A novel soft-switching grid-connected PV inverter and its implementation

This paper proposes a novel soft-switching PV inverter formed by a ZVT-PWM boost converter, a ZVS-ZCS-PWM buck converter and a low frequency full-bridge inverter. The ZVT-PWM boost converter maintains the dc-bus voltage and provides an auxiliary current source for the soft-switching cell of the buck converter. The buck converter consists of a main switch and an auxiliary switch, with ZVS and ZCS features respectively, which generates a semi-sinusoidal current output. The semi-sinusoidal current is inverted into sinusoidal and fed to the utility grid by the low frequency full-bridge inverter. The overall efficiency is improved and the size is dramatically reduced due to high frequency operation. The operating principles are presented and the circuit is implemented to a 1000W prototype machine. The experimental results with a maximum overall efficiency up to 97% at 100 kHz, about 1.5%´s improvement compared to the hard-switching one, verify the proposal.