No description available.

No description available.

No description available.

No description available.

No description available.

This research work is devoted to the design, development and implementation of a Current Source Converter (CSC) based Active Power Filter (APF) for Medium Voltage (MV) applications. A new approach has been proposed to the design of the CSC based APF for reducing the converter kVA rating considerably. This design approach is called the Selective Harmonic Amplification Method (SHAM), and is based on the amplification of some selected harmoniccurrent components of the CSC by the input filter, and the CSC control system, which is specifically designed for this purpose. The proposed SHAM has been implemented on the first industrial CSC based APF for the elimination of 11th and 13th current harmonics of 12-pulse rectifiers fed from Medium Voltage (MV) underground cables in order to comply with IEEE Std. 519-1992. 450 kVA rated APF with only 205 kVA CSC rating has been connected to the MV bus via a coupling transformer of 600kVA, 34.5/1.1 kV. The power stage of the CSC based APF is composed of water-cooled high voltage IGBT and diode modules. Reference currents to be generated by the CSC are obtained by the use of a selective harmonic extraction method, by mploying synchronously rotating reference frames for each selected harmonic component. An Active damping method is also used to suppress the oscillations around the natural frequency of the input filter, excluding the harmonic components to be eliminated by APF. Simulation and field test results have shown that SHAM can successfully be applied to a CSC based APF for reduction of converter kVA rating, thus making it a cost- competitive alternative to voltage source converter based APFs traditionally used in industry applications.

The present doctoral thesis concentrate efforts in the consolidation of the benefits introduced by the plug-in repetitive action in the performance of pulse-width modulated voltage source inverters. The work is focused in the application of these inverters in double conversion uninterruptible power systems to comply the most demanding requirements of the international standards. The use of the plug-in repetitive action, in this application, is suitable because the inverter demands the advantageous characteristics of cyclic disturbance rejection by it introduced. In this scenario, this thesis is divided in two parts. The first one comprise the proposition of algorithms to solve some disadvantageous characteristics of the repetitive actions, such as the reduced stability margin and the unsuitable performance under reference signals with variable frequency. The second one, by the other hand, comprise the questions related to the design of these repetitive action controllers. It is included the proposition of a methodology that link the design of these controllers with the output filter of a double conversion UPS. Finally, it is worth to emphasize that are presented simulation and experimental results, obtained on a 1kVA laboratory prototype, that validate the proposes carried out. / A presente tese de doutorado concentra esforços na consolidação dos benefícios introduzidos pela ação de controle repetitiva auxiliar no desempenho de inversores de tensão modulados por largura de pulso. O trabalho está focado na aplicação destes inversores em fontes ininterruptas de energia (UPS) de dupla conversão, com o intuito de atender aos mais exigentes requisitos de desempenho das normas internacionais. A utilização da ação de controle repetitiva auxiliar, nesta aplicação, é adequada porque o inversor demanda as características vantajosas de rejeição de distúrbios cíclicos por ela introduzida. Neste contexto, esta tese se divide em duas partes. A primeira parte compreende na proposição de algoritmos para solucionar algumas das características desvantajosas dos controladores de ação repetitiva, tal como a reduzida margem de estabilidade e o desempenho não satisfatório para sinais de referências de freqüência variável. A segunda parte, por outro lado, trata das questões relacionadas ao projeto destes controladores de ação repetitiva, sendo proposta uma metodologia que integra o projeto destes controladores ao filtro de saída de uma UPS de dupla conversão. Por fim, destaca-se que são apresentados resultados de simulação e experimentais, obtidos em um protótipo de 1kVA, para validar as propostas deste trabalho.

Experimental research on high-power converters, particularly in an academic environment, faces severe infrastructural constraints. Usually, power source and loads of required ratings are not available. Further, more importantly, the energy consumption is huge. One possibility is to establish an experimental research platform, comprising of a network of high-power converters, through which power is circulated and which draws only the losses from the mains. This work deals with the establishment of a circulating power test set-up, comprising of two line-side PWM converters, inclusive of control and modulation methods for the two converters. Two types of circulating power test setups are developed. In the first setup, the converters are connected in parallel, on ac as well as dc sides, such that real and/or reactive power is circulated between them. In the second test setup, the dc buses of the converters are separated; hence, only reactive power circulation is possible. These setups are used to conduct heat-run tests with low energy expenditure on the PWM converters at various operating conditions up to power levels of 150 kVA. Further, these are used to validate analytically-evaluated thermal characteristics of high-power PWM converters. A safe thermal limit is derived for such converters in terms of apparent power (kVA) handled, power factor and switching frequency. The effects of voltage sag and of unequal current sharing between parallel IGBT modules on the safe thermal limit are studied. While the power drawn by the circulating-power setup from the grid is much lower than the ratings of the individual converters, the harmonic injection into the mains by the setup could be significant since the harmonics drawn by both converters tend to add up. This thesis investigates carrier interleaving to improve the waveform quality of grid current, drawn by the circulating-power test setup. The study of carrier interleaving is quite general and covers various applications of parallel-connected converters such as unity power factor rectification, static reactive power compensation and grid-connected renewable energy systems. In literature, carrier interleaving has been employed mainly for unity power factor rectifiers, sharing a common dc load equally. In such case, the fundamental components of the terminal voltages of the parallel converters are equal. However, when the power sharing between the two converters is unequal, or when power is circulated between the two converters, the terminal voltages of the two converters are not equal. A method to estimate rms grid current ripple, drawn by parallel-connected converters with equal and/or unequal terminal voltages, in a synchronous reference frame is presented. Further, the influence of carrier interleaving on the rms grid current ripple is studied. The optimum interleaving angle, which minimizes the rms grid current ripple under various applications, is investigated. This angle is found to be a function of modulation index of the converters in the equal terminal voltages case. In the unequal terminal voltages case, the optimum interleaving angle is shown to be a function of the average modulation index of the two parallel converters. The effect of carrier interleaving is experimentally studied on the reactive power circulation setup at different values of kVA and different dc bus voltages. The grid current ripple is measured for different values of interleaving angle. It is found experimentally that the optimum interleaving angle reduces the rms grid current ripple by between 37% and 48%, as compared without interleaving, at various operating conditions. Further, the reactive power circulation test set-up is used to evaluate and compare power conversion losses corresponding to different PWM techniques such as conventional space-vector PWM (CSVPWM), bus-clamping PWM (BCPWM) and advanced bus-clamping PWM methods for static reactive power compensator (STATCOM) application at high power levels. It is demonstrated theoretically as well as experimentally that an advanced bus-clamping PWM method, termed minimum switching loss PWM (MSLPWM), leads to significantly lower power conversion loss than CSVPWM and BCPWM techniques at a given average switching frequency.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents contributions to the sinusoidal acceleration control of electrodynamic shakers applied in vibration testing. Considering the importance of sine tests to identify critical frequencies of operation and to determine mechanical weakness in the specified performance of specimens, vibration controllers are designed to reproduce the amplitude and the frequency of the reference acceleration specifically at the interface between the shaker and the structure under test. Two distinct approaches are considered to solve the control problem: time domain control, where the acceleration instantaneous value is adjusted to track the sinusoidal reference, and frequency domain control, in which only the amplitude or the root mean square value of the acceleration is compensated to follow the reference magnitude. The solutions developed based on these two different approaches are implemented in a digital control platform and experimentally evaluated. The development of vibration controllers is complemented by contributions to the study of the shaker dynamic model, as well as to the instrumentation applied to measure and feedback the acceleration and to the voltage control of switching-mode power amplifiers designed to drive the shaker. Regarding the vibration machine dynamic model, a method is proposed to experimentally identify the mechanical parameters of a two degrees of freedom system that represents the suspension resonance and the finite armature stiffness of the electrodynamic shaker. A procedure is developed to design and implement charge mode preamplifiers and signal conditioning circuits for piezoelectric accelerometers. A robust model reference adaptive algorithm is applied to control the output voltage of an industrial switching-mode power amplifier. The experimental analysis of the adaptive controller considers not only the improvements on the power amplifier performance, but also the of impact over the behavior of a commercial digital vibration control system. / Este trabalho apresenta contribuições ao controle de aceleração senoidal de vibradores eletrodinâmicos utilizados em ensaios de vibração. Considerando a importância de testes com aceleração senoidal para identificar freqüências críticas de operação e determinar a resistência de materiais e estruturas, são desenvolvidos controladores para a máquina de vibração com o propósito de garantir que a amplitude e a freqüência da aceleração imposta à estrutura sob teste correspondam aos valores de referência. Na solução do problema, admitem-se duas abordagens distintas: controle no domínio do tempo, onde o valor instantâneo da aceleração é ajustado para seguir a referência senoidal, e controle no domínio da freqüência, no qual apenas a amplitude ou o valor eficaz da aceleração é regulado conforme a magnitude de referência. As técnicas propostas com base nestas abordagens são implementadas numa plataforma de controle digital e avaliadas experimentalmente. O desenvolvimento dos controladores de vibrações é complementado por contribuições ao estudo do modelo dinâmico do vibrador, à instrumentação aplicada para realimentar a aceleração e ao controle da tensão de amplificadores de potência que utilizam inversores com modulação por largura de pulso para acionar a máquina. Com relação ao modelo do vibrador, é descrito um método que permite determinar experimentalmente os parâmetros mecânicos de um modelo com dois graus de liberdade, o qual representa o comportamento da máquina devido à suspensão e à rigidez finita da armadura. Um procedimento de projeto e realização prática de pré-amplificadores de carga e de um circuito de condicionamento para acelerômetros piezoelétricos é apresentado. Um algoritmo adaptativo robusto por modelo de referência é avaliado no controle da tensão de saída de um amplificador industrial projetado para excitar o enrolamento da armadura do vibrador. A análise experimental do impacto do controlador adaptativo é realizada considerando não apenas a melhoria no desempenho do amplificador, mas também em termos dos reflexos na performance de uma plataforma comercial de controle de ensaios de vibrações.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-11T12:39:13Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação Mestrado M276 - Gilberto.pdf: 3559945 bytes, checksum: e0e92cec09c72c5a7b8b98260c3b9a8e (MD5) / Made available in DSpace on 2017-07-11T12:39:13Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação Mestrado M276 - Gilberto.pdf: 3559945 bytes, checksum: e0e92cec09c72c5a7b8b98260c3b9a8e (MD5) Previous issue date: 2016-03-22 / Este trabalho apresenta um estudo comparativo de conversores monofásicos aplicados a sistemas fotovoltaicos sem transformador. Topologias de inversores sem transformador têm menores custos, tamanho e peso. Contudo, a não utilização do transformador pode ser responsável por consideráveis valores de correntes de fuga. A associação em série de vários módulos fotovoltaicos se faz necessária para alcançar o nível de tensão desejado no barramento c.c.. Com o intuito de reduzir o número de módulos fotovoltaicos em série, topologias com característica de elevação de tensão (boost) podem ser utilizadas. Portanto, topologias que possuem estas características e que possam apresentar baixos valores de correntes de fuga devem ser escolhidas para o estudo. As topologias presentes neste trabalho são: o conversor de dois estágios, o inversor fonte Z monofásico com diodo adicional, e o inversor fonte Z de três estados. / This work presents a comparative study of single-phase converters applied to transformerless photovoltaic systems. Topologies of transformerless inverters have lower costs, size and weight. However, not using it may cause considerable amounts of leakage currents. The association in series of several PV modules is needed to achieve the voltage level desired in d.c. bus. In order to reduce the number of photovoltaic modules in series, topologies with voltage boost characteristic can be used. Therefore, topologies that have voltage boost characteristic and can have low leakage current values are chosen for the study. Topologies present in this work are: the two stages single-phase converter, the single-phase Z-source inverter with additional diode, and the single-phase three switch three state Z-source inverter.