Maximum Torque Output Strategy of Bearingless Induction Motor in the Field-Weakening Region

Abstract

In order to realize the maximum torque output (MTO) in the field-weakening region for a bearingless induction motor (BIM) stator vector control, a flux feedforward control strategy is proposed. Firstly, based on the restrictions of the stator flux oriented control and the dynamic characteristics of the current in the BIM field-weakening region, the optimal distribution of the torque current and excitation current and the dynamic model of the maximum torque output strategy are analyzed. Then, the fieldweakening region could be divided into two parts according to the change of slip. It can be proved that the BIM works under the voltage and current limitations in the field-weakening region I, and works under the voltage and torque limitations in the field-weakening region II. By this way, the optimal flux mathematical model of the BIM can be obtained. Finally, the MTO in the field-weakening region is proved. The simulation and experiment results show that the proposed flux feedforward control strategy in the field-weakening region can make the output torque and current tracking effect improve significantly when the BIM runs beyond the rated speed. At the same time, the good suspension performance of the BIM is realized.