Research On Beatless Control Strategy Of Electric Traction System

In the traction transmission system of high-speed train,because of the dc side is supplied by single-phase rectifier,the pulsating voltage of the power grid frequency is twice as high as that in the intermediate dc link.General use LC resonance filter to filter in second harmonic,the existence of filter inductance increases the weight of the body,to meet the requirements of train lightweight,CRH2 emu cancelled the second filter branch.In this paper,the traction system is analyzed and studied by using the relevant data of CRH2 motor vehicle.This paper first introduces the CRH2 emu traction system adopts three level inverter circuit topology,specific steps and methods of SVPWM control,including regional judgment,vector effect time calculation,vector sequence and the role of time allocation,aimed at the halfway point of the three level inverter voltage deviation problem,through the reasonable distribution of redundant small vector,which can realize neutral voltage control function.Finally,the vector control principle and mathematical model are given.Established the mathematical model of three level four quadrant converter,and has carried on the simulation,the simulation results show that cancel the secondary filter rectifier voltage contains large second harmonic component,and analyses the influence of dc side voltage ripple component of inverter output voltage,the influence of the traction motor stator current and torque,the causes of the phenomenon of beat frequency is given.In this paper,the suppression method of the beat frequency induced by secondary filter is studied.A SOGI-FLL adaptive filter is designed for the extraction of dc pulsation voltage.According to the principle of volt-second equilibrium,a frequency-frequency suppression method is given to compensate the output voltage amplitude and frequency of the inverter.In the Matlab/Simulink simulation software,the simulation model of the direction vector control of the traction converter and the motor is set up,and the control strategy under different power supply schemes is verified.The simulation results show that after adding compensation control,motor phase current generated by the angular frequency of the beat frequency of cxirrent harmonic is reduced,the motor torque ripple is reduced,got inhibition beat phenomenon.