Field-oriented control of an induction motor with robust on-line tuning of its parameters

This paper proposes new torque control of an induction motor, which is robust against primary resistance and adaptable to leakage inductance, magnetizing inductance, and secondary time constant. The control is based on flux feedback with a flux simulator. Since the simulator is based on a rotor current model, it is independent of the primary resistance, but uses the magnetizing inductance and secondary time constant values to estimate the flux. Parameter mismatch in the simulator detrimentally affects flux and torque responses. In order to compensate for degradation of the responses, an identifier for the magnetizing inductance and the secondary time constant is introduced. The identifier is insensitive to the primary resistance because it is based on instantaneous reactive power of the motor. Also, a leakage inductance identifier is introduced to achieve perfect compensation, which is robust against other parameters owing to instantaneous harmonic reactive power. To verify feasibility of the proposed technique, digital simulations and experimental tests have been conducted. The results have proven excellent characteristics of the drive system, which confirms validity of the scheme.