Stability Analysis of the Direct Field Oriented Control System of the Induction Motor without a Speed Sensor using the Adaptive Rotor Flux Observer

Abstract

The vector control of the induction motor without a speed sensor required the estimations of the rotor flux and the rotor speed. Since the estimations use the machine parameters and the stator voltage and current components as input quantities, the stability of the systems is sensitive to the variations of the machine parameters and the measured stator voltage errors and the current control errors compared with the vector control systems with a speed sensor.
In this paper, the small signal stability analysis is carried out on the direct field oriented control system of the induction motor without a speed sensor using the adaptive rotor flux observer (MRAS method) and allows for the stability effects of the stator resistance and rotor resistance and the gain of the speed controller to be studied. The stability effects of the MRAS method are compared with that of the vector control system of the induction motor without a speed sensor based on _??__1q-feedback control (_??__1q-feedback method). Furthermore, theoreitical step responses of the rotor speed are compared with the experimental results.