Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-25Bitstream added on 2014-06-13T20:09:50Z : No. of bitstreams: 1 furini_ma_me_ilha.pdf: 1020610 bytes, checksum: d3a4a2f6ec4cb8559c7d3d6b770ec955 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O objetivo desta Dissertação de Mestrado é apresentar a possibilidade de fornecer amortecimento às oscilações de baixa freqüência do sistema elétrico de potência através dos dispositivos FACTS (Flexible Alternating Current Transmission System) TCSC (Thyristor Controlled Series Capacitor) e UPFC (Unified Power Flow Controller). Para isso realiza-se o desenvolvimento e implementação do Modelo de Sensibilidade de Potência para sistemas multmáquinas. Na seqüência são introduzidos os dispositivos TCSC e UPFC, bem como os seus controladores. Apresentam-se resultados de acordo com a evolução dos modelos que representam os dispositivos FACTS, ou seja, parte-se de uma compensação fixa, passando para um modelo dinâmico de primeira ordem e por fim, é incluído o controlador POD (Power Oscillation Damping). A utilização de sinais locais e remotos para entrada do controlador POD também é analisada. Além disso são mostrados os resultados obtidos pela técnica clássica de introdução de amortecimento através de sinais suplementares (os estabilizadores de sistemas de potência – PSS: Power System Stabilizers). O projeto dos controladores POD e PSS é baseado no método da compensação de fase, utilizando a teoria de controle clássico. Fatores de participação, autovetores, autovalores e resíduos de funções de transferência são utilizados como índices para examinar a melhor alocação dos controladores POD e PSS no sistema elétrico de potência. / The objective of this work is to present the possibility to provide damping to low frequencies oscillations of the electrical power systems by FACTS devices (Flexible Alternating Current Transmission System): TCSC (Thyristor Controlled Series Capacitor) and UPFC (Unified Power Flow Controller). This is developed and implemented using the Power Sensitivity Model for multimachine systems. Afterwards, the TCSC and UPFC devices are introduced as well as the controllers. Results are presented according to the evolution of the models that represent the FACTS devices, i.e., it starts with a fixed compensation, passing through a first order dynamic model and finally, it is included a POD controller (Power Oscillation Damping). It is also analyzed the inclusion of local and remote signals for the input of the POD controller. Besides, results obtained by classical techniques of introducing damping by supplementary signals (Power Systems Stabilizer – PSS) are shown. The project of POD and PSS controllers are based on the Phase Compensation Method using the classical control theory. Participation Factor like eigenvalues, eigenvectors and transfer function residues are used as index to examine the best allocation of the POD and PSS controllers on the electrical power systems.

Orientador: Percival Bueno de Araujo / Banca: Anna Diva Plasencia Lotufo / Banca: Igor Kopcak / Resumo: Este trabalho apresenta estudos referentes à modelagem do dispositivo FACTS STATCOM para posterior inclusão nas equações do Modelo de Sensibilidade de Potência multimáquinas. O objetivo final da modelagem é o estudo da estabilidade a pequenas perturbações de sistemas elétricos de potência. São considerados dois modelos para o dispositivo: um primeiro modelo permite apenas a compensação de potência reativa, enquanto que num segundo modelo é possível a compensação tanto de potência ativa como de potência reativa. Também são sugeridos controladores para o dispositivo FACTS STATCOM e, neste trabalho, estes controladores são descritos por blocos de primeira ordem. Com o equacionamento do sistema elétrico realizado, seu modelo é implementado computacionalmente para se efetuar simulações para se avaliar a estabilidade a pequenas perturbações. As simulações estão baseadas na análise no domínio do tempo e no domínio da frequência, utilizando os dois modelos desenvolvidos para o STATCOM. A partir dos resultados obtidos pelas simulações, análises são realizadas, e discutidos os principais aspectos referentes à estabilidade a pequenas perturbações de sistemas elétricos de potência / Abstract: This work presents studies referred to the modeling of the FACTS STATCOM device to include in multi-machine Power Sensitivity Model equations. The aim is to study electrical system stability under small perturbations. Two models are considered for the device: the first one allows only the reactive power compensation, while the other one allows the reactive or active compensation. Controllers for the FACTS STATCOM device are also suggested, and in this work they are described by first order blocks. As the electrical system equations are finalized, the model is computationally implemented to effectuate simulations and evaluate the stability under small perturbations. The simulations are based on the time and frequency domain using the two models developed for the FACTS STATCOM device. Considering the results obtained by the simulations the analysis are realized and discussed the principal aspects referred to the electrical Power system stability under small perturbations / Mestre

Orientador: Percival Bueno de Araujo / Banca: Antonio Padilha Feltrin / Banca: Wellington Santos Mota / Resumo: O objetivo desta Dissertação de Mestrado é apresentar a possibilidade de fornecer amortecimento às oscilações de baixa freqüência do sistema elétrico de potência através dos dispositivos FACTS (Flexible Alternating Current Transmission System) TCSC (Thyristor Controlled Series Capacitor) e UPFC (Unified Power Flow Controller). Para isso realiza-se o desenvolvimento e implementação do Modelo de Sensibilidade de Potência para sistemas multmáquinas. Na seqüência são introduzidos os dispositivos TCSC e UPFC, bem como os seus controladores. Apresentam-se resultados de acordo com a evolução dos modelos que representam os dispositivos FACTS, ou seja, parte-se de uma compensação fixa, passando para um modelo dinâmico de primeira ordem e por fim, é incluído o controlador POD (Power Oscillation Damping). A utilização de sinais locais e remotos para entrada do controlador POD também é analisada. Além disso são mostrados os resultados obtidos pela técnica clássica de introdução de amortecimento através de sinais suplementares (os estabilizadores de sistemas de potência - PSS: Power System Stabilizers). O projeto dos controladores POD e PSS é baseado no método da compensação de fase, utilizando a teoria de controle clássico. Fatores de participação, autovetores, autovalores e resíduos de funções de transferência são utilizados como índices para examinar a melhor alocação dos controladores POD e PSS no sistema elétrico de potência. / Abstract: The objective of this work is to present the possibility to provide damping to low frequencies oscillations of the electrical power systems by FACTS devices (Flexible Alternating Current Transmission System): TCSC (Thyristor Controlled Series Capacitor) and UPFC (Unified Power Flow Controller). This is developed and implemented using the Power Sensitivity Model for multimachine systems. Afterwards, the TCSC and UPFC devices are introduced as well as the controllers. Results are presented according to the evolution of the models that represent the FACTS devices, i.e., it starts with a fixed compensation, passing through a first order dynamic model and finally, it is included a POD controller (Power Oscillation Damping). It is also analyzed the inclusion of local and remote signals for the input of the POD controller. Besides, results obtained by classical techniques of introducing damping by supplementary signals (Power Systems Stabilizer - PSS) are shown. The project of POD and PSS controllers are based on the Phase Compensation Method using the classical control theory. Participation Factor like eigenvalues, eigenvectors and transfer function residues are used as index to examine the best allocation of the POD and PSS controllers on the electrical power systems. / Mestre

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The purpose of this work is to present an active and reactive power flow controller applied to inverter paralelism with the stiff AC system. An additional loop is implemented into a conventional control loop based on the characteristic curves of active power versus frequency and reactive power versus voltage. This loop uses the active power variation as feedback to generate the load angle of the voltage reference of the inverter, when it is connected in parallel with the electric network. As a consequence, the active and reactive transitory power oscillations are atenuated, without producing undesirable colateral effects as significative voltage and reactive power variations presented in the utilization of PSS (Power System Stabilizer), another technique used to improve the system damping, [Martins, M. P., 2004]. A dynamic model of the system based on the small signal analysis is presented. The root locus graphics, showing the system poles under parametric variations are also presented, allowing the analysis of the system stability. The simulation results and the experimental ones using a laboratory prototype with and without the additional loop are showed, which validate the obtained small signal model. / Este trabalho apresenta um controlador de fluxos de potência ativa e reativa aplicado ao paralelismo de um inversor com a rede elétrica. Uma malha adicional de controle é inserida a um controlador convencional, o qual é baseado nas curvas características de potência ativa versus freqüência e potência reativa versus tensão. Essa malha utiliza a realimentação da própria variação da potência ativa para a geração do ângulo de carga da tensão de referência do inversor, quando o mesmo é conectado em paralelo com a rede elétrica. Como resultado as oscilações transitórias das potências ativa e reativa são melhor atenuadas, sem produzir efeitos colaterais indesejáveis tais como as variações de tensão e potência reativa presentes na utilização do PSS (Power System Stabilizer Estabilizador de Sistemas de Potência), outra técnica usada para melhorar o amortecimento do sistema, [Martins, M. P., 2004]. Um modelo dinâmico do sistema baseado na análise para pequenos sinais é apresentado. Gráficos do lugar das raízes, mostrando os pólos do sistema diante de variações paramétricas também são apresentados, permitindo a análise de estabilidade do sistema. Resultados de simulação e resultados experimentais utilizando-se um protótipo de laboratório, com e sem a malha de realimentação adicional são mostrados, os quais validam o modelo para pequenos sinais obtido. / Doutor em Ciências

Orientadores: Vivaldo Fernando da Costa, Luiz Carlos Pereira da Silva / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-08T18:53:13Z (GMT). No. of bitstreams: 1 Kopcak_Igor_D.pdf: 1188245 bytes, checksum: e1912d198506d0fd20e05f9202486e80 (MD5) Previous issue date: 2007 / Resumo: O estressamento dos sistemas elétricos tem voltado o interesse de engenheiros e pesquisadores para a definição e avaliação de margens de segurança relacionadas a critérios dinâmicos. Neste trabalho é proposta uma ferramenta que permite a avaliação de quatro diferentes critérios de estabilidade: margem de amortecimento, margem oscilatória, margem de estabilidade de tensão e o ponto de máximo carregamento. A metodologia baseia-se em um fluxo de carga expandido que incorpora as características de regime permanente de dispositivos dinâmicos, fornecendo pontos de equilíbrio precisos e mais condizentes com a resposta "real" dos sistemas elétricos quando sujeitos a perturbações. As margens são calculadas através da análise modal aplicada aos pontos de equilíbrio de curvas PV. Além disso, estudos preliminares são conduzidos objetivando a expansão da análise modal estática, fornecendo fatores de participação para todas as barras do sistema, dos pontos de vista das potências ativa e reativa. Portanto, a plataforma não só permite a identificação dos pontos onde ocorreria o colapso do sistema, como fornece a indicação das medidas corretivas mais efetivas para evitar problemas de instabilidade / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

Power systems have been historically designed at a time when the production was<p>centralized and the electricity had to be transmitted to the loads from the closest power<p>plant. Nowadays, there is an increasing integration of decentralized and intermittent pro-<p>duction. Moreover, the energy market coupling has enabled the transfer of electric power<p>for economical purposes. Also, former isolated power systems are now interconnected for<p>reliability and financial reasons.<p>All of these changes make difficult to predict the future behavior of the grid. Studies<p>are done in order to plan for the future needs of the system. However, building new in-<p>frastructures takes time and it is expected that these needs will not be completely fulfilled<p>in all the parts of the grid. Therefore, transmission of active power could be limited by<p>the existing infrastructure. For example, the presence of inter-area oscillations is often<p>the limiting factor when a high active power is transmitted on a long transmission line<p>between two groups of generators. Since higher levels of active power are exchanged on<p>longer distances, problems of inter-area oscillations may arise in power systems previously<p>not affected by this phenomenon.<p>In this work, a measurement-based approach, able to predict in the short-term the<p>future behavior of oscillations, is presented. This approach is complementary to the<p>long-term planning of the grid.<p>The mandatory first step towards a measurement-based approach is to have the ability<p>to extract useful information among a huge quantity of data. To face this issue, some<p>comparisons of data mining algorithms are performed. The proposed method combines<p>two decision tree algorithms to obtain both prediction accuracy and comprehensibility.<p>The second required step for building a measurement-based model is to take into<p>account the limitations of the measurements. Two types of wide area measurements are<p>used, synchronized measurements from PMUs and traditional unsynchronized data from<p>the SCADA/EMS system. Oscillation monitoring using PMUs is especially of interest<p>and an approach is presented to post-process damping estimates. This post-processing<p>method consists in a noise reduction technique followed by a damping change detection<p>algorithm.<p>Finally, the method, combining these two steps, is implemented to analyze the Con-<p>tinental European grid. This implementation takes place in the context of the European<p>project Twenties. The results, using several months of measurements, are described in<p>detail before being discussed. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Small signal oscillation has been always a major concern in the operation of power systems. In a generator, the electromechanical coupling between the rotor and the rest of the system causes it to behave in a manner similar to a spring mass damper system, which exhibits an oscillatory behaviour around the equilibrium state, following any disturbance, such as sudden change in loads, fluctuations in the output of turbine and faults etc. The use of fast acting high gain AVRs and evolution of large interconnected power systems with transfer of bulk power across weak transmission links have further aggravated the problem of these low frequency oscillations. Small oscillations in the range of about 0.1Hz to 3.5Hz can persist for long periods, limiting the power transfer capability of the transmission lines. Power System Stabilizers (PSS’s) were developed as auxiliary controllers on the generators excitation system to produce additional damping by modulating the generator excitation voltage. Designing effective PSS for all operating conditions specially in large interconnected power systems still remains a difficult and challenging task. The conventionally designed Power System Stabilizer (CPSS) is the most cost-effective electromechanical damping controller till date. However, continual changes in the operating condition and network parameters in large systems result in corresponding large changes in system dynamics. This constantly changing nature of power system makes the design of CPSS a difficult task. The design and tuning of PSS for robust operation is a laborious process. The existing PSS design techniques require considerable expertise, the complete system information and extensive eigenvalue calculations which increases the computational burden as the system size increases. This thesis proposes a method for designing robust power system damping controllers that ensures a minimum robustness under model uncertainties. The minimum performance required for the PSS is set a priori and accomplished over a range of operating conditions. A generalized robust controller design methodology has been first implemented on a Single Machine Infinite Bus (SMIB) power system model. The robust controller places the closed loop rotor modes of the system to the desire location while keeping the electrical modes intact. Unlike conventional lead/lag PSS design, the proposed PSS design is based on pole assignment technique which takes into account of various model uncertainties. For the proposed stabilizer design in a multi-machine systems a new decentralized method has been used which requires system data only upto secondary bus of the unit transformer in a generating station. The proposed robust controller design based on modified Nevanlinna-Pick theory has been designed and tested extensively on SMIB and multi-machine systems to establish the efficacy of the controller in damping small signal oscillations. The thesis is organized in four chapters as follows. The first chapter discusses the basic concepts related to the rotor angle stability in power system. The conventional and other methods of countering this instability by power system stabilizers have been described. The relative merits of the various stabilization techniques have been discussed. The scope of present work, i.e design of decentralized robust power system controllers has been defined. In second chapter a modified robust power system stabilizer for SMIB system is developed. It has been shown that under specific conditions the modified Nevanlinna-Pick theory can also be applied for designing damping controllers in system with lightly damped rotor modes. Third chapter proposes a decentralized approach based on modified Nevanlinna-Pick theory for designing a power system stabilizer for interconnected power systems. The performance of the controller which is not based on external system information has been investigated on three widely used multi-machine test systems to established its efficacy in damping out low frequency oscillations. The fourth chapter gives a brief summary of the work done and also includes a section on the scope of future work relating to design of power system stabilizers.

This Thesis addressed the challenge of ensuring balanced currents in the phases of a multi-kW, interleaved dc-dc converter by means of closed-loop digital control. The Thesis examines uniformly-sampled, valley-current, peak-current and average-current control for a dual interleaved boost converter with inter-phase transformer which might form part of the power train of an electric vehicle. Also, an enhancement of the average-current control is investigated in which the transistor duty-ratio is updated more rapidly, which allows an improvement of approximately ten times in the response speed of the system. Based on the theoretical analysis, the average-current control methodology was determined to be the most suitable technique for this type of converter as it ensures well-balanced phase currents over a wide range. To provide a basis for control system analysis and design for interleaved converters, a modelling methodology is developed based on a combination of multi-rate data-sampled theory and a small-signal averaged converter model. The model is shown to represent accurately the interaction between the interleaved phases, revealing a reduced stability range compared with a non-interleaved converter. The modelling and control methods are validated using switched and average value simulations obtained with the SABER software and by experimental results from a 25 kW, 30 kHz converter prototype. The control techniques were implemented on a Texas Instruments TMS320F28335 digital signal controller.

No description available.

With ambitions of reducing the environmental pollution, power systems integrate larger shares of Renewable Energy Sources (RES) to phase out conventional thermal and nuclear generators. Since RES (such as wind and solar power) are connected to the grid through power electronics devices, they do not inherently contribute to system inertia. With decreasing inertia, the Instantaneous Frequency Deviation (IFD), which follows a power unbalance, is significantly impacted. Frequency Containment Reserves (FCR) are designed to provide a fast dynamic response, counteract power imbalances and stabilize the frequency within a short time interval. Besides inertia, the significant factors affecting frequency behavior are the available amount of FCR and the capability of their fast and stable response. System operators define the list of requirements that a generating unit has to satisfy to participate in FCR. Generators, which are the major part of FCR, have different governors and turbines properties. This study assesses the dynamical performance of typical generators in both open-loop testing and closed-loop varying inertia systems. The goal is to evaluate if specific FCR requirements present a sufficient condition for the desired response, and which governor properties are capable of satisfying them. As an additional, and sometimes necessary, support to FCR, HVDC interconnections are utilized in the form of Emergency Power Control (EPC). This thesis investigates which of the EPC methods performs appropriately in terms of IFD improvement, closed-loop stability, and power and energy provided. The analysis is a continuation from the previous investigation on FCR, and mainly compare two EPC methods related to Nordic Power System (NPS) test case: ramp/step method which is currently implemented in the NPS, and droop frequency-based EPC, proposed by this study for the future operation in the NPS. Apart from ensuring a proper system frequency response, the influence of implemented HVDC supplementary active power control is analyzed to rotor angle stability. In further, this thesis presents a comprehensive analysis of the impact that proposed HVDC supplementary power control has on the linearized dynamics of power systems. By building a generic system, this analytical study is the first of its kind that includes both higher order generator dynamics, and local angle/frequency input of the controller. The methodological approach here analytically formulates the impact the HVDC supplementary control has mainly on the generator synchronizing and damping torque components. The positive impact of the droop frequency-based HVDC power support is highlighted using both single and multi-machine systems. In that way, the implementation of desired droop frequency-based HVDC control to mainly improve system frequency is motivated furthermore. It shows that a proper HVDC supplementary control may impose the various positive impacts for future variable and low inertia scenarios, and ensure a proper power system sustainability. / <p>QC 20200907</p> / multiDC - Advanced Control and Optimization Methods for AC and HVDC Grids