Current References for Minimum Copper Loss and Torque Ripple in the Full Torque-Speed Range for Symmetrical Six-Phase PMSMs With Nonsinusoidal Back-EMF Under an Open-Phase Fault

Abstract

Current-reference generation based on lookup tables (LUTs) is here proposed for star-connected symmetrical six-phase nonsalient PMSMs with nonsinusoidal back-EMF under an open-phase fault. Fourier coefficients for all healthy phases are computed offline, enabling unbalanced nonsinusoidal currents. A lexicographic optimization minimizes torque ripple and then copper loss, subject to torque, zero-current-sum, peak-current, peak-voltage, and torque-ripple constraints. Cogging torque can be included for compensation. Simulations show a higher feasible speed limit: about 30% at low torque and 23% along an example load curve. Finite-element analysis shows a 77% reduction in peak-to-peak torque ripple with cogging-torque compensation.