The design and implementation of a dynamic voltage restorer (DVR) is presented in this thesis. The proposed DVR can restore the end-user voltage to its normal level by rapidly injecting a compensating voltage onto the power line against the upstream power disturbances. The control algorithm uses the concept of reference voltage tracking method. Based on the electric circuit theory, the filter of the DVR is also analyzed. Besides, performance of the proposed method is simulated and compared with other different control methods by using Matlab-simulink/PSB. The results show the effectiveness of the proposed method. A 2.18 KVA DVR prototype is implemented to verify the performance of the proposed method.

O restaurador dinâmico de tensão (DVR) é uma solução baseada em eletrônica de potência para minimizar os problemas causados por afundamentos e elevações de tensão em equipamentos ou cargas sensíveis a esses tipos de distúrbios. Basicamente a operação do DVR consiste em injetar na rede tensões de correção com a finalidade de anular o afundamento ou a elevação na tensão aplicada à carga. Tipicamente, a estrutura do controlador utilizado em um DVR é composta por uma malha interna de corrente e uma malha externa de tensão. Usualmente um controlador do tipo proporcional ou proporcional integral é utilizado na malha interna de corrente e um controlador ressonante é utilizado na malha externa de tensão. O presente trabalho apresenta um projeto de controlador robusto para rastreamento da tensão injetada pelo DVR que garante estabilidade robusta do sistema com respeito à variação dos parâmetros da carga. Além disso, o controlador proposto garante valores pré-definidos para o erro de rastreamento e para a rejeição do distúrbio causado por correntes de carga distorcidas na tensão injetada pelo DVR. A síntese do controlador robusto de tensão é feita com base no método de projeto H? pela formulação da sensibilidade mista. Todas as especificações de desempenho e robustez são impostas por meio de restrições nos diagramas de resposta em frequência do sistema em malha fechada (funções sensibilidade e sensibilidade complementar). O desempenho do controlador proposto é verificado e a metodologia de projeto é validada por simulações e experimentos realizados em um DVR de baixa potência. / The Dynamic Voltage Restorer (DVR) is a power electronics based solution for mitigation of voltage sags and swells effects on sensitive loads, which basically injects voltages in series with the grid. Typically the controller structure for a DVR is composed by an inner current loop and an outer voltage loop. Usually proportional or a proportional-integral controller is used for the current loop and a resonant controller is used for the voltage loop. This paper presents the design of a robust controller for the voltage tracking loop of a DVR that guaranties the robust stability against load parameters variation. Moreover, the proposed controller assures the tracking of a sinusoidal voltage waveform, as well the rejection of the non linear load current influence, both with a pre specified error. The voltage controller design is based on H? mix-sensitivity parameter specification approach. All the performance and robustness requirements are specified and analyzed based on the frequency response plot of closed loop transfer function (sensitivity and complementary sensitivity functions). The proposed controller performance is validated by simulation and by experiments carried out on a low scale DVR prototype.

O restaurador dinâmico de tensão (DVR) é uma solução baseada em eletrônica de potência para minimizar os problemas causados por afundamentos e elevações de tensão em equipamentos ou cargas sensíveis a esses tipos de distúrbios. Basicamente a operação do DVR consiste em injetar na rede tensões de correção com a finalidade de anular o afundamento ou a elevação na tensão aplicada à carga. Tipicamente, a estrutura do controlador utilizado em um DVR é composta por uma malha interna de corrente e uma malha externa de tensão. Usualmente um controlador do tipo proporcional ou proporcional integral é utilizado na malha interna de corrente e um controlador ressonante é utilizado na malha externa de tensão. O presente trabalho apresenta um projeto de controlador robusto para rastreamento da tensão injetada pelo DVR que garante estabilidade robusta do sistema com respeito à variação dos parâmetros da carga. Além disso, o controlador proposto garante valores pré-definidos para o erro de rastreamento e para a rejeição do distúrbio causado por correntes de carga distorcidas na tensão injetada pelo DVR. A síntese do controlador robusto de tensão é feita com base no método de projeto H? pela formulação da sensibilidade mista. Todas as especificações de desempenho e robustez são impostas por meio de restrições nos diagramas de resposta em frequência do sistema em malha fechada (funções sensibilidade e sensibilidade complementar). O desempenho do controlador proposto é verificado e a metodologia de projeto é validada por simulações e experimentos realizados em um DVR de baixa potência. / The Dynamic Voltage Restorer (DVR) is a power electronics based solution for mitigation of voltage sags and swells effects on sensitive loads, which basically injects voltages in series with the grid. Typically the controller structure for a DVR is composed by an inner current loop and an outer voltage loop. Usually proportional or a proportional-integral controller is used for the current loop and a resonant controller is used for the voltage loop. This paper presents the design of a robust controller for the voltage tracking loop of a DVR that guaranties the robust stability against load parameters variation. Moreover, the proposed controller assures the tracking of a sinusoidal voltage waveform, as well the rejection of the non linear load current influence, both with a pre specified error. The voltage controller design is based on H? mix-sensitivity parameter specification approach. All the performance and robustness requirements are specified and analyzed based on the frequency response plot of closed loop transfer function (sensitivity and complementary sensitivity functions). The proposed controller performance is validated by simulation and by experiments carried out on a low scale DVR prototype.

This thesis presents the application of a series interconnection module for small distributed generation (DG) or renewable energy systems integration in the distribution network. The concept used one set of voltage source converter (VSC) with battery energy storage system to control the injected voltage magnitude and phase angle for power injection and voltage sag mitigation applications. Through an energy storage device and the VSC, the module allows storage of surplus energy during off peak period and release for use during daytime peak load period, therefore, exhibits a load leveling characteristic. Due to its series connection characteristic, it is convenient in preventing islanding operation and suitable for voltage sag mitigation. The concept is suitable for locations where the voltage phase shift is not a problem. Due to the use of only one set of VSC, it is economic for customer site distributed energy resource applications.

Among most severe power system disturbances those degrading power quality are voltage sags and transient interruptions. Even voltage sags lasting only a few tens of milliseconds are enough to bring entire production lines to standstill, causing considerable economic damage as well as endangering the production equipment. Therefore necessary measures have to be taken to protect sensitive loads which are susceptible to these voltage disturbances. Among the solution candidates such as, Uninterruptible Power Supplies, Motor-Generator Sets, etc, Dynamic Voltage Restorer (DVR) which is an effective custom power device has been proposed to mitigate such bus voltage sags on sensitive loads with its excellent dynamic performance. In this study, load side connected shunt converter topology was chosen for the implementation of DVR. The performance DVR was tried to be improved by improving the control strategy used. Super Film located in Gaziantep which is one of the SANKO subsidiary company was chosen to simulate the operation of DVR as actual case of Turkish industry. All the simulations in this study were carried on PSCAD/EMTDC Software.

A pollen-restorer sugarbeet inbred, developed by four generations of selection of highly fertile plants from a CMS X table beet cross, was studied to determine if a change from sterile to fertile cytoplasm had occurred. Data showed that the fertility expressed by the restorer inbred was the result of genetic factors and not cytoplasmic reversion. Linkage tests with the Rf gene showed independence of the YRB group, m and vi4. A yellow-loaf mutant was inherited as a simple recessive factor. A partial pollen-restorer character, found in the yellow-leaf material, was inherited as a single dominant gene. The restorer factor was independent of yl and m, while the yl gene showed independence of m and B.

When more induction generator based wind farms are integrated into the power system, the system voltage dips and stability problems may arise due to the draw of reactive power by induction generators. The power system short-circuit event induced wind turbine trips could result in power imbalance and lead to power system instability. This thesis studies the influence of two compensation techniques on the wind turbine low voltage ride-through (LVRT) capability. One of which is based on a parallel compensation by a static synchronous compensator (STATCOM), and the other one is a series compensation by a dynamic voltage restorer (DVR). In this study, Matlab tools and models are used to simulate an active-stall controlled fixed-speed induction generator connected to a power system. Two system configurations are used to simulate three phase faults and compare the improvement of wind turbine LVRT capability due to the two studied compensation techniques. Simulation results indicate that wind turbine compensated by DVR would have better LVRT performance than that by STATCOM in dealing with the low voltage situations due to system faults.

Made available in DSpace on 2015-05-08T14:57:17Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2400808 bytes, checksum: 3c7c682278f78e771b9fee7c273a134b (MD5) Previous issue date: 2013-10-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work presents a technique to suppress saturation in series transformers applied to dynamic voltage restorer (DVR) systems. The technique consists in correcting the voltages which are injected through the transformers into the power system to compensate voltage sags. The presented method ensures complete elimination of the DC flux-linkage or shifts the flux-linkage curve, restricting their AC amplitude, so that the flux level does not exceed the limits of the transformer, preventing it works in the saturation region. The validation of this method will be realized from simulations and experimental results. / Este trabalho apresenta uma técnica para evitar a saturação dos transformadores de tensão em série aplicados em um restaurador dinâmico de tensão (DVR). A técnica consiste em alterar as tensões que são injetadas através dos transformadores para compensar afundamentos de tensão no sistema de potência. O método apresentado assegura uma eliminação completa do fluxo c.c. ou desloca a curva de fluxo, restringido sua amplitude c.a., de maneira que o nível de fluxo não exceda os limites do transformador, evitando que o mesmo trabalhe na região de saturação. A validação deste método será realizada a partir de simulações e resultados experimentais.

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Chez les plantes à fleurs, la gynodioécie -- système dans lequel coexistent des individus femelles et des individus hermaphrodites -- est le système de reproduction le plus commun après l'hermaphrodisme. La question de l'évolution et surtout du maintien de la gynodioécie et du polymorphisme génétique sous-jacent a intrigué les chercheurs depuis le 19e siecle. Aujourd'hui, les grands principes de son évolution sont posés mais beaucoup de zones d'ombres persistent. Durant ma thèse, j'ai exploré trois aspects de la gynodioécie en utilisant une approche expérimentale chez l'espèce Silene nutans et une approche théorique. Je me suis en premier lieu intéressée au déterminisme génétique de la gynodioécie grâce à la réalisation de croisements contrôlés qui m'ont permis de montrer que le déterminisme génétique du sexe était cytonucléaire, c'est à dire contrôlé par plusieurs gènes de stérilité mâle cytoplasmique (CMS) et plusieurs restaurateurs nucléaires de fertilité. En parallèle, j'ai porté une attention particulière aux plantes gynomonoïques -- celles où coexistent sur le même pied des fleurs pistillés (femelles) et des fleurs parfaites (hermaphrodites) -- fréquentes chez Silene nutans comme chez d'autres espèces gynodioïques. J'ai montré que les caractéristiques reproductrices et florales de ce troisième phénotype sexuel étaient souvent intermédiaires entre celles des femelles et des hermaphrodites mais pouvaient dépendre de la proportion de fleurs pistillées sur la plante. Par ailleurs et contrairement à ce qui avait été suggéré, la plasticité du phénotype gynomonoïque s'est révélée être relativement réduite, suggérant un déterminisme génétique dont la caractérisation est encore en cours. La troisième partie de ma thèse a été motivée par les preuves récentes d'hétéroplasmie -- coexistence de différents génomes mitochondriaux au sein d'un individu -- et de la transmission occasionnelle du génome mitochondrial par le pollen chez Silene vulgaris. J'ai montré théoriquement que la présence d'un gène de stérilité mâle cytoplasmique favorisait l'évolution de la fuite paternelle de mitochondries. J'ai également vérifié expérimentalement l'hérédité mitochondriale chez Silene nutans par le génotypage des descendances de croisements contrôlés. / In flowering plants, gynodioecy -- a system in which females and hermaphrodites coexist within populations -- is the most common sexual system after hermaphroditism. The evolution and maintenance of gynodiocy and its underlying polymorphism have puzzled evolutionary biologists since the 19th century. The main principles of its evolution are well known but some points remain vague. During my PhD, I explored three aspects of gynodioecy using an experimental approach in the species Silene nutans and a theoretical approach. First, I studied the genetic determination of gynodioecy using controlled crosses that showed that the genetic determination of sex was cytonuclear, i.e. controlled by several cytoplasmic male sterility (CMS) genes and several nuclear restorers of fertility. Second, I focused on gynomonoecious plants -- those that carry both pistillate (female) flowers and perfect (hermaphrodite) flowers -- that are frequently found in Silene nutans as in other gynodioecious species. I showed that the floral and reproductive traits of this third sex phenotype were often intermediate between those of females and hermaphrodites but varied with varying proportions of pistillate flowers on the plant. Contrary to what was previously thought, the plasticity of the gynomoneocious phenotype was found to be limited, suggesting a genetic determination whose characterization is still in progress. The third part of my PhD was motivated by recent evidences of heteroplasmy -- the coexistence of different mitochondrial genomes within an individual -- and occasional transmission of the mitochondrial genome through pollen in Silene vulgaris. I showed theoretically that the occurrence of a cytoplasmic male sterility gene can favor the evolution of paternal leakage of mitochondria. I also investigated mitochondrial inheritance in Silene nutans by genotyping progenies from controlled crosses.