Effect of thermal loading definitions on the mission profile-based reliability evaluation of power devices in PV inverters

The long-term mission profile-based lifetime evaluation of a PV inverter plays an important role in the Design for Reliability approach to ensure the required reliability performance. In previous studies, different thermal loading definitions have been considered for the mission profile-based lifetime estimation of power devices. It may affect the reliability prediction result considerably but its impact has not yet been studied. In this paper, the effect of thermal loading definitions on the predicted reliability of power devices in a PV inverter is investigated. The thermal loadings and reliability of power devices of a single-phase five-level T-type inverter by considering four different thermal loading definitions are comparatively analyzed and further discussed. Finally, some guidelines for selecting the thermal loading definition are suggested.