Safe Startup Method for Zero-Voltage-Switching MOSFET Grid Inverter

Zero-voltage-switching (ZVS) mosfet grid inverter has distinct advantages such as higher efficiency and higher power density. However, the ZVS inverter may lose ZVS condition during startup stage if it does not start properly. It may increase the voltage stress on mosfets and even destroy the power semiconductor device. In order to achieve the ZVS condition for ZVS inverter during the startup stage, this paper proposes a safe startup method with an auxiliary clamping capacitor pre-charging circuit and designed ZVS pre-charging pulse sequence. The pre-charging circuit is enabled only at the startup stage. Theoretical analysis shows that the proposed method is capable of reducing the voltage stress during the startup stage for the ZVS inverter. Finally, the proposed safe startup method is verified on a 3 kW grid inverter.