A PWM Frequency Harmonic Suppression Scheme for Driving Permanent Magnet Synchronous Motors Using Three-Level Inverters with Zero-Vector Switching Spread Spectrum Modulation

This paper presents a hybrid harmonic suppression scheme for three-level inverter-fed permanent magnet synchronous motor drives. By embedding spread-spectrum modulation into the zero-vector switching SVPWM (ZSSVPWM) framework, the proposed approach simultaneously suppresses odd- and even-order PWM harmonics. ZSSVPWM inherently eliminates harmonics at odd multiples of the carrier frequency through rearrangement of zero-vector sequences; the addition of random or periodic carrier frequency modulation further flattens the remaining harmonic peaks across the entire spectrum. Two integrated strategies—zero-vector switching random carrier frequency modulation (ZSRCFM) and zero-vector switching periodic carrier frequency modulation (ZSPCFM)—are developed and evaluated. Simulation and experimental results demonstrate that both methods significantly reduce total harmonic distortion and acoustic noise compared to conventional SVPWM and ZSSVPWM.