Impact of Grid-Connected Inverters on Medium-Voltage Grid Currents During Phase-to-phase Faults

The growing incorporation of renewable energies (RE) into France’s Enedis medium-voltage grid via static converters necessitates a thorough assessment of their impact, both under typical operating conditions and in the event of faults. Understanding this issue is vital for ensuring the effective operation of protection relays at the substation level, distinct from those at the electrical energy producers sites due to variations in behavior and contribution arising from different control mechanisms compared to synchronous machines.This project has two primary objectives. Firstly, it aims to ensure that the grid-connected inverter (GCI) we intend to deploy adheres strictly to the medium-voltage grid codes, including Low Voltage Ride Through (LVRT) and potential dynamic voltage support during grid faults. This is imperative as these requirements may not be part of Enedis technical specifications, and compliance may vary among electrical energy producers. Thus, it is pertinent to investigate this scenario. Secondly, we seek to analyze the behavior of the GCI and its influence on the measured current at the source substation during phase-to-phase faults on the medium voltage network and the potential impact on fault currents. This is significant as the settings of the overcurrent protection on the Enedis side rely on phase-to-phase fault currents. By gaining insights into the GCI’s operation and its effects on the overcurrent relay (OC) of the electrical network during faults, we aim to enhance the resilience and efficiency of electrical systems.Preliminary findings indicate that the GCI can impact the source substation’s contribution to faults by reducing current injection. This phenomenon may lead to relay blinding and malfunction if the influence of GCI is not appropriately considered.To our knowledge, very few references address the issue of the impact of the GCI on the prospective current provided by the substation and therefore the impact on the settings of its associated protection relay.