Power Distribution Control Strategy Of On-board Supercapacitor Energy Storage System Of Railway Vehicle

ABSTRACT:Urban rail transit system, with large transportation quantity, fast-speed, on-time and all-weather, has been relieving the problem of traffic jam and congestion effectively, promoting the city's modernization process. But urban rail transit costs high energy, and regeneration failure greatly reduces energy saving effect. Supercapacitor, with high power density and long cycle life, has unique advantages and development prospects in avoiding regeneration failure, improving the braking force in high-speed range and realizing catenary-free operation.In this paper, on-board supercapacitor energy storage system is studied on. Firstly, the characteristics of supercapacitor are analyzed and equivalent circuit model is established, then the charge-discharge performance is discussed. Supercapacitor energy storage system contains supercapacitor bank and bi-directional DC-DC converter. The structure of the energy storage system and the principle of bi-directional DC-DC converter are analyzed in detail. Taking Guangzhou Metro Line 4 for example, the steps of capacity configuration for rail transit is summarized. Based on the traditional control method, this paper proposes a power distribution control strategy for on-board supercapacitor energy storage system. The fuctions of the line current loop, the line voltage loop and supercapacitor current loop are illustrated. The control concept that power distribution, energy distribution are realized through current limiter, is proposed. Based on the theory foundation above, a 3kW supercapcacitor energy storage system experimental platform with the controller of TMS320F28335 is designed. Finally, simulation research on this system is carried out and experiment is finished.The simulation results verify the feasibility of control strategy. The experiments test the characteristics of capacitance and ESR, and verify the system structure and parameters. Two different current limit curve experiments verify the proposed control strategy. By comparing the results of two groups, the relationship of current limiter, capacity configuration and energy saving rate is derivated.