A Consideration and Improving Method about Stability of Vector Controlled Induction Motor System without Speed Sensor Driven with Controlled Voltage Source Using Adaptive Secondary Flux Observer

Abstract

In this paper, the stability of vector controlled induction motor system without speed sensor driven with controlled voltage source using adaptive secondary flux observer (CVSS) is analyzed, and the improving method is proposed.First, the stability of the system including the estimators of the primary resistance and motor rotational speed on the conventional method for already reporting is clarified in the equilibrium points vicinity. As the result, it was proved that the stability of the conventional method was worse than the stability of vector controlled induction motor system without speed sensor driven with controlled current source using adaptive secondary flux observer(CISS), because the primary voltages of induction motor and those of observer are different in conventional method. Next, a new CVSS is proposed, in which the primary voltages applied to induction motor is equal to those applied to observer. The stability of new system is clarified, and it is better than the stability of the conventional method. Furthermore, it is clarified that the stability is the same as CISS, which is applied practically. In addition, the unstable regions is clarified by the mathematical expressions under the regenerating condition.The appropriateness of investigation results are confirmed by the simulations.