三电平模块化光伏并网系统的差模环流抑制

Differential Mode Circulating Current Reduction for Three-level Modular Photovoltaic Grid-connected System

针对基于LC滤波器的三电平模块化光伏并网系统的差模环流问题,建立差模环流的等效模型,并根据路径不同将差模环流分成两类,分析Ⅰ类、Ⅱ类差模环流导纳与频率和漏感比关系,得出Ⅰ类差模环流远大于Ⅱ类差模环流的结论,并采用LCL滤波器的并联方案,合理选择电感比大小,有效抑制了三电平模块化光伏并网系统的差模环流。对10 kW的三电平模块化光伏并网系统进行实验,证明了差模环流模型分析和抑制方法的正确性。

According to the problem that differential mode circulating current exists in the three-level modular grid- connected photovohaic system with LC filter,the equivalent model of differential mode circulating current is proposed.Differential mode circulating current is divided into two types according to different loops.The admittance curves of differential mode circulating current between frequency and leakage inductance ratio are analyzed, and the conclusion is made that the first type of differential mode circulating current is much larger than the second type.Then, the parallel scheme with LCL filter is used, and the inductance ratio is reasonably designed to reduce the differential mode circulating current effectively.A three-level modular grid-connected photovoltaic system rated 10 kW is built, and simulation results and experimental results demonstrate the correctness of the model analysis and reduction methods of zero-sequence circulating current.