Transient performance improvement control for IFO induction motor drive in field-weakening region

The transient performance improvement for an indirect field-oriented (IFO) induction motor drive with field-weakening is studied. In the proposed field-weakening control method, the saturation effect of magnetising inductance is considered by representing it using a fitted quadratic polynomial of flux current. The flux current command is composed of three parts, namely the no-load, the loading compensating and the transient compensating components. The first one is represented by a third-order polynomial of rotor speed, which is estimated at no-load to consider the effects of nonlinear magnetising inductance and motor voltage limit. The other two compensating components are used to further weaken the field such that current tracking performances during loaded conditions and transient period can be improved. It follows that the torque generating capability and speed response are also enhanced accordingly. However, the speed response trajectory for a field-weakened IFO induction motor may vary significantly owing to the variations of flux level and system parameters. Hence, finally, the nominal motor drive dynamic model is estimated and a simple speed model following control scheme is designed to yield improved speed tracking and regulation transient responses.