Network Design And Operational Optimization Of Battery Electric Buses System

Due to its low energy consumption,zero emission and other advantages,the battery electric bus plays an important role in solving the problem of insufficient supply and environmental pollution associated with public transport sector in large cities.The electrification of public bus will be of great importance to sustainable development of public transport and green bus revolution.Nevertheless,with the expansion of battery electric bus and the increase of passenger flow,the problem of high operation cost and poor service level not only brings great pressure to enterprises,but also hinders the rapid development of battery electric bus.Therefore,for the battery electric bus network and operation management,the key factors affecting the service level and operation efficiency of battery electric bus are found,and operation characteristics of battery electric bus under different charging facilities are analyzed.Moreover,optimization framework on battery electric transit planning and operation have been established.The theoretical and methodology are indispensable for supporting decisions made by authorities to planning and Management battery electric bus.The primary research works are as follows:1.Considering the characteristics of fast charging station in reducing the charging time and the range requirements of battery electric buses,electric transit network and fast charging stations must be simultaneously and strategically deployed.Given the passenger demand and candidate bus stations,a bi-level programming model is developed to formulate the electric transit route network design problem.The upper-level problem aims to minimize the weighted sum of unsatisfied demand,total passengers' travel time,total operator cost.The lower-level problem is a transit assignment problem with capacity constraints.The modified genetic algorithm(GA)is developed to solve the bi-level problem,different from the traditional GA,specific genetic operators are developed to search all possible route structures.A numerical example from Swiss road network is employed to demonstrate the performance of the proposed algorithm and the applicability of the formulated model.Through sensitivity analysis,the interrelationships between the layout of fast charging station,passenger travel cost and vehicle battery capacity are discussed.2.On a linear bus line with battery electric bus system,this study considers the unbalanced distribution of passengers along the corridor.The short turning operation strategy is introduced to improve the capacity utilization of battery electric bus during peak hours.The functions of passenger waiting time and system operation cost are calculated based on a microeconomic approach.Then,Analytical results of frequency optimization for both inside and outside short cycle are obtained applying first order conditions.Finally,we use enumeration method to analyze the optimal short turning scheduling scheme and corresponding benefit under different demand profiles.Results show that the short turning strategy could yield benefit if the demand is concentrated in the route,and its benefit depends on both passenger distribution and the duration of operation period.3.Based on the above research,we further study the short turning strategy on the bus network with battery electric bus.Considering the high demand sections may be asymmetric and unidirectional,integrated deadheading-short-turning lines and interlining lines are deployed to cover high demand sections distributed in the entire network.First,a heuristic generation algorithm,based on switch points section and route enumeration,is proposed to generate the set of virtual lines.Then,by developing a mixed-integer nonlinear programming model,the optimal combination of originally planned and virtual lines could be found.The numerical experiments of Beijing Third Ring bus network show that the strategy yields benefit for the bus network,but the cost savings are relatively small,which is mainly because the high demand segments are separated and there is a long distance between the segments.4.For the operational panning,the vehicle scheduling problem of battery electric bus considering time-of-use price is investigated.Based on the discrete time,task constraints meeting the requirements of normal strategy and short turning strategy are proposed.Then,a mixed integer linear programming model is developed to minimize the electric charge and determine the statuses of buses in each time interval.Numerical studies show the advantages of short turning strategy in terms of the number of vehicles used and the cost of charging.Moreover,the number of battery electric buses cannot be effectively reduced by increasing battery capacity or charging power alone.