Multilevel inverter modulation method to reduce common-mode voltage and overvoltage at the motor terminals

Multilevel inverter topologies have been a widely researched topic, especially for high-power applications. Its more sinusoidal output voltage waveform is preferred over traditional two-level inverters. Common-mode voltages are known to cause motor bearing currents and to be a source for electromagnetic interference. Traditional multilevel modulation methods still produce common-mode voltage, and this can result in bearing failure. In this paper, a modulation method that reduces the common-mode voltage and mitigates the motor terminal voltage oscillation caused by long motor leads, is discussed. The method is compared with a traditional multilevel inverter modulation method and another common-mode voltage reducing method.