Overnight Charging Scheduling Optimization for Electric Battery Buses with Controllable Charging Completion Levels

In the application of battery electric buses, cruising range anxiety, high charging cost, and unreasonable allocation of charging resources are essential factors hindering their promotion. This study aims to identify an overnight charging schedule for battery electric buses to minimize battery charging-related operation costs. Among them, the impact of battery degradation cost and nonlinear charging function on the charging schedule is mainly considered. One novel feature of the considered problem is a controllable charging completion level. Therefore, we describe the overnight charging of battery electric buses as a parallel machine scheduling problem with a controllable task completion level. To solve this problem, mixed-integer linear programming formulations are developed. An efficient heuristic algorithm is proposed for solving large-scale instances, and numerical experiments verify the effectiveness of the proposed algorithm. A case study further reveals that the optimal charging schedule can save at least 10% of operation costs and has the potential to be applied in the operation of large-scale bus fleets.