三相逆变器并联系统中零序环流的研究

The Research of Zero-sequence Circulating Currents Between Parallel Three-phase Inverters

现有的文献已经论证了在三相逆变器并联系统中,存在着零序环流的通路。然而,这些结论基本上都是在无输出变压器及忽略了三磁柱电感磁路耦合的前提下得出的。事实上,在三相逆变器中,出于体积和成本的考虑,滤波电感和输出变压器通常都采用三磁柱铁芯来绕制,由此带来的三相问磁路耦合使得三相逆变器的零序相量特性与三个单相逆变器构成的三相逆变器是完全不同的,这对三相逆变器并联系统中的零序环流也产生了很大的影响。该文基于三磁柱变压器及三磁柱电感的动态方程建立了带三磁柱电感及三磁柱变压器的三相逆变器瞬时零序分量模型。基于该模型的分析发现,三相逆变器并联系统中,三磁柱电感及三磁柱变压器的采用使得零序环流的大小和通路发生了很大的变化。仿真与实验验证了上述结论。

It is well known that zero-sequence circulating currents could exist in parallel three-phase converters. However, these conclusions are normally drawn out without considering the magnetic couples caused by the three-pole transformers and three-pole reactors. In fact, for the cost and size, the three-phase reactors and transformers used in three-phase inverters normally have only three poles. In parallel three-phase inverter systems, the magnetic couples between three phases in each three-phase inverter make the zero-sequence circulating currents behave differently from those of three-phase inverters with only three single-phase reactors and three single-phase transformers. In this paper, the instantaneous model of zero-sequence circulating current between parallel three-phase inverters with three-pole reactors and three-pole transformers is established. The analysis based on this model indicates that magnetic couples caused by three-pole reactors and transformers have great influence on the zero-sequence circulating currents. Simulations and experiments validated the above conclusion.