High-buck in Buck and High-boost in Boost Dual-Mode Inverter (Hb2DMI)

The application of the dual-mode time-sharing technique in a novel transformerless photovoltaic (PV) inverters is proposed and investigated. The simultaneous high step-down or high step-up conversion with 97.6 % peak efficiency and injected current with THD < 2% is achieved. The leakage current problem, which is a main concern with the transformerless PV inverters, is around 20 mA. The indirect current control, especially at transition modes of operation is highly improved by utilizing a fast dead-beat control scheme. The working principles of the proposed converter show that the step-down and the step-up voltage gains are (D/(1-D)) 2 and D/(1-D) 2 , respectively. Furthermore, a 1 kW, 220 VAC and 200 VDC experimental prototype is implemented to confirm the theoretical achievements.