Three-Level Optimized Pulse Patterns with Eliminated Torque Harmonics

Abstract

This paper presents the computation of three-level optimized pulse patterns (OPPs) that minimize, and, when physically possible, eliminate the low-order torque harmonics by incorporating explicit constraints into the optimization problem. To prevent the consequent deterioration in the output current quality, the symmetry constraints typically imposed on OPPs are relaxed. As a result, the proposed OPPs not only suppress the targeted torque harmonics but also keep the current harmonics low and close to those of conventional OPPs, as demonstrated by the presented numerical results. At the same time, the torque ripple produced by the proposed OPPs is comparable to-or, for some modulation indices, even lower than-that of conventional programmed modulation methods.