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

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

Orientadores: Jose Antenor Pomilio, Simone Buso / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T01:54:00Z (GMT). No. of bitstreams: 1 Machado_RicardoQuadros_D.pdf: 40226020 bytes, checksum: 3daf262738d5d4691a16184af4e741f1 (MD5) Previous issue date: 2004 / Resumo: Esta tese apresenta uma nova forma de conexão direta entre um gerador de indução trifásico e uma rede monofásica, situação típica de ambientes rurais, com possibilidade de geração local de energia. O funcionamento do sistema prevê que seja garantida ao usuário local energia elétrica de boa qualidade. Por energia de boa qualidade entende-se: tensões senoidais e equilibradas, freqüência fixa e boa regulação de tensão. Para a rede monofásica, controla-se o fluxo de potência de modo que o fator de potência resultante seja unitário. A obtenção destes comportamentos se dá com o uso de um conversor CC-CA PWM trifásico, conectado em derivação no ponto de acoplamento das cargas locais. Por este conversor flui uma parcela da potência da carga relacionada com desequilíbrios e distorções. A maior parte da potência ativa não precisa ser processada pelo conversor, o que dá a esta solução um rendimento maior do que se obtém com as alternativas de dupla conversão. O sistema completo de geração distribuída pode receber energia, da geração CA (gerador de indução), de uma fonte CC (células a combustível, painéis fotovoltáicos ou bancos de baterias) conectada ao barramento CC do conversor PWM ou da rede monofásica. No caso de alimentação apenas pela rede, tem-se uma estrutura de conversão mono-trifásica interativa com a linha / Abstract: This thesis proposes a novel solution to connect a three-phase induction generator directly to a single-phase feeder. Typical situations are found in rural areas in which is possible to obtain local power generation. High power quality at the customers such as sinusoidal and balanced voltages, constant frequency and regulated AC voltage, is provided. Additionally, unity power factor on the feeder is obtained. A three-phase shunt voltage source inverter VSI-PWM is connected at the point of common coupling. This converter processes a fraction of the load power that is associated with unbalances, reactive power and harmonics, as well. The efficiency of the partial power processing is higher when compared to double-conversion systems. On the other hand, the system is able to manage a DC source as a fuel cells, a solar panel and batteries. If only the single-phase source is available, the system operates as a single to three-phase line-interactive converter / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

This paper investigates the various parameters that effect voltage stability in sub-transmission power networks. The paper first looks at contributions from equipment: generators, transmission lines, transformers, capacitors, SVCs and STATCOMs. The paper also looks at the effects of loads on voltage stability. Power flow solutions, PV and VQ curves are covered. The study models an existing voltage problem i.e., a long, radial, 115 kV sub-transmission network that serves a 65 MW load. The network model is simulated with the following voltage instability countermeasures: adding a capacitor, adding an SVC, adding a STATCOM, tying to a neighboring transmission system, adding generation and bringing in a new 230 kV source. Then, using the WECC heavy-winter 2012 power flow base case and Siemens PTI software, VQ and PV curves are created for each solution. Finally, the curves are analyzed to determine the best solution.

Thesis (D.Tech (Engineering Electrical)) - Central University of Technology, Free State, 2005 / When Thomas Edison invented his carbon filament lamp in 1879, gas shares fell overnight. A committee of inquiry was set up to examine the future possibilities of the new method of lighting, and had reached the conclusion that electric light in the home was fanciful and absurd. Today electric light burns in practically every house in the civilised world, with many great advances in the production and use of electricity and electric power supplied by various utilities. The objective of the electric utility to deliver pure sinusoidal voltage at fairly constant magnitude throughout their system is complicated by the fact that there are currently loads on the system that produce harmonic voltages, which result in distorted voltages and currents that can adversely impact on the system performance in different ways. Because the numbers of harmonic producing loads have increased over the years, it has become necessary to address their influence, when making any additions or changes to an installation. Quality of supply measurements have long been used to characterise non-linearity on the power system, and have traditionally been measured with expensive portable analysers. A potentially faster, more integrated, and more flexible solution to measure the harmonics with a Supervisory System is accomplished by this research. Any script which aspired to cover in full detail the whole field of a subject so enormous as techniques to measure the quality of electricity supply on a SCADA system, would hardly be practical in less than a few volumes. The pretensions of this research are both modest and of a more immediate value to the reader.

O presente trabalho se propõe a elaborar algoritmos para controle robusto de sistemas de potência. O modelo de sistema de potência multimáquinas utilizado é o de pequenas perturbações, e o objetivo principal é aumentar o amortecimento dos autovalores críticos do sistema, garantindo sua estabilidade e desempenho em diversas condições operativas. Para isso, são utilizadas as Desigualdades Matriciais Lineares (ou LMI\'s), muito adequadas ao tratamento de problemas de controle robusto por sua flexibilidade e possibilidade de agrupamento de diversos requisitos de desempenho. São propostos, entre outros, três algoritmos fundamentais para controle robusto: dois estão relacionados ao controle descentralizado e com controladores de estrutura fixa, o que é muito comum na indústria de potência atualmente, e o outro está relacionado ao controle hierarquizado, que consiste na integração de várias camadas de controle utilizando sinais remotos. Os algoritmos de controle descentralizado propostos são inovadores, pois ambos os métodos permitem a utilização de controladores de estrutura fixa (qualquer que seja ela), e o algoritmo de controle hierarquizado propõe uma estrutura de controle inédita que utiliza aproximações de Padé de diversas ordens para representar os atrasos de comunicação no sistema. Durante a fase de projeto, pode-se escolher o atraso de comunicação, bem como a ordem da aproximação de Padé desejada. Nos algoritmos de controle robusto descentralizado, realizamos uma minimização da norma da matriz de ganhos estáticos do controlador, o que impede que o resultado do algoritmo sejam parâmetros de valores muito elevados e infactíveis para os controladores. A técnica utilizada para os três controladores propostos é o posicionamento de pólos, o que garante que os autovalores do sistema de potência em malha fechada estejam numa dada região do plano complexo, relacionada ao amortecimento mínimo desejado para os autovalores do sistema. Os testes e simulações realizados para validação dos algoritmos de controle robusto foram feitos em ambiente MATLAB, e foram utilizados diversos sistemas de potência: sistema New England de 39 barras e 9 geradores, sistema New England de 69 barras e 16 geradores e sistema New England de 39 barras utilizando modelos de termogeradores. Os testes sugerem que as técnicas propostas são eficazes, pois todas elas garantem boas taxas de amortecimento para os sistemas de potência utilizados. Ao final, simulações não-lineares comprovam a eficácia e a eficiência de um dos controladores projetados para o sistema New England de 39 barras. / The aim of this work is to elaborate robust control algorithms to power systems. The mathematical model employed to describe the multimachine power system is that used in small signal studies, and the main goal is to increase the damping of the critical eigenvalues of the system, guaranteeing its stability and performance in various operating conditions. To do this, we apply the Linear Matrix Inequalities (or simply LMI\'s), suitable to deal with robust control problems due to its flexibility and possibility to group many performance requisites. We propose three robust control algorithms: two of them are related to decentralized control with controllers of predefined structure, which are commonly used in the power industry, and the other one is related to the hierarchized control, which consists on the integration of various controllers layers using remote signals. The decentralized robust control algorithms proposed are novel, because both methods make possible the development of controllers of pre-defined structure, and the hierarchized control algorithm suggests a novel control structure that uses Padé approximations of different orders to represent the communication delays in the system. During the design, we can choose the communication delay, as well as the order of the Padé approximation desired. The decentralized robust control algorithms solve minimization problems over the controller gain matrix norm, which guarantees that the final values of the controller\'s parameters will not be much high and impracticable. The technique employed for the three types of controllers proposed is the pole placement, which ensures that the eigenvalues of the closed loop power system will be in a certain region of the complex plane, related to the minimum damping required for the system. Tests and simulations are done in MATLAB to validate the robust control algorithms, and we apply these algorithms to various power systems: 39-bus 9-machine New England power system, 69-bus 16-machine New England power systems and 39-bus New England power system with thermo machine models. The tests suggest that the proposed techniques work well, once all of them guarantee good damping rates to the power systems considered. To complete the tests round, nonlinear simulations proof the efficiency of the controllers designed for the 39-bus New England power system.

This thesis is devoted to the development of new models for a recently-implemented FACTS (flexible alternating current transmission system) device, the unified power flow controller (UPFC), and the control coordination of power systems with FACTS devices in steady-state operating mode. The key objectives of the research reported in the thesis are, through online control coordination based on the models of power systems having FACTS devices, those of maximising the network operational benefit and restoring system static security following a disturbance or contingency. Based on the novel concept of interpreting the updated voltage solutions at each iteration in the Newton-Raphson (NR) power-flow analysis as dynamic variables, the thesis first develops a procedure for representing the unified power flow controllers (UPFCs) in the steady-state evaluation. Both the shunt converter and series converter control systems of a UPFC are modeled in their dynamical form with the discrete time variable replaced by the NR iterative step in the power-flow analysis. The key advantage of the model developed is that of facilitating the process of UPFC constraint resolution during the NR solution sequence. Any relative priority in control functions pre-set in the UPFC controllers is automatically represented in the power-flow formulation. Although the developed UPFC model based on the dynamic simulation of series and shunt converter controllers is flexible and general, the number of NR iterations required for convergence can be large. Therefore, the model is suitable mainly for power system planning and design studies. For online control coordination, the thesis develops the second UPFC model based on nodal voltages. The model retains all of the flexibility and generality of the dynamic simulation-based approach while the number of iterations required for solution convergence is independent of the UPFC controller dynamic responses. Drawing on the constrained optimisation based on Newton’s method together with the new UPFC model expressed in terms of nodal voltages, a systematic and general method for determining optimal reference inputs to UPFCs in steady-state operation is developed. The method is directly applicable to UPFCs operation with a high-level line optimisation control (LOC) for maximising the network operational benefit. By using a new continuation technique with adaptive parameter, the algorithm for solving the constrained optimisation problem extends substantially the region of convergence achieved with the conventional Newton’s method. Having established the foundation provided by the comprehensive models developed for representing power systems with FACTS devices including the UPFC, the research, in the second part, focuses on real-time control coordination of power system controllers, with the main purpose of restoring power system static security following a disturbance or contingency. At present, as the cost of phasor measurement units (PMUs) and wide-area communication network is on the decrease, the research proposes and develops a new secondary voltage control where voltages at all of the load nodes are directly controlled, using measured voltages.

This thesis is devoted to the development of new approaches for control coordination of PSSs (power system stabilisers) and FACTS (flexible alternating current transmission system) devices for achieving and enhancing small-disturbance stability in multi-machine power systems. The key objectives of the research reported in the thesis are, through optimal control coordination of PSSs and/or FACTS devices, those of maintaining satisfactory power oscillation damping and secure system operation when the power system is subject to persisting disturbances in the form of load demand fluctuations and switching control. Although occurring less frequently, fault disturbances are also considered in the assessment of the control coordination performance. Based on the constrained optimisation method in which the eigenvalue-based objective function is minimised to identify the optimal parameters of power system damping controllers, the thesis first develops a procedure for designing the control coordination of PSSs and FACTS devices controllers. The eigenvalue-eigenvector equations associated with the selected electromechanical modes form a set of equality constraints in the optimisation. The key advance of the procedure is that there is no need for any special software system for eigenvalue calculations, and the use of sparse Jacobian matrix for forming the eigenvalue-eigenvector equations leads to the sparsity formulation which is essential for large power systems. Inequality constraints include those for imposing bounds on the controller parameters. Constraints which guarantee that the modes are distinct ones are derived and incorporated in the control coordination formulation, using the property that eigenvectors associated with distinct modes are linearly independent. The robustness of the controllers is achieved very directly through extending the sets of equality constraints and inequality constraints in relation to selected eigenvalues and eigenvectors associated with the state matrices of power systems with loading conditions and/or network configurations different from that of the base case. On recognising that the fixed-parameter controllers, even when designed with optimal control coordination, have an inherent limitation which precludes optimal system damping for each and every possible system operating condition, the second part of ii the research has a focus on adaptive control techniques and their applications to power system controllers. In this context, the thesis reports the development of a new design procedure for online control coordination which leads to adaptive PSSs and/or supplementary damping controllers (SDCs) of FACTS devices for enhancing the stability of the electromechanical modes in a multi-machine power system. The controller parameters are adaptive to the changes in system operating condition and/or configuration. Central to the design is the use of a neural network synthesised to give in its output layer the optimal controller parameters adaptive to system operating condition and configuration. A novel feature of the neural adaptive controller is that of representing the system configuration by a reduced nodal impedance matrix which is input to the neural network.

Security analysis of a power system requires a process called contingency analysis that analyzes results from all possible single contingencies (i.e. outages) in the system. The process of contingency analysis requires the definition of a parameter that is used to monitor a certain aspect of the system, which is called a performance index. The performance index definitions used traditionally have been highly nonlinear, and the results have not accurately predicted the outcome of the performance index in some cases. These incorrect results are referred to as misrankings since the contingency results are usually placed in order of severity so that the most severe cases are evident. This thesis considers a new definition of contingency ranking using a more linearized definition of the performance index. The construction of both the new, proposed definition and the classic definition both consider the current loading of circuits in the system as compared to their rated values. Specifically, the parameter measured by the proposed definition measures the difference, while the more nonlinear definition uses a ratio of the two quantities, which is then raised to a higher power. A small, four bus test system is used to demonstrate the benefits of the new, more linearized definition. The average percent error for all single line contingencies of the system decreased by over 9.5% using the proposed definition as compared to the previous one. This decrease in error allows this performance index to monitor a similar parameter (comparing current loading and current rating of the lines) and achieve a higher degree of accuracy. Further linearization of this proposed definition also shows a reduction in the average percent error by an additional 22% so that when compared to the original, highly nonlinear definition, the average error is reduced by almost 30%. By linearizing the definition of the performance index, the results are more accurate and misrankings are less likely to occur from the security analysis process.

M. Tech. Electrical Engineering. / Discusses the practical management of electrical networks, no perfect monitoring of an electrical power system state is available, either because it is expensive or technically unfeasible due to the poor quality of the available measurements in the control centre. To have a stable network, the control centre must receive the network information to be able to provide a proper security in unforeseen situation. As a power system network is a complex and a non-linear system, it is important to use more advanced methods for its analysis and control in a real time environment. The aim of this research work is therefore, to apply several state estimation algorithms using artificial intelligence by developing their mathematical models for the purpose of comparing their performances in estimating the state variable of the power system. The three types of state estimation algorithms investigated for this research work are: the Particle Swarm Optimisation (PSO), the Genetic Algorithm (GA) and the Newton method for state estimation (NSE).