Integrated vehicle and bidirectional charging scheduling for V2G-enabled electric bus system

Electric bus (EB) fleets are transformed into flexible energy resources through vehicle-to-grid (V2G) technology while maintaining regular transit services. This paper investigates the joint optimization of vehicle operations and bidirectional charging decisions for a multi-route EB system with limited bidirectional and unidirectional chargers. A time-expanded network is constructed to capture EB's daily operations, supporting optimization of partial charging and discharging decisions. Considering the effect of upward and downward regulation demands of the power grid, a mixed-integer programming model is established to minimize operating costs and regulation deviation. Then, a column-generation-based diving heuristic algorithm incorporating two dominance strategies is further designed to efficiently search for a high-quality solution. Finally, numerical experiments based on real-world bus routes are conducted, and results indicate that the optimized scheme enhances both the economic performance and grid-friendly operation of the EB system. Specifically, the discharging revenues effectively offset the electricity purchase and battery degradation costs, while the EB fleet meets 86.3% of the regulation demand. In addition, the two dominance strategies reveal different advantages, dominance strategy I reduces total costs by 28.7 CNY, whereas dominance strategy II shortens the solution time by 39.6%.