基于MMC互连的交直流混合微电网中MSI与MMC环流分析

Circulating current analysis of micro source inverter and MMC of a hybrid AC/DC micro-grid connected by MMC

文中以基于模块化多电平变流器(modular multilevel converters,MMC)互连的交直流混合微电网中微源逆变器(micro source inverter,MSI)与MMC之间的环流问题为研究对象,分析了环流的产生机理及影响因素。首先,给出了基于MMC互连的交直流混合微电网的系统结构及等效拓扑,并得到MSI与MMC的等效数学模型。其次,以MSI中a、b及MMC中am、bm两相为例,得出该环流是由MSI输出电压与MMC交流侧电压存在矢量差引起的结论。最后,通过仿真表明电压幅值差主要影响有功环流、相位差主要影响无功环流,且MMC桥臂电抗值的增大会减小环流。

The circulating current between micro source inverter and modular multilevel converter of a hybrid AC / DC micro-grid connected by MMC as research object, the circulating current mechanism and influencing factors are analyzed. Firstly, the system structure and equivalent topology of a hybrid AC / DC micro grid based on MMC are presented, and the equivalent mathematical model of MSI and MMC are obtained. Secondly, taking the phase of MSI and phase of MMC as example, it is concluded that circulating current is caused by the vector difference between the MSI output voltage and the AC side voltage of MMC. Finally, the simulation results indicate that the power circulating current mainly affected by the voltage amplitude difference and voltage phase difference mainly affect the reactive circulating current, and the increase of the reactance value of the MMC bridge will reduce circulating current.