Lifetime-oriented SVPWM for thermally-overloaded power devices in three-level inverters

Boosting lifetime of power components in multilevel inverters is a major aim to enhance the total system reliability and performance. This paper presents a space vector pulse width modulation (SVPWM) strategy for lifetime prolongation of thermally-overloaded power devices in multilevel inverters. When a thermal overloading is detected in one of the power devices, the proposed algorithm is applied to relieve the overloaded device and therefore preventing dangerous circumstances such as open-or short-circuit faults. The proposed methodology relies on using the redundancy property between the switching states in multilevel inverters to continuously evaluate the junction temperature of the thermally-overloaded power devices for all the possible switching sequences, then it identifies the optimal relieving switching sequence. The proposed methodology is valid for both/either of the power switching devices and/or DC-link capacitors. The proposed strategy is simple, and does not require any additional hardware. Furthermore, it does not deteriorate the output power. Accordingly, lifetime and reliability of multilevel inverters have been enhanced considerably. The proposed methodology has been designed and validated by simulation and experimental prototyping of a three-level T-type inverter system to investigate its feasibility and effectiveness.