Research On Energy Management Strategy Optimization Of Stationary Supercapacitor Energy Storage System Based On Full Life Cycle

With the rapid development of urban rail transit,the effective use of regenerative braking energy has been widely concerned.Since the supercapacitor has the advantages of high power density and long cycle life,it is an ideal energy storage element for absorbing and using regenerative braking energy.During the operation of the energy storage system,different energy management strategies have different effects on the energy saving and life of the system.Based on the calculation and analysis of power flow among the energy storage system,the substation and the train,and the characteristic test of the supercapacitor,this paper proposes a dynamic threshold energy management strategy that takes into account the train operation state,characteristics and life of supercapacitor.Firstly,the advantages and disadvantages of the supercapacitor model are compared and analyzed.The equivalent circuit model,thermal model and life model of supercapacitor suitable for urban rail transit energy storage applications are built.Then the constant current charging and discharging test of supercapacitor is carried out by using the Arbin instrument.The equivalent circuit model and the thermal model are identified based on the IEC standard and the least square method respectively.Finally,the high temperature accelerated cycle life test was carried out on the supercapacitor using a temperature chamber,and its health status index,capacity C,was monitored.The test results well verified the accuracy of the life model.Secondly,in order to study the energy flow relationship among trains,rectifier units and energy storage device,each part of the traction power supply system is modeled;based on the current iteration method,the power flow analysis of the traction power supply system with energy storage devices was carried out,the energy consumption of the system was analyzed.According to the single train operation model and the double train operation model,the influence of the charging threshold on the energy flow relationship and the regenerative braking energy recovery efficiency of the system is analyzed,and the charging threshold energy management strategy based on the running state of the train is given.At the same time,in order to prolong the lifetime of supercapacitor without affecting the energy saving of the system,a dynamic sequence optimization of the charging thresholds in different charging intervals is performed based on immune genetic algorithm.According to the optimization results and power flow analysis results,a dynamic threshold control strategy based on charging interval division and a threshold adjustment strategy considering the aging of supercapacitor are proposed.The effectiveness of the proposed strategy is verified by the actual simulation examples of the Beijing Metro Batong Line.Finally,the power hardware-in-the-loop experiment was completed based on the battery/ supercapacitor hybrid energy storage platform and RTLAB.The battery energy storage device is used to follow the voltage fluctuation of the traction network bus,and the super capacitor energy storage device recovers the regenerative braking energy of the trains.The experimental results well verify the effectiveness of the dynamic threshold energy management strategy proposed in this paper.