Efficient Control of a Multimode PM Motor With Optimal Torque Distribution

This article proposes a new optimized control strategy for a multimode permanent magnet (MMPM) motor to realize a wider efficient operation range. The key is the optimal torque distribution control under copper loss minimization constraint. The MMPM motor has four operating modes because of its special dual-stator structure, namely, mode I for main drive output, mode II for auxiliary drive output, mode III for simultaneous output of main and auxiliary drives, and mode IV for main drive output and excitation by auxiliary drive. For the four operating modes of the MMPM motor, different constraint conditions are applied under each operating condition, and the optimal assignment currents are obtained by the Lagrange multiplier method. Moreover, by optimizing the current distribution ratio, torque distribution is re-carried out, which improves the motor efficiency. Meanwhile, the high-efficiency operation interval of the motor in four operating modes is identified, and the principle of selecting the operating mode under the wide range of high-efficiency requirements is revealed. Finally, experimental results demonstrate the effectiveness of the proposed control strategy.