Dynamic Voltage Support for PV-BESS Systems Using VSG-Based Grid-Forming Inverters

Abstract

A high penetration of grid-following inverter-based resources can degrade voltage stability because these inverters depend on grid voltage references and provide limited dynamic support during disturbances. This paper proposes a virtual synchronous generator (VSG)-based grid-forming (GFM) inverter controlled by finite control set model predictive control (FCS-MPC) to improve voltage stability in renewable-dominated distribution systems. The proposed system integrates a solar photovoltaic (PV) source and a battery energy storage system (BESS) on a common DC bus, where FCS-MPC is applied to both the GFM inverter and the bidirectional DC-DC converter. The BESS supports active-power balancing, while the proposed Volt-VAR controller regulates active and reactive power during voltage step changes. MATLAB/Simulink results demonstrate improved voltage support, reducing voltage deviation to one percent of nominal in both load-removal and load-addition scenarios. The results also confirm DC-link regulation under irradiance variations.