A transformer assisted zero-voltage soft-switching three-level active neutral-point-clamped converter

A novel transformer assisted three-level zero-voltage switching (ZVS) converter is proposed in this paper. The proposed topology features simple structure and good ZVS performance. The auxiliary circuit structure and the modulation method are as simple as in the two-level converter. Only two auxiliary switches, four auxiliary diodes and a two-winding transformer are needed to achieve the soft-switching of all the main switches in one phase leg. Besides the great losses reduction on main device, the auxiliary circuit operates only at the switching transition and has a lower current rating and no switching losses. The operation principle is analyzed and an eighty kW half-bridge prototype was built. The experimental results are provided to verify the effectiveness of the topology.