A Quasi-Three-Level Modulation Scheme to Combat Motor Overvoltage in SiC-Based Drives with Open-End Stator Winding Configurations

The emergence of silicon carbide (SiC) power devices is considered an enabling technology toward more efficient and compact motor drives. This returns to the primary advantages of the SiC power devices, that result from their fast switching speed and elevated temperature capabilities. However, the high voltage slew rate (dv/dt) associated with the fast switching transitions has been a concern for SiC-based motor drives with interconnection power cables due to potential motor overvoltage that can degrade the winding insulation and cause premature failure. This paper proposes a quasi-three-level PWM scheme to combat the motor overvoltage oscillations in cable-fed drives with open-winding configurations. The proposed scheme reshapes the PWM voltage pulses at the inverter side to counterbalance the voltage reflections across the cable, resulting in alleviated motor overvoltage within tolerable insulation design level. The proposed scheme is conceptually illustrated in this paper and applied to dual three-phase SiC inverter for open-winding motor drives. The performance of the motor drive system under the proposed modulation scheme is verified through simulation and experimentation.