em fase de utilização o estudo de comportamentos que necessitam de serem corrigidos devido a serem potencialmente indesejáveis; Offshore Wind Energy Conversion System Connected to the Electric Grid: Modeling and Simulation Abstract: The thesis focuses on the modeling and simulation of offshore wind energy conversion systems connected to the electric grid either by an alternated current link or by a direct current link in a view of timeliness developments on electricity sector restructuring and integrating the relevant dynamics. Besides the electricity transmission, the system consists of a semi-submersible floating platform; a variable speed wind turbine; a mechanical transmission system described respectively by one, two, three, or five masses; a synchronous generator with excitation provided by means of permanent magnets; an electronic power converter, respectively described by a two-level converter or by a multi-level converter in a multiple point clamped topology of three, four, five, or p levels. The control of the system uses PWM by space vector modulation associated with sliding mode and classic PI or fractional order PIcontrollers. The behaviors due to fact that wind energy is a variable, intermittently, source of energy, as well as, due to eventual malfunctions of devices controlling the systems are studied in the thesis, using computer simulations. The fundamental contributions involve the modeling of the p levels converter, the capacitor banks current associated with the voltage level, the control strategy of the multilevel converter for the voltage vector selection. The computer simulations allow to conclude on the favourable performance of the system and simultaneously allow data on mechanical and electric quantities, allowing either in design phase or in usage phase the study of behaviors that need to be corrected because of the potentially undesirability.

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20

Tan, Benjamin H. "A Novel Arc Welding Power Supply with Improved Power Factor Correction." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2199.

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This paper presents the design and development of a novel Arc Welding Power Supply utilizing a modified two-switch forward converter topology. The proposed design improves the power quality by improving power factor to near unity and reducing total harmonic distortion. State space analysis of the proposed circuit showed that the circuit followed a boost-buck input output relationship. Simulation of the circuit was first implemented in LTspice to verify the functionality of the new topology. Hardware implementation of the proposed design was built on a scaled-down prototype for a proof-of-concept of the new topology. The prototype specifications were created for a 5A, 20V output with a 20-24V, 60Hz input. This project demonstrated that the proposed new topology was successful in obtaining a near unity power factor and a total harmonic distortion of less than 2%. Additionally, the prototype followed the simulation and calculations of a boost-buck function while varying duty cycle, and the final measurements aligned well with waveforms from the simulation.

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21

Zu, Ying. "Cross-Correlation Cluster Cosmology." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376958777.

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22

Gouws, Liesbeth-Helena. "Redshift-space distortions as a probe of dark energy." Thesis, University of Western Cape, 2014. http://hdl.handle.net/11394/3342.

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>Magister Scientiae - MSc
We begin by finding a system of differential equations for the background and linearly perturbed variables in the standard, ɅCDM model, using the Einstein Field Equations, and then solving these numerically. Later, we extend this to dynamical dark energy models parameterised by an equation of state, w, and a rest frame speed of sound, cs. We pay special attention to the large-scale behaviour of Δm, the gauge invariant, commoving matter density, since the approximation Δm ≃ δm, where δm is the longitudinal gauge matter density, is more commonly used, but breaks down at large scales. We show how the background is affected by w only, so measurements of perturbations are required to constrain cs. We examine how the accelerated expansion of the universe, caused by dark energy, slows down the growth rate of matter. We then show the matter power spectrum is not in itself useful for constraining dark energy models, but how redshift-space distortions can be used to extract the growth rate from the galaxy power spectrum, and hence how redshift-space power spectra can be used to constrain different dark energy models. We find that on small scales, the growth rate is more dependent on w, while on large scales, it depends more on cs.

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23

Al-Saedi, Waleed Abood Baddai. "Optimal Control of Power Quality in Microgrids Using Particle Swarm Optimisation." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/611.

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Driven by environmental protection, economic factors, conservation of energy resources, and technical challenges, the microgrid has emerged as an innovative small-scale power generation network. Microgrids consist of a cluster of Distributed Generation units that encompass a portion of an electric power distribution system and may rely on different energy sources. Functionally, the microgrid is required to provide adequate levels and quality of power to meet load demands. The issue of power quality is significant as it directly affects the characteristics of the microgrid’s operation. This problem can be defined as an occurrence of short to long periods of inadequate or unstable power outputs by the microgrid. In a stand-alone operation mode, the system voltage and frequency must be established by the microgrid, otherwise the system will collapse due to the variety in the microgrid component characteristics. The harmonic distortion of the output power waveforms is also a serious problem that often occurs because of the high speed operation of the converter switches. The long transient period is a critical issue that is usually caused by changing the operation mode or the load demand. Power sharing among the Distributed Generation units is also an important matter for sharing the load appropriately, particularly given that some renewable energy resources are not available continuously. In a utility connected microgrid, the reliable power quality mainly depends on the regulation of both active and reactive power, because the microgrid’s behaviour is mostly dominated by the bulk power system. Therefore, an optimal power control strategy is proposed in this thesis to improve the quality of the power supply in a microgrid scenario. This controller comprises an inner current control loop and an outer power control loop based on a synchronous reference frame and conventional PI regulators. The power control loop can operate in two modes: voltage-frequency power control mode and active-reactive power control mode. Particle Swarm Optimisation is an intelligent searching algorithm that is applied here for real-time self-tuning of the power control parameters. The voltage-frequency power controller is proposed for an inverter-based Distributed Generation unit in an autonomous operation mode. The results show satisfactory system voltage and frequency, high dynamic response, and an acceptable harmonic distortion level. The active-reactive power controller is adopted for an inverter-based Distributed Generation unit in a utility operation mode. This controller provides excellent regulation of the active and reactive power, in particular when load power has to be shared equally between the microgrid and utility. The voltage-frequency and active-reactive power control modes are used for a microgrid configured from two DG units in an autonomous operation mode. The proposed control strategy maintains the system voltage and frequency within acceptable limits, and injects sustained output power from one DG unit during a load change. The reliability of the system’s operation is investigated through developing a small-signal dynamic model for the microgrid. The results prove that the system was stable for the given operating point and under the proposed power controller. Consequently, this research reveals that the microgrid can successfully operate as a controllable power generation unit to support the utility, thus reducing the dependency on the bulk power system and increasing the market penetration of the micro-sources.

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24

Alaoui, Fdili Othmane. "Optimisation multicritères de la qualité de service dans les réseaux de capteurs multimédia sans fil." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0016/document.

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Les progrès réalisés en systèmes micro-électro-mécaniques couplés avec leur convergence vers les systèmes de communication sans fil, ont permis l'émergence des réseaux de capteurs sans fil (RCSF). Les contraintes de ces réseaux font que tous les efforts soient fournis pour proposer des solutions économes en énergie. Avec les récents développements des technologies CMOS, des capteurs d'images à faible coût ont été développés. En conséquence, un nouveau dérivé des RCSF, qui sont les Réseaux de Capteurs Vidéo Sans Fil (RCVSF), a été proposé. La particularité des données vidéo ainsi que les contraintes inhérentes aux nœuds ont introduit de nouveaux défis. Dans cette thèse, nous proposons deux solutions basées sur l'approche inter-couches pour la livraison de la vidéo sur les RCVSF. La première solution propose un nouveau schéma de compression vidéo adaptatif, efficace en énergie et basé sur la norme de compression vidéo H.264/AVC. Le flux vidéo est ensuite géré par une version améliorée du protocole MMSPEED que nous proposons et notons EQBSA-MMSPEED. Les résultats des simulations montrent que la durée de vie du réseau est étendue de 33%, tout en améliorant la qualité du flux vidéo reçu de 12%. Dans la deuxième solution, nous enrichissons le schéma de compression de modèles mathématiques pour prévoir la consommation d'énergie et la distorsion de l'image lors des phases d'encodage et de transmission. Le flux vidéo est géré par un nouveau protocole de routage efficace en énergie et à fiabilité améliorée noté ERMM. Comparée à une approche basique, cette solution réalise une extension de la durée de vie du réseau de 15%, tout en améliorant la qualité du flux vidéo reçu de 35%
Thanks to the valuable advances in Micro Electro-Mechanical Systems coupled with their convergence to wireless communication systems, the Wireless Sensor Networks (WSN). In the WSN context, all the efforts are made in order to propose energy-efficient solutions. With the recent developments in CMOS technology, low-cost imaging sensors have been developed. As a result, a new derivative of the WSN, which is the Wireless Video Sensor Network (WVSN), has been proposed. The particularities of the video data as well as the inherent constraints of the nodes have introduced new challenges. In this thesis, we propose two cross-layer based solutions for video delivery over the WVSN. The first solution proposes a new energy efficient and adaptive video compression scheme dedicated to the WVSNs, based on the H.264/AVC video compression standard. The video stream is then handled by an enhanced version of MMSPEED protocol, that we propose and note EQBSA-MMSPEED. Performance evaluation shows that the lifetime of the network is extended by 33%, while improving the video quality of the received stream by 12%. In the second solution, we enrich our compression scheme with mathematical models to predict the energy consumption and the video distortion during the encoding and the transmission phases. The video stream is then handled by a novel energy efficient and improved reliability routing protocol, that we note ERMM. Compared to a basic approach, this solution is extending the network lifetime by 15%, while improving the quality of the received video stream by 35%

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25

Carvalho, Antonio Carlos de. "Estudo de caso : diagnóstico do consumo e da qualidade de energia numa indústria metalúrgica /." Ilha Solteira : [s.n.], 2004. http://hdl.handle.net/11449/87247.

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Orientador: José Carlos Rossi
Banca: Antonio Carlos Delaiba
Banca: Carlos Alberto Canesin
Resumo: Este trabalho tem por objetivo a proposição de um estudo de caso realizado em uma planta industrial, cuja linha de produção se concentra na área da metalurgia. O principal enfoque foi direcionado na avaliação e nos efeitos causados pelas correntes distorcidas, geradas por cargas não lineares, nos barramentos e alimentadores da industria. Com o objetivo de avaliar o impacto das cargas elétricas, com características não lineares, as instalada e a serem instaladas no sistema elétrico da industria. Foi realizada também uma avaliação geral da planta da indústria através da análise das faturas de energia elétrica buscando identificar nos principais indicadores, os desvios no sistema elétrico da planta. Entre estes, podemos destacar a demanda, o consumo, os reativos excedentes e outros. Todos os procedimentos desenvolvidos neste trabalho foram direcionados no sentido de se usar racionalmente a energia elétrica e controlar o seu desperdício.
Abstract: This work aims to study a case carried out in an industrial plant, whose production line is concentrated on the metallurgy field. The main objective was addressed in the evaluation and in the effects caused by the distortion of the currents, due to nonlinear loads connected at the industry busbar and feeders. With the objective of evaluating the impact of the electric loads, with non- linear characteristics, or installed in the industry electric system. It was also accomplished a general evaluation of the industry plant by analyzing the electric power invoices looking for identifying, in the main quality power indicators, the deviations in the electric plant system. Among these, we can mention the demand, the consumption, the exceeding reactives and others. All the procedures developed in this work were addressed aiming to use the electric power rationally and to control its waste.
Mestre

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26

Viljoen, Jan-Albert. "Testing gravity with redshift-space distortions, using MeerKAT and the SKA." University of the Western Cape, 2019. http://hdl.handle.net/11394/6793.

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>Magister Scientiae - MSc
The growth rate of large-scale structure is a key probe of gravity in the accelerating Universe. Standard models of Dark Energy within General Relativity predict essentially the same growth rate, whereas Modified Gravity theories without Dark Energy predict a different growth rate. Redshift-space distortions lead to anisotropy in the power spectrum, and extracting the monopole and quadrupole allows us to determine the growth rate and thus test theories of gravity. We investigate redshift-space distortions in the intensity maps of the 21cm emission line of neutral hydrogen (HI) in galaxies after the Epoch of Reionization: HI intensity mapping delivers very accurate redshifts. We first use the standard approach based on the Fourier power spectrum. Then we explored an alternative approach, based on the spherical-harmonic angular power spectrum. Fisher forecasting was used to make predictions of the accuracy with which MeerKAT will measure the growth rate parameter, via the proposed MeerKAT Large Area Synoptic Survey (MeerKLASS). Then we extend the forecasts to consider the planned HI intensity mapping survey in Phase 1 of the Square Kilometre Array. These forecasts enable us to predict at what level of accuracy General relativity and various alternative theories could be ruled out.

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27

Carvalho, Antonio Carlos de [UNESP]. "Estudo de caso: diagnóstico do consumo e da qualidade de energia numa indústria metalúrgica." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/87247.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho tem por objetivo a proposição de um estudo de caso realizado em uma planta industrial, cuja linha de produção se concentra na área da metalurgia. O principal enfoque foi direcionado na avaliação e nos efeitos causados pelas correntes distorcidas, geradas por cargas não lineares, nos barramentos e alimentadores da industria. Com o objetivo de avaliar o impacto das cargas elétricas, com características não lineares, as instalada e a serem instaladas no sistema elétrico da industria. Foi realizada também uma avaliação geral da planta da indústria através da análise das faturas de energia elétrica buscando identificar nos principais indicadores, os desvios no sistema elétrico da planta. Entre estes, podemos destacar a demanda, o consumo, os reativos excedentes e outros. Todos os procedimentos desenvolvidos neste trabalho foram direcionados no sentido de se usar racionalmente a energia elétrica e controlar o seu desperdício.
This work aims to study a case carried out in an industrial plant, whose production line is concentrated on the metallurgy field. The main objective was addressed in the evaluation and in the effects caused by the distortion of the currents, due to nonlinear loads connected at the industry busbar and feeders. With the objective of evaluating the impact of the electric loads, with non- linear characteristics, or installed in the industry electric system. It was also accomplished a general evaluation of the industry plant by analyzing the electric power invoices looking for identifying, in the main quality power indicators, the deviations in the electric plant system. Among these, we can mention the demand, the consumption, the exceeding reactives and others. All the procedures developed in this work were addressed aiming to use the electric power rationally and to control its waste.

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28

Zadeh, Ramin Agha. "Performance control of distributed generation using digital estimation of signal parameters." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/47011/1/Ramin_Agha_Zadeh_Thesis.pdf.

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The Queensland University of Technology (QUT) allows the presentation of a thesis for the Degree of Doctor of Philosophy in the format of published or submitted papers, where such papers have been published, accepted or submitted during the period of candidature. This thesis is composed of seven published/submitted papers, of which one has been published, three accepted for publication and the other three are under review. This project is financially supported by an Australian Research Council (ARC) Discovery Grant with the aim of proposing strategies for the performance control of Distributed Generation (DG) system with digital estimation of power system signal parameters. Distributed Generation (DG) has been recently introduced as a new concept for the generation of power and the enhancement of conventionally produced electricity. Global warming issue calls for renewable energy resources in electricity production. Distributed generation based on solar energy (photovoltaic and solar thermal), wind, biomass, mini-hydro along with use of fuel cell and micro turbine will gain substantial momentum in the near future. Technically, DG can be a viable solution for the issue of the integration of renewable or non-conventional energy resources. Basically, DG sources can be connected to local power system through power electronic devices, i.e. inverters or ac-ac converters. The interconnection of DG systems to power system as a compensator or a power source with high quality performance is the main aim of this study. Source and load unbalance, load non-linearity, interharmonic distortion, supply voltage distortion, distortion at the point of common coupling in weak source cases, source current power factor, and synchronism of generated currents or voltages are the issues of concern. The interconnection of DG sources shall be carried out by using power electronics switching devices that inject high frequency components rather than the desired current. Also, noise and harmonic distortions can impact the performance of the control strategies. To be able to mitigate the negative effect of high frequency and harmonic as well as noise distortion to achieve satisfactory performance of DG systems, new methods of signal parameter estimation have been proposed in this thesis. These methods are based on processing the digital samples of power system signals. Thus, proposing advanced techniques for the digital estimation of signal parameters and methods for the generation of DG reference currents using the estimates provided is the targeted scope of this thesis. An introduction to this research – including a description of the research problem, the literature review and an account of the research progress linking the research papers – is presented in Chapter 1. One of the main parameters of a power system signal is its frequency. Phasor Measurement (PM) technique is one of the renowned and advanced techniques used for the estimation of power system frequency. Chapter 2 focuses on an in-depth analysis conducted on the PM technique to reveal its strengths and drawbacks. The analysis will be followed by a new technique proposed to enhance the speed of the PM technique while the input signal is free of even-order harmonics. The other techniques proposed in this thesis as the novel ones will be compared with the PM technique comprehensively studied in Chapter 2. An algorithm based on the concept of Kalman filtering is proposed in Chapter 3. The algorithm is intended to estimate signal parameters like amplitude, frequency and phase angle in the online mode. The Kalman filter is modified to operate on the output signal of a Finite Impulse Response (FIR) filter designed by a plain summation. The frequency estimation unit is independent from the Kalman filter and uses the samples refined by the FIR filter. The frequency estimated is given to the Kalman filter to be used in building the transition matrices. The initial settings for the modified Kalman filter are obtained through a trial and error exercise. Another algorithm again based on the concept of Kalman filtering is proposed in Chapter 4 for the estimation of signal parameters. The Kalman filter is also modified to operate on the output signal of the same FIR filter explained above. Nevertheless, the frequency estimation unit, unlike the one proposed in Chapter 3, is not segregated and it interacts with the Kalman filter. The frequency estimated is given to the Kalman filter and other parameters such as the amplitudes and phase angles estimated by the Kalman filter is taken to the frequency estimation unit. Chapter 5 proposes another algorithm based on the concept of Kalman filtering. This time, the state parameters are obtained through matrix arrangements where the noise level is reduced on the sample vector. The purified state vector is used to obtain a new measurement vector for a basic Kalman filter applied. The Kalman filter used has similar structure to a basic Kalman filter except the initial settings are computed through an extensive math-work with regards to the matrix arrangement utilized. Chapter 6 proposes another algorithm based on the concept of Kalman filtering similar to that of Chapter 3. However, this time the initial settings required for the better performance of the modified Kalman filter are calculated instead of being guessed by trial and error exercises. The simulations results for the parameters of signal estimated are enhanced due to the correct settings applied. Moreover, an enhanced Least Error Square (LES) technique is proposed to take on the estimation when a critical transient is detected in the input signal. In fact, some large, sudden changes in the parameters of the signal at these critical transients are not very well tracked by Kalman filtering. However, the proposed LES technique is found to be much faster in tracking these changes. Therefore, an appropriate combination of the LES and modified Kalman filtering is proposed in Chapter 6. Also, this time the ability of the proposed algorithm is verified on the real data obtained from a prototype test object. Chapter 7 proposes the other algorithm based on the concept of Kalman filtering similar to those of Chapter 3 and 6. However, this time an optimal digital filter is designed instead of the simple summation FIR filter. New initial settings for the modified Kalman filter are calculated based on the coefficients of the digital filter applied. Also, the ability of the proposed algorithm is verified on the real data obtained from a prototype test object. Chapter 8 uses the estimation algorithm proposed in Chapter 7 for the interconnection scheme of a DG to power network. Robust estimates of the signal amplitudes and phase angles obtained by the estimation approach are used in the reference generation of the compensation scheme. Several simulation tests provided in this chapter show that the proposed scheme can very well handle the source and load unbalance, load non-linearity, interharmonic distortion, supply voltage distortion, and synchronism of generated currents or voltages. The purposed compensation scheme also prevents distortion in voltage at the point of common coupling in weak source cases, balances the source currents, and makes the supply side power factor a desired value.

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29

Souza, Wesley Angelino de [UNESP]. "Desenvolvimento de sistema de aquisição e processamento para aplicações em qualidade de energia." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/87201.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Este trabalho teve como o desenvolvimento de um sistema de aquisição e processamento de dados para aplicações em Qualidade de Energia Elétrica (QEE). Do ponto de vista dos circuitos de hardware desenvolvidos, buscou-se utilizar componentes de precisão elevada para o sensoriamento e condicionamento dos sinais de tensão e corrente. Além disso, foi implementado um algoritmo de auto calibração das medidas, em função da temperatura no medidor implementado. O processamento dos dados foi realizado através de um processador digital de sinais (DSP, Digital Sinal Processor) de 32 bits, com aritmética de ponto flutuante. Também foi agregado ao sistema um módulo de comunicação sem fio, de forma que os dados medidos pudessem ser enviados a outros dispositivos para armazenamento ou análise remota. Do ponto de vista da aplicação em Qualidade de Energia, foram implementados diversos algoritmos de indicadores de QEE, tais como o de Distorção Harmônica Total (DHT), para a validação preliminar do sistema desenvolvido. Entretanto, do ponto de vista dos estudos e pesquisas realizadas pelo Grupo de Automação e Sistemas Integráveis (GAS/UNESP), no que diz respeito à análise de circuitos elétricos sob condições de formas de onda não sensoriais e/ou desequilibradas, o sistema desenvolvido foi também utilizado para avaliar o comportamento e desempenho da Teoria de Potência Conservativa, proposta recentemente por Tenti et al. e de novos fatores de conformidade (ou desempenho) para a avaliação da QEE em sistemas polifásicos com cargas não lineares. Diversos resultados de simulação e experimentais foram apresentados e constrastados a fim de validar os algoritmos utilizados no DSP utilizado, bem como para permitir a avaliação da Teoria de Potência Conservativa para interpretação de diferentes circuitos e condições de operações
This study aimed to develop a data acquisition and processing system for Power Quality applications. From the hardware point of view, high precision components have been used for the vallage and current sensing and signal conditioning. In addition, a self-calivration algorithm has been implemented in order to adjust the measured values in terms of the estimated temperature. The data processing was performed by means of 32-bit floating point digital signal processor (DSP). A wirelless communication module has also been added, so that the measured data could be sent to other storage devices or remote analyzers. From the perspective of power quality applications, several algorithms have implemented, such as the Total Harmonic Distortion (THD) for the preliminary validation of the developed system. However, considering the studies and surveys carried out by the studies and survey carried out by the Group of Automation and Integrated Systems (GASI/UNESP), especially those related to the analysis of electrical circuits under non-sinusoidal and/or unbalanced waveform conditions, the implemented system has been applied to the evaluation of the Conservative Power Theory (CPT), recently proposed by Tenti et al. Several simulation and experimental results have been depicted and compared in order to validate the practical DSP implementation of the required algorithms, as well as, for the purpose of analyzing different circuit's interpretation by means of the CPT

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30

Reichenbach, Johanna [Verfasser]. "Analysis of carbon mitigation policies : feed-in tariffs, energy and carbon price interactions and competitive distortions on carbon markets / Johanna Reichenbach." Kiel : Universitätsbibliothek Kiel, 2011. http://d-nb.info/1020201657/34.

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31

Schwanz, Daphne. "Análise da distorção harmônica de um parque eólico através da sua modelagem no domínio do tempo e da frequência." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/96479.

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Neste trabalho será apresentado um estudo de caso sobre o cálculo da distorção harmônica gerada por um parque eólico através da sua modelagem nos domínios do tempo e da frequência. Será analisada a propagação das frequências harmônicas na rede básica e a influência da modelagem das linhas de transmissão nos resultados de distorção harmônica. Para este estudo serão utilizados os programas EMTP (ElectroMagnetic Transient Program) e HarmZs para as simulações no domínio do tempo e da frequência, respectivamente. Os parques eólicos simulados utilizam geradores do tipo multipolar síncrono, e para a sua conexão à rede elétrica um conversor de frequência. Os resultados obtidos com o programa EMTP serão comparados para validação com os dados obtidos através da simulação no domínio da frequência utilizando o programa de simulação HarmZ. Já a análise da propagação das frequências harmônicas será simulada somente no domínio do tempo. Assim, através dos resultados obtidos será possível comparar os programas de simulação, determinar os níveis de distorção harmônica em diversos pontos do sistema elétrico e a influência dos modelos utilizados.
This work will present a case study on the calculation of the harmonic distortion generated by a wind farm. Time and frequency domain simulations will be performed. Harmonic propagation will be analyzed. Furthermore, the influence of transmission lines and underground cables models will be verified when there are several frequencies present in the system. Softwares EMTP (ElectroMagnetic Transient Program) and HarmZs will be used for the simulations in the time and frequency domain, respectively. The simulated wind farm use multipolar synchronous generators and their connection to the grid is made through a frequency converter. The results obtained with EMTP will be compared for validation with the results obtained with HarmZs. Thus, by the obtained results it will be possible to compare simulation programs and to determine the levels of harmonic distortion at several points of the electrical system.

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32

Souza, Wesley Angelino de. "Desenvolvimento de sistema de aquisição e processamento para aplicações em qualidade de energia /." Bauru : [s.n.], 2011. http://hdl.handle.net/11449/87201.

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Resumo: Este trabalho teve como o desenvolvimento de um sistema de aquisição e processamento de dados para aplicações em Qualidade de Energia Elétrica (QEE). Do ponto de vista dos circuitos de hardware desenvolvidos, buscou-se utilizar componentes de precisão elevada para o sensoriamento e condicionamento dos sinais de tensão e corrente. Além disso, foi implementado um algoritmo de auto calibração das medidas, em função da temperatura no medidor implementado. O processamento dos dados foi realizado através de um processador digital de sinais (DSP, Digital Sinal Processor) de 32 bits, com aritmética de ponto flutuante. Também foi agregado ao sistema um módulo de comunicação sem fio, de forma que os dados medidos pudessem ser enviados a outros dispositivos para armazenamento ou análise remota. Do ponto de vista da aplicação em Qualidade de Energia, foram implementados diversos algoritmos de indicadores de QEE, tais como o de Distorção Harmônica Total (DHT), para a validação preliminar do sistema desenvolvido. Entretanto, do ponto de vista dos estudos e pesquisas realizadas pelo Grupo de Automação e Sistemas Integráveis (GAS/UNESP), no que diz respeito à análise de circuitos elétricos sob condições de formas de onda não sensoriais e/ou desequilibradas, o sistema desenvolvido foi também utilizado para avaliar o comportamento e desempenho da Teoria de Potência Conservativa, proposta recentemente por Tenti et al. e de novos fatores de conformidade (ou desempenho) para a avaliação da QEE em sistemas polifásicos com cargas não lineares. Diversos resultados de simulação e experimentais foram apresentados e constrastados a fim de validar os algoritmos utilizados no DSP utilizado, bem como para permitir a avaliação da Teoria de Potência Conservativa para interpretação de diferentes circuitos e condições de operações
Abstract: This study aimed to develop a data acquisition and processing system for Power Quality applications. From the hardware point of view, high precision components have been used for the vallage and current sensing and signal conditioning. In addition, a self-calivration algorithm has been implemented in order to adjust the measured values in terms of the estimated temperature. The data processing was performed by means of 32-bit floating point digital signal processor (DSP). A wirelless communication module has also been added, so that the measured data could be sent to other storage devices or remote analyzers. From the perspective of power quality applications, several algorithms have implemented, such as the Total Harmonic Distortion (THD) for the preliminary validation of the developed system. However, considering the studies and surveys carried out by the studies and survey carried out by the Group of Automation and Integrated Systems (GASI/UNESP), especially those related to the analysis of electrical circuits under non-sinusoidal and/or unbalanced waveform conditions, the implemented system has been applied to the evaluation of the Conservative Power Theory (CPT), recently proposed by Tenti et al. Several simulation and experimental results have been depicted and compared in order to validate the practical DSP implementation of the required algorithms, as well as, for the purpose of analyzing different circuit's interpretation by means of the CPT
Orientador: Fernando Pinhabel Marafão
Coorientador: Ivando Severino Diniz
Banca: Lourenço Matakas Junior
Banca: Marcelo Nicoletti Franchin
Mestre

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Freitas, Stefani Carolline Leal de [UNESP]. "Estudos teóricos e experimentais da operação conjunta de um supressor eletromagnético e de um filtro ativo de potência." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/111136.

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Com vistas à mitigação das distorções harmônicas, sempre que possível, são adotadas medidas operacionais relacionadas à adequação das cargas geradoras de harmônicas, fazendo-se uso de tecnologias menos poluentes, multiplicação do número de pulsos em instalações conversoras de grande porte, alteração da topologia das redes elétricas, entre outras. Ocorre, que, em diversas vezes, tais medidas são inviáveis sob o ponto de vista econômico, ou mesmo insuficientes para garantir o funcionamento adequado do sistema e/ou atender os limites estabelecidos pelas normas e recomendações técnicas. Nesses casos, torna-se indispensável o uso de equipamentos especiais para atenuação de distorções harmônicas. O uso de filtros e dispositivos de compensação constituem as técnicas mais aplicadas para redução das componentes harmônicas. Essas técnicas podem ser separadas em dois grandes grupos, dependendo do modo operacional, ativo ou passivo, sendo ambos amplamente conhecidos e aplicados nos mais distintos setores da engenharia. Considerando a aplicação de estruturas compensadoras em sistemas elétricos a quatro fios com carregamentos monofásicos não lineares, apresenta-se nesta tese um novo arranjo de compensação harmônica que incorpora simultaneamente filtragem ativa e passiva, e que apresenta todas as funcionalidades no que tange à compensação harmônica de um filtro ativo de quatro braços. Nessa perspectiva, a filtragem harmônica das componentes de sequências positiva e negativa é realizada por um filtro ativo de três braços, enquanto que, a filtragem das harmônicas homopolares fica atribuída ao supressor eletromagnético de sequência zero. Considerando o mesmo nível de potência a ser processado, presume-se que os custos dos dispositivos eletromagnéticos sejam menores quando comparados aos dispositivos de estado sólido, notadamente as chaves eletrônicas e ...
With a view to mitigate harmonic distortion, whenever possible are adopted operational attitudes related to the suitability of harmonic generating loads, making use of cleaner technologies, multiplying the number of pulses in large converting installations, changes in electric grid topology, among others. Occurs that, in several times, such attitudes are not feasible under the economic point of view or even insufficient to ensure proper system operation and/or meet the limits set by standards and technical recommendations. In these cases, it becomes necessary to use special equipments to mitigate harmonic distortion. The use of filters and compensation devices constitute the techniques applied to reducing harmonic components. These techniques can be separated into two major groups, depending on the operating mode, active or passive, both widely known and applied in the most diverse sectors of engineering. Considering the expectation of compensating structures application in four-wire electrical systems with single-phase nonlinear loads, this thesis presents a new arrangement of harmonic compensation that incorporates both active and passive filtering, and that presents all the features regarding the harmonic compensation of a four-arm active filter. In this perspective, the harmonic filtering of positive and negative sequences components is performed by a three-arm active filter, while the filtering of zero sequence harmonics is attributed to the electromagnetic zero sequence suppressor. Considering the same power level to be processed, it is assumed that the costs of electromagnetic devices are smaller when compared to solid state devices, notably the electronic switches and sensors, which can be eliminated of the four-arm active filter when the responsibility to compensate homopolar harmonic is of the electromagnetic suppressor, which is a robust and reliable device. This thesis, therefore, ...

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34

Freitas, Stefani Carolline Leal de. "Estudos teóricos e experimentais da operação conjunta de um supressor eletromagnético e de um filtro ativo de potência /." Ilha Solteira, 2014. http://hdl.handle.net/11449/111136.

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Orientador: Luís Carlos Origa de Oliveira
Co-orientador: João Luiz Afonso
Co-orientador: Priscila da Silva Oliveira
Banca: Júlio Borges de Souza
Banca: Falcondes José Mendes de Seixas
Banca: Arnulfo Barroso de Vasconcellos
Resumo: Com vistas à mitigação das distorções harmônicas, sempre que possível, são adotadas medidas operacionais relacionadas à adequação das cargas geradoras de harmônicas, fazendo-se uso de tecnologias menos poluentes, multiplicação do número de pulsos em instalações conversoras de grande porte, alteração da topologia das redes elétricas, entre outras. Ocorre, que, em diversas vezes, tais medidas são inviáveis sob o ponto de vista econômico, ou mesmo insuficientes para garantir o funcionamento adequado do sistema e/ou atender os limites estabelecidos pelas normas e recomendações técnicas. Nesses casos, torna-se indispensável o uso de equipamentos especiais para atenuação de distorções harmônicas. O uso de filtros e dispositivos de compensação constituem as técnicas mais aplicadas para redução das componentes harmônicas. Essas técnicas podem ser separadas em dois grandes grupos, dependendo do modo operacional, ativo ou passivo, sendo ambos amplamente conhecidos e aplicados nos mais distintos setores da engenharia. Considerando a aplicação de estruturas compensadoras em sistemas elétricos a quatro fios com carregamentos monofásicos não lineares, apresenta-se nesta tese um novo arranjo de compensação harmônica que incorpora simultaneamente filtragem ativa e passiva, e que apresenta todas as funcionalidades no que tange à compensação harmônica de um filtro ativo de quatro braços. Nessa perspectiva, a filtragem harmônica das componentes de sequências positiva e negativa é realizada por um filtro ativo de três braços, enquanto que, a filtragem das harmônicas homopolares fica atribuída ao supressor eletromagnético de sequência zero. Considerando o mesmo nível de potência a ser processado, presume-se que os custos dos dispositivos eletromagnéticos sejam menores quando comparados aos dispositivos de estado sólido, notadamente as chaves eletrônicas e ...
Abstract: With a view to mitigate harmonic distortion, whenever possible are adopted operational attitudes related to the suitability of harmonic generating loads, making use of cleaner technologies, multiplying the number of pulses in large converting installations, changes in electric grid topology, among others. Occurs that, in several times, such attitudes are not feasible under the economic point of view or even insufficient to ensure proper system operation and/or meet the limits set by standards and technical recommendations. In these cases, it becomes necessary to use special equipments to mitigate harmonic distortion. The use of filters and compensation devices constitute the techniques applied to reducing harmonic components. These techniques can be separated into two major groups, depending on the operating mode, active or passive, both widely known and applied in the most diverse sectors of engineering. Considering the expectation of compensating structures application in four-wire electrical systems with single-phase nonlinear loads, this thesis presents a new arrangement of harmonic compensation that incorporates both active and passive filtering, and that presents all the features regarding the harmonic compensation of a four-arm active filter. In this perspective, the harmonic filtering of positive and negative sequences components is performed by a three-arm active filter, while the filtering of zero sequence harmonics is attributed to the electromagnetic zero sequence suppressor. Considering the same power level to be processed, it is assumed that the costs of electromagnetic devices are smaller when compared to solid state devices, notably the electronic switches and sensors, which can be eliminated of the four-arm active filter when the responsibility to compensate homopolar harmonic is of the electromagnetic suppressor, which is a robust and reliable device. This thesis, therefore, ...
Doutor

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35

Pignatti, Alex Almeida. "O impacto da topologia de conexão de transdutores na obtenção de indicadores de qualidade de energia." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-15072013-154428/.

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A Agência Nacional de Energia Elétrica (ANEEL) deverá estabelecer a regulamentação para distúrbios de qualidade de energia em um futuro próximo. Há ainda questões em aberto sobre os procedimentos de medição e limites máximos para os indicadores de qualidade de energia. Este trabalho aborda uma dessas questões, que é a conexão de transdutores e os impactos nos índices de qualidade de energia associados. Simulações em ATPDraw e campanhas de medição foram realizadas de modo a identificar o comportamento dos indicadores de distorção harmónica sob as duas configurações possíveis de conexão de transdutores: dois equipamentos com ligação entre fases ou três com ligação fase-neutro. Os resultados das simulações e os valores medidos mostram grandes discrepâncias entre ambas as configurações, e as diferenças tornam-se ainda mais significativas com o incremento do desequilíbrio do sistema elétrico. As causas subjacentes deste fenômeno são investigadas e discutidas
The Brazilian electricity regulatory agency (ANEEL) is expected to establish a legal framework for quality disturbances in the near future. There are still some open questions regarding metering procedures and maximum limits for Power Quality indicators. This work addresses one of such issues, namely the connection of the associated transducers and its impact on PQ indexes. Simulations in ATPDraw and on-field measurement campaigns were carried out so as to identify the behavior of harmonic distortion indicators under the two possible transducer configurations: two phase-to-phase or three phase-to-neutral transducers. Simulation results and measured values show large discrepancies between both configurations, and the differences become more significant as the electrical systems unbalance increases. The underlying causes of this phenomenon are investigated and discussed.

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36

Leiter, Augustin. "Geotermální energie - vliv geometrie vrtu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-390268.

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Geothermal energy is one of the oldest forms of energy on our planet. Its use by humanity dates back to the beginning of the ages. The forms of this energy gradually changed from the direct heat of the hot springs, through the heating of the buildings and the baths to the later use of superheated steam for industrial use. Nowadays, there is a large share of the use of large number of ground geothermal boreholes with heat exchangers drilled in the matrix. The geometric arrangement of such system has a considerable impact on its operation. Specific examples show that, unlike the design, actual boreholes in such system can often be drilled non vertically or even curved. These imperfections then usually deteriorate the thermal properties of the system. This thesis demonstrates the influence analysis of the borehole geometry distortion on the system thermal properties, it also informs about the development of a special measuring device designed to obtain information about the actual geometric shape of the investigated borehole and about the development of software for in situ rapid borehole system properties evaluation. The theoretical part of thesis contains the derivation of a simplified numerical model of heat conduction in the vicinity of the borehole system. Its results serve to compare the different borehole variants and the inaccuracy of borehole shaping. Using the simulations, the influence of inaccuracies in the borehole system on its thermal properties is demonstrated in several model configurations. This effect does not occur in a single borehole, but it is significantly visible in organized geothermal borehole systems. It may deteriorate system properties, but under certain circumstances its properties may improve. Verification of the results of these simulations was performed by the FEFLOW simulation software. In the practical part the development of a special instrument for measuring the shape of a geothermal energy borehole is documented. ....

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37

Gamito, Marcos Aparecido Ruiz. "Influência do sistema de aterramento na presença de distorção harmônica." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-16112016-155721/.

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Com o surgimento das novas tecnologias aplicadas aos equipamentos e arranjos geométricos das fontes renováveis de energia, o sistema de aterramento passou a operar com correntes de várias frequências, diferentes da componente fundamental. Estas correntes são provenientes das novas cargas não lineares conectadas e das condições de falta, tornando mais difícil a equipotencialização do sistema de aterramento, devido, principalmente, ao seu tamanho e sua geometria. Neste cenário, esta pesquisa tem como objetivo o estudo do comportamento de um sistema de aterramento operando na presença de correntes com distorção harmônica. Para a modelagem do sistema de aterramento teste, foi utilizada a teoria de linhas de transmissão, considerando parâmetros distribuídos, pela qual o condutor foi modelado em porções ao longo de seu comprimento. Para a modelagem e análise do sistema de aterramento foram utilizados o programa ATP (Alternative Transients Program) e uma ferramenta computacional comercial, com o intuito de validar os valores da resistência da malha de aterramento observados. Pelos resultados encontrados, têm-se argumentos para alertar os projetos futuros de sistemas de aterramento para a necessidade e uma melhor análise das situações operacionais passíveis de ocorrência no sistema elétrico que venham a apresentar uma composição harmônica diferente e não desprezível em relação ao componente fundamental.
With the rise of new technology applied to devices and geometric arrangements related to renewable energy sources, grounding systems have started to operate with currents of multiple frequencies, deviating from its fundamental component. These currents come from the connection of new nonlinear loads and fault conditions, which makes the equipotential bonding harder for the grounding system, mainly due to its size and geometry. In this scenario, this research aims to study the behavior of a grounding system operating in the presence of harmonically distorted currents. The transmission line theory was used to model the testing grounding system, based on distributed parameters, through which the conductor was modeled in increments along its length. For modeling and studying the grounding system, the ATP (Alternative Transients Program) and a commercial software tool were used in order to validate the resistance values observed in the grounding grid. Based on the results found, there are arguments to alert future grounding system projects about the need for a better assessment of operational scenarios likely to occur in the electrical system, which may display a different harmonic composition that is not negligible in relation to the fundamental component.

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Nain, Vaibhav. "Efficient thermomechanical modeling of large parts fabricated by Directed Energy Deposition Additive Manufacturing processes." Thesis, Lorient, 2022. http://www.theses.fr/2022LORIS630.

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Les procédés de fabrication additive laser par dépôt de poudre offrent une opportunité unique pour la fabrication de grandes pièces à géométrie complexe. Cependant, les déformations mécaniques induites par ces procédés entrainent des défauts pouvant conduire à des pièces rebutées. Au cours de cette thèse, différents modèles ont donc été développés pour mieux comprendre l’apparition de ces déformations en fonction des paramètres opératoires. Un premier modèle thermomécanique prédit le comportement élastoplastique lors de la construction d’un mur en acier inoxydable 316L. L’apport de chaleur est modélisé par une source double ellipsoïdale mobile et la construction des couches se fait à l’aide d’une méthode hybride « Quiet/Active élément ». Un écrouissage isotrope non linéaire est considéré, avec prise en compte de la restauration d’écrouissage à hautes températures. Afin de réduire drastiquement les temps de calcul, une nouvelle source de chaleur est proposée utilisant une source ellipsoïdale allongée qui moyenne l’énergie sur un intervalle d’espace et de temps. Cependant, un intervalle d’espace trop grand diminue la précision du modèle. De nouveaux paramètres sont alors introduits afin d’identifier le meilleur compromis entre temps de calcul et précision. L’ensemble des modèles proposés est confronté avec succès avec des données expérimentales en termes de température et déplacement et ce pour différents paramètres opératoires. Enfin, des modèles multi-échelles basés l’activation par couche ou les méthodes de déformations inhérentes sont étudiés en vue de réduire les temps de calcul
Directed Energy Deposition (DED) Additive Manufacturing technology offers a unique possibility of fabricating large-scale complex-shape parts. However, process-induced deformation in the fabricated part is still a big obstacle in successfully fabricating large-scale parts. Therefore, multiple numerical models have been developed to understand the accumulation of induced deformation in the fabricated part. The first model predicts the thermo-elastoplastic behaviour that captures the laser movement. The laser-material interaction and metal deposition are modeled by employing a double ellipsoid heat source and the Quiet/Active material activation method respectively. The model considers isotropic non-linear material hardening to represent actual metal behaviour. It also employs an instantaneous stress relaxation model to simulate the effects of physical phenomena like annealing, solid-state phase transformation, and melting. Using this model as a reference case, an efficient model is developed with an objective to reduce the computation time and make it feasible to simulate large-part. The model employs an Elongated Ellipsoid heat source that averages the heat source over the laser path which reduces the computational burden drastically. However, averaging over large laser path results in inaccurate results. Therefore, new parameters are developed that identify the best compromise between computation time reduction and accuracy. Both models are validated with experimental data obtained from several experiments with different process parameters. Finally, other Multi- scale methods such as the Layer-by-layer method and Inherent Strain-based methods are implemented and explored

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MAIA, Ayslan Caisson Norões. "Sistemas de conversão de energia multiníveis obtidos através da interconexão de módulos de conversores estáticos de potência de dois níveis." Universidade Federal de Campina Grande, 2016. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1561.

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Nesse trabalho são apresentadas contribuições na área de identificação de sistemas representados em espaço de estados. É proposta uma metodologia completa para estimação de modelos que representem as principais dinâmicas de proessos industriais. O fluxo natural dos procedimentos de identificação consiste da coleta experimental dos dados, seguido pela esolha dos modelos candidatos e da utilização de um critério de ajuste que selecione o melhor modelo possível. Nesse sentido é proposta uma metodologia para estimativa de modelos em espaço de estados, utilizando excitações pulsadas. A abordagem desenvolvida combina algoritmos precisos e eficientes com experimentos rápidos, adequados a ambientes industriais. O projeto das excitações é realizado em tempo real, por meio de informações coletadas em um curto experimento inicial, baseado em uma única oscilação de uma estrutura realimentada por um relé. Esse mecanismo possibilita uma estimativa preliminar do atraso e da constante de tempo dominante do sistema. O método de identificação proposto é baseado na teoria de realizações de Kalman. É apresentada uma reformulação do problema de realizações clássico, para comportar sinais de entrada pulsados. Essa abordagem se mostra computacionalmente e cliente, assim como apresentar resultados semelhantes aos métodos de benchmark. A técnica possibilita também a estimativa de atrasos de transporte e a inserção de conhecimentos prévios por meio de um problema de otimização com restrições via LMI Linear Matrix Inequalities. Em muitos casos, somente as caraterísticas principais dos sistema são relevantes em um projeto de sistema de controle. Portanto é proposta uma técnica para obtenção de modelos de primeira ordem com atraso, a partir da redução de modelos balanceados em espaço de estados. Por fim, todas as contribuições discutidas nesse trabalho de teses não validadas em uma série de plantas experimentais em salas de laboratório. Plantas essas, projetadas e construídas com o intuito de emular o cotidiano operacional de instalações industriais reais.
Static converters are a widely used equipment in power systems to control the electrical energy low between sources and loads. In this context, it is observed a demand for converters topologies that generate high quality waveforms and are capable of supplying loads with ever larger powers. In high power applications such as industrial and power systems, the development of a special class of converters topologies, denominated multilevel converters, has been widely recognized as a viable solution to overcome the operational limits of semiconductor devices. In this work are developed and analyzed multilevel structures of type DC-AC applied to the six-phase machines drives and of type AC-DC-AC feeding singlephase and three-phase loads. These topologies are obtained by interconnecting two-level converters modules in order to optimize the system: reduction of losses in the semiconductor devices, harmonic distortion of the signals and ratings of voltage and/or current in the power switches. For this investigation were performed steady state analyzes, where the operatinglimits of the structures to the imposed control conditions and the behavior of the fundamental component of voltage and current are evaluated. In addition, for each investigated topology, were developed: dynamic models, PWM techniques, control strategies, simulation results and experimental results. The impact of this optimization is quanti ed by calculating the THD and WTHD of the current and voltage signals generated by the converter and by estimating losses in the semiconductor devices. Finally, a comparative study is done using conventional converters as reference in order to evaluate the performance of the proposed topologies

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Fugita, Sergio Date. "Smart meter integrado a analisador de qualidade de energia para propósitos de identificação de cargas residenciais." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-23022015-133145/.

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Este trabalho consiste em apresentar o desenvolvimento de um Smart meter, integrado a um analisador de qualidade de energia, para análise de distorções harmônicas, utilizando método de redes neurais artificiais embarcado em hardware. Tal Smart meter está incluído dentro dos conceitos de Smart Grid, que serão apresentados também neste trabalho. O intuito do desenvolvimento do Smart meter para análise de distorções harmônicas é auxiliar concessionárias de energia elétrica a identificar que tipo de carga o consumidor utiliza em sua residência, a fim de contribuir para a tomada de decisões apropriadas, tais como a diminuição da emissão de correntes harmônicas, demanda de energia, detecção de falhas no fornecimento de energia elétrica e faturas diferenciadas de acordo com a quantidade de harmônicas injetadas na rede elétrica. Adicionalmente, observou-se que o Smart meter desenvolvido pode ser ainda utilizado para detectar fenômenos de VTCD, como elevação, afundamento e interrupção de energia. Todo o processo de desenvolvimento do Smart meter é apresentado no decorrer desta tese de doutorado.
This thesis consists to present the development of a Smart Meter integrated to power quality analyzer for the analysis of harmonic distortion, using methods based on artificial neural networks in embedded hardware. This Smart Meter is included within the concepts of Smart Grid, which will be also presented in this work. The intention of the development of the Smart Meter for analysis of harmonic distortion is to assist utilities companies to identify what loads type the consumer uses at your residence in order to contribute for supporting decisions, such as reducing the emission of the harmonic currents, power demand and faults detection in electric energy supply and distinct bills according to the amount of harmonics injected into the power grid. In addition, it was observed that this developed Smart Meter can be even used to detect the VTCD phenomena, such as swell, sag and interruption of the energy supply. All development steps of this Smart Meter is presented in this doctoral thesis.

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Mertens, Junior Ernesto Alberto. "Análise e aplicação de compensação reativa em redes secundária de distribuição com cargas não lineares /." Ilha Solteira : [s.n.], 2008. http://hdl.handle.net/11449/87132.

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Orientador: Luis Carlos Origa de Oliveira
Banca: José Carlos Rossi
Banca: Olivio Carlos Nascimento Souto
Resumo: O presente trabalho avalia a viabilidade técnica da aplicação de compensação reativa em circuitos secundários aéreos de baixa tensão, através da aplicação de capacitores e / ou filtros para aplicação em Baixa Tensão, buscando assim uma otimização dos reativos presentes nas redes secundárias. Considerando-se as constantes mudanças que vêm ocorrendo no cenário de distribuição de energia elétrica, devido ao grande avanço da eletrônica de potência e de cargas não lineares cada vez mais presentes no sistema elétrico, fazem-se necessários estudos para diagnosticar como e em que níveis tais mudanças podem estar afetando as características das redes de distribuição. Verifica-se que tais cargas, possuem um baixo fator de potência, e podem aumentar significativamente o nível de correntes harmônicas devido às técnicas de chaveamento utilizadas nestes dispositivos. Com isto, acentuam-se os problemas da propagação das distorções de forma de onda das correntes às tensões da rede, além de aumentar consideravelmente as perdas de energia elétrica ao longo de seus condutores e transformadores. Há necessidade de se conhecer as características dessas cargas de forma a permitir a correta modelagem das mesmas. O objetivo deste trabalho é identificar o perfil da rede secundária frente aos níveis de harmônicos e fator de potência, permitindo a adequada aplicação de filtros e capacitores para instalação no secundário dos transformadores de distribuição, visando a correção do fator de potência nos circuitos, redução do reativo circulante, das perdas elétricas e eventualmente dos níveis de distorção harmônica. Avaliando-se as interferências no carregamento dos transformadores de distribuição e melhoria do perfil da tensão de alimentação. Neste sentido, foi feita uma campanha de monitoramento em alguns circuitos selecionados... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This paper seeks to evaluate the technical feasibility of applying for compensation reactive side air circuits in low-voltage, by the application of capacitors and / or filters for use in the Low Voltage, thereby seeking an optimization of reactive present in the secondary networks. Analysis with a focus on secondary distribution network should consider a new factor, which is the proliferation of non-linear loads. Considering the constant changes that are occurring in the scenario of distribution of electric energy, due to the general advancement of power electronics and nonlinear loads increasingly present in the electrical system, are made necessary studies to diagnose how and to what levels such changes may be affecting the characteristics of distribution networks. It appears that such loads, have a low power factor, and can significantly increase the level of harmonic currents because of the techniques used in these switching devices. With this, stressing the problems of the spread of distortions of waveform of the current tensions to the network, in addition to considerably increase the loss of power over their drivers and processors. Thus, the objective of this study is to identify the profile of the network front secondary levels of harmonics and power factor, allowing the proper implementation of filters and capacitors for installation of transformers in the secondary distribution, aiming to correct the power factor in circuits, Reducing the reactive stock, loss of electrical and possibly the levels of harmonic distortion. Judging is interference in the shipment of processors for distribution and improving the profile of the supply voltage. In this sense, there was a campaign tracking in some selected circuits, computer simulations were also conducted, equipment developed and deployed pilot projects.
Mestre

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42

Fortes, Rárison Roberto Acácio [UNESP]. "Distorções harmônicas produzidas por inversores de geração distribuída fotovoltaica em condição de ressonância paralela." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138262.

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Fundação de Amparo à Pesquisa do Estado do Acre (FAPAC)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Como os sistemas de energia têm sido tradicionalmente projetados para produção centralizada, a penetração de sistemas de geração distribuída na rede tem causado mudança nesse perfil, criando novos desafios operacionais que se fazem importantes para a reestruturação dos sistemas tradicionais. No entanto, este novo cenário do sistema elétrico, introduzido pela resolução 482/2012 da Agência Nacional de Energia Elétrica – ANEEL, trouxe às distribuidoras de energia um novo panorama para as atividades de operação e manutenção de suas redes e ativos, principalmente devido à bidirecionalidade do fluxo de potência na rede, originado pela conexão de sistemas de geração distribuída. Os impactos técnicos devem ser previstos e analisados, sobretudo em redes de distribuição, para garantir os padrões mínimos de qualidade da energia no ponto de consumo e evitar o comprometimento das cargas alimentadas. Dentre os impactos, destaca-se o efeito sobre os bancos de capacitores devido à injeção de distorções harmônica produzida pelos inversores de sistemas fotovoltaicos, que sob certas condições, produzem conteúdo harmônico com nível acima do limite normatizado, podendo excitar uma condição prévia de ressonância no barramento. Neste contexto, esta dissertação tem como principal objetivo analisar o comportamento do sistema elétrico em condição de ressonância paralela e avaliar o grau de comprometimento dos bancos de capacitores instalados no sistema de distribuição com presença de frequências harmônicas e sugerir rotinas técnicas para evitar sua operação contingenciada.
As energy systems have been traditionally projected for centralized production, the penetration of distributed generation systems have caused a change in this profile, creating new operational challenges that are important for traditional systems restructuring. However, this new electrical system scenario, introduced by resolution 482/2012 of Brazilian Electricity Regulatory Agency – ANEEL, brought to energy distributors a new view to the operational and maintenance activities of their nets and actives, specially due to the net power flow bidirectionality, created by the distributed generation systems connection. Technical impacts must be estimated and analyzed, specially in distribution nets, to ensure minimum energy quality standards in the consumption point and avoid fed charges commitment. Among the impacts stands out the capacitor bench effects due to harmonic distortions injection produced by photovoltaic systems inverters, that under some conditions, produce harmonic content over the regulated limit, being able to excite a preview condition of resonance in the bus. In this context, this essay has the main objective to analyze the electrical system behavior in parallel resonance condition and evaluate the degree of commitment of the capacitor bench installed in the distribution system with harmonic frequencies and suggest technical routines to avoid the contingent operation.
FAPAC: 6068-14-0000093

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43

Fortes, Rárison Roberto Acácio. "Distorções harmônicas produzidas por inversores de geração distribuída fotovoltaica em condição de ressonância paralela /." Ilha Solteira, 2016. http://hdl.handle.net/11449/138262.

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Orientador: Luís Carlos Origa de Oliveira
Resumo: Como os sistemas de energia têm sido tradicionalmente projetados para produção centralizada, a penetração de sistemas de geração distribuída na rede tem causado mudança nesse perfil, criando novos desafios operacionais que se fazem importantes para a reestruturação dos sistemas tradicionais. No entanto, este novo cenário do sistema elétrico, introduzido pela resolução 482/2012 da Agência Nacional de Energia Elétrica – ANEEL, trouxe às distribuidoras de energia um novo panorama para as atividades de operação e manutenção de suas redes e ativos, principalmente devido à bidirecionalidade do fluxo de potência na rede, originado pela conexão de sistemas de geração distribuída. Os impactos técnicos devem ser previstos e analisados, sobretudo em redes de distribuição, para garantir os padrões mínimos de qualidade da energia no ponto de consumo e evitar o comprometimento das cargas alimentadas. Dentre os impactos, destaca-se o efeito sobre os bancos de capacitores devido à injeção de distorções harmônica produzida pelos inversores de sistemas fotovoltaicos, que sob certas condições, produzem conteúdo harmônico com nível acima do limite normatizado, podendo excitar uma condição prévia de ressonância no barramento. Neste contexto, esta dissertação tem como principal objetivo analisar o comportamento do sistema elétrico em condição de ressonância paralela e avaliar o grau de comprometimento dos bancos de capacitores instalados no sistema de distribuição com presença de frequências harmô... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: As energy systems have been traditionally projected for centralized production, the penetration of distributed generation systems have caused a change in this profile, creating new operational challenges that are important for traditional systems restructuring. However, this new electrical system scenario, introduced by resolution 482/2012 of Brazilian Electricity Regulatory Agency – ANEEL, brought to energy distributors a new view to the operational and maintenance activities of their nets and actives, specially due to the net power flow bidirectionality, created by the distributed generation systems connection. Technical impacts must be estimated and analyzed, specially in distribution nets, to ensure minimum energy quality standards in the consumption point and avoid fed charges commitment. Among the impacts stands out the capacitor bench effects due to harmonic distortions injection produced by photovoltaic systems inverters, that under some conditions, produce harmonic content over the regulated limit, being able to excite a preview condition of resonance in the bus. In this context, this essay has the main objective to analyze the electrical system behavior in parallel resonance condition and evaluate the degree of commitment of the capacitor bench installed in the distribution system with harmonic frequencies and suggest technical routines to avoid the contingent operation.
Mestre

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44

Mertens, Junior Ernesto Alberto [UNESP]. "Análise e aplicação de compensação reativa em redes secundária de distribuição com cargas não lineares." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/87132.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O presente trabalho avalia a viabilidade técnica da aplicação de compensação reativa em circuitos secundários aéreos de baixa tensão, através da aplicação de capacitores e / ou filtros para aplicação em Baixa Tensão, buscando assim uma otimização dos reativos presentes nas redes secundárias. Considerando-se as constantes mudanças que vêm ocorrendo no cenário de distribuição de energia elétrica, devido ao grande avanço da eletrônica de potência e de cargas não lineares cada vez mais presentes no sistema elétrico, fazem-se necessários estudos para diagnosticar como e em que níveis tais mudanças podem estar afetando as características das redes de distribuição. Verifica-se que tais cargas, possuem um baixo fator de potência, e podem aumentar significativamente o nível de correntes harmônicas devido às técnicas de chaveamento utilizadas nestes dispositivos. Com isto, acentuam-se os problemas da propagação das distorções de forma de onda das correntes às tensões da rede, além de aumentar consideravelmente as perdas de energia elétrica ao longo de seus condutores e transformadores. Há necessidade de se conhecer as características dessas cargas de forma a permitir a correta modelagem das mesmas. O objetivo deste trabalho é identificar o perfil da rede secundária frente aos níveis de harmônicos e fator de potência, permitindo a adequada aplicação de filtros e capacitores para instalação no secundário dos transformadores de distribuição, visando a correção do fator de potência nos circuitos, redução do reativo circulante, das perdas elétricas e eventualmente dos níveis de distorção harmônica. Avaliando-se as interferências no carregamento dos transformadores de distribuição e melhoria do perfil da tensão de alimentação. Neste sentido, foi feita uma campanha de monitoramento em alguns circuitos selecionados...
This paper seeks to evaluate the technical feasibility of applying for compensation reactive side air circuits in low-voltage, by the application of capacitors and / or filters for use in the Low Voltage, thereby seeking an optimization of reactive present in the secondary networks. Analysis with a focus on secondary distribution network should consider a new factor, which is the proliferation of non-linear loads. Considering the constant changes that are occurring in the scenario of distribution of electric energy, due to the general advancement of power electronics and nonlinear loads increasingly present in the electrical system, are made necessary studies to diagnose how and to what levels such changes may be affecting the characteristics of distribution networks. It appears that such loads, have a low power factor, and can significantly increase the level of harmonic currents because of the techniques used in these switching devices. With this, stressing the problems of the spread of distortions of waveform of the current tensions to the network, in addition to considerably increase the loss of power over their drivers and processors. Thus, the objective of this study is to identify the profile of the network front secondary levels of harmonics and power factor, allowing the proper implementation of filters and capacitors for installation of transformers in the secondary distribution, aiming to correct the power factor in circuits, Reducing the reactive stock, loss of electrical and possibly the levels of harmonic distortion. Judging is interference in the shipment of processors for distribution and improving the profile of the supply voltage. In this sense, there was a campaign tracking in some selected circuits, computer simulations were also conducted, equipment developed and deployed pilot projects.

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Fortes, Rárison Roberto Acácio. "Propagação de harmônicas produzidas por inversores fotovoltaicos e transformadores assimetricamente magnetizados na geração distribuída /." Ilha Solteira, 2018. http://hdl.handle.net/11449/180210.

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Orientador: Luís Carlos Origa de Oliveira
Resumo: As profundas mudanças que os sistemas de distribuição de energia elétrica vêm experimentando, devido à crescente penetração de unidades de Geração Distribuída (GD), têm resultado, inevitavelmente, na efetiva ruptura da forma tradicional de controlar e operar o sistema elétrico. A conexão em larga escala de unidades de GD impõe às distribuidoras de energia uma série de desafios técnicos, econômicos e regulatórios, necessários para preservar a continuidade e o nível de Qualidade da Energia Elétrica (QEE) na rede. Além dos benefícios que justificam o investimento, os sistemas de GD contribuem com alguns impactos negativos para o sistema elétrico, entre eles, destacam-se aqui a geração de harmônicas e a injeção de corrente contínua (CC) na rede, em regime permanente, e seus efeitos sobre os transformadores de potência. O incremento de uma componente de fluxo CC em seu enrolamento secundário altera o ponto de operação natural e eficiente do transformador, trazendo prejuízo não só à sua vida útil, mas também à sua funcionalidade na rede. Esta condição favorece a geração e propagação de harmônicas adicionais no sistema alimentador, afetando negativamente o sistema elétrico, sendo esta análise uma contribuição original deste trabalho. Neste sentido, considera-se com grande relevância o estudo de comportamento dos equipamentos projetados para operar essencialmente com sinais em corrente alternada (CA) e que passam a ser submetidos, simultaneamente, a excitações com corrente contínua. ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The deep changes that electric power distribution systems have been experiencing due to the increasing number of Distributed Generation (GD) units, have inevitably resulted in the effective rupture of the traditional way of controlling and operating the electrical system. The large-scale connection of GD units imposes on energy utilities many technical, economic and regulatory challenges necessary to preserve the continuity and the Electric Power Quality (EPQ) level on the grid. In addition to the benefits that justify the investment, GD systems have some negative impacts to the electrical system, among them, the harmonic generation and Direct Current (DC) injection on the grid, and its effects in the power transformers. The increase of a DC flow component in the secondary winding changes the standard and efficient operational point of the transformer, causing damage not only to its lifespan but also to its functionality on the grid. This condition favors the additional harmonics generation and propagation in the feeder system, adversely affecting the electrical system, being this analysis an original contribution of this work. In this way of thinking, it is considered with great relevance the study of the equipment behavior designed to operate essentially with signals in alternating current (AC) and simultaneously subjected to excitations with direct current (DC). Whereas the objective of analyzing not only the effect but also the cause of the double excitation, this thesis ... (Complete abstract click electronic access below)
Doutor

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Silva, Sérgio Ferreira de Paula. "Uma proposta para o compartilhamento das responsabilidades sobre as distorções harmônicas." Universidade Federal de Uberlândia, 2007. https://repositorio.ufu.br/handle/123456789/14368.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The quality of the electric energy emerges as an area of great interest to both consumers and supply authorities. Searching half the subject prescribed, it is recognized, in the present time, the national and international existence of recommendations, norms and criteria directed toward the orientation of the boundary-values or reference for the diverse pointers that characterize the desired standard of quality. Inside of this context, if a measured harmonic voltage distortion exceeds that which is permitted, mitigation procedures must be promptly considered. These procedures can cause great conflict between the supplier and the consumer due to a lack of consensus on who is the mainly responsible for the harmonic distortions. The objective of this study is to establish a just procedure for sharing the responsibility for actual harmonic voltage distortion at a given point of common coupling between the supplier and the consumer. The methodology is based on the analysis of measured voltage and current signals at the PCC and on information related to the harmonic impedances involved in the process. Both the supply and the load impedances are considered and an approach for coupling with consumer representation is presented. The method is applied to a laboratory arrangement which uses a programmable voltage source in combination with a load comprising linear and nonlinear components. The results highlight the consistence of the proposal when identifying the individual contribution of the supplier and the consumer. By finding the supply and load harmonic contributions it is possible to achieve fairer cost sharing when mitigation procedures are needed to reduce voltage distortion to admissible legislation limits.
A qualidade da energia elétrica se apresenta como uma área de grande interesse para os consumidores e concessionárias de energia. Buscando meios para regulamentar o assunto, reconhece-se, na atualidade, a existência de recomendações, normas e critérios nacionais e internacionais voltados para a orientação dos valores limites ou de referência para os diversos indicadores que caracterizam o padrão de qualidade desejado. Dentro deste contexto, as distorções harmônicas nos sinais de tensão e corrente surgem como uma das questões mais preocupantes. Almejando, pois a preservação da qualidade do suprimento no que tange às distorções harmônicas, assim como para os demais itens de definição da qualidade, faz-se, muitas vezes necessário, a utilização de técnicas para a identificação da responsabilidade entre supridores e consumidores quanto à presença de distorções harmônicas de tensão junto aos pontos de acoplamento comum das redes de suprimento. Focando este tema, esta tese encontra-se direcionada ao estabelecimento e avaliação de desempenho de um procedimento sistematizado para o compartilhamento das responsabilidades entre supridores e consumidores, quanto à presença de distorções harmônicas de tensão junto aos pontos de acoplamento comum entre as partes. A metodologia é fundamentada na análise de sinais de tensão e corrente, obtidos dos sistemas, e em informações associadas com as impedâncias harmônicas próprias aos sistemas elétricos envolvidos no processo. A questão da modelagem da carga é ressaltada de modo especial. O método almeja contribuir na direção do estabelecimento de medidas de compensação quando os valores limites das distorções são superiores àqueles previstos pela legislação. Finalmente, objetivando ilustrar a aplicabilidade da proposta, ensaios laboratoriais são realizados a fim de evidenciar sua potencialidade.
Doutor em Ciências

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Silva, Cintia Gonçalves Mendes da. "Diagnóstico sobre a utilização das lâmpadas fluorescentes compactas (LFC) como promotoras de eficiência energética nos sistemas de iluminação no Brasil." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/86/86131/tde-30042008-163006/.

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O aumento do consumo no Brasil aparte com problemas de abastecimento de energia elétrica na década de 90, durante um período de más condições hidrológicas causou uma preocupação e instou uma pesquisa sobre as formas de redução do consumo. A qualidade de energia não era uma prioridade, cargas não eram tão sensíveis, nem os processos existentes exigiam tanto na qualidade do fornecimento de energia elétrica. A preocupação sobre a qualidade do abastecimento de energia aumentou, principalmente no setor industrial, com o aumento da concorrência nos mercados nacionais e no exterior. A qualidade e a quantidade da produção tornaram-se um item para distinguir o lucro. Desta forma, a qualidade do fornecimento de energia e a continuidade das linhas de produção tornaram-se mais importante. Este trabalho pretende mostrar resultados de um estudo experimental sobre lâmpadas fluorescentes compactas com reator integrado, e algumas conseqüências da sua utilização generalizada.
The increase of the consumption in Brazil aside with problems of supply of electrical energy in the decade of 90, during a period of bad hydrological conditions caused a concern and urged a search for ways of reduction of the consumption. The quality of power was not a priority, loads were not so sensitive nor the existing processes demanded as much as quality of the supply of electric energy. The concern on quality of energy supply increased, mainly in the industrial sector, with the increase of the competition in the domestic markets and overseas. The quality and the amount of production became a distinguished item for the profit. In this way, the quality of energy supply and the continuity of the production lines became more important. This work aims to show results of an experimental survey about compact fluorescent light bulbs with integrated reactor, and some consequences of its generalized use.

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Soares, Junior Dirceu. "Análise de filtros híbridos aplicados a um forno elétrico a Arco." Universidade Federal do Espírito Santo, 2011. http://repositorio.ufes.br/handle/10/6222.

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Made available in DSpace on 2016-12-23T14:07:27Z (GMT). No. of bitstreams: 1 Dissertacao de Dirceu Soares Junior Parte 1.pdf: 2325132 bytes, checksum: 944653981d05fdcc1c69ff97b342de4f (MD5) Previous issue date: 2011-09-22
Uma planta siderúrgica caracteriza-se pela existência em seu processo produtivo de cargas não lineares de elevada potência. Dentre estas cargas, as siderúrgicas do tipo mini-mill possuem normalmente Forno Elétrico a Arco (FEA) na sua fase inicial de produção do aço, que ocorre a partir da fusão de sucatas metálicas como principal matéria-prima utilizada. Os fornos elétricos absorvem uma corrente distorcida da rede elétrica, causando assim uma distorção de tensão no ponto de acoplamento comum (PAC) e inúmeros problemas de qualidade de energia elétrica. Uma solução muito utilizada para a mitigação harmônica neste tipo de carga elétrica é obtida através do uso de filtros passivos, com vários estágios de filtragem. Porém esta é uma solução que pode levar ao efeito da ressonância harmônica, elevando com isto a distorção harmônica no sistema elétrico e causando sobrecarga no sistema de filtragem. Neste trabalho é apresentado um estudo de caso em uma siderúrgica não integrada (siderúrgica que possui sucata metálica e ferro gusa como matérias-primas principais na fabricação do aço), localizada na região da Grande Vitória. Por meio de medições na subestação principal da usina, são apresentadas as principais formas de onda das correntes e tensões, em conjunto com seus espectros harmônicos, que comprovam a existência de distorções harmônicas, sobretudo provenientes da corrente do forno elétrico a arco. As medições consideradas no trabalho, para simulação dos modelos contendo os filtros híbridos, foram aquelas originadas da condição operacional mais crítica do processo, sob o ponto de vista de momento onde o comportamento da carga acarreta o maior desvio quanto à qualidade de energia nas variáveis elétricas medidas. O modelo utilizado para o sistema em questão apresenta forte grau de correlação com o sistema real, retratado através das medições elétricas efetuadas. De posse do modelo é realizada uma análise comparativa por meio de simulação entre duas topologias de filtragem híbrida, o filtro híbrido série e o filtro híbrido paralelo, para a compensação harmônica e amortecimento da ressonância. Os resultados das simulações e das análises das ressonâncias mostraram que o filtro híbrido paralelo é a topologia que permite a maior redução das distorções harmônicas de corrente e de tensão no PAC, utilizando-se um filtro ativo com a menor potência nominal. Contudo, a filtragem híbrida paralela não provê a eliminação por completo da ressonância paralela. E, quanto à ressonância série, o filtro utilizado não possui a capacidade de interferir na condição de amplificação harmônica existente no sistema elétrico. Finalmente, o estudo propõe que a definição da melhor alternativa de filtragem leve em consideração a escolha do ganho do filtro ativo e, consequentemente, a sua potência, de forma bem alinhada aos objetivos de melhoria na qualidade de energia elétrica que são esperados para o sistema em questão
A steelmaking plant is characterized for having in its productive process non linear loads of high power. For these loads, the steelmaking industries called mini-mill normally have Electric Arc Furnace (EAF) in its initial steel production phase that happen with metallic scrap melting being the principal raw material used. The EAF absorb a distorted current from the electric main, causing voltage distortion in its point of common coupling (PCC) and many problems with respects the electric power quality. A standard solution used for the harmonic mitigation in this application is obtained through the use of composite passive filter. However this is a solution that can cause harmonic resonance, increasing the harmonic distortion in the electrical system and causing overload in the filtering system. In this work, a case in a non integrated steel industry, located at Grande Vitoria region, is presented. Through measurements in the main substation of the plant, the main current and voltage waveforms are presented, along with its harmonic spectrum, that confirm the existence of harmonic resonance phenomenon, mainly from Electric Arc Furnace current. The measurement considered in this work to simulate the hybrid filters models, was that originated from operational condition with higher process criticism, under viewpoint of the moment where the behavior of the load brings to a major deviation regarding the power quality at the measured variables. The model used for the system under study shows strong correlation with the real system portrayed through the electrical measurements done. Using the model, a comparative simulation analysis is done, between two hybrid topologies, the series hybrid filter and the parallel hybrid filter, with the objective of harmonic compensation and resonance damping. The results of simulations and resonance analysis showed that the parallel hybrid filter is the topology that allows the greatest reduction in harmonic distortion of current and voltage in the PCC (Point of Common Coupling), using an active filter with the lowest nominal power rating. However, the parallel hybrid filtering does not provide the complete elimination of parallel resonance, and for the series resonance, the filter used does not have the ability to interfere in the harmonic amplification condition existing in the electrical system. Finally, the study proposes that the best filtering alternative takes into account the choice of the active filter gain and consequently its power, so well aligned with the objectives of improving the power quality that are expected for the system under analysis

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Golfieri, Carolina Iovance. "Estudo investigativo da análise modal aplicada a sistemas de distribuição frente às distorções harmônicas." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-30102018-100229/.

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Esta pesquisa apresenta um estudo investigativo da análise modal aplicada a Sistemas de Distribuição (SDs) frente às distorções harmônicas, no contexto da Qualidade da Energia Elétrica (QEE). A partir do método de análise da ressonância modal, foi conduzido um estudo investigativo para apontar quais barramentos são mais sensíveis e permitem uma melhor observação frente às distorções harmônicas. Vale adiantar que o método de análise de ressonância modal, o qual é fundamentado na decomposição espectral da matriz de admitância do sistema elétrico, já apresenta interessantes trabalhos voltados para sistemas de transmissão. O desafio desta pesquisa foi então investigar a sua aplicação para SDs com um direcionamento às distorções harmônicas, bem como ao seu monitoramento. Dentre os resultados encontrados no desenvolvimento da pesquisa, destaca-se um melhor entendimento do problema das distorções harmônicas, o qual permitiu evidenciar a sensibilidade e a observabilidade dos SDs testes frente ao problema definido no contexto da QEE.
This research presents an investigative study of the modal analysis applied to Distribution Systems (DSs) in the context of Power Quality (PQ) considering the harmonic distortions. From the modal resonance analysis, an investigative study was conducted to indicate which bus bars are more sensitive and allow better observation in face of harmonic distortions. It is worth mentioning that the method of modal resonance analysis, which is based on the spectral decomposition of the admittance matrix of the electric system, already presents interesting applications focused on transmission systems. The challenge of this research was to investigate its application to DSs focusing on harmonic distortions, as well as their monitoring. Among the observed results of the research development, a better understanding of the harmonic distortions problem was achieved, which made it possible to highlight the sensitivity and observability of the DSs tests against the problem defined in the context of the PQ.

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Ghasemi, Negareh. "Improving ultrasound excitation systems using a flexible power supply with adjustable voltage and frequency to drive piezoelectric transducers." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/61091/1/Negareh_Ghasemi_Thesis.pdf.

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The ability of a piezoelectric transducer in energy conversion is rapidly expanding in several applications. Some of the industrial applications for which a high power ultrasound transducer can be used are surface cleaning, water treatment, plastic welding and food sterilization. Also, a high power ultrasound transducer plays a great role in biomedical applications such as diagnostic and therapeutic applications. An ultrasound transducer is usually applied to convert electrical energy to mechanical energy and vice versa. In some high power ultrasound system, ultrasound transducers are applied as a transmitter, as a receiver or both. As a transmitter, it converts electrical energy to mechanical energy while a receiver converts mechanical energy to electrical energy as a sensor for control system. Once a piezoelectric transducer is excited by electrical signal, piezoelectric material starts to vibrate and generates ultrasound waves. A portion of the ultrasound waves which passes through the medium will be sensed by the receiver and converted to electrical energy. To drive an ultrasound transducer, an excitation signal should be properly designed otherwise undesired signal (low quality) can deteriorate the performance of the transducer (energy conversion) and increase power consumption in the system. For instance, some portion of generated power may be delivered in unwanted frequency which is not acceptable for some applications especially for biomedical applications. To achieve better performance of the transducer, along with the quality of the excitation signal, the characteristics of the high power ultrasound transducer should be taken into consideration as well. In this regard, several simulation and experimental tests are carried out in this research to model high power ultrasound transducers and systems. During these experiments, high power ultrasound transducers are excited by several excitation signals with different amplitudes and frequencies, using a network analyser, a signal generator, a high power amplifier and a multilevel converter. Also, to analyse the behaviour of the ultrasound system, the voltage ratio of the system is measured in different tests. The voltage across transmitter is measured as an input voltage then divided by the output voltage which is measured across receiver. The results of the transducer characteristics and the ultrasound system behaviour are discussed in chapter 4 and 5 of this thesis. Each piezoelectric transducer has several resonance frequencies in which its impedance has lower magnitude as compared to non-resonance frequencies. Among these resonance frequencies, just at one of those frequencies, the magnitude of the impedance is minimum. This resonance frequency is known as the main resonance frequency of the transducer. To attain higher efficiency and deliver more power to the ultrasound system, the transducer is usually excited at the main resonance frequency. Therefore, it is important to find out this frequency and other resonance frequencies. Hereof, a frequency detection method is proposed in this research which is discussed in chapter 2. An extended electrical model of the ultrasound transducer with multiple resonance frequencies consists of several RLC legs in parallel with a capacitor. Each RLC leg represents one of the resonance frequencies of the ultrasound transducer. At resonance frequency the inductor reactance and capacitor reactance cancel out each other and the resistor of this leg represents power conversion of the system at that frequency. This concept is shown in simulation and test results presented in chapter 4. To excite a high power ultrasound transducer, a high power signal is required. Multilevel converters are usually applied to generate a high power signal but the drawback of this signal is low quality in comparison with a sinusoidal signal. In some applications like ultrasound, it is extensively important to generate a high quality signal. Several control and modulation techniques are introduced in different papers to control the output voltage of the multilevel converters. One of those techniques is harmonic elimination technique. In this technique, switching angles are chosen in such way to reduce harmonic contents in the output side. It is undeniable that increasing the number of the switching angles results in more harmonic reduction. But to have more switching angles, more output voltage levels are required which increase the number of components and cost of the converter. To improve the quality of the output voltage signal with no more components, a new harmonic elimination technique is proposed in this research. Based on this new technique, more variables (DC voltage levels and switching angles) are chosen to eliminate more low order harmonics compared to conventional harmonic elimination techniques. In conventional harmonic elimination method, DC voltage levels are same and only switching angles are calculated to eliminate harmonics. Therefore, the number of eliminated harmonic is limited by the number of switching cycles. In the proposed modulation technique, the switching angles and the DC voltage levels are calculated off-line to eliminate more harmonics. Therefore, the DC voltage levels are not equal and should be regulated. To achieve this aim, a DC/DC converter is applied to adjust the DC link voltages with several capacitors. The effect of the new harmonic elimination technique on the output quality of several single phase multilevel converters is explained in chapter 3 and 6 of this thesis. According to the electrical model of high power ultrasound transducer, this device can be modelled as parallel combinations of RLC legs with a main capacitor. The impedance diagram of the transducer in frequency domain shows it has capacitive characteristics in almost all frequencies. Therefore, using a voltage source converter to drive a high power ultrasound transducer can create significant leakage current through the transducer. It happens due to significant voltage stress (dv/dt) across the transducer. To remedy this problem, LC filters are applied in some applications. For some applications such as ultrasound, using a LC filter can deteriorate the performance of the transducer by changing its characteristics and displacing the resonance frequency of the transducer. For such a case a current source converter could be a suitable choice to overcome this problem. In this regard, a current source converter is implemented and applied to excite the high power ultrasound transducer. To control the output current and voltage, a hysteresis control and unipolar modulation are used respectively. The results of this test are explained in chapter 7.

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