Application of Periodic Carrier Frequency Modulation for Harmonic and EMI Reduction in GaN-Based Motor Drive

The increase of pulse width modulation (PWM) switching frequency in motor drive can increase the control bandwidth, reduce torque ripple and obtain a near-ideal sinusoidal current. However, traditional fixed frequency pulse width modulation (FFPWM) typically causes harmonic and common mode (CM) electromagnetic interference (EMI) in motor drive. Besides, the high switching frequency and high-speed switching operation of wide bandgap (WBG) power devices make this situation even worse. For the harmonic and CM EMI generated by FFPWM, this paper analyzes the causes from the perspective of mathematics. The mechanism for suppressing harmonic and CM EMI by periodic carrier frequency modulation (PCFM) is also analyzed in detail. Moreover, a wait-free and phase-continuous implementation method of PCFM is applied to solve the issue of harmonic and CM EMI. Finally, the experimental results on a GaN-based motor drive verify the accuracy of the theoretical analysis and the effectiveness of the algorithm.