Energy management concept of a 200 kVA battery grid-forming inverter in island grid operation

The increasing integration of renewable energy sources into power grids requires adaptive strategies to maintain stability, espe-cially in island and distribution grids. This paper presents the development of a 200 kVA battery inverter with grid-forming control for the integration of photovoltaics (PV) into island grids. The inverter uses a three-phase ANPC topology with two interleaved legs and a DC-DC converter with flying capacitor topology. Usually, PV systems shut down as soon as they detect an island grid. However, the integration of renewable energy is crucial for future grid reliability, especially in isolated or disaster-affected regions. The energy management system aims to integrate PV systems into the grid during island grid operation, prevent battery overcharging and ensure grid-serving functionalities. Using the VDE 4105 guidelines, the system controls PV active power by adjusting the grid frequency and optimizes the battery's state of charge (SoC) for reliability and durability. Laboratory tests with Power-Hardware-in-the-Loop (P-HiL) demonstrate the effectiveness of the system in maintaining uninterrupted grid operation and adapting PV power generation to the needs of the microgrid.