Reliability-Oriented Application Method of Discontinuous PWM for Single-Phase Five-Level T-Type NPC Inverter

Discontinuous pulsewidth modulation (DPWM) is generally used for improving the efficiency of inverters, but it reduces the power quality. Therefore, in previous research, the efficiency and power quality are typically considered when DPWM methods are applied. Even though it also affects the power losses of the power devices and dc-link capacitors and thus their reliability, a study on the effect of DPWM on the reliability of inverters is insufficient. In this article, the impact of different DPWM methods on the reliability of a single-phase five-level T-type neutral-point clamped (NPC) inverter is comparatively investigated by considering the lifetime of the power devices and dc-link capacitors. Then, the reliability-oriented application method of DPWM called ED²PWM(PON) is proposed based on the analysis results. Finally, the feasibility and effectiveness of the proposed DPWM strategy are verified through simulations and experiments. The proposed ED²PWM(PON) reduces the negative effect on the lifetime of the dc-link capacitor compared with the existing DPWM methods while keeping the advantages of power loss reduction and lifetime improvement of the power devices. Consequently, the inverter under the proposed method has the longest lifetime.