Power Efficiency Improvement of Three-Phase Split-Output Inverter Using Magnetically Coupled Inductor Switching

The conventional three-phase split-output inverter (SOI) has been used for grid-connected applications because it does not require dead time and has no shoot-through problems. Recently, the conventional inverter uses the silicon carbide (SiC) schottky diodes for the freewheeling diodes because of its no reverse-recovery problem. Nevertheless, in a practical design, the SiC schottky diodes suffer from current overshoots and voltage oscillations. These overshoots and oscillations result in switching-power losses, decreasing the power efficiency of the inverter. To alleviate this drawback, we present a three-phase SOI using magnetically coupled inductor switching technique. The magnetically coupled inductor switching technique uses one auxiliary diode and coupled inductor for each switching leg in the three-phase SOI. By the operation of the coupled inductor, the main diode current is shifted to the auxiliary diode without the reverse-recovery process. The proposed inverter reduces switching-power losses by alleviating current overshoots and voltage oscillations of SiC schottky diodes. It achieves higher power efficiency than the conventional inverter. We discuss experimental results for a 1.0 kW prototype inverter to verify the performance of the proposed inverter.