Study On Energy-saving Control System For Regenerative Braking Of Urban Rail Trains

When a rail train is in a braking state,it generates considerable regenerative braking energy and feeds back into the traction network,but it also causes the traction network voltage to rise.Therefore,the braking energy is recycled under the premise of controlling the voltage of the traction network within the allowable fluctuation range,which not only improves the economic benefits,but also plays an important role in the mitigation of the energy shortage.In this paper,the supercapacitor energy storage control strategy for urban rail regenerative braking under the guidance of PMSM is proposed,and the combination of urban rail traction drive and super capacitor regenerative braking energy storage control is analyzed.Firstly,the advantages and disadvantages of the train's five modes of regenerative braking energy absorption are analyzed,and the super-capacitor energy storage method is used.The traction drive part of the SVPWM vector control of the 24 pulse rectification traction substation and permanent magnet synchronous motor is modeled.According to the structure and characteristics of the supercapacitor,the charge and discharge characteristics of the supercapacitor are studied through modeling and simulation,and the equivalent circuit is determined.Using the energy and power constraint conditions,the parameters of the series-parallel connection and the equivalent model of the super capacitor bank are obtained.Secondly,the DC/DC converter topology of the energy storage control system is selected,and the filter capacitor inductance and energy storage inductance parameters in the structure are designed.The bidirectional DC/DC is used to model the system using the state-space averaging method to derive the mathematical model.The Bode diagram is used to analyze and correct the effects of the double closed-loop controllers of the system voltage outer loop and current inner loop.Then build and simulate the model of the energy storage control system based on the designed parameters and controller.Finally,combined with the characteristics of the start and braking of urban rail transit trains,the traction substation model,train model,and super capacitor energy storage system model are combined to form a supercapacitor energy storage system for urban rail trains to build a rail transit traction drive energy storage system.The overall model of the control system uses MTLAB/Simulink simulation software to perform overall simulation of the traction drive and regenerative braking energy control of the train under traction,idle,and brake operating conditions.The analysis of the simulation results shows the feasibility of regenerative braking energy recovery and the improvement of the traction network voltage.