Comparative investigation of PWM techniques for a new drive for electric vehicles

Results of a comparative investigation of deterministic and random pulsewidth modulation (PWM) techniques to be employed in a new ac drive for electric vehicles are presented. The study, employing the advanced simulation package SABER from Avant! Corporation, was focused on the reduction of electromagnetic interference (EMI) when a deterministic PWM strategy is replaced with an RPWM method. To assess the impact of the PWM technique on the drive performance, the drive efficiency, torque ripple, and dynamic response of the current control system were also investigated. Two RPWM techniques characterized by random variations of switching frequency of the inverter were considered: one with the sampling frequency of the modulator varying in step with the switching frequency, and one with a fixed sampling frequency equal to the average switching frequency. The study has demonstrated good EMI-mitigating potentials of RPWM techniques, whose use results in EMI reduction by 10 dB and more, while the drive performance is barely affected. Index Terms--AC drives, electric cars, electromagnetic interference (EMI), inverter control, random pulsewidth modulation (RPWM).