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published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 92-96).

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / by Pierre Dersin. / Ph.D.

Approved for public release; distribution is unlimited / This thesis explores Benders decomposition for solving interdiction problems on electric power grids, with applications to analyzing the vulnerability of such grids to terrorist attacks. We refine and extend some existing optimization models and algorithms and demonstrate the value of our techniques using standard reliability test networks from IEEE. Our implementation of Benders decomposition optimally solves any problem instance, in theory. However, run times increase as Benders' cuts are added to the master problem, and this has prompted additional research to increase the decomposition's efficiency. We demonstrate empirical speed ups by dropping slack cuts, solving a relaxed master problem in some iterations, and using integer but not necessarily optimal master-problem solutions. These mixed strategies drastically reduce computation times. For example, in one test case, we reduce the optimality gap, and the time that it takes to achieve this gap, from 16% in 75 hours to 5% in 16 minutes. / FUNDED BY: 2002-GT-R-057 / Lieutenant Commander, United States Navy

M.Ing. / The increased used of non-linear loads within the power system during recent years have resulted in deviations from the perfect sinusoidal voltage and current waveform. This deviation from the perfect sinusoidal waveform can be expressed according to Fourier analysis by a set of co-sinusoidal waveforms having frequencies, which are a multiple of the fundamental frequency, referred to as harmonics. Non-linear loads are generally characterised by harmonic currents. It is therefore often preferred to express the harmonic emission limits in terms of harmonic currents rather than harmonic voltages. In order to translate the harmonic currents into harmonic voltages the harmonic impedance of the power system must be known. The power system's harmonic impedance can be assessed via computational, simulation and measurement techniques. The study will concentrate on the estimation of the harmonic impedance of a 33kV power system by implementing two online frequency domain measurement techniques. Both techniques are applied at the point of delivery of a dominant nonlinear load during normal and energisation load conditions with its power factor correction capacitor bank in and out off service. The estimated harmonic impedance is then compared with the calculated and simulated harmonic impedance.

Orientador: Percival Bueno de Araujo / Banca: Anna Diva Plasencia Lotufo / Banca: Carlos Roberto Mendonça Rocha / Resumo: Com o crescimento do consumo de energia, aliado às restrições ambientais que dificultam a construção de unidades geradoras e/ou de linhas de transmissão, os sistemas elétricos de potência se tornaram cada vez maiores e complexos. Para aumentar sua confiabilidade, diferentes sistemas foram interligados e passaram a trabalhar próximo de seus limites. Este trabalho apresenta estudos referentes à estabilidade a pequenas perturbações de um sistema elétrico de potência multimáquinas. Busca-se fornecer amortecimento às oscilações eletromecânicas de baixa freqüência com a utilização dos dispositivos Estabilizadores de Sistemas de Potência (ESP) e também o dispositivo FACTS Capacitor Série controlado a tiristor (TCSC), equipado com um controlador adicional (POD). Para se conseguir este objetivo é realizada a modelagem do sistema elétrico de potência, seguindo de sua modificação para a inclusão do TCSC. São também modelados os controladores ESP e POD. O ajuste dos parâmetros dos controladores é feito pelo Método da Compensação de Fase e a localização destes dispositivos no sistema elétrico é discutida. A partir dos modelos implementados computacionalmente são realizadas simulações e os resultados obtidos são discutidos e conclusões são apresentadas a respeito da estabilidade às pequenas perturbações do sistema elétrico de potência. / Abstract: As the electrical energy demand increases, associated to environmental restrictions that difficult the construction of new generator unities and/or transmission lines, the electrical power systems are becoming large and complex. To increase the reliability, different systems are interconnected and working close to their limits. This work presents studies referred to small perturbations stability of a multimachine electrical power system. Low frequency electromechanical oscillations are damped using stabilizer devices like Power Systems Stabilizer (PSS) and also FACTS devices as tiristor control series capacitor (TCSC) equipped with an additional controller (POD). This objective is attained modeling the electrical power system and modifying it to include the TCSC. The ESP and POD controllers are also modeled. The controller parameter adjustments are effectuated by the Phase Compensation Method and the positioning of these devices on the electrical power system is discussed. Simulations are realized from the models computationally implemented and the results are discussed emphasizing the stability to small perturbations of the electrical power system. / Mestre

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