Reliability-Oriented Optimal DPWM Strategy for Single-Phase Five-Level T-Type Inverter in PV Systems

Abstract

Many efforts have been devoted to improving the reliability of PV inverters with a focus on reliability-critical components such as power devices and capacitors. Discontinuous pulsewidth modulation (DPWM) methods are representative of improving the reliability of power devices by decreasing their thermal loadings. However, although the DPWM method affects the ripple current of the DC-link capacitor, prior-art research is only focusing on the power devices. There is a lack of study on the effect of applying the DPWM method on the reliability of the DC-link capacitor. It may have a negative effect on the reliability of the DC-link capacitor and thus affects the reliability of overall PV inverters. In this article, the influence of the DPWM method with different clamping periods on the reliability of power devices and DC-link capacitors of the single-phase five-level T-type inverter is investigated, where a 7-kW PV system and annual mission profile of PV system are considered as a case study. Then, a reliability-oriented optimal DPWM strategy is presented for the target lifetime of the T-type inverter by considering system-level reliability, including the lifetimes of both power devices and DC-link capacitors.