Energy-efficient Operation Optimization For Express/Local Trains In A Metro System

With the rapid development of economy and society,the population of big cities is increasing in number and density.The contradiction between the daily travel demand of urban residents and limited urban traffic resources increases correspondingly.Urban rail transit,as an efficient,convenient,punctual,reliable,safe and independent transportation method,has become an indispensable choice for residents of big cities.In recent years,cities have built urban rail transit lines which adopt the express/local operation,which is used to reduce the long commuting time due to the separation of workplace and residence in cities.In addition,with the large scale construction of urban rail transit and the rapid expansion of the network operations scale,the energy consumption of urban rail transit systems has shown a continuous growth trend.Train traction energy consumption accounts for about a half of the total energy consumption.Therefore,it is of practical significance to reduce the train traction energy consumption and use train regenerative braking energy effectively.The current research about energy-saving operation mainly focus on subway lines with the standard stop mode.The existing research has not considered enough about the difference of stop mode,the interaction between trains in the process of overtaking,and the difference in the utilization of regenerative braking energy between the trains.Therefore,it is necessary to search the energy-saving operation optimization of urban rail transit trains for the skip-stop line.This paper aims to propose a cooperative control model for the skip-stop line with the objective of minimizing the net energy consumption.A case study is performed on the actual operational data to optimize the train operation and verify the effectiveness of the algorithm.The main content of the paper is as follows:(1)The differences between the express/local stop mode and the standard stop mode are summarized,and an optimized driving strategy considering the characteristics of the skip-stop metro line is proposed to minimize the traction energy consumption of trains within multi-station operation.(2)A multi-train schedule optimization model for the skip-stop line is proposed to minimize the net energy consumption,which considers the headway between the express/local trains and the dwell time in each station.This model considers the use of regenerative braking energy for trains with overpassing conditions on the running line and the optimization of net energy consumption for train operations.Finally,a particle swarm optimization algorithm is developed to solve the proposed model.(3)Based on the actual skip-stop line data and line operation status,the validity demonstration and case study of the model are conducted.The case is arranged with following scenarios: energy-saving operation optimization of a single train with the express/local stop mode;a case study based on the existing express/local lines is conducted to study the influence on energy consumption considering the ratio of express/local trains;analysis and comparison of the regenerative braking energy utilization considering the different departure plans in the originating station.