An Improved Zero-Switching-Loss Inverter with Low Conduction Loss

Zero-Switching-Loss (ZSL) transformerless inverter (TLI) is beneficial for increasing switching frequency for distributed photovoltaic generation systems. However, existing ZSL-TLIs bear high conduction loss because of the coupling between the resonance tanks and the main power loops. In order to solve this problem, an improved zero-switching-loss H6 inverter (IZSL-H6) with low conduction loss composed of novel resonance tanks and H6 inverter has been proposed in this paper. The resonance tanks provide zero-current switching (ZCS) for H6 inverter switches, and the auxiliary devices of the resonance tanks are also turned on and off with ZCS. Compared with the existing ZSL-H6, IZSL-H6 reduces conduction loss by avoiding resonant current flow through the main switches during resonant capacitor charging mode and reducing the number of power devices in the main power loops during the freewheeling mode. Resonant parameters design, soft-switching criteria, and common mode voltage characteristics is discussed. Finally, a 1000W prototype has been developed to verify the theoretical analysis of the proposed IZSL-H6.