Anti-Parallel SBDs Optimization for Loss Minimization of SiC Motor Drive Converters

In Silicon Carbide based motor drive converters, there are contradictions for adding Schottky barrier diode (SBD). On the one hand, SBD eliminates the reverse recovery process and reduces the dead time loss. On the other hand, the switching loss is increased by additional capacitance brought by SBD. In this paper, four different rated SBDs are selected and the power loss of a three-phase motor drive voltage source inverter (VSI) is investigated. The current distribution in channel, body diode and external SBD is analyzed to ensure current safety of devices. A loss calculation method for VSI is developed. A double pulse test (DPT) is implemented to evaluate the switching loss. Impacts of SBD junction capacitance on switching characteristics for both turn-on and turn-off transitions are analyzed. The overall loss of different configurations is calculated. It appears that VSI using smaller rated SBDs exhibits superior performance among all configurations in vast working conditions. Selection guidance of SBDs is given and the optimized selection in this work increases efficiency by maximum 1% compared with conventional selection strategy. This paper confirms the feasibility of smaller rated SBDs selection.