多逆变器直接并联系统环流建模与分析

Modeling and Analysis of Circulating Current of Direct Connected Multi-central Inverter System

对于多台逆变器直接并联后通过双绕组变压器接入中压配网的系统,以三相两电平逆变器为例,对系统共模、差模环流产生的机理进行了详细分析,给出了相应的等效电路。同时,在多逆变器直接互联的工况下,对单机并网常见的直流中点与交流中性点互联来抑制共模电流方法的效果进行了分析,指出其在多机互联系统中的局限性。而后,在各逆变器作为并网电流源的基础上,分别对各逆变器调制度不同、载波角度不同对共模、差模环流的影响进行了量化分析,并通过仿真与试验进行了验证。

For multi-central inverter system connected directly to MV distribution grid with a two winding transformer,take 3-phase 2-level inverter for example,common-mode and differential-mode circulating current produced mechanism and equivalent circuit were analyzed in detail.At the same time,the effect of DC mid-point connected with AC neutral point method,which is usually adapted to suppress common-mode circulating current in the case of single inverter connected to grid,was analyzed,and the limit of this method in the case of multi-central inverter system was pointed out.And then,based on every inverter in grid-connected current source mode,the influence of individual modulation depth and angle of different carrier waves on the common-mode and differentialmode circulating current of multi-central inverter system was analyzed quantitatively,this conclusion is validated by the simulation and experiment.