Optimization Of Metro Timetable And Train Control To Reduce Energy Consumption And Passenger Travel Time

Reducing energy consumption and improving passenger service quality are main concerns of maintaining sustainable development of urban rail transit system.This paper focuses on train operation and timetable optimization that aim at reducing energy consumption and providing satisfactory transport service.First,train operation strategy with the given timetable and track profile is optimized,which aims to cut down traction energy consumption.Then,the utilization of regenerative braking energy is taken into account.Together with traction energy,train operation and timetable are simultaneously optimized to reduce system operating energy.At last,service quality is considered during optimizing the timetable,and passenger waiting time as well as in-vehicle time are used to indicate passenger service level.A bi-objective model is developed to optimize passenger service level as well as system operating energy consumption.(1)The traditional energy-efficient train control strategy(maximum traction-cruising-coasting-maximum braking)may use braking force to keep speed constant at downhill slopes,which is not beneficial for reducing energy consumption.In this paper,the sequence of operating regimes is optimized and an improved train control strategy is proposed.Brute force algorithm is implemented to attain the optimal solution.Case studies show that the improved train control strategy can achieve good energy-saving effects,especially in stations with low speed limit,sharp declines and short running time.(2)The practical energy consumption equals consumed traction energy minus utilized regenerative braking energy,thus the most traction energy-efficient operating strategy may not have the lowest system operating energy.On the basis of traction energy-efficient train control strategy,the utilization of regenerative braking energy is optimized by adjusting timetable.An integrated optimization model on train control and timetable is proposed to minimize operating energy and solved by a NS-GAA algorithm.Cases studies show that optimized operating strategy lead to a slight increment in traction energy,while the production and utilization of regenerative braking energy have remarkable increments.Compared with original timetable and train control strategy,the system operating energy reduced by 5%in the integrated optimization model.(3)The adjustment of train timetable may effect passenger service quality and increase their travel time.To address this issue,a bi-objective optimization model is developed which simultaneously considering energy consumption and passenger time.A NSGA-? algorithm is designed to solve the model.Considering the passenger boarding process is affected by constraints of train capacity and dwell time,spatial and temporal constraints are proposed to calculate passenger time.Case studies show that passenger boarding time may greater than scheduled dwell time.In this condition,extending dwell time in a reasonable range and recover the nominal timetable by compressing inter-station running time is the proper strategy to improve service quality.According to the Pareto optimal front which attained by NSGA-II algorithm,the passenger travel time can be reduced more than 3%without increasing energy consumption.