Control of induction motors for both high dynamic performance and high power efficiency

The authors attempt to control induction motors with maximum power efficiency as well as high dynamic performance by means of decoupling of motor speed (or motor torque) and rotor flux. For maximum power efficiency, the squared rotor flux is adjusted according to a minimum power search algorithm until the measured power input reaches the minimum. Since the motor speed is dynamically decoupled from the rotor flux, this can be done successfully without any degradation of motor speed responses. The controller depends on rotor resistance but not on stator resistance. However, the performance of the control scheme is robust with respect to variations in rotor resistance because an identification algorithm for rotor resistance is employed. The identification algorithm for rotor resistance has some advantages over the previous methods. To demonstrate the practical significance of the results, some experimental results are presented