Reliability Analysis of IGBT Modules of Multilevel Inverters Operating in Hostile Environments

Throughout the industry, pulse width modulation voltage source inverters (PWM-VSI) are commonly utilized with adjustable speed drives (ASD) to control, most commonly, induction motors. Especially in the mining and petroleum industries, long cables connecting motors and inverters are often present, which can cause several problems. As an innovative solution, an alternative system configuration has been previously proposed, in which the rectifier is kept in its typical location, and the inverter bridge and DC bus capacitors are installed near the driven motor. Long cables are used as a DC transmission line, mitigating the high-frequency problems resulting from the inverter-cable-motor interaction. On the other hand, new concerns regarding the reliability of the power devices arise once the inverter is installed in harsh ambient conditions. In this context, this work proposes a reliability analysis of such drive configuration, applying the physics of failure (PoF) approach combined with the design for reliability (DfR) methodology to carry out the design adjustments to achieve the reliability required for the application, focusing on the inverter IGBT modules. Moreover, this paper will evaluate widely accepted multilevel inverter topologies and modulation strategies, verifying those capable of minimizing implementation costs and ensuring adequate reliability indexes for the system—aiming to enable the commercial use of this promising configuration. The results show that a three-level active neutral point clamped inverter (3L-ANPC) topology applying two pulse width modulation (PWM) strategies and 400 A – 6.5 kV IGBTs would be the most appropriate from this study's reliability and feasibility analyses.