Switched-DC Inverter based Variable Switching Frequency DPWM Technique for Spreading the Harmonic Energy with Reduced Current THD

A variable switching frequency based Discontinous PWM (DPWM) technique along with a modified inverter topology is proposed in this paper, for achieving reduced stator current distortion while spreading the harmonic energy for a PMSM drive. A detailed analysis of current ripple for conventional bus-clamping sequences is carried out. The proposed logic adopts a trapezoidally varying sub-cycle sampling period for spreading the stator current spectrum. The presented strategy achieves 26.6% reduction in stator current THD and 35% reduction in dominant harmonics compared to conventional bus-clamped PWM, demonstrating its competency as a promising variable switching frequency scheme. The harmonic performance of the suggested technique is verified in simulation using a 1.07 kW vector controlled PMSM drive.