A discrete random PWM technique for acoustic noise reduction in electric traction drives

This paper investigates various random PWM (RPWM) techniques for conventional two-level inverter-fed traction drives and proposes a discrete RPWM technique for acoustic noise reduction. The proposed RPWM technique randomizes within a set of predefined switching frequencies compared with the continuous nature of randomization in conventional RPWM techniques. The proposed method was compared with conventional SVPWM and other RPWM techniques with respect to the A-weighted IEC 61672-2013 standard acoustic noise profile. The proposed RPWM method spreads the narrowband harmonic clusters effectively and, compared to the conventional RPWM techniques, reduces broadband noise by 2-6 dB over the full modulation index range, thus producing a better acoustic noise profile.