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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