A siting and sizing strategy for distribution grid energy storage systems accounting for reliability and battery lifespan

High renewable penetration increases outage risk in distribution networks, while battery degradation during long-term operation significantly affects the economy and reliability of battery energy storage system (BESS) planning. To address this issue, this study proposes a decision-level coupled siting-sizing framework for BESS in distribution networks, in which reliability evaluation and battery degradation are directly embedded into the planning optimization process. A unified objective is constructed by monetizing degradation cost and integrating it with reliability improvement, and the problem is solved using a binary-discrete hybrid particle swarm optimization under typical-day scenarios. Results on the IEEE 33-bus system show that the proposed framework can effectively improve distribution system reliability while reducing the annualized total cost, achieving a better balance among reliability, battery lifetime, and economic performance. The proposed method provides an effective approach for coordinated BESS siting and sizing in distribution networks with explicit consideration of both reliability enhancement and battery lifespan.