Resistances and Speed Estimation in Sensorless Induction Motor Drives Using a Model With Known Regressors

This paper addresses the problem of stator and rotor resistances identification in speed sensorless induction motor (IM) drives. The IM model that is transformable into the adaptive observer form is sought, for which the speed and rotor resistance adaptive observer can be established with rigorous stability arguments under the assumption of constant unknown parameters. However, further inclusion of stator resistance estimation leads to the overparameterization problem. As a result, the adaptive observer based on the first-order approximation of the error dynamics is proposed. This is feasible because the regressors of the adopted IM model consist of known signals only. An experiment is carried out to verify the effectiveness of a sensorless drive with the proposed adaptive observer. Compared with the existing methods, estimation of speed and resistances during a regeneration mode as well as successful slow-speed reversal operation is found possible in the experiments.