Optimal charging strategy for large-scale electric buses considering resource constraints

Abstract

• Limited charging resources and time-dependent electricity prices are considered. • A column-generation-based model is proposed for electric bus fleet charging problem. • Charging continuity is emphasized for battery's state of health in the subproblems. • The utilization rate of nighttime charging resources can be increased to 97.96%. • Large scale real-world cases can be solved within a short computation time. The large-scale application of electric buses highlights a series of practical problems, such as high charging costs, unreasonable utilization of charging resources, and chaotic charging schedules. In this study, a mixed integer programming model was first proposed to reduce the total charging cost of electric bus fleets by optimizing the charging power and charging time. Meanwhile, to improve the efficiency of the model under large-scale charging scenarios, a column-generation-based algorithm is developed to decompose the original model into a master problem and several subproblems, where each electric bus’s charging strategy is solved in an independent subproblem to guarantee a stable operational bus fleet schedule and to avoid intermittent charging. An experimental analysis is carried out. The results show that the optimal charging strategy can reduce the charging cost by approximately 36.1% compared with the uncontrolled charging strategy, which carries the potential to be applied in large-scale bus fleet operation.