Random Asymmetric Carrier PWM Method for PMSM Vibration Reduction

The underwater noise can be caused by the radial electromagnetic vibration of permanent magnet synchronous motor (PMSM) for electric propulsion. The difficulty in decreasing the underwater noise is not only the high-frequency but also low-frequency vibration reduction. This paper proposes a novel random asymmetric carrier pulse width modulation (RACPWM) method for PMSM vibration reduction in the whole frequency range. Instead of the conventional symmetric triangular carrier PWM, the asymmetric carrier PWM (ACPWM) is used to decrease the low-frequency phase current harmonics and the associated low-frequency vibration. Meanwhile, in order to suppress the high-frequency vibration, the RACPWM control based on the amplitude randomization of the sawtooth carrier is further presented to reduce the high-frequency phase current harmonics. Moreover, the RACPWM is equivalent to the random slope ACPWM in view of the output signals. Furthermore, without the need of any additional circuits in the drive, the presented method is simple to implement by software. Simulation and experimental results show that the proposed RACPWM method can effectively reduce both the low-frequency and the high-frequency vibration.