Research On On-line Optimal Control Strategy Of Urban Rail Transit Super-capacitor Energy Storage System

The application of wayside super-capacitor energy storage system in traction power supply system of metro can realize the recovery and utilization of regenerative braking energy of trains,which has a significant effect on reducing energy consumption of train operation.In the actual operation of the super-capacitor energy storage system,the fluctuation of the no-load voltage of the traction power supply system and the headway will affect the recovery and utilization effect of the regenerative braking energy of the energy storage system.Based on the traditional fixed charge and discharge threshold control strategy,the influence factors of energy saving effect are analyzed,and the control strategy of wayside super-capacitor energy storage system is optimized considering the regenerative braking characteristics and the headway.Firstly,the mathematical model of traction power supply system is established,including traction substation,traction network,train and super-capacitor energy storage system.Especially,the train model considers braking resistor characteristics.The paper analyzes the actual data of Batong line of Beijing metro,and verifies the accuracy of the model by comparison with the experimental results.On this basis,the influence of train braking characteristics,starting interval,output characteristics of the rectifier unit and other factors on the energy saving effect of the energy storage system is analyzed in detail.The train braking characteristics affect the energy recovery effect of regenerative braking energy,the fluctuation of the no-load voltage of the traction power supply system influences the energy release effect of the energy storage system,and the recommended setting range of charge and discharge threshold is given,and the validity of the analysis is verified by simulation.Considering the shortcomings of off-line control parameters in practical application,this paper proposes an on-line optimization control strategy of super-capacitor energy storage system based on operating state,which is based on the maximization of energy storage system energy saving.The off-line optimization and on-line threshold adjustment are adopted in this strategy.The optimal threshold control parameters are obtained by combining the genetic algorithm with the urban rail transit power supply system simulation platform.The online optimization algorithm takes the offline optimization parameters as the input value and supervises the operating state of the super-capacitor energy storage system and the rectifier unit,adjusts the charge and discharge threshold of the super-capacitor energy storage system according to the threshold optimization rules,and achieves the maximum energy saving,and the effectiveness of the control strategy is verified by simulation.In this paper,1MW wayside super-capacitor energy storage system hanging net experiment was completed in the traction substation of Liyuan substation in BaTong line of Beijing Subway.The experimental results validate the feasibility of the proposed control strategy.