Optimal Sizing and Placement of Li-ion BESS for Virtual Inertia and Frequency Stability Enhancement in Grids with High Solar Penetration

The global trend of large-scale high-capacity photovoltaic power generation has led to high instability due to inherent intermittency of solar energy and lack of mechanical inertia. Battery energy storage systems (BESS) as a solution can provide quick-response virtual inertia emulation (VIE). This study focused on the optimal combined sizing and location of lithium-ion BESS to achieve optimal virtual inertia supply and improve the frequency stability for grid networks with up to 40%-PV penetration. The optimization scheme aims to reduce the Life-Cycle Cost (LCC) and system penalties related to frequency deviations, the maximum frequency deviation and maximum allowable rate of change of frequency using the Teaching-Learning Based Optimization (TLBO). Simulations on modified IEEE 14 and 30 benchmark systems showed quantifiable benefits in optimal sizing of the assigned rating and capacities, namely the 44.4 MW and 193.9 MWh at Bus 8 on the 14-bus system, leading to significant attenuation of frequency deviation; in the 30-bus test case during a generator outage scenario, the frequency deviation was reduced from 0.503 Hz without BESS to 0.312Hz with BESS, and recovery time was reduced from 25s to 8s. In addition, the reliability indicators were improved, as shown with a decrease of the SAIDI index from 180 h/yr to 160 h/yr.