Research on Suppression Method of Bearing Current for Electric Vehicle Motor Driven by SiC Inverter

Silicon carbide (SiC) inverter can bring great advantages in volume, efficiency and power density of the electric drive system for electric vehicle (EV) applications. However, the high voltage and high frequency common mode voltage of the inverter will aggravate the problem of bearing electric corrosion and shorten the life of the electric drive system. Based on the theoretical analysis and experimental test of bearing voltage and bearing current, this paper analyzes the characteristic of bearing voltage and current driven by IGBT inverter and SiC inverter, respectively. Then, active zero state pwm (AZSPWM) strategy is adopted to suppress the common-mode voltage from the root of common-mode interference, thus reducing the bearing voltage and bearing current. Furthermore, a hybrid modulation strategy combining AZSPWM-l and near state pwm (NSPWM) is proposed in this paper, which can reduce the switching loss as much as possible while maintaining the suppression effect of bearing voltage and bearing current. Finally, the experiment verifies the suppression effect of the proposed suppression method on bearing voltage and bearing current.