Collaborative optimization of electric bus fleet size and charger deployment
To ensure bus energy supply and smooth operation of an electric bus system,this study for-mulates a two-level route-oriented optimal deployment model of electric buses and chargers consider-ing the stochastic route traveling time in the scenario of multiple bus routes and charging stations.This model makes optimization decisions on the fleet size of each route,number of chargers in each charging station,and assignment of each route to the charging station,with the objective of minimiz-ing the sum of the capital costs of buses and chargers and the passenger waiting cost.To reflect the impact of the bus charging process on route operation under the stochastic route traveling time,a multiserver queuing model with limited system capacity is introduced in the lower-level model to characterize the charging process under the fixed assignment of route to charging station;in the up-per model,the assignment of route to charging station is optimized considering the capacity con-straints of the charging stations and bus depots.To address this problem,an algorithm is designed based on a queuing model to obtain the optimized fleet size and number of chargers for a given route assignment to a charging station.The commercial solver CPLEX is thereafter used to determine the optimal assignment solution for all routes to the charging stations.In the numerical experiments,in-stances with different scales are designed to confirm the effectiveness of the two-level model and the proposed solution framework.The results demonstrate that the proposed two-level model and solu-tion framework can minimize passenger waiting and ownership costs of buses and chargers,consider-ing the capacity constraints of charging stations and bus depots.Compared to the two artificial empir-ical methods,the proposed solution framework generates a more optimized solution with decreases of 5.65%and 4.54%in the objective function value.
urban transportationdeployment optimizationqueuing modelelectric busfleet sizenumber of chargers
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