Optimal Placement of Grid-Forming controlled Converters for Small Signal Stability Enhancement of Power Systems by Yahya Lamrani-THESE Présentée en vue d’obtenir le grade de DOCTEUR En Spécialité : Génie Électrique Par Yahya LAMRANI DOCTORAT DELIVRE PAR CENTRALE LILLE

 

CENTRALE LILLE THESE Présentée en vue d’obtenir le grade de DOCTEUR En Spécialité : Génie Électrique Par Yahya LAMRANI DOCTORAT DELIVRE PAR CENTRALE LILLE 

Titre de la thèse : Localisation optimale des convertisseurs grid forming sur les réseaux de transport pour l'amélioration de la stabilité petits signaux Optimal Placement of Grid-Forming controlled Converters for Small Signal Stability Enhancement of Power Systems

 

 Abstract The massive deployment of renewable energy sources in the context of the energy transition has brought new challenges to the power system. The integration of renewable energy is mostly achieved by means of power electronics. High Voltage DC (HVDC) links, wind and solar parks all utilize Voltage Source Converters (VSC) to connect to the power system. Conventionally, the VSCs are controlled using the Grid Following (GFL) scheme. This control mode is reported to challenge the Small-Signal Stability (SSS) of the power systems. Grid Forming (GFM) control has emerged as an alternative technology to counter the issues resulting from the increasing penetration of power electronics in modern and future power systems. This thesis aims to propose a method for estimating power system needs for GFM- controlled converters, and determining their optimal placement within the network to en- hance the system SSS. First, the stabilizing effect of GFM is highlighted; various types of GFM controls are tested under different operating points and in different networks. The stability analysis is conducted using a state-space model and then confirmed by Electromag- netic Transients (EMT) simulations. The results indicate that all GFM controls provide a stabilizing effect. However, this effect varies significantly: all things being equal, the use of a current loop in the control structure makes the GFM less stabilizing and less robust to network variations (topology, operating point, type of loads). To best exploit the established stabilizing GFM properties, an iterative methodology for placing GFM-controlled convert- ers is proposed. This approach relies on two main indicators: the Frequency Averaged Grid Impedance (FAGI) to identify the weakest system bus, and the Modal Non-Passivity In- dex (MnPI) to assess the system stability. Both tools are based on the impedance model of the network and converters, extended beyond the fundamental frequency. Using this methodology, the minimal volume of GFM converters to be installed and their placement is determined. A realistic case study is considered to test the methodology and to determine the network short- and long-term needs for GFM converters.

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Grid-Following and Grid-Forming Control in Power Electronic Based Power Systems: A Comparative Study Gao, Xian; Zhou, Dao; Anvari-Moghaddam, Amjad; Blaabjerg, Frede-AAU Energy Aalborg University Aalborg, DK-9220, Denmark

 

Grid-Following and Grid-Forming Control in Power Electronic Based Power Systems: A Comparative Study Xian Gao, Dao Zhou, Amjad Anvari-Moghaddam, and Frede Blaabjerg

 Abstract - The stability of frequency is at risk with increasing penetration of power electronic converters. In this case, the power grid will lack the moment of inertia to maintain a stable voltage and frequency in the event of a large disturbance. In order to improve the stability of the power grid, traditional grid-following control is needed to be transformed to grid-forming control. This paper analyzes the control structure of grid-following control and grid-forming control. Moreover, a case study is exemplified to compare the performance of two control strategies responding to frequency disturbances. Finally, a simulation model of 15 kW grid-connected converter is built in Matlab/Simulink to discuss the performance of the grid-following and grid-forming converters under different working conditions.

View full paper :https://vbn.aau.dk/ws/portalfiles/portal/452850850/Final_Grid_Following_and_Grid_Forming_Control_in_Power_Electronic_Based_Power_Systems_A_Comparative_Study.pdf 

Grid-forming control to achieve a 100% power electronics interfaced power transmission systems by Taoufik Qoria -”Nouvelles lois de contrˆole pour former des r´eseaux de transport avec 100% d’´electronique de puissance”

 

´ECOLE DOCTORALE SCIENCES ET M´ETIERS DE L’ING´ENIEUR L2EP - Campus de Lille TH`ESE pr´esent´ee par : Taoufik QORIA soutenue le : 5 Novembre 2020 pour obtenir le grade de : Docteur d’HESAM Universit´e pr´epar´ee `a : ´Ecole Nationale Sup´erieure d’Arts et M´etiers Sp´ecialit´e : G´enie Electrique Grid-forming control to achieve a 100% power electronics interfaced power transmission systems

 Résumé The rapid development of intermittent renewable generation and HVDC links yields an important increase of the penetration rate of power electronic converters in the transmission systems. Today, power converters have the main function of injecting power into the main grid, while relying on synchronous machines that guaranty all system needs. This operation mode of power converters is called "Grid-following". Grid-following converters have several limitations: their inability to operate in a standalone mode, their stability issues under weak-grids and faulty conditions and their negative side effect on the system inertia.To meet these challenges, the grid-forming control is a good solution to respond to the system needs and allow a stable and safe operation of power system with high penetration rate of power electronic converters, up to a 100%. Firstly, three grid-forming control strategies are proposed to guarantee four main features: voltage control, power control, inertia emulation and frequency support. The system dynamics and robustness based on each control have been analyzed and discussed. Then, depending on the converter topology, the connection with the AC grid may require additional filters and control loops. In this thesis, two converter topologies have been considered (2-Level VSC and VSC-MMC) and the implementation associated with each one has been discussed. Finally, the questions of the grid-forming converters protection against overcurrent and their post-fault synchronization have been investigated, and then a hybrid current limitation and resynchronization algorithms have been proposed to enhance the transient stability of the system. At the end, an experimental test bench has been developed to confirm the theoretical approach. 

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DIRECT LINK: https://pastel.hal.science/tel-03078479v1/document 

Conception et pilotage de réseaux de convertisseurs génériques dans un contexte Smartgrids Antoine Bulteau

THÈSE Pour obtenir le grade de DOCTEUR DE L’UNIVERSITÉ GRENOBLE ALPES École doctorale : EEATS - Electronique, Electrotechnique, Automatique, Traitement du Signal (EEATS)

 Spécialité : GENIE ELECTRIQUE Unité de recherche : Laboratoire de Génie Electrique Conception et pilotage de réseaux de convertisseurs génériques dans un contexte Smartgrids Design and control of a network of generic cluster converters for Smartgrids Présentée par : Antoine BULTEAU

Summary The desire to integrate more renewable energy into the electrical grid necessitates an evolution in its architecture. This evolution will shift grid generation sources from centralized to decentralized production, facilitating and distributing the placement of renewable and intermittent generation sources across the grid. However, this decentralized integration raises a number of issues, notably the use of power electronics to facilitate access to these energy sources while simultaneously providing grid services. This thesis initially focuses on a pair of converters designed to address this grid

VIEW FULL THESIS: https://theses.hal.science/tel-04206778v1

 evolution and to perform potentially necessary grid services. This pair of converters is termed an energy router due to the grid services it offers.

Grid-forming control strategies of power electronic converters in transmission grids: application to HVDC link BY Ebrahim Rokrok

 

Grid-forming control strategies of power electronic converters in transmission grids : application to HVDC link Ebrahim Rokrok 

THESE présentée en vue d’obtenir le grade de DOCTEUR en Spécialité: Génie Électrique par Ebrahim Rokrok 

DOCTORAT DELIVRE PAR CENTRALE LILLE 

 Summary 

 The rapid development of converter-based devices such as converter-interfaced renewable generations and high-voltage direct-current (HVDC) transmission links is causing a profound change into the very physics of the power system. In this scenario, the power generation is shifted from the pollutant synchronous generators based on nuclear or fossil fuels to converter-based renewable resources. The modeling, control, and stability of the power converters are now one of the focuses of attention for researchers. Today, power converters have the main function of injecting power into the utility grid, while relying on synchronous machines that ensure all system needs (eg, ancillary services, provision of inertia and reliable power reserves). This operation mode of power converters is called "Grid-following". Grid-following converters have several limitations, such as: inability to operate in a standalone mode, stability issues under weak grids and faulty conditions and also, negative side effect on the system inertia. To tackle these challenges, the grid-forming control as an alternative has shown its appropriate performance that could make this kind of control a promising solution to respond to the system needs and to allow a stable and safe operation of power system with high penetration rate of power electronic converters. In this thesis, a fundamental description of grid-forming control with a simplified quasi-static modeling approach aiming to regulate the converter active power by a voltage source behavior is presented. From the description, several variants of grid-forming strategies are identified that represent some differences in terms of active power dynamic behavior, inertia emulation capability and system frequency support. Hence, the presented grid-forming variants are then classified according to their capabilities/functionalities. 

View Full Thesis : https://theses.hal.science/tel-04041405v1

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 ability to operate under very weak grid conditions. Moreover, the ancillary services such as inertial response and frequency support are appropriately provided to the AC grid.