EMF feedback control strategy of induction motor for wide speed range

Variation of winding resistance, magnetic saturation and iron loss in the induction motor result in field angle estimation error, which causes detuning problems. Especially, in cases when the iron loss and change of inductance cannot e neglected, ordinary resistance identification methods may lead to incorrect results. To solve this problem, a new method to directly revise the observed field position is proposed in this paper. The position angle of rotor flux observed can be continuously revised by adding a feedback compensator of electro-magnetic force (EMIT), which guarantees the correct direction of rotor flux. The principle of compensation is introduced, and in order to verify the validity of this method, various tests have been done on a 60 kW induction machine. The simulation and experimental results indicate that the flux orientation of an induction motor field oriented control (FOC) system with EMF feedback control strategy is more accurate than an ordinary FOC system, especially in high speed range.