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Greater numbers of power electronics (PEs) converters are being connected to energy systems due to the development of renewable energy sources, high-voltage transmission, and PE-interfaced loads. Given that power electronics-based devices and synchronous machines have very different dynamic behaviours, some modelling approximations, which may commonly be applied to run transient simulations of transmission systems, may not be optimal for future grids. Indeed, the systematic utilisation of the phasor approximation for power lines, implemented in most transient simulation programs, is increasingly not appropriate anymore. In order to avoid the requirement for full electromagnetic transient simulations, which can be resource-demanding and time-consuming, this paper proposes a combination of an event-based state residualisation approximation and the Kron reduction technique. The proposed technique has the advantage of allowing accurate transient simulations based on the optimal reduction of the number of state variables, depending on the observed variables, the considered events, and the tolerated approximation error, along with simplifying power systems equations for accelerated simulations.

The fast development of renewable energies leads to an increase in the power electronics penetration in transmission systems. This is particularly true if one considers a 100% renewable energies power system, where wind and solar photovoltaic energies, which make most of the renewable energies connections today, are connected to the grid through power electronics converters. Because power electronics-based generators and synchronous machines-based generators have very different dynamic behaviours, some approximations usually used to run transient simulations of transmission systems might not be optimal for future grids. The systematic use of the phasor approximation applied to the power lines, implemented in most of the Transient Simulation Programs, is indeed not relevant any more. To avoid the use of Electromagnetic Transient simulations, that are resource-demanding and time-consuming, this paper presents a novel Model Order Reduction technique for large grids with a high penetration of power electronic devices. Compared to the classical phasor approximation, this event-based state residualization approximation allows accurate transient simulations and at the same time an optimal reduction of the number of the system's state variables depending on the observed variables, the considered events and the tolerated approximation error.

Outils et Méthodes pour l’Analyse et la Simulation de Réseaux de Transport 100% Electronique de Puissance RESUME : Le développement des énergies renouvelables et des liaisons HVDC conduit à une augmentation de la pénétration de l’électronique de puissance dans les réseaux de transport d’électricité. Comme les convertisseurs possèdent des propriétés physiques différentes de celles des alternateurs synchrones, une évolution des contrôles employés s’avère nécessaire. Au vu de la taille des ensembles à simuler, la validation de solutions innovantes doit être réalisée par des simulations numériques et il est nécessaire d’être vigilant sur les outils utilisés afin d’éviter des temps de calcul prohibitifs. Dans cette thèse, des outils et des méthodes pour l’analyse et la simulation de réseaux de transport 100 % électronique de puissance sont développés. Une partie importante des travaux est consacrée à la modélisation des convertisseurs, ce qui permet de réaliser des simulations numériques plus ou moins précises en fonction du cahier des charges de l’étude et d’appliquer ou de développer des méthodes d’analyse de stabilité. Un modèle simplifié du réseau Irlandais est utilisé comme réseau exemple de façon à valider les méthodes et outils développés dans le cadre de la thèse. Mots clés : Analyse des réseaux de transport, 100% Électronique de Puissance, Simulation de réseaux électriques, Réduction de modèles Tools and Methods for the Analysis and Simulation of Large Transmission Systems Using 100% Power Electronics ABSTRACT: The development of renewable generation and HVDC links lead to an important increase of the penetration of power electronics in the transmission systems. As Power Electronics converters have completely different physical behavior than synchronous machines, an evolution in the way TSOs control transmission systems is needed. It is impossible to build a real size prototype of a transmission system. The validation of the solutions must be done using dynamic numerical simulations. Because of the size of the studied systems, we have to be careful with the simulation tools that we use, in order to reduce the computation time. In this PhD tools and methods for the analysis and simulation of large transmission systems using 100% power electronics are developed. An important part of the work looks at the models of the converters. Those models allow us to do numerical simulations and to apply and develop stability and performance analysis methods for the considered system. A simple model of the Irish network will be used as an example in order to assess the developed methods. Keywords : Power Systems Analysis, 100% Power Electronics, Power System Simulation, Model order reduction