An Optimal Periodic Carrier Frequency PWM Scheme for Suppressing High-Frequency Vibrations of Permanent Magnet Synchronous Motors

High-frequency vibration caused by pulse width modulation (PWM) is a critical problem of permanent magnet synchronous motor (PMSM) drives for low-noise applications. Periodic carrier frequency PWM (PCFPWM) can effectively reduce high-frequency vibrations by dispersing concentrated harmonics over a wider frequency band. However, the resulting vibration spectra are normally far from ideal and still contain several local peaks because the uneven vibration frequency response of the motor is not taken into account. To address this problem, this paper proposes an optimal PCFPWM scheme that minimizes vibration spectral peaks of the motor by considering its vibration frequency response function (VFRF). A time series of PWM carrier frequency is carefully devised such that the amplitude of the induced electromagnetic (EM) force is inversely related to the VFRF of the motor, thereby shaving peaks in the vibration spectra. Finally, the optimal PCFPWM scheme is experimentally verified and demonstrates improved vibration suppressing performance.