Common-mode voltage mitigation in multiphase electric motor drive systems

Common-mode voltage (CMV) produces serious reliability and electromagnetic interference (EMI) issues in modern pulse-width modulated (PWM) electric drives. Such issues will become more prominent in the near future, as industry moves towards the introduction of wide-bandgap (WBG) semiconductor technologies operating at higher switching frequencies and also with greater dvdt. In this context, multiphase electric drive technologies can be of great interest, as their additional degrees of freedom can be exploited to reduce CMV. This work aims to study the potential of multiphase electric motor drive systems for CMV mitigation. To do so, a comprehensive review of the most recent scientific literature is conducted, mainly focusing on high impact works published recently. As a result, a clear and up-to-date picture of the most common multiphase technologies, i.e., (m+1)-leg, multiple three-phase, open-end and star-connected multiphase systems is provided along with their CMV reduction potential. Not only the topologies themselves but also modulation techniques are analysed and presented, mainly focusing on star-connected systems. As a conclusion, it can be stated that such multiphase systems are promising candidates to substitute conventional three-phase motor drives as, apart from their well-known advantages (efficiency, power density, power splitting, and fault tolerance), their CMV reduction potential is confirmed. The technical information provided in this work will help researchers and field engineers to design and develop high-performance multiphase electric drives.