Les nouvelles stratégies de contrôle d’onduleurs pour un système électrique 100% interfacé par électronique de puissance by Guillaume Denis-

 From grid-following to grid-forming: The new strategy to build 100 % power-electronics interfaced transmission system with enhanced transient behavior Les nouvelles stratégies de contrôle d’onduleurs pour un système électrique 100% interfacé par électronique de puissance 

 Thèse présentée en vue d’obtenir le grade de Docteur En Spécialité: Génie Électrique Par Guillaume Denis Doctorat délivré par Centrale Lille Résumé 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.

VIEW FULL THESIS: https://hal.science/tel-01905827v1

Direct AC Voltage Control for Grid-Forming Inverters Taoufik Qorai , Chuanyue Li , Ko Oue , Francois Gruson , Fréderic Colas , Xavier Guillaud

Direct AC Voltage Control for Grid-Forming Inverters Taoufik Qorai (1) , Chuanyue Li (1) , Ko Oue (1) , Francois Gruson (1) , Fréderic Colas (1) , Xavier Guillaud (1) 

 Résumé 

 Grid-forming inverters usually use inner cascaded controllers to regulate output AC voltage and converter output current. However, at the power transmission system level where the power inverter bandwidth is limited, i.e., low switching frequency, it is difcult to tune controller parameters to achieve the desired performances because of control loop interactions. In this paper, a direct AC voltage control-based state-feedback control is applied. Its control gains are tuned using a linear quadratic regulator. In addition, a sensitivity analysis is proposed to choose the right cost factors that allow the system to achieve the imposed specifcations. Conventionally, a system based on direct AC voltage control has no restriction on the inverter current. Hence, in this paper, a threshold virtual impedance has been added to the state-feedback control in order to protect the inverter against overcurrent. The robustness of the proposed control is assessed for diferent short-circuit ratios using smallsignal stability analysis. Then, it is checked in diferent grid topologies using time domain simulations. An experimental test bench is developed in order to validate the proposed control.

FUL PAPER: https://hal.science/hal-02458108v1

Resilient microgrids with high dynamic stability in the presence of massive integration of variable renewables BY Kevin Banjar Nahor -THÈSE Pour obtenir le grade de DOCTEUR DE LA COMMUNAUTE UNIVERSITE GRENOBLE ALPES Spécialité : Génie Electrique

 

Resilient microgrids with high dynamic stability in the presence of massive integration of variable renewables Kevin Banjar Nahor 

Abstract This thesis deals with the stability issues introduced by the interconnection of massive renewables into an isolated microgrid. This research aims to identify the problems related to the topic, the indices to help understand the issues, and the strategy to enhance microgrid stability from the power system point of view.In the first part, a state of the art on the evolution of power stability is addressed. A short history of power system stability since its first identification and how it has evolved is firstly presented. This part also provides a literature review of the power system stability, including its classification, and how it has evolved due to two reasons: the microgrid concept and the trend towards the integration of more inverter-based generation. A review of the practical indices for grid stability assessment is also reported, including the ones that we propose. This part is also useful for analyzing the positioning of this PhD research.The second part of thesis presents the efforts to enhance the dynamic stability of microgrids characterized by massive renewable penetration. The main challenges and the current efforts are reviewed, which have shown that the current solutions focus on maintaining the philosophy of a classical power grid. With the advent of more intermittent energy, the current efforts have proven to be costly. Therefore, a new perspective is proposed. Here, the generating elements and the customers are exposed with higher deviations in voltage and frequency, which are necessary so that that the power equilibrium and the stability of the microgrid can be maintained. This perspective is suitable with the microgrid concept to realize the dream of universal electricity.The concept is then developed into a novel regulation strategy in which the system frequency and voltage are maintained in such a way to keep their ratio essentially constant around 1 (p.u. voltage to p.u. frequency). This strategy can potentially be implemented on all grid forming technologies. The benefits of employing this strategy include assurance that the electrical machinery is not harmed, plug-and-play feature, compatibility with current grid-tied inverter technologies, and no need for fast communication systems. Finally, this proposed strategy is easy to implement and does not require revolution in terms of power system equipment and control. This implementation of this concept provides a very valuable piece of flexibility: time, which enhances the resilience and stability of a microgrid. However, wider frequency and voltage deviations occur and have to be accepted by all the actors within the microgrid. A validation through computer simulations in Power Factory and real-time hardware in the loop experiments has been carried out with satisfactory results.

LINK FULL THESIS: https://hal.science/tel-03042626v1

Analysis and control of the stability of power systems with a high penetration of renewable energy BY Hung Cuong Nguyen-Pour obtenir le grade de DOCTEUR DE L’UNIVERSITÉ GRENOBLE ALPES École doctorale : EEATS - Electronique, Electrotechnique, Automatique, Traitement du Signal Spécialité : Génie électrique Unité de recherche : CEA - Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les Nanomatériaux

DOCTEUR DE L’UNIVERSITÉ GRENOBLE ALPES École doctorale : EEATS - Electronique, Electrotechnique, Automatique, Traitement du Signal Spécialité : Génie électrique Unité de recherche : CEA - Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les Nanomatériaux 

Analyse et contrôle de la stabilité des réseaux électriques à fort taux d'énergie renouvelable. Analysis and control of the stability of power systems with a high penetration of renewable energy. Présentée par : Hung Cuong NGUYEN

ABSTRACT In response to the challenges associated with the use of fossil fuels, there is a global energy transition towards renewable energy sources (RES), such as solar photovoltaic (PV) and wind energy, which offer cleaner and more sustainable alternatives. However, the variable nature of RES energy production, which depends on weather conditions, introduces intermittency and poses challenges for the reliability of power systems. Additionally, RES are typically connected to the grid through power electronic interfaces, which have low inertia compared to synchronous generators (SGs). These characteristics of RES negatively affect grid stability, influencing frequency, voltage, and rotor angle stability.Historically, stability studies focused on rotor angle stability and voltage stability in systems with rotating machines. With the integration of RES and power electronic inverters, and the consequent reduction in conventional synchronous generators, it has become necessary to perform more comprehensive studies, particularly on grids with high levels of RES penetration. Our thesis addresses this issue by using both static and dynamic analyses to assess grid stability, with a particular focus on frequency stability.The contributions of this thesis include the following:• State of the Art on the Impacts of RES on Stability: Analyzing how the lack of inertia and the intermittent nature of RES production lead to instability issues such as frequency, rotor angle, and voltage instability, and studying methods to enhance system stability.• Stability Analysis via Simulation: Using dynamic simulation methods to examine the impact of high RES penetration on overall grid stability, identifying the thresholds of RES integration beyond which grids become unstable.• Stochastic Simulations: Utilizing stochastic simulations to identify extreme scenarios that could lead to instability in power systems integrated with RES after disturbances, due to the intermittent nature of RES production.• Innovative Solutions: Proposing methods to stabilize power systems in critical scenarios, aiming for up to 100% RES integration while maintaining grid reliability. This includes the application of Fault Ride-Through (FRT) requirements and Energy Storage Systems (ESS).• Parameter Optimization: Using particle swarm optimization (PSO) to determine the optimal parameters for ESS controllers and Power System Stabilizers (PSS), thereby improving the quality and resilience of system responses.• Hybrid AC-DC Grids: Investigating the effects of hybrid AC-DC grids integrated with RES and proposing strategies to improve grid stability. This includes using HVDC-VSC technology as a firewall against disturbances and optimizing HVDC-VSC parameters to accommodate higher levels of RES penetration.

ORIGINAL LINK: https://theses.hal.science/tel-04998145v1

Institut für Elektrische Anlagen und Netze, Digitalisierung und Energiewirtschaft Lehrstuhl für Aktive Energieverteilnetze Einfluss netzbildender Umrichter auf die ungewollte Teilnetzbildung in Verteilnetzen

Erläuterung zum Dokument Die Inhalte dieses Berichts sind im Rahmen der wissenschaftlichen Studie „Technisch- wirtschaftliche Auswirkungen netzbildender Umrichter im Hinblick auf die ungewollte Teil- netzbildung in Verteilnetzen” entstanden, die das IAEW der RWTH Aachen University im Jahr 2023 im Auftrag der Westenergie AG durchgeführt hat. Das vorliegende Dokument beschreibt Teilergebnisse dieser Studie in Form von grundlegenden technischen Voruntersu- chungen zum Einfluss netzbildender Umrichter auf die Wahrscheinlichkeit der ungewollten Teilnetzbildung in elektrischen Verteilnetzen. Das Institut für Elektrische Anlagen & Netze, Digitalisierung & Energiewirtschaft (IAEW) gehört zur Fakultät für Elektrotechnik und Informationstechnik der RWTH Aachen Univer- sity. Unter der Leitung von Univ.-Prof. Dr. sc. A. Ulbig, Univ.-Prof. Dr. W. Leterme und Univ.-Prof. Dr.-Ing. A. Moser bilden mathematische Simulationen, Optimierungen und die Bewertung des technisch-wirtschaftlichen Ausbaus und Betriebs von Energieversorgungssys- temen Schwerpunkte in Forschung, Lehre und Industrieprojekten am IAEW. Das Institut hat in Deutschland und im europäischen Ausland eine Reputation in der professionellen und verständlichen Kommunikation energiewirtschaftlicher und netztechnischer Sachverhalte er- worben und ist als objektiver Gutachter in strategischen Fragen – auch gegenüber Regulie- rungsbehörden – anerkannt. Der Fokus am Lehrstuhl für Aktive Energieverteilnetze gilt insbe- sondere der Konzipierung sowie der simulativen und labortechnischen Analyse zukunftsfähiger dezentraler Energiesysteme. Durch langjährige Erfahrung in der Markt-, Netz- und System- analyse verfügt der Lehrstuhl über detaillierte Kenntnisse zur Bewertung von Potenzialen der Sektorenkopplung auf Verteilnetzebene, Netzausbaumaßnahmen und resilientem Netzbe- trieb, dezentralen Geschäftsmodellen, Chancen digitaler Technologien und Infrastrukturen, Schutzkonzepten und Stabilitätsanalysen mit einer objektiven Ergebnisinterpretation.

FULL PAPER: https://d-nb.info/1335581138/34