Zero-voltage-transition DC-link techniques for three-phase AC-DC-AC PWM converters

New soft-switching topologies are proposed for AC-DC-AC power converters by applying a soft-switching mechanism to the common DC link, and using a single auxiliary circuit, which provides the soft-switching function to all of the twelve main switches. The switches in the AC-DC power converter and the DC link switch are turned on with zero voltage, while the switches in the DC-AC power converter are turned off with zero-voltage, resulting in much reduced switching losses. With coordinated control of the AC-DC and the DC-AC power converters, the soft-switching circuit is actuated only once in every switching cycle, and has much less power loss than in existing schemes.