Torque Ripple Reduction in Sectored Multi Three-Phase Machines Based on PWM Carrier Phase Shift

The interest in multiphase machines for high power and reliable drives has been growing, and many control algorithms have been proposed to improve their torque performance. This article presents a new approach to the modeling of a multi three-phase drive, aiming at the minimization of the torque ripple introduced by the pulsewidth modulation (PWM) voltage excitation, by the shift of carrier phase angles among different three-phase inverters. The underlying idea is to use standard three-phase converters feeding the individual segment and to apply a phase shift between the PWM carriers. For the torque ripple analyzed in this article, only the interaction between the armature field, resulting from the PWM voltage excitation, and the fundamental component of the permanent-magnet field is considered. The proposed carrier phase-shift angles are obtained for a case study of a sectored triple three-phase synchronous permanent-magnet machine. Analytical, numerical and finite-element analysis results are presented to explain how the carrier shift angles affect the current and torque ripple. Finally, experimental results are presented to validate the model and the control algorithm.