Coordinated Hybrid VAR Compensation Strategy with Grid-Forming BESS and Solar PV for Enhanced Stability in Inverter-Dominated Power Systems

This paper proposes a coordinated hybrid VAR compensation strategy that leverages the dynamic support capabilities of a grid-forming (GFM) battery energy storage system (BESS) and solar photovoltaic (PV) plant to enhance the stability of inverter-dominated power systems. The hybrid compensator integrates a VSC-based static synchronous compensator (STATCOM) with a thyristor-switched capacitor (TSC), combining the fast dynamic response of the STATCOM with the high reactive power capacity of the TSC. A coordinated control framework is developed to enable seamless interaction between the hybrid VAR compensator and the GFM-controlled PV and BESS units, ensuring improved voltage regulation and transient stability under varying operating conditions. The PV plant operates at maximum power Point while maintaining its grid-forming capability, thereby maximizing renewable energy utilization while contributing to frequency and voltage support. The effectiveness of the proposed strategy is validated through FPGA-based real-time simulations under scenarios including large load variations, solar irradiance fluctuations, and grid disturbances. Results show that the coordinated operation enhances voltage stability, strengthens reactive power support, mitigates low-frequency oscillations, and significantly improves the dynamic performance of low-inertia, inverter-dominated grids.