L'optique adaptative a révolutionné l'imagerie astronomique en permettant de corriger en temps réel les déformations du front d'onde introduites l'atmosphère, et d'atteindre la limite de diffraction des télescopes. Plus récemment, différentes modalités d'optique adaptative grand-champ ont permis de repousser les limites d'utilisation de ces instruments, compensant l'anisoplanétisme de l'atmosphère, et la faible couverture du ciel. L'asservissement de ces systèmes est sans aucun doute un point clé pour améliorer encore les performances de ces systèmes, pour ainsi converger vers les programmes scientifiques des futurs ELT.Le premier objectif de ces travaux de thèse est de définir un outil général d'analyse de performance, permettant de comparer, sous la forme de budgets d'erreur, différents régulateurs linéaires. Ceci permet d'améliorer les instruments actuels, ou de faire des choix dans la conception des futurs instruments des ELT. Pour cela, un formalisme d'analyse fréquentielle est développé dans le cadre de l'optique adaptative classique, et étendu au cas grand-champ. On montre que cet outil permet aussi bien de décomposer les performances calculées en simulation qu'à partir de données télémétriques enregistrées sur le ciel. De nouvelles stratégies de commande, basées sur de nouveaux modèles de perturbation sont proposées, et leur apport en performance discuté au regard de leur budget d'erreur. Ces résultats ont servi à la caractérisation d'une commande LQG tip-tilt avec filtrage de vibration qui doit être intégrée à l'instrument d'optique adaptative multi-conjuguée GeMS, au Chili. / Adaptive Optics (AO) systems have revolutionized ground-based astronomical imagery, allowing for real-time compensation of turbulence-induced deformations of the optical wavefront, and therefore allowing to reach the diffraction limit. More recently, wide-field AO modalities have been proposed to expand the operational range of instruments by compensating anisoplanatism and increase sky coverage. Controlling such systems is certainly a key issue to further improve their performance and to converge towards the goals of the ELTs science programs.The first objective of this thesis work is to define a general-purpose performance analysis tool, enabling to compare different linear controllers through their error budgets, in order to improve existing instruments or make choices in the design of future instruments. To achieve this aim, a frequency-domain formalism is developed for single-conjugated AO and extended to wide-field configurations. It is shown that this tool allows to decompose controller performance using either simulations or on-sky data. New control strategies based on new disturbance models (turbulence, vibrations...) are proposed, and the improvement in performance is discussed based on their error budget. Furthermore, these results contributed to characterize an LQG controller with vibration mitigation that is to be integrated in the tip/tilt loop of the multi-conjugate AO system GeMS, at Gemini South Observatory, in Chile.

This dissertation embodies a comprehensive approach towards resilient monitoring of frid events using Structure Preserving Energy Functions (SPEFs) and introduces a novel control architecture in Multi Terminal Direct Current (MTDC) grids, for inter-area oscillation damping and achieving robustness to AC as well as DC side, post-contingency events in the modern power grid. This work is presented as a collection of several publications which investigate and address the proposed research topics. At first, SPEFs are derived for multi-machine IEEE benchmark models with the help of the Wide-Area Measurements (WAMs). A physics-based hybrid approach to develop one-to-one mapping between properties of energy function components with respect to the type of fault in the system is introduced. The proposed method is tested offline on a IEEE-39 bus, New England Test System (NETS), with particular interest in monitoring the most sensitive energy functions during relay misoperations. Such events can be precipitated by zone 3 trips in distance relays due to load encroachment during stressed conditions. These might include a genuine misoperation, a false trip due to cyber-attacks, or a load encroachment, all of which are undesirable under normal operating circumstances. An online monitoring scheme is introduced in an actual blackout simulation in the Western Electricity Coordinating Council (WECC) to examine what further indications these energy function components can provide, especially during a cascading sequence, and how they could supervise critical tripping decisions by distance relays. Next, a futuristic grid comprised of Voltage Source Converter (VSC) based AC-MTDC is considered due to its recent proliferation in integrating offshore wind farms to onshore grids, and additionally improving strength of weak AC grids. A robust control is designed using the converter station poles as actuators to provide damping support to the surrounding AC grid. Further, a design problem is envisioned and implemented that introduces disturbance rejection into control architecture by designing a novel explicitly modeled disturbance plant in the Linear Matrix Inequality (LMI) framework. Finally, a novel robust inter-area oscillation damping controller is designed that proves its effectiveness in inter-area mode settling times, and provides robustness to (n-1) contingencies in the AC as well as the DC side of the meshed AC-MTDC grid.