Research On Control Strategy Of Traction Drive System Of Subway Asynchronous Motor

Asynchronous motors are widely used in my country’s urban rail transit industry because of their simple structure,stability and reliability,and high work efficiency,and the traction drive system is the core and key of the urban rail transit vehicle control system.Therefore,analyzing and solving the problems existing in the traction drive system is the premise and guarantee for the smooth,safe and efficient operation of subway vehicles.In this paper,the voltage coupling problem and decoupling algorithm in the vector control strategy of subway asynchronous traction motor,the improvement of the flux linkage observer in the full speed range of the motor,and the DC side oscillation problem and suppression strategy of the traction drive system are studied in depth.At present,the vector control strategy based on rotor field oriented control is relatively common in the control of subway asynchronous motors.In this paper,a voltage feedforward decoupling control algorithm is proposed for the voltage coupling relationship between the d and q axes of the stator in this control strategy.In the control process,the coupling between the d and q axes of the stator is eliminated,so that the d and q axis voltages can independently control the corresponding two-axis currents.The simulation results show that this strategy has a good decoupling effect and effectively improves the system.responding speed.Aiming at the limitation of the application range of the commonly used current-type and voltage-type flux linkage observers,this paper proposes an optimized hybrid flux linkage observer suitable for the full-speed range,which overcomes the problem of simply using current or voltage-type flux linkage observers.The limitation brought by the chain observer enables the asynchronous motor to accurately observe the rotor flux linkage in the full speed range,which improves the overall performance of the vector control system,and the accuracy of the method is verified by simulation.The negative impedance characteristic of the converter reduces the system damping,which leads to oscillation on the DC side of the traction drive system,which affects the stability of the system.Aiming at this problem,this paper uses the relevant theorems to analyze the system stability and influencing factors,analyzes and explains the nature of the negative impedance characteristics of the DC side of the traction drive system and the specific reasons for the formation of oscillation,and according to the characteristics of the actual operating environment of subway vehicles,the oscillation is suppressed.The algorithm is integrated into the motor vector control strategy,and it is proposed to extract the DC component and the oscillation component from the DC side capacitor voltage to generate a suppression factor,so as to correct the given torque current,so that the system damping increases,and the converter presents a positive The oscillation suppression strategy of the active damping method of impedance characteristics is verified,and the effectiveness of the oscillation suppression strategy is verified by simulation.