A Zero-Current-Transition HERIC-type Transformerless Photovoltaic Grid-Connected Inverter with Reduced Peak Current

The fundamental goal of soft-switching (SS) techniques is to reduce switching losses, and keep low conduction losses as well. For pursuing this goal, especially for keeping low conduction losses for transformerless Photovoltaic grid-connected inverters (TLIs), a new resonance-trajectory is planned. Compared with the zero-current-transition H6-I (ZCT-H6-I) topology published in a previous literature, the proposed resonance-trajectory can precisely compensate for losses of resonant tanks, and a complete resonant behavior is finished before the turn-on moment of high-frequency main switches every switching period. As a result, there is an obvious reduction in the peak value of the current through main switches at switching frequency scale. In order to realize this idea based on TLIs, a ZCT-HERIC topology is derived from the proposed resonance-trajectory, and then, its detailed operation principle and performance characteristics are analyzed. Finally, comprehensive simulation results of a 1 kW prototype at 50 kHz switching frequency are provided to verify the effectiveness of the derived inverter.