Load Process Simulation And Optimization Design Of AC Traction Power Supply System With Energy Storage Device

With the increasing demand of transportation,the energy consumption of railway system is increasing.It is of great significance to study the energy-saving operation method of electrified railway to reduce the operating cost of traction power supply system,promote the low-carbon development of railway system and improve the competitiveness of railway in the transportation industry.Optimizing train driving strategy can reduce the traction energy consumption of the train,the access of energy storage device can realize the utilization of regenerative braking energy and peak shaving and valley filling of traction load,both measures can reduce the energy consumption of the existing traction power supply system.In addition,when the line is built or reconstructed,the co-phase traction power supply technology will further improve the utilization rate of regenerative braking energy between trains.How to simulate the load process of AC traction power supply system with energy storage device,and optimize the train driving strategy and configuration parameters of energy storage device are worth further study.In this paper,the following researches are conducted on this issue:(1)The topology and working states of the hybrid energy storage device composed of ultracapacitors and batteries are analyzed.For the existing power supply system,the trackside access scheme of hybrid energy storage is given,and the control strategy of hybrid energy storage is formulated.For the co-phase power supply system,the power flow controller DC bus access scheme of hybrid energy storage is studied,the grid-side voltage imbalance constraint is considered,the energy control strategy of power flow controller and hybrid energy storage is proposed.(2)The driving strategy is described by the train speed-distance curve,the train traction calculation model based on spatial state conversion is established.The mathematical models of electric locomotive,traction network and traction substation are analyzed.Based on the access scheme and control strategy of hybrid energy storage,the load process simulation model of AC traction power supply system with energy storage device is established,which provides a basis for the comprehensive optimization of AC traction power supply system.(3)The electricity cost of the traction power supply system under the two-part electricity price and the life cycle cost of the hybrid energy storage device are analyzed.A comprehensive optimization model of AC traction power supply system with energy storage devices is established,the goal is the lowest comprehensive cost,the optimization variables include not only the discrete train speed-distance curve,but also the power,capacity,and location of the hybrid energy storage device.A genetic-particle swarm hybrid algorithm is adopted to optimize the problem.(4)Taking a typical line as an example,the comprehensive optimization analysis of the traction power supply system under the existing power supply mode and the co-phase power supply mode is carried out respectively.The calculation results of four cases shows that,compared with the initial case(case 1),when the train driving strategy is optimized separately(case 2),the comprehensive cost of the existing and co-phase power supply system can be reduced by 12.95% and 15.97%;when the hybrid energy storage device is connected separately(case 3),the reduction can be 12.76% and 8.86% respectively;when the comprehensive optimization(case 4),the reduction can be 18.27% and 25.62%respectively.Compared with the existing power supply system,the comprehensive cost of the co-phase power supply system in the four cases can be reduced by 7.95%,11.158%,3.83%,and 16.23%,respectively.The above analysis verifies the correctness of the model proposed in this paper,and shows that the co-phase power supply system has great economic efficiency and application prospects.