Sensorless vector controller for induction motor drives with parameter identification

A sensorless vector controller for induction motor drives based on the theory of model reference adaptive system (MRAS) has been presented in previous papers, which identifies synchronous speed of motor drives using the error of reactive power as the reference input of adaptation mechanism. Moreover, as shown by the authors in a previous paper (see Proc. European Power Electronics Conf., vol.4, p.480-5, 1997) the MRAS-based synchronous speed identification scheme requires neither rotor time constant nor stator resistance in both adjustable and reference models. However, rotor resistance is still used for the estimation of shaft speed. In this paper, a stator resistance identification scheme based upon MRAS using the error of active power as the reference input of adaptation mechanism and details about the stability of the identification scheme is presented. Moreover, the rotor resistance is adjusted using the variation rate of stator resistance. Simulation and experimental results are presented to confirm the theoretical analysis.