On the control of a field-weakened induction motor having improved transient and static performances

The field-weakening control of an indirect field-oriented (IFO) induction motor (IM) drive with good dynamic and static performances is studied. First, the operating characteristics of an IFO induction motor drive under conventional field-weakening control are studied to comprehend its limitations. In the proposed field-weakening control scheme, the normal d-axis flux current command is the first set. It consists of a major component generated based on conventional 1 /ω_r approach and a loading compensating component. Then the normal command is augmented with transient and static compensating components to automatically further improve its defects. During the transient period, the former component is generated from the torque current tracking error and added to adaptively further adjust the field such that the current tracking control performance is improved; hence, the transient torque generating capability is also enhanced accordingly. Finally, a robust current controller and a detuning compensator are developed to enhance the current tracking performance of a detuned induction motor. As the transient is elapsed and enters the static period, the static compensating flux current command is tuned using the proposed intuitive approach to let the motor quickly reach a stable condition having better static torque generating capability, thus the energy conversion efficiency is improved. Effectiveness of the proposed field-weakening control method is demonstrated experimentally.