Discontinuous Pulse Width Modulation Strategy for Single-phase Five-level T-type NPC Inverter considering Symmetric Thermal Loadings of Power Devices

Discontinuous pulse width modulation (DPWM) increases the efficiency of the single-phase 5-level T-type NPC inverter by reducing the switching losses of power devices. Furthermore, it improves the reliability of power devices by reducing the junction temperature of the power devices that have the highest one. However, when the DPWM is applied, even if the same clamping period is applied to the reference voltage of each leg of the inverter, a thermal loading imbalance occurs between the power devices of the two legs of the inverter according to the order of clamping application. Consequently, the effect of improving the reliability of power devices by DPWM is reduced. In this paper, the DPWM strategy for a single-phase five-level T-type NPC inverter is proposed for achieving symmetric thermal loadings between power devices of two legs. The feasibility and effectiveness of the proposed method are verified through simulations and experiments.