Sensorless vector control strategy of induction motor with large torque output

This paper describes a new sensorless vector control strategy for induction motor which can meet the requirements of constant large load torque, based on the comparative study of two observation methods for flux linkage, which are high-frequency signal injection method (HFSIM) and full order flux observer. In the low speed region, a high-frequency signal is injected, which is independent of the motor parameters. The rotor speed is identified by extracting the high frequency current. In the higher speed region, the rotor speed is obtained through full order flux observer to prevent the high-frequency torque ripple caused by HFSIM. An appropriate state switcher is proposed, in order to ensure smooth transition as the speed rises, as well as to ensure the accurate estimation of the rotor flux orientation angle within the whole speed range. The overall control strategy can output constant torque and satisfy heavily loaded condition. The experimental motor control test proves the correctness and effectiveness of the proposed strategy.