Optimal Design of Mixed Charging Station for Electric Transit with Joint Consideration of Normal Charging and Fast Charging

In this paper, we propose a bi-level model to optimize the design of mixed charging station deployed at the terminal station for electric transit. At the lower level, the service schedule and charging strategy of electric buses is optimized under the given design of mixed charging station. The lower-level model is a management optimization at the operational level, aiming at minimizing the total daily operational cost. The model is formulated as a mixed integer programing subject to limited charging facilities of multiple types. At the upper level, the design of charging station is optimized based upon the results obtained at the lower level. It is a kind of decision making at the tactical level, with the objective of minimizing the sum of operational cost of electric bus fleet (i.e., objective function of the lower-level model) and installation cost of charging infrastructure. We conducted numerical cases to validate the applicability of the proposed model and some managerial insights stemmed from the numerical case studies are discussed, which can help transit agencies design charging station scientifically.