Dans un contexte de développement des énergies renouvelables et des liaisons HVDC dans les systèmes électriques, les travaux présentés s’attachent au fonctionnement technique de tels systèmes. La génération éolienne, photovoltaïque et les liaisons HVDC sont interfacées par dispositifs d’électronique de puissance au réseau de transport électrique. Dès lors, serait-il envisageable d’alimenter la demande électrique uniquement via des sources électriques interfacées par des convertisseurs statiques ?Le pilotage du système électrique par électronique de puissance constitue un changement radical du fonctionnement dynamique des réseaux. La traditionnelle stratégie de commande « grid-following » des onduleurs a montré ses limites lorsque la pénétration de ces dispositifs devient importante. Elle doit être révisée au profit de stratégies dîtes « parallel grid-forming ».Dans cette thèse, les besoins fondamentaux du système électrique sont d’abord analysés pour définir les exigences de la stratégie « parallel grid-forming », ainsi que les défis associés. Selon ces spécifications, une méthode de synchronisation de sources « grid-forming » est ensuite proposée ainsi qu’un contrôle de tension, adapté aux limitations physiques des convertisseurs de tension PWM. La stabilité de la solution est discutée pour différentes configuration de réseau. Enfin, une stratégie de limitation du courant a été spécifiquement développée pour palier la sensibilité des VSC aux sur courants, lors d’évènements réseaux éprouvant. Les idées développées sur un convertisseur unique sont appliquées à petits réseaux afin d’extraire des interprétations physiques depuis des simulations temporelles / In the context of renewable energy and HVDC links development in power systems, the present work concerns the technical operations of such systems. As wind power, solar photovoltaics and HVDC links are interfaced to the transmission grid with power-electronics, can the system be operated in the extreme case where the load is fed only through static converters?Driving a power system only based on power electronic interfaced generation is a tremendous change of the power system paradigm that must be clearly understood by transmission grid operators. The traditional “grid-feeding” control strategy of inverters exhibits a stability limit when their proportion becomes too important. The inverter control strategy must be turned into a “parallel grid-forming” strategy.This thesis first analyses the power system needs, proposes the requirements for “parallel grid-forming” converters and describes the associated challenges. Accordingly, the thesis gives a method for designing a stable autonomous synchronization controls so that grid-forming sources can operate in parallel with a good level of reliability. Then, a method is proposed to design a voltage control for a grid-forming PWM source taking into account the limited dynamic of large converters. The robustness of the solution is discussed for different configuration of the grid topology. A current limiting strategy is presented to solve the current sensitivity issue of grid-forming converters, subject to different stressing events of the transmission grid. The ideas developed on a single converter are then applied on small grids with a limited number of converters to allow a physical interpretation on the simulation results.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / New trends and emerging technologies motivate the design of analog-to-digital converters (ADCs) which must fit in increasingly constrained environments. Within this context, one design metric which is constantly forced towards reduction is the power consumption, leading the designers to come up with improvements in both the architecture and circuit levels. This work aims to push forward the energy efficiency of the successive approximation charge sharing ADC, which is a relatively new and unexplored architecture. Therefore, three complete ADCs are designed throughout this work, each one bringing novelties that help decreasing the power consumption. The techniques devised here include novel manners of dealing with the tracking of the input signal and a circuit to reduce power drained in the pre-charge cycle. Also, three different architectures of digital controller for this ADC topology are designed. Moreover, a novel bootstrapping switch circuit is presented, which provides lower devices-count and a extremely high energy efficiency. / As novas tendências e tecnologias emergentes motivam o projeto de conversores analógico-digitais (ADCs) que precisam suprir especificações cada vez mais restritivas. Nesse contexto, uma métrica de projeto que é constantemente forçada em direção à redução é o consumo de potência, fato esse que leva à concepção de melhorias tanto em nível arquitetural como em nível de circuito elétrico. Este trabalho tem como objetivo elevar a eficiência energética dos ADCs por aproximações sucessivas e compartilhamento de carga, visto que essa é uma arquitetura relativamente nova e inexplorada. Portanto, três ADCs completos são projetados ao longo deste trabalho, e cada um traz inovações que ajudam a reduzir o consumo de potência. As técnicas concebidas aqui incluem maneiras novas de efetuar a captura do sinal de entrada e um circuito para reduzir a potência drenada no ciclo de pré-carga. Além disso, três arquiteturas diferentes de controlador digital para essa topologia de ADC são expostas. Mais, um novo circuito de chave com bootstrapping é apresentado, o qual apresenta um número de dispositivos menor e uma eficiência energética extremamente alta.