Low CM Leakage Current and High Efficiency H6 Inverter with Active Clamping for Transformerless PV System

In order to solve the problem of the common-mode (CM) leakage current and obtain high efficiency of the transformerless photovoltaic (PV) system, a novel H6 based inverter with active clamping topology is proposed. The active clamping circuit prevents the resonance of the output inductors and the power switches' parasitic junction capacitance, so as to improve the suppression ability of the leakage current. Also, MOSFETs can be used in this typology to significantly reduce conduction losses as compared to the case with IGBTs. Meanwhile, the total harmonic distortion (THD) of the grid-connected current is very low due to no dead time between the main power switches in one PWM cycle. The working principle of the proposed topology, PWM modulation strategy, CM and differential-mode (DM) characteristics are analyzed. Finally, a 300 W experimental prototype was performed to verify the theoretical analysis, and experimental results show that the good performances with low CM leakage current of 11.257mA and high efficiency of 98.1%.