Common-Mode Voltage Elimination in Multilevel Power Inverter-Based Motor Drive Applications

The industry and academia are focusing their efforts on finding more efficient and reliable electrical machines and motor drives. However, many of the motors driven by pulse-width modulated converters face the recurring problem of common-mode voltage (CMV). In fact, this voltage leads to other problems such as bearing breakdown, deterioration of the stator winding insulation and electromagnetic interferences (EMI) that can affect the lifespan and correct operation of the motors. In this sense, multilevel converters have proven to be a useful tool for solving these problems and mitigating CMV over the past few decades. Among other reasons, because they provide additional degrees of freedom when comparing with two-level converters. However, although there are several proposals in the scientific literature on this topic, no complete information has been reviewed about the CMV issues and the different multilevel alternatives that can be used to solve it. In this context, the objective of this work is to determine how multilevel power converters provide additional degrees of freedom to make the reduction of the CMV possible by using specific modulation techniques, making it easier for engineers and scientists in this field to find solutions to this problem. This document consists of a descriptive study that collects the strengths and weaknesses of most important multilevel power converters, with special emphasis on how CMV affects each of them. In addition, the differences of modulation techniques aimed to the CMV reduction are explained in terms of output voltage, operating linear range, and generated CMV. Considering this last, it is recommended to use those modulation techniques that allow the generation of CMV levels of 0 V in order to be able to completely eliminate said voltage.