非隔离型三相三电平光伏逆变器的共模电流抑制

Leakage Current Reduction for Transformerless Three-phase Three-level Photovoltaic Inverters

针对非隔离型三相三电平光伏逆变器的共模电流问题,在分析三电平共模等效模型的基础上,采用改进型LCL滤波器,将滤波电容公共点接回到直流侧中性点,滤除寄生电容电压的高频分量,使共模电流大幅衰减。改进型LCL滤波器改变了三电平直流侧中点不平衡的机理,传统中点平衡算法,如分配因子法不再适用,为此,对分配因子法进行修正,提出广义的分配因子法,使中点电位得到有效地控制。实验证明了理论分析和算法的正确性。

Aiming at leakage current reduction for transformerless three-phase three-level photovoltaic inverters,this paper proposed the common mode model of three-level inverters.Then a kind of improved LCL filter,where the capacitor common point was linked to the DC neutral point,was used to eliminate the leakage current.However,this improved LCL filter changes the mechanism of the neutral-point potential.Traditional algorithms,such as the distribution factor algorithm,are no longer applicable.Therefore,in order to control the neutral-point potential,the distribution factor algorithm was improved and a new generalized distribution factor algorithm was proposed in this paper.Experimental results demonstrate the availability and correctness of the theoretical analysis and algorithm.