This thesis presents a novel modulation scheme, called feedback dithering modulation, for DC to AC power converters. The feedback dithering modulator consists of a quantizer and a recently reported feedback dithering circuit, performing multilevel modulation with improved linearity and signal quality as opposed to the conventional modulation schemes. By combining the feedback dithering modulation and optimal control, a single-phase DC to AC power converter is built and tested. The resulting total harmonic distortion can be as low as 0.38% for a 25£[ load, or 0.47% when the output is open. Under the various operating conditions with DC voltages source varying from 190 V to 300 V and output powers from 0 to 600 W, the power converter always maintains a total harmonic distortion less than 1%, exhibiting high performance and excellent robustness.

The ever-increasing demands for transmission capacity are the cause for the quick evolution of optical communication systems. Channel transmission at 100 Gb/s is already being considered by network operators. The major transmission impairments at these high rates are intra-channel and inter-channel nonlinearities, nonlinear phase noise, and polarization mode dispersion. By implementing LDPC-coded modulation schemes with soft decoding and Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm for equalization we have demonstrated significant improvements in system performance experiencing several impairments simultaneously. The new turbo-equalization scheme is used as a mean to simultaneously mitigate both linear and nonlinear impairments. This approach is general and applicable to both direct and coherent detection.We provide comprehensive study of LDPC codes suitable for implementation in high-speed optical transmission systems. We determine channel capacity based on the forward step of the BCJR algorithm and show that by using LDPC codes we can closely approach the maximum transmission capacity that is possible. We propose the multilevel maximum a posteriori probability (MAP) turbo equalization scheme based on multilevel BCJR algorithm and an LDPC decoder, which considers independent symbols transmitted over both polarizations as two dimensional super-symbols. The use of multilevel modulation schemes provide higher spectral efficiency, while all related signal processing is performed at lower symbol rates, where dealing with PMD compensation and fiber nonlinearities mitigation is more manageable. We show significant improvement in system performance over a system employing an equalizer that considers symbols transmitted in different polarizations as independent.

Les structures de conversion multi-niveaux parallèles permettent de faire transiter de fortscourants tout en gardant une bonne puissance massique ; celles-ci sont réalisées en parallélisantdes cellules de commutation. Cette parallélisation permet de réduire le courant dans chaquecellule et ainsi de revenir dans des gammes plus standard de composants de puissance. Laparallélisation, en utilisant une commande adaptée, améliore les formes d’onde en sortie duconvertisseur. Ce manuscrit se focalisera sur une structure de conversion multiniveaux parallèlespécifique constituée de bras de hacheur dévolteur en parallèles couplés magnétiquement. Eneffet du fait de la commande entrelacée mise en place, l’ondulation du courant de sortie se voitréduite mais en contrepartie l’utilisation d’inductances séparées sur chaque bras entraine uneaugmentation de l’ondulation des courants de bras, directement liée au nombre de cellules decommutation, en fonction de l’ondulation du courant de sortie. Afin de palier à ce problème cesinductances sont remplacées par un (ou plusieurs) coupleur(s) magnétique(s) qui permet(tent) deréduire l’ondulation de courant dans chaque bras. Cependant dans le but de garantir la nonsaturation ainsi qu’une bonne intégration des coupleurs il est nécessaire de s’assurer del’équilibrage des courants de chaque bras malgré une différence entre les paramètres. Ainsi cemanuscrit s’est axé vers la détermination de différentes méthodes de modélisation découplant lesystème permettant le maintien de l’égale répartition des courants en utilisant des différences derapports cycliques. Ces méthodes de modélisation ont été généralisées afin de réaliser unalgorithme permettant de générer des lois de commande quel que soit le nombre de cellules enparallèle. Dans une dernière partie ces lois de commande ont été testées sur un prototype en lesimplémentant sur FPGA afin de procéder à une vérification expérimentale / The parallel multilevel converters allow high current with a high power-weight ratio by associatingcommutation cells in parallel. This parallelization reduces the current in each cells and so onpermits to use standard range of components. With an adapted command the quality of the outputwaveforms is improved. This report will focus on a specific structure made off Buck converter withmagnetic coupling. Indeed thanks to the interleaved command, the output current ripple is reducedbut in return using separated inductances on each leg leads an increasing of the leg current ripple,directly linked to the number of leg and the ripple of the output current. In order to avoid thisproblem those inductances are replaced by one or more intercell transformers (ICT) that reducethe ripple of each leg current. However in a way to ensure unsaturated ICTs and good integrationit is necessary to balance the current of each leg despite parameter variation. Thus this report isfocused on modeling uncoupling methods for the system ensuring an equal distribution of thecurrents with duty cycles differences. Those modeling methods were generalized to achieve to analgorithm which generate control law whatever the number of leg. In the last part those controllaws are tested on a test bench by implementing them on a FPGA board to validate experimentallythe results

A crescente demanda por fontes alternativas de energia, voltada principalmente a minimizar impactos ambientais provenientes do uso de combustíveis fósseis na geração de energia elétrica, tem impulsionado as pesquisas tanto no âmbito acadêmico como no setor privado. Dessa forma, estudos científicos vêm abordando painéis fotovoltaicos, aerogeradores, células combustível, dentre outros, no sentido de gerar energia limpa por meio de conversores estáticos CC-CC e CC-CA, conectados na rede de distribuição elétrica, configurando um cenário de Geração Distribuída. Devido ao uso de tais conversores, têm-se introduzido perturbações harmônicas nas redes de distribuição. Sendo assim, a qualidade de energia tornouse uma questão de suma importância no contexto energético contemporâneo, de tal modo que esta tese se apresenta um estudo voltado ao desenvolvimento e implementação de uma plataforma experimental de um Condicionador Unificado de Qualidade de Energia (UPQC) monofásico com compensação ativa de potência série e paralela, com uma potência de 1 kW, capaz de minimizar perturbações harmônicas em redes de distribuição. O sistema realiza a supressão de harmônicos e a compensação de afundamentos e elevações de tensão em redes elétricas, além de manter a tensão na carga regulada e com baixa taxa de distorção harmônica. Além disso, esse dispositivo realiza compensação de potência reativa e supressão de harmônicos da corrente de carga, o que resulta em uma efetiva correção do fator de potência. Nesse sentido, o dispositivo atua como um filtro ativo universal, realizando compensação da corrente de entrada, como também da tensão de saída. Para este fim, dois conversores monofásicos ANPC de 5 níveis são empregados, sendo estes o filtro ativo série (FAS), que atua como fonte de corrente senoidal, e o filtro ativo paralelo (FAP), que atua como fonte de tensão senoidal, em que ambos são controlados de tal forma a operar em fase com a tensão da rede elétrica. Com o objetivo de realizar as compensações harmônicas, é utilizado o algoritmo de extração de referência, conhecido como Compensação Cooperativa baseada na Teoria de Potência Conservativa. / The growing demand for alternative sources of energy, aimed mainly at minimizing environmental impacts from the use of fossil fuels in electric power generation, has driven research in both the academic and private sectors. Thus, scientific studies have addressed photovoltaic panels, aerogenerators, fuel cells, among others, in order to generate clean energy by means of static converters CC-CC and CC-CA, connected in the electric distribution network, configuring the Distributed Generation. Due to the use of such converters, harmonic disturbances have been introduced in the distribution networks. Thus, the quality of energy has become a matter of paramount importance in the contemporary energy context, such that this thesis presents a study aimed at the development and implementation of an experimental platform of a single-phase Unified Energy Quality Conditioner (UPQC) with active series and parallel power compensation, with a power of 1 kW, capable of minimizing harmonic disturbances in distribution networks. The system performs the suppression of harmonics and the compensation of sags and tensions in electrical networks, besides maintaining the voltage at the regulated load and with a low harmonic distortion rate. In addition, this device performs reactive power compensation and harmonic suppression of the load current, which results in an effective power factor correction. In this sense, the device acts as a universal active filter, performing compensation of the input current, as well as the output voltage. For this purpose, two 5-level ANPC single-phase converters are used, which are the series active filter (FAS), which acts as a sinusoidal current source, and the parallel active filter (FAP), which acts as a sinusoidal voltage source, in that both are controlled in such a way to operate in phase with the mains voltage. In order to perform the harmonic compensations, the reference extraction algorithm, known as Cooperative Compensation based on the Conservative Power Theory, is used.