Joint optimization of bifunctional fast-charging station considering shared operating capacity

• Novel biFCS model improving economics through shared capacity mechanisms. • Integrated framework handling EBFC-EVFC interactions under shared constraints. • EV demand assessment methodology evaluating co-utilization strategies. • Bi-level optimization model achieving joint EB scheduling and EVFC co-utilization. • Optimal EVFC configuration method balancing investment and revenue. Electric bus fast-charging stations (EBFCS) face high operating capacity but low utilization rates, leading to poor economic performance. This study develops a joint optimization framework for bifunctional fast-charging stations (biFCS) that integrates electric vehicle ultra-fast chargers (EVFC) with EBFCS to utilize idle capacity and reduce costs. The proposed biFCS model incorporates electric vehicle (EV) charging demand simulation and electric bus (EB) charging optimization based on shared operating capacity. A bi-level optimization method is proposed where the upper level optimizes operating capacity allocation and EVFC co-utilization strategy, while the lower level optimizes EB charging scheduling. Simulations demonstrate that adopting the biFCS framework reduces costs by 21.3 %, while the proposed optimization strategy that maintains EB charging service quality while optimizing EVFC availability achieves an additional 17.1 % cost reduction. Sensitivity analysis reveals that the EV density and investment cost impact biFCS cost-effectiveness, with 5 EVFC units being optimal in the case study, providing critical EVFC deployment guidance. When integrated with photovoltaic-energy storage systems, the EV charging demand attracted by biFCS enhances photovoltaic consumption benefits. The findings indicate that the biFCS model efficiently utilizes idle EBFCS capacity and generates revenue, the joint optimization approach providing practical guidance for EB charging operators’ cost reduction.