Decoupled Modeling of Three-phase TCM Inverters Utilizing Three Different Conduction-Modes for ZVS Operation

To improve the power-density of ac-dc converters with wide-bandgap devices, zero-voltage switching (ZVS) schemes have widely been widely investigated. Triangular conduction-mode (TCM) generate a reverse current which discharges a junction capacitance before a MOSFET turns on. Such a method has been extended to three-phase applications by operating the other two phase into two different conduction-modes; discontinuous conduction mode (DCM) and clamp-mode similar to a discontinuous PWM (DPWM) scheme [1]–[4]. However, the presence of a three-phase coupling and transitions of the conduction-modes along the line-cycle arise complexity in the modeling and control. In this paper, a modeling approach is presented for three-phase inverters utilizing three different conduction-modes for ZVS operation. It is revealed that the modeling and analysis for an equivalent single-phase TCM and DCM inverter can be directly extended to the three-phase case. The impact of the DCM phase can simply be calculated and compensated. Control schemes for single-phase inverters can be extended to the three-phase counterparts. The proposed modeling approach is verified by SIMPLIS simulation and an experiment with the prototype three-level three-phase TCM inverter.