Study On Urban Rail Transit Wayside Super Capacitor Energy Storage Device Control Strategy

ABSTRACT:Urban rail transit vehicle regeneration failure is an important reason of electrical energy waste and brake shoe loss. Using super capacitor energy storage system can effectively absorb the surplus regenerative braking energy, meanwhile release the energy when trains are in traction condition, so as to achieve the purpose of saving energy, stabilizing voltage and preventing regeneration failure occurs.This article firstly simplifies equivalent circuit model of a super capacitor group, based on super capacitor generic equivalent circuit model and the actual situation of urban rail transit; and studies its working characteristics including temperature, frequency and voltage, etc. Next, topology selection and electrical parameters design are accomplished for super capacitor energy storage system, which uses a bidirectional DC-DC converter control the charging and discharging of super capacitor group.Control strategy of super capacitor energy storage system is the focus of this article. Uses a double loop cascade control strategy which traction network voltage is outer loop and super capacitor current is inter loop. System modeling is completed in buck and boost mode using the state-space averaging method, obtains the transfer function of each part. Designed bi-directional DC-DC converter and super capacitors parameters are brought into the transfer function to complete control system modeling, analyses the control effect of current inter loop and voltage outer loop using the complex frequency domain bode plot response method, and discusses the influence of different circuit working conditions and compensation coefficient on control performance.Completes the super capacitor energy storage system control strategy and work mode simulation with Matlab, simulation results verify the accuracy of the controller design and analysis, as well as the good match between main circuit and control circuit. Builds urban rail transit vehicle operating conditions simulation platform and200kW super capacitor energy storage system prototype in the laboratory, the platform joint debugging verifies the stability and reliability of the control strategy; comparison of the train’s two operating circles illustrates the role of super capacitor energy storage system in regenerative braking energy absorption and traction network voltage stability.