This paper focuses on iron core loss compensation of a direct field-oriented induction motor drive incorporating robust parameter identification. The principle of the control is based on direct field orientation by using a rotor flux estimator. Motor parameters in the flux estimator, i.e. magnetizing inductance and rotor resistance, are identified insensitively to stator resistance. However, owing to a model mismatch caused by the equivalent core loss resistance, neither the field orientation nor the parameter identification can be achieved as is expected, which results mainly in degradation of torque control accuracy. The paper discusses precise measurement of the motor parameters under various operating conditions, influence of the core loss on the field orientation and the parameter identification, and compensation technique for the purpose of gaining higher accuracy in the torque control. The effects of the compensation have been verified through computer simulations and the torque error has been improved down to less than 1% as a result.
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