Analysis and Suppression of Common Mode Voltage for Motor Drive in EV

Common-mode voltage (CMV) which would bring common mode electromagnetic interference (EMI) and damage to motor bearings is an important performance index in electric drive system. With the application of SiC devices, this problem will become more serious because of the faster switching speed. However, the impact of high switching speed and high switching frequency on common-mode voltage is still ambiguous. Theoretical analyses are conducted by FFT to study the influence of high switching speed and high switching frequency on CMV and then the experimental verifications are carried out. The PWM strategy which can suppress the CMV is introduced. CMV can also be suppressed by hardware methods. The experimental results show that either has the ability to restrain CMV. But, the best inhibition effect can be achieved by combining both.