交流牵引系统PWM策略切换研究

交流牵引系统在多模式调制方式下运行时会产生切换电流冲击,为保证平滑切换,论述了一种先由异步SPWM调制向普通同步SPWM调制切换,再由普通同步SPWM调制向分段特定谐波消除脉宽调制(SelectedHarmonic Eliminate Pulse Width Modulation,简称SHEPWM)切换,最后在SHE分段同步调制下不同载波比进行切换调制的控制模式。基于变流器输出电压频谱特性及各调制模式特点,建立了仿真模型,通过对各调制模式间切换时仿真波形的分析和比较,确定两种调制模式切换的合理位置,并通过机车牵引实验对切换位置的合理性进行了验证,有效避免了切换引起的电流冲击。该研究为机车牵引控制方案的选择提供了直接依据。

Research on Transition Between Different PWM Strategies for AC Traction System

There will be current transients when the traction drive is switching between different PWM strategies.To assure smooth transitions,a set of switching methods of PWM strategies is presented,including firstly from asyn-chronous PWM to synchronous PWM,secondly synchronous PWM to SHEPWM,and finally switching between different carrier ratios among SHEPWM.Based on the output voltage spectrum characteristic and the modulation patterns fea-ture,simulation model is established.By analyzing and comparing the simulated waveforms of switching different mod-ulation modes,the right points of switching are determined,which are confirmed by the experiments on an AC traction system and the current transients are effectively avoided.The research provides a basis for the design of control system of AC traction experiment.