Inverse Models and Harmonics Compensation for Suppressing Torque Ripples of Multiphase Permanent Magnet Motor

This paper presents two methods to derive an inverse model in harmonic forms for analyzing the interactions between the torque/current gains and currents, and for suppressing the torque ripples of a multiphase permanent magnet (PM) motor. The first method directly calculates the desired current harmonics from a pseudo-inverse model of a multiphase PM motor with no input-voltage saturation, which is independent of its rotor displacements, for torque ripple compensation. The second is an iterative-free method formulating the inverse model as an optimization problem that minimizes the copper loss subject to torque constraints while accounting for the effects of the input-voltage saturation. The formulation and significance of the two methods are illustrated with a multiphase PM motor for which published measurements are available for model validation and compared with three other commonly used current waveforms for benchmark comparison in terms of torque-ripples and copper losses.