Abstract

As promising and suitable candidates for high-power applications, multilevel inverters have become one of the most promising solutions in various applications. However, power switching devices are highly subjected to thermal overheating, which leads to shortened lifetime and reduced reliability. Thermal overheating may result from the degradation of power switching devices due to continuous overloading and power cycling. In addition, degradation and faults in the cooling system of power switching devices may cause thermal stresses as well. A new overheating-tolerant space vector modulation algorithm is proposed in this paper to alleviate thermal stresses from overheated power switching device. The proposed algorithm relies on using the redundancy property between switching states in multilevel inverters to continuously evaluate a cost function of the junction temperature of the overheated device for all possible switching sequence sets and then selects the optimal switching sequence. In addition, the proposed algorithm preserves the DC-link capacitor voltage without reduction in the output current of the inverter. The proposed algorithm is general, which can be applied to n-level inverters. Both simulation and experimental results reveal the efficient performance of the proposed algorithm using a three-level T-type inverter as a case study. Accordingly, the lifetime and reliability of the inverter are enhanced considerably using the proposed algorithm. (c) 2016 Institute of Electrical Engineers of Japan. Published by John Wiley Sons, Inc.