无零序环流三相PWM变流器线路级并联策略

Circuit-level Parallel Strategies of Three Phase PWM Converters without Zero Sequence Circulating Current

三相PWM变流器模块线路级并联是在不增加单模块容量的前提下进行系统扩容的有效方式。变流器线路级载波移相并联,可以成倍提高等效的开关频率,降低开关损耗,减小滤波器尺寸,但与此同时也带来了并联模块间零序环流的问题。通过分析、仿真和实验,指出了使用载波移相技术多模块并联存在零序环流的机理,为有效抑制环流,提出并联模块使用独立直流母线的有效方法,并给出相应的仿真和实验验证。

Circuit-level parallel of three phase PWM converter modules is an effective method to expand the system capacity without increasing the single module capacity.The strategies of circuit-level parallel are analyzed.The carrier-shifted technology applied to the circuit level parallel can heighten the equivalent switching frequency times higher,lower the switching loss and reduce the size of the filter, but at the same time it leads to zero sequence circulating current problems. This paper points out the cause of the zero sequence circulating current of two PWM converters by analysis, simulation and experiments.To restrain the crrcutating current caused by the carrier-shifted technology, the independent DC bus applied to the two parallel modules is proposed with the simulation and experimental validation.