Optimal Sizing of BESS for Attaining Frequency Stability Under High PV Penetration

Frequency stability has become a major concern for grid operators as photovoltaic (PV) penetration increases in existing grids. Battery energy storage system (BESS) is an intriguing supporting mechanism that assists in enhancing the frequency response of such grids. However, excess BESS installation can impose substantial financial issues, whereas inadequate installation may fail to support the grid. To this end, we propose a novel methodology for determining the optimal BESS size focusing on frequency stability. Particle swarm optimization (PSO) is utilized to execute the optimization in the Python-DIgSILENT PowerFactory co-platform. The method is then implemented in different PV penetration scenarios, and the method's validity is evaluated. Additionally, synchronous condensers (SCs) are installed in the grid to compare performance with optimized BESS. All the dynamic simulations are conducted on a modified IEEE 39 Bus New England test system. The results demonstrate that, in every case, optimized BESS utilization prevents the activation of the Under Frequency Load Shedding (UFLS) scheme during a major synchronous generator outage event. Thus, the optimized BESS enhances grid frequency stability with high precision while adhering to all of the specified constraints. Furthermore, they outperform SCs of similar size that fail to prevent UFLS activation in every scenario. This research will benefit future BESS installations in large-scale PV integrated grids to obtain higher frequency stability with the smallest feasible size.