Research On Suppression Of Harmonics And Beat-frequency Of CRH5 EMUs’ Electric Traction Drive System

As the power source of high-speed EMUs,electric traction drive system plays an important role in train operation.However,in order to meet the lightweight requirements of high-speed trains and reduce the maintenance difficulties of hardware equipment,the LC resonance circuit is cancelled in the electric traction drive system of CRH5 high-speed EMUs.However,the cancellation of LC resonance circuit makes it impossible to filter out the pulsating voltage of the intermediate DC link,thus leading to a large number of low-order current harmonics on the grid side and lowering the current quality.The pulsating voltage also leads to beat-frequency phenomenon of traction motor,which affects the stable operation of trains.In order to suppress the low-order current harmonics of the grid side and the beat-frequency phenomenon of traction motor,improve the current quality of the grid side and improve the reliability of train operation,this thesis takes the electric traction drive system of CRH5 high-speed EMUs as the research object,and studies the optimization and improvement of the control strategies of the four-quadrant pulse rectifier and the inverter-traction motor.Firstly,the topology and working principle of electric traction drive system of CRH5high-speed EMUs are introduced,and the mathematical models of four-quadrant pulse rectifier and inverter-traction motor are established to provide theoretical basis for studying control strategies of four-quadrant pulse rectifier and inverter-traction motor.Secondly,the control strategy of electric traction drive system of CRH5 EMUs is studied.The transient direct current control strategy is adopted for the four-quadrant pulse rectifier,and the bipolar sinusoidal pulse width modulation(SPWM)method is adopted to modulate the four-quadrant pulse rectifier,and the operation efficiency of the rectifier is improved by combining the dual-carrier phase shifting technology.The rotor field oriented vector control strategy is adopted for inverter-traction motor,and the space vector pulse width modulation(SVPWM)technique is adopted for modulation.It lays a theoretical foundation for the optimization and improvement of the control strategies of four-quadrant pulse rectifier and inverter-traction motor.Thirdly,the generation mechanisms of low-order current harmonics on the grid side and the beat phenomenon of traction motor are analyzed.According to the generation mechanism of low-order current harmonics on the grid side,the control strategy of the four-quadrant pulse rectifier is optimized,and the suppression strategy of low-order current harmonics on the grid side based on Butterworth filter and quasi-proportional resonance(PR)controller is proposed to effectively suppress the low-order current harmonics.Aiming at the generation mechanism of traction motor beat-frequency phenomenon,the control strategy of inverter-traction motor is optimized,and the beat-frequency suppression strategy based on power balance control is proposed to suppress the beat-frequency phenomenon of traction motor.Finally,the simulation model of CRH5 EMU electric traction drive system is built using Matlab/Simulink platform.The low-order current harmonic suppression strategy based on Butterworth filter and quasi-proportional resonance controller,and the beat-frequency suppression strategy based on power balance control are simulated and verified.The simulation results show that the low-order current harmonics suppression strategy based on Butterworth filter and quasi-proportional resonance controller has good suppression effect on low-order current harmonics and improves the dynamic performance of the control system.The beat-frequency suppression strategy based on power balance control can effectively reduce the harmonic component in the stator current and torque ripple of the motor.