A novel three-phase zero-current-transition and quasi-zero-voltage transition (ZCT-QZVT) inverter/rectifier with reduced stresses on devices and components

This paper proposes a new soft-switching strategy for three-phase inverter and rectifier applications. All the main switches and auxiliary switches are turned on and turned off under zero-current-transition (ZCT) conditions. Compared to existing ZCT techniques, the diode reverse recovery is reduced, and the main switch turn-on voltage is reduced to less than the DC link voltage from full DC link voltage-referred to as quasi-zero-voltage-transition (QZVT). In addition, the current stress in the auxiliary switches is reduced and evenly distributed, and the resonant capacitor voltage stress is reduced to 1.3~1.4 times the DC link voltage from twice the DC link voltage. The operational principle, state plane analysis, and design aspects are described. Both simulation and experiment results are provided for verification. Based on the proposed technique, finally presented is an application example of three-phase soft-switching inverter for electric vehicle propulsion