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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Damping Interarea Oscillations in Power Systems with DFIG

Thapa, Ravi Chandra January 2011 (has links)
With rapid depletion of fossil fuels and increasing environmental concerns, the trend to capture renewable energy, especially through wind energy resources, is increasing. The doubly fed induction generator (DFIG) is the most widely used generator for wind energy conversion because of its various advantages over other types of generators. In a DFIG, the rotor is fed through back to back converters via slip rings. The converters enable the generation control. This control property can be used to support reliable operation of a grid network system. Interarea oscillation has been a major factor in limiting power transfers in interconnected power systems. Poorly damped modes can trigger oscillatory instability, potentially leading to cascading blackouts in such systems. We consider a two-area system where DFIG based wind generation is integrated with conventional synchronous generators. A simple controller is proposed for the DFIG to improve damping of interarca oscillations. To support the proposition, case studies are conducted in Matlab/Simulink. The effectiveness of the proposed controller is then analyzed by eigenvalue analysis and verified with time domain simulation results. The results show that a properly tuned controller can increase the damping of dominant oscillatory mode by nearly 5% while improving the area transfer by about 200 MW of wind power. The results further show that with the proposed control strategy, damping of dominant oscillatory mode increased by more than 10%. / North Dakota State University. Graduate School / North Dakota State University. Department of Electrical and Computer Engineering
42

Estimation of Synchronous Generator Parameters using Time-domain Responses

Galbraith, A. S. G. 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Power system stability simulations are of growing importance for studying the operational integrity of modern power systems, especially in developing economies where generating and transmission capacity lead the demand by relatively small margins. The relevant model topologies, i.e. for synchronous generators, automatic voltage regulators (AVR) and governor control systems, and the simulation software tools are well established. The MATLAB® Power System Blockset provides engineers with a versatile power system stability simulation environment, particularly where the focus is on individual units or small systems. In comparison with dedicated power system simulation tools such as DIgSILENT®, the MATLAB® environment features a superior set of advanced data processing and data analysis features. This includes features such as optimisation and parameter estimation functions. The main aim of this project is to make use of the MATLAB® package in a bid to test an alternative platform with which to estimate the synchronous machine parameters. Conditioning of field data can delay the process considerably, thus the secondary task of this thesis is to solve this issue by ensuring that only one platform is needed for the entire process starting in the field and ending in the modelling and parameter estimation environment within MATLAB®. In closing, the following points summarise the essential aims of this project: • An application using MATLAB® Script must be created that is responsible for importing and processing the data, so it is suitable for analysis purposes. The processing could include cropping, scaling and filtering of data. • Once the data has been imported it must be used with appropriate models to estimate for machine parameters. This will require the use of the Power Systems Blockset. The actual estimation process also requires the creation of an effective cost function, thus a number of different scenarios will have to be investigated before a solution can be found.
43

Coordination of reactive power scheduling in a multi-area power system operated by independent utilities

Phulpin, Yannick Dominique 22 October 2009 (has links)
This thesis addresses the problem of reactive power scheduling in a power system with several areas controlled by independent transmission system operators (TSOs). To design a fair method for optimizing the control settings in the interconnected multi-TSO system, two types of schemes are developed. First, a centralized multi-TSO optimization scheme is introduced, and it is shown that this scheme has some properties of fairness in the economic sense. Second, the problem is addressed through a decentralized optimization scheme with no information exchange between the TSOs. In this framework, each TSO assumes an external network equivalent in place of its neighboring TSOs and optimizes the objective function corresponding to its own control area regardless of the impact that its choice may have on the other TSOs. The thesis presents simulation results obtained with the IEEE 39 bus system and IEEE 118 bus systems partitioned between three TSOs. It also presents some results for a UCTE-like 4141 bus system with seven TSOs. The decentralized control scheme is applied to both time-invariant and time-varying power systems. Nearly optimal performance is obtained in those contexts.
44

Integrated control of wind farms, facts devices and the power network using neural networks and adaptive critic designs

Qiao, Wei. January 2008 (has links)
Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Ronald G. Harley; Committee Member: David G. Taylor; Committee Member: Deepakraj M. Divan; Committee Member: Ganesh Kumar Venayagamoorthy; Committee Member: Thomas G. Habetler. Part of the SMARTech Electronic Thesis and Dissertation Collection.
45

On-line, remote and automatic switching of consumers' connections for optimal performance of a distribution feeder.

Popoola, Olawale. January 2008 (has links)
M. Tech. Electrical Engineering / Investigates the growing consensus that significant advantages can be achieved through the automation of distribution feeder switches In order to ensure quality and reliability of supply to single phase consumers by electrical utilities, a need arose to minimize unbalance. it is then postulated the unbalance due to uneven distribution of single-phase loads at the secondary side of the distribution network can be minimized using automatic and remote sensing technology.
46

Feeder reconfiguration scheme with integration of renewable energy sources using a Particle Swarm Optimisation method

Noudjiep Djiepkop, Giresse Franck January 2018 (has links)
Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018. / A smart grid is an intelligent power delivery system integrating traditional and advanced control, monitoring, and protection systems for enhanced reliability, improved efficiency, and quality of supply. To achieve a smart grid, technical challenges such as voltage instability; power loss; and unscheduled power interruptions should be mitigated. Therefore, future smart grids will require intelligent solutions at transmission and distribution levels, and optimal placement & sizing of grid components for optimal steady state and dynamic operation of the power systems. At distribution levels, feeder reconfiguration and Distributed Generation (DG) can be used to improve the distribution network performance. Feeder reconfiguration consists of readjusting the topology of the primary distribution network by remote control of the tie and sectionalizing switches under normal and abnormal conditions. Its main applications include service restoration after a power outage, load balancing by relieving overloads from some feeders to adjacent feeders, and power loss minimisation for better efficiency. On the other hand, the DG placement problem entails finding the optimal location and size of the DG for integration in a distribution network to boost the network performance. This research aims to develop Particle Swarm Optimization (PSO) algorithms to solve the distribution network feeder reconfiguration and DG placement & sizing problems. Initially, the feeder reconfiguration problem is treated as a single-objective optimisation problem (real power loss minimisation) and then converted into a multi-objective optimisation problem (real power loss minimisation and load balancing). Similarly, the DG placement problem is treated as a single-objective problem (real power loss minimisation) and then converted into a multi-objective optimisation problem (real power loss minimisation, voltage deviation minimisation, Voltage stability Index maximisation). The developed PSO algorithms are implemented and tested for the 16-bus, the 33-bus, and the 69-bus IEEE distribution systems. Additionally, a parallel computing method is developed to study the operation of a distribution network with a feeder reconfiguration scheme under dynamic loading conditions.
47

Metodologia de projeto de controladores de amortecimento para posicionamento parcial de polos de modelos multimáquinas de sistemas de potência

Rossi, Carlos Henrique 10 August 2012 (has links)
Este trabalho propõe uma metodologia de projeto de controladores para o amortecimento de oscilações eletromecânicas de baixa frequência em sistemas elétricos de potência. O problema de controle é estruturado na forma de desigualdades matriciais, as quais permitem a busca por uma solução numérica para o problema de controle. Os controladores de amortecimento baseados na realimentação dinâmica de saída, gerados por metodologias de projeto na forma de desigualdades matriciais, geralmente apresentam ordem elevada. Além disso, projetos considerando sistemas de potência de médio porte demandam elevado tempo computacional. Nesse contexto, o presente trabalho propõe uma metodologia de projeto capaz de gerar controladores de ordem reduzida. A metodologia proposta adota um índice de desempenho que possibilita a redução do tempo computacional demandado no projeto. O índice de desempenho adotado para o sistema em malha fechada é a energia do sinal de saída do sistema. Essa energia corresponde à integral do valor quadrático do sinal adotado como saída do sistema. A metodologia proposta permite especificar um índice de desempenho apenas para aos modos de resposta de interesse do sistema, contornando as limitações das metodologias baseadas em posicionamento regional de polos. A relação entre o valor da energia do sinal de saída do sistema e seu fator de amortecimento é estabelecida por meio de uma equação algébrica. Neste trabalho, a metodologia é aplicada na geração de controladores de amortecimento para geradores síncronos. Entretanto, o procedimento proposto é genérico o suficiente para ser aplicado a outros tipos de geradores (gerador de indução empregado em unidades eólicas, por exemplo), a dispositivos FACTS (do Inglês, Flexible AC Transmission System) assim como a outros tipos de sistemas dinâmicos. A metodologia gerou um controlador eficaz para um caso onde a formulação baseada no tradicional posicionamento regional de polos é incapaz de gerar um controlador que assegure uma boa margem de estabilidade para o modo de resposta de interesse. / This work proposes a methodology for the design of controller to damp low frequency electromechanical oscillations in power systems. The control problem is structured in the form of matrix inequalities, which allows obtaining a numerical solution for the control problem. The damping controllers based on dynamic output feedback, generated by design methodologies in the form of matrix inequalities, usually presents high order. In addition, the design of this controller, considering large power systems, usually requires excessive computational effort. In this context, this work proposes a methodology for the design of reduced order controllers. The proposed methodology employs a performance index that is less costly in terms of computational effort when compared to the one with the traditional regional pole placement. The adopted performance index for the closed loop system is the energy of the system output. This energy corresponds to the integral of the signal squared regarding the system output. The proposed methodology allows specifying a performance index only for the response modes of interest, overcoming the limitations of the methodologies based on regional pole placement. The relation between the energy value of the output signal of the system and its damping factor is established by means of an algebraic equation. In this paper, the methodology is applied to generate damping controller for synchronous generators. However, the proposed procedure is general enough to be applied to other kinds of power plants (wind generation, for example), to FACTS devices, as well as to other dynamic systems. The methodology has generated an effective controller for a case where the formulation based on the regional pole placement is unable to generate a controller which assures a good stability margin for the response mode of interest.
48

Metodologia de projeto de controladores de amortecimento para posicionamento parcial de polos de modelos multimáquinas de sistemas de potência

Rossi, Carlos Henrique 10 August 2012 (has links)
Este trabalho propõe uma metodologia de projeto de controladores para o amortecimento de oscilações eletromecânicas de baixa frequência em sistemas elétricos de potência. O problema de controle é estruturado na forma de desigualdades matriciais, as quais permitem a busca por uma solução numérica para o problema de controle. Os controladores de amortecimento baseados na realimentação dinâmica de saída, gerados por metodologias de projeto na forma de desigualdades matriciais, geralmente apresentam ordem elevada. Além disso, projetos considerando sistemas de potência de médio porte demandam elevado tempo computacional. Nesse contexto, o presente trabalho propõe uma metodologia de projeto capaz de gerar controladores de ordem reduzida. A metodologia proposta adota um índice de desempenho que possibilita a redução do tempo computacional demandado no projeto. O índice de desempenho adotado para o sistema em malha fechada é a energia do sinal de saída do sistema. Essa energia corresponde à integral do valor quadrático do sinal adotado como saída do sistema. A metodologia proposta permite especificar um índice de desempenho apenas para aos modos de resposta de interesse do sistema, contornando as limitações das metodologias baseadas em posicionamento regional de polos. A relação entre o valor da energia do sinal de saída do sistema e seu fator de amortecimento é estabelecida por meio de uma equação algébrica. Neste trabalho, a metodologia é aplicada na geração de controladores de amortecimento para geradores síncronos. Entretanto, o procedimento proposto é genérico o suficiente para ser aplicado a outros tipos de geradores (gerador de indução empregado em unidades eólicas, por exemplo), a dispositivos FACTS (do Inglês, Flexible AC Transmission System) assim como a outros tipos de sistemas dinâmicos. A metodologia gerou um controlador eficaz para um caso onde a formulação baseada no tradicional posicionamento regional de polos é incapaz de gerar um controlador que assegure uma boa margem de estabilidade para o modo de resposta de interesse. / This work proposes a methodology for the design of controller to damp low frequency electromechanical oscillations in power systems. The control problem is structured in the form of matrix inequalities, which allows obtaining a numerical solution for the control problem. The damping controllers based on dynamic output feedback, generated by design methodologies in the form of matrix inequalities, usually presents high order. In addition, the design of this controller, considering large power systems, usually requires excessive computational effort. In this context, this work proposes a methodology for the design of reduced order controllers. The proposed methodology employs a performance index that is less costly in terms of computational effort when compared to the one with the traditional regional pole placement. The adopted performance index for the closed loop system is the energy of the system output. This energy corresponds to the integral of the signal squared regarding the system output. The proposed methodology allows specifying a performance index only for the response modes of interest, overcoming the limitations of the methodologies based on regional pole placement. The relation between the energy value of the output signal of the system and its damping factor is established by means of an algebraic equation. In this paper, the methodology is applied to generate damping controller for synchronous generators. However, the proposed procedure is general enough to be applied to other kinds of power plants (wind generation, for example), to FACTS devices, as well as to other dynamic systems. The methodology has generated an effective controller for a case where the formulation based on the regional pole placement is unable to generate a controller which assures a good stability margin for the response mode of interest.
49

Estudo para classificação de contingencias sob o aspecto da estabilidade de tensão / Contingency ranking for voltage stability

Dester, Mauricio 22 August 2006 (has links)
Orientador: Carlos Alberto de Castro Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-07T06:07:11Z (GMT). No. of bitstreams: 1 Dester_Mauricio_M.pdf: 1510731 bytes, checksum: 2d78f28f0e947ab2f8b733433312aa84 (MD5) Previous issue date: 2006 / Resumo: O objetivo deste trabalho é propor um método que permita, de forma rápida e segura, estabelecer uma lista de contingências ordenada por severidade considerando a óptica da estabilidade de tensão. Em linhas gerais, o procedimento consiste em obter o estado da rede após a simulação de uma determinada contingência e calcular o índice de performance correspondente à mesma. Estes passos devem ser repetidos para todos os ramos da rede. Ao final tem-se um índice associado a cada contingência. Para a obtenção da lista ordenada por severidade, classificam-se as contingências considerando como fator de ordenação o valor do índice de performance calculado para cada uma delas. De posse desta lista, pode-se lançar mão de ferramentas que permitam uma análise mais detalhada para o grupo contingências com maior severidade e a tomada de ações no sentido de minimizar as conseqüências causadas por estas contingências. Este método pode ser utilizado como suporte à operação em tempo real, pois permite a seleção das contingências mais severas, de forma rápida, para então posteriormente realizar uma análise mais detalhada das mesmas. Não há, portanto, a necessidade da análise detalhada de todas as contingências da rede, o que permite uma economia de tempo, esforço humano e computacional, recursos estes de fundamental importância considerando a operação em tempo real / Abstract: The aim of this work is to propose a fast and reliable method to rank a list of contingencies ordered by severity under the voltage stability point of view. The basic steps of the method consist of computing the system's post-contingency state and computing the respective performance index. These steps must be repeted for contingencies associated to all system branches. So an ordered contingency list is built considering the performance index of each contingency as a merit factor. With this list it is possible to pick the most severe contingencies and submit them to conventional tools that allow a more complete analysis and appropriate decisions to avoid operating system in insecure conditions if one of the severe contingencies occurs. It is possible to use this method as a real time tool due to its efficiency. Little computational effort is made to get the ordered contingency list and it is possible to focus the human and computational effort on the most severe contingencies. The real time operation requires efficient decision-making procedures and this method brings up the possibility of saving time since it is no longer necessary to analize all system contingencies to find out the most severe one. It suffices to analize the top-ranked contingencies captured by the proposed method / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica
50

Alocação otima de reguladores de tensão em redes de distribuição de energia eletrica / Optimal placement of voltage regulators in distribution systems

Pereira, Carlos Alberto Nogueira 13 August 2018 (has links)
Orientador: Carlos Alberto de Castro Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T12:20:41Z (GMT). No. of bitstreams: 1 Pereira_CarlosAlbertoNogueira_M.pdf: 1167781 bytes, checksum: 59548f165acd2e595bebd984ef043c53 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho apresenta-se o desenvolvimento de um método heurístico para o dimensionamento e alocação de reguladores de tensão ao longo dos alimentadores primários de sistemas radiais de distribuição de energia elétrica, objetivando a melhoria do perfil de tensão, a minimização das perdas de potência ativa nos trechos de rede e a minimização dos custos de instalação dos equipamentos. O algoritmo desenvolvido para alocação ótima de reguladores de tensão em redes de distribuição radiais é composto por duas etapas. A primeira etapa visa a seleção, a instalação e o ajuste do tap dos reguladores de tensão nas barras que proporcionam melhores condições técnicas (menor desvio de tensão e redução das perdas de potência ativa). Na segunda etapa, procura-se reduzir o número de reguladores de tensão inicialmente alocados, movendo-os adequadamente quando possível até que a melhor condição econômica (mínimos custos de instalação e manutenção) seja obtida. Em conjunto com o desenvolvimento do trabalho, foi elaborado um programa computacional com a finalidade de verificar a funcionalidade e eficiência do método. Foram realizadas simulações em sistemas de distribuição teóricos e reais, sob condições de carga leve e pesada, obtendo-se rapidez e eficiência durante a execução do algoritmo proposto e resultados confiáveis. São apresentados os resultados de simulações para um sistema de 70 barras, e estes são comparados com um método já proposto na literatura. São também apresentados resultados de simulações para redes de distribuição reais de 136 barras, 202 barras e 400 barras / Abstract: This dissertation reports the development of a heuristic method for sizing and allocating voltage regulators in distribution radial primary feeders. The goals are to improve the voltage profile, to minimize the real power losses and to minimize equipment installation and maintenance costs. The proposed algorithm for the optimal allocation of voltage regulators in radial distribution networks comprises two steps. The first step aims to select, install and set the tap of voltage regulators at buses that result in the best technical conditions (smallest voltage deviation and real power losses reduction). In the second step, an attempt is made to reduce the number of voltage regulators initially allocated in the first step, by moving them appropriately until the best economical condition (minimum installation and maintenance costs) is reached. A computational program was implemented to evaluate the efficiency of the proposed method. Simulations have been carried out for theoretical and realistic distribution systems, for light and heavy load conditions, and the method showed to be fast and efficient, providing reliable results. Simulations results for a 70-bus distribution system and the comparison with those provided by another method proposed in the literature are shown. Also, simulation results are shown for realistic 136-, 202-, and 400-bus realistic systems / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

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