Torque Ripple Reduction in Double-Inverter Fed Wound Rotor Induction Machine Drives Using PWM Techniques

This paper deals with torque ripple estimation and reduction in a vector controlled double-inverter-fed wound rotor induction machine (DI-WRIM) drive by employing different pulsewidth modulation (PWM) techniques applied to stator and rotor side voltage source inverters (VSIs). The influence of PWM switching sequences on torque ripple is studied in terms of stator and rotor flux ripples. A novel rotor speed independent transformation has been proposed to visualize the nature of stator and rotor flux ripples from a common frame of reference. The expression for instantaneous torque ripple is formulated and a PWM combination is proposed resulting in lower root mean square (rms) and peak-peak torque ripple. The estimated instantaneous, rms, and peak-peak torque ripple is verified through simulation and experimental results from a 3-kW vector controlled DI-WRIM drive.