Stability conditions of adaptive pseudo-reduced-order flux observer for vector-controlled sensorless IM drives

Vector-controlled induction motor drive systems without speed sensors have been widely studied. Speed estimation can be treated as a problem of parameter estimation using the model reference adaptive system (MRAS) theory. In these cases, the convergence and robustness of the system are major issues. We discuss the stability of an MRAS that includes an adaptive pseudo-reduced-order flux observer (APFO) of the IM and is used for estimating the rotor speed and identifying the stator resistance as well. To our knowledge, the stability problem of APFO for a sensorless IM drive has not received any attention in previous research. The stability conditions of APFO are discussed. The rotor speed and stator estimation results are provided to show that the proposed scheme is hyperstable.