Compensation for parameter variation of induction motor improved torque control characteristics in low‐ and high‐speed regions

In the vector control system using the slip frequency control method, the rotor resistance of an induction motor is used to calculate a slip frequency. Thus the change in temperature of the rotor resistance causes the deterioration of the torque control characteristic. This paper presents a new method of compensating for the rotor resistance change which is robust for the stator resistance change. A current control loop is composed of the λ-δ axes in which the λ axis is coincident to the stator current. In this method, the stator voltage error on the δ axis which is directly obtainable from this current control loop was used. The change in the stator voltage was able to be detected accurately, therefore the torque control accuracy was improved, particularly in the low-speed region. The experimental results of the current response and the compensation for the rotor resistance deviation also are shown. Moreover, although the mutual inductance has been treated as an invariable value, the value does change by a frequency and an exciting command. In this control method, an initial tuning of the equivalent mutual inductance was achieved by detecting the deviation component of the stator voltage on the δ axis at the no-load running condition. Furthermore, in the region with the constant power where the field weakening control was achieved, the excellent experimental results of the compensation for the deviation of the equivalent mutual inductance are shown.