Research On Identification And Suppression Of Low Frequency Oscillation In Traction Power Supply System

With the acceleration of railway electrification construction in China,by 2020,the electrified railway will reach more than 120,000 kilometers,while the high-speed railway will reach more than 19,000 kilometers.At the same time,the coupled oscillation between high-speed railway and traction power supply system is becoming more and more obvious,which seriously affects the normal order of high-speed railway.Taking CRH5 EMU as the research object,a time-domain simulation model of low-frequency oscillation of vehicle network is built.The mechanism of low-frequency oscillation of vehicle network is analyzed emphatically.Two methods for identifying low-frequency oscillation of vehicle network and two measures for suppressing low-frequency oscillation are proposed,which provide theoretical and model support for solving the phenomenon of low-frequency oscillation of vehicle network in engineering.Finally,using the simulation method of MATLAB/Simulink,the cause verification and suppression method of low-frequency oscillation of vehicle network are realized.Firstly,aiming at the problem of low-frequency oscillation in traction power supply system of electrified railway in our country,each part of the traction power supply system is modeled,the traction network,locomotive inverters and traction motors are rationally simplified,and the time domain simulation model of low-frequency oscillation of the coupled system is established.Secondly,the mechanism of low-frequency oscillation in traction power supply system of electrified railway is analyzed and elaborated by using the criterion of damping ratio.Through the analysis of the working principle of single-phase pulse rectifier and the transient DC control strategy,a small signal model of the train network is built.The influence of PI parameters of the control strategy of the grid-side converter and the number of locomotives on the low-frequency oscillation is analyzed,which provides a way to suppress the low-frequency oscillation of the It has important basis.In addition,aiming at the related characteristics and mechanism of low-frequency oscillation in traction power supply system,an improved Prony low-frequency oscillation detection and recognition method based on particle filter is proposed.The validity of these methods in identifying low-frequency oscillation in vehicle network is proved by theoretical analysis and simulation data comparison.Finally,in order to suppress the occurrence of low-frequency phenomena in the vehicle network,the feasibility of optimizing PI parameters to suppress low-frequency oscillation is verified by combining the relevant criteria of low-frequency oscillation.At the same time,an improved DQ decoupling active damping compensation control method for the network-side converter controller is designed.The simulation with MATLAB/Simulink software shows that this control method has better performance than the traditional transient DC control strategy.Low frequency oscillation suppression effect.