Enhanced HERIC based transformerless inverter with hybrid clamping cell for leakage current elimination

Abstract

The transformerless inverters are widely employed in grid-tied PV systems, since they feature higher efficiency and lower cost compared with the transformer based inverters. One of the critical problems for transformerless inverters is the common-mode leakage current issue, which leads to serious safety and EMI problems. This paper proposed an enhanced HERIC based single-phase transformerless inverter with hybrid clamping cell to further eliminate the common-mode leakage current. Firstly, the leakage current problem caused by the parasitic parameters in the HERIC inverter is explored. Then, an enhanced HERIC based topology is proposed with its modulation and leakage current elimination principle. Through hybrid voltage clamping provided by the clamping cell, the common-mode voltage can be kept as constant, which helps reduce the leakage current and achieve excellent differential-mode characteristics. Finally, a 2kW test bench is built to verify the effectiveness of the proposed enhanced HERIC based inverter by comparing its performance with the HERIC inverter.