Vibration and acoustic noise, especially the sideband vibro-acoustics in high-frequency bands, are the meaningful factors influencing NVH performance of electric vehicles (EV). This paper presents a study of different pulse-width modulation (PWM) techniques in an electric driven system equipped with a permanent magnet synchronous machine (PMSM) for the purpose of evaluating the sideband current and vibro-acoustics. Firstly, it explores the principle and implementation of representative space vector PWM (SVPWM) and discontinuous PWM (DPWM) techniques. Secondly, the characteristics of related sideband components, including the sideband current harmonics and vibro-acoustic responses, are examined with analytical derivations. Moreover, all possible PWM schemes can be improved with a random PWM technique for reducing the sideband components. Experiments were carried out based on a 12/10 prototype PMSM for verification. It has been shown that sideband components introduced by the PWM techniques are generally concentrated around the carrier frequency with specific frequency distributions. Compared with SVPWM, the overall levels of the proposed DPWMs are obtained without deterioration. Furthermore, randomization of the carrier frequency allows for a significant suppression, about 10 dBA lower, in acoustic noise responses.
