Optimal efficiency control of field-oriented induction motor drive and rotor resistance adaptive identifying

Conventional field-oriented induction motor drives operate at rated flux even at low load. To improve the efficiency of the existing induction motors, it is important to regulate the magnetization flux of the motor in the desired operating range. Additionally, accurate knowledge of the rotor resistance is necessary requiring on-line sensing and adaptive approaches in field-oriented control of induction motor drives. In this paper, a new control strategy is proposed which is simple in structure and has the straightforward goal of maximizing the efficiency for a given load torque. In conjunction with the efficiency optimization control, a scheme for rotor resistance identifying based on the rotor flux observer was proposed. Digital computer simulation for an induction motor demonstrates the effectiveness of the proposed method. Simulation results have confirmed that this method yields the optimal efficiency and good torque response without any degradation in the transient characteristics.