Sensorless vector control of induction motor with stator resistance identification based on augmented error

This paper proposes a speed sensorless vector control system of induction motors which is stable in regenerating region as well as motoring one. In speed sensorless vector controls of induction motors with adaptive observers, the speed identification system becomes unstable for the major part of the regenerating region. Moreover, it is pointed out that the stator resistance variation influences the speed identification. Thus, it is necessary to find an adaptive scheme which can stabilize the identification system in whole region. Although several methods have been proposed to stabilize the identification system, they discuss only on the design of the observer gain. In these cases, the following problems exist.. The design parameter is determined by trial and error. Resulting observer gain tends to violate stability of the observer. The induction motor is assumed to be at steady state. Therefore, the stabilization of the parameter identification should be improved by designs of identification laws. In this paper, to stabilize the identification system of the speed and the stator resistance, the augmented error is introduced, yielding the transfer function of an error system becomes "I". Next, an adaptive scheme for the speed and the stator resistance is proposed which stabilizes the identification system. Furthermore, the proposed adaptive scheme is simplified to reduce the amount of calculation. Finally, effectiveness of the proposed method is shown by experiments.