Simulation And Design Of Harmonic Compensation Device For Electric Railway

In the development process of electrified railway,high-speed and heavy load have become the normal operation of railway in the new era.With the expanding of network size and a large number of high-speed trains put into use,load current deteriorates caused by the changes of running state and running environment,resulting in a decline in the power factor or other power quality problems,affecting the health of traction power supply system during running.So,management or compensation method must be taken to deal with the power quality problems.In this thesis,CHB-APF is used as the harmonic compensation scheme,and some related issues are studied.In order to fundamentally understand the harmonic characteristics of the traction power supply system,firstly,a simulation model of the electrified railway and two electric locomotives are built,and the harmonic characteristics of two typical trains under traction conditions are analyzed.The urgency of traction network power quality management is pointed out.Subsequently,the modulation strategy and harmonic detection method of the CHB structure are selected.The modulation method of the unipolar frequency-doubled carrier phase-shifted SPWM suitable for the multi-level converter is adopted,and a new multi-function variable step size is proposed.The LMS adaptive filtering algorithm effectively improves the problem of the contradiction between the steady-state accuracy and response speed against the traditional adaptive detection algorithm.This article introduces the active compensation scheme of CHB-APF,and explains the working principle of the grid connection and the parameter design process of the main circuit device.In order to achieve the best working effect of CHB-APF,the voltage and current control strategies of the control system are analyzed.In order to ensure the stability of the DC side capacitor voltage,the upper layer smooth voltage control and the lower layer balanced voltage control are used to adjust the voltage of each sub-module to ensure the DC side voltage stability.In terms of current comprehensive control,repeat control is superimposed on the basis of the more advanced deadbeat control at present,and the method of compound control is used to predict the harmonic current to achieve fast and accurate tracking of the harmonic current.Finally,with the help of Matlab/Simulink platform,an electrified railway locomotive network integrated system with compensation device is built to explore the harmonic distribution characteristics of trains running at different positions and different numbers under traction conditions.In addition,the parameter debugging and simulation verification of the designed CHB-APF related technology and control strategy are carried out to prove the advancement of the overall strategy.Subsequently,the compensation device is connected to the grid to check the compensation effect and verify the practicability of the proposed compensation structure for harmonic control of electrified railways.