Study On Harmonic Feature And Compensation Strategy For Traction Power Supply System Of Freight Railway

The DC drive electric locomotives represented by SS4G and the AC drive electric locomotives represented by HX_D3 are currently in a mixed application state for the electrified freight railway,and this state will remain for a long time.The safe operation of electric locomotive requires traction power supply system to provide high-quality power,but its non-linear characteristics is the main reason for generating harmonics,and the vehicle filter branch does not have the ability to eliminate all harmonic components.Therefore,it is of great practical significance to carry out the harmonic distribution characteristics analysis and the filtering suppression strategy study of traction power supply system by the combination of theoretical analysis?main circuit analysis,mathematical modeling,control strategy research?and digital simulation verification?MATLAB/simulink modeling and simulation?.The SS_4G and HX_D3 electric locomotives as the engineering background,the load current as the main research object to carry out relevant research work,and the 25kV direct-connected active filter method is proposed in this paper.Firstly,the main circuit physical model of SS_4G locomotive is established by using the working characteristics of phase-controlled rectifier circuit and the engineering calculation method of thyristor trigger angle,and its harmonic distribution characteristics are obtained through simulation results.Secondly,the simulation model of HX_D3 locomotive main circuit is established based on the working principle and mathematical model of PWM rectifier,motor driver and traction motor of HXD3 locomotive,and its harmonic distribution characteristics are analyzed through simulation results.Thirdly,a 25kV direct-connected active filter system with control strategy is designed to eliminate harmonic currents and retain fundamental current component,and its ability to suppress harmonics is verified by simulation.Finally,the three models?traction power supply system,the locomotive electric drive system and high-voltage active filter system?are built in the special condition that the two trains are running in the same traction substation based on the actual transportation condition of freight railway,and the joint simulation of three systems is carried out.The simulation results show that the proposed method can not only effectively compensate harmonic current,but also has the advantages of clear principle,fast response and strong operability.