并联型三相PWM变换器双载波SPWM环流抑制策略

A Dual-Carrier SPWM Control Strategy to Suppress Circulating Current in Parallelly Connected Three-Phase PWM Converter System

三相PWM变换器并联以及载波移相的使用能够显著增大变流器的容量并提高交流侧的电能质量,但直接并联会使系统内部产生环流,从而导致变换器损耗增加甚至系统崩溃。通过分析模块并联系统零序环流产生的原理,得出环流大小与零序开关状态相关,从而提出了一种双载波正弦脉宽调制(sinusoidal pulse width modulation,SPWM)控制方法,通过对开关状态的调整来实现抑制环流。该方法不需要增加额外的硬件,具有动态响应快、环流抑制效果好等优点。仿真和实验结果验证了所提控制策略的有效性。

The utilization of parallel connection of three-phase PWM converter and carrier phase-shifting can enlarge the capacity of converters obviously and improve the power quality at AC side,however the direct parallel connection of PWM will cause circulating current inside the converter system,it leads to the increase of power loss in converters and even makes the converter system collapsed.On the basis of analyzing the reason to produce zero-sequence circulating current in parallelly connected module system,a conclusion that the size of circulating current is related with the state of zero-sequence switch,and a dual carrier sinusoidal pulse width modulation（SPWM） control strategy,which suppress the circulating current by adjusting the switch state and needs not additional hardware,is proposed.The proposed control strategy possesses advantages such as fast dynamic response and satisfied circulating current suppression effect.Results of both simulation and experiments show that the proposed control strategy is effective.