Ground Leakage Current Analysis A Suppression In A 60-kw 5-level T-type Transformerless Sic Pv Inverter

In this paper, ground leakage current suppression in a 60-kW 5-level T-type (5LT(2)) transformerless SiC photovoltaic (PV) inverter has been presented. The common mode (CM) equivalent circuit is analyzed based on a high frequency (HF) CM loop and a low frequency (LF) CM loop, respectively. In the 5LT(2) inverter, the derived HF CM voltage (CMV) is found to have 86% reduction compared to that of a 3-level T-type (3LT(2)) inverter. The simulation and experiment results are provided to demonstrate the advantages of 5LT(2) inverter on HF leakage current suppression. In addition, LF CMV caused by neutral point (NP) voltage oscillation has been analyzed in this paper. It is shown that the LF CMV is nearly proportional to the NP voltage oscillation. Furthermore, an LF CMV compensation method is proposed to suppress the LF CMV by 64%, which is verified by simulation and experiment results. Finally, the leakage current shows 79% reduction in the 5LT(2) inverter compared to the conventional 3LT(2) inverter in the experiment. A further 52% leakage current reduction is achieved by the LF CMV compensation in the 5LT(2) inverter.