An Application of Variable Switching Frequency PWM on SiC-Based Paralleled Inverters for Motor Drive

SiC power devices applied in motor drives have brought the advantages of higher efficiency and power density, but with the problem of more serious electromagnetic interference (EMI). Using advanced topologies can help to mitigate EMI, including the paralleled inverters. In this paper, the variable switching frequency PWM (VSFPWM) for paralleled inverters based on predicted circulating current is used to make better use of the coupled inductor’s saturation limit, which is determined by the high frequency circulating current peak. Under the high-frequency operating conditions of the SiC inverter, the VSFPWM strategy will allow the switching frequency to change in a wide range, and the switching losses and EMI will be well improved relative to the constant switching frequency PWM (CSFPWM), while the circulating current peak is controlled within the limit. Moreover, the higher normal frequency (fsN), the larger EMI attenuation after VSF operation. Experimental results are provided to verify the proposed method.