A simple on-line method for rotor resistance updating in indirect rotor flux orientation

Rotor resistance plays a dominant role in the loss of decoupling in rotor flux indirect vector control. To maintain high performance in these drives, estimation of the rotor resistance is required to adapt the decoupling regulator against the variations of the actual rotor resistance of the motor. This paper presents a new simple method for on-line estimation of the rotor resistance in rotor flux, current-controlled voltage-fed vector drives of induction motors. Small perturbations are applied to the rotor resistance programmed in the decoupling controller and the resulting response at the output of the d-axis proportional-integral current regulator is analyzed to provide a useful information on the actual rotor resistance of the motor. In addition of being independent of the motor state model and requiring no additional sensors, the proposed technique distinguishes from other conventional methods, such as extended Kalman filter, MRAS and neural networks identifiers, by the fact that it is simpler to implement and that it does not require complex computations. Simulation results are presented for a current-controlled, voltage-fed, indirect rotor flux drive to illustrate the efficiency of the proposed approach.