Optimal Sizing of Battery Energy Storage System for Grid Stability in Western Kenya

Increased penetration of variable renewable energy sources (vRES) in utility power grids in the East African region poses significant technical and economic challenges. Resource variability and intermittency, coupled with inverter interfaced grid connection, impact the utility power system's steady-state and dynamic behavior, and introduce bi-directional power flow patterns. Traditional utility power grids are structured to balance the variability of power demand and resource availability using dispatchable generators, mainly fossil-fuel-based. Decarbonization, intermittency mitigation, and electric vehicles'(EV) rollout have put a premium on flexible grids and energy storage. Utility-scale battery energy storage systems (BESS) have emerged as an alternative in providing frequency and voltage regulation, emergency response and peak regulation, improving power system planning and operations in utilities. This paper presents an optimal sizing approach to provide BESS-based dispatchable power in Western Kenya. The objective was to size and site an optimal BESS in South Nyanza region to help mitigate the rampant load management experienced in the area especially during evening peak load times due to voltage instability and/or transmission line load capacity limitation. The simulation study was conducted on PSS/E with loss minimization and voltage profile variations per Kenya Grid Code requirements as the optimization criteria. Results showed that a BESS of approximately 45MW/180MWh adequately solves this problem and eliminates unserved energy during the evening peak period. Benefits include approximately 1.84 GWh and Kshs. 1.60 billion in annual energy loss savings and fuel displacement costs respectively, optimal utilization of the geothermal resources and improved grid operation even with increased penetration of vRES.