Secondary Frequency Modulation Strategy for SiC Inverters Based on Periodic Spread Spectrum Modulation

This paper aims to design the modulation strategy of SiC motor controller for vehicles with low EMI, low device loss and low voltage/current ripple. The equivalent evaluation model of input voltage, output current and switching loss of the inverter under periodic spread spectrum modulation strategy is constructed, and the quantitative relationship between each parameter of spread spectrum modulation and the three indicators is established. The input/output performance and loss level of the inverter under different spread spectrum modulation strategies are evaluated. On this basis, based on the carrier frequency distribution characteristics of periodic signal spread spectrum modulation, a "secondary frequency modulation" strategy is proposed to reduce the inverter-conducted EMI to a greater extent under the limited spread spectrum range. Experimental results show that compared with the single periodic signal spread spectrum modulation, the "secondary frequency modulation" strategy can reduce the peak value of inverter-conducted EMI to a greater extent without increasing the ripple and loss of the inverter.