A startup scheme for zero-voltage-switching PV inverter

In order to guarantee all the switching devices of the inverter working in the safe operation area, zero voltage switching (ZVS) operation is needed even at the startup stage. To help the ZVS inverter achieving completely soft switching at the startup stage, a startup scheme is proposed. The startup scheme adds a pre-charge stage before the general startup stage. The pre-charge stage is realized by a simple pre-charge circuit and a ZVS pre-charge pulse sequence. The pre-charge circuit works before the general startup stage only and is guaranteed by principle to be deactivated during the normal operation stage. The pre-charge pulse sequence is designed to achieve ZVS operation in the pre-charge stage. The experiment on a 3kW prototype shows the startup scheme realizes ZVS operation at the startup stage and the voltage stress on the power devices is minimized.