A Position-Sensorless Control of Doubly Fed Induction Machine by Stator-Equation-Based Adaptive Reduced-Order Observer

A position-sensorless control is developed for doubly fed induction machines (DFIM). In this article, an adaptive reduced-order observer is used to estimate both rotor speed and position. The proposed reduced-order observer is based on the stator equation, and four issues are explored. First, the stator equation is used to realize the adaptive reduced-order observer, by which the structure is simple without flux calculation. Second, the stability of adaptive reduced-order observer is analyzed by the linearization method, which paves the way for design procedure of observer's feedback gain. Third, the tracking performance of the rotor-position estimation is investigated through the acceleration/deceleration of rotor speed; an explicit guideline is provided to design the adaptation integral gain to satisfy the specified tracking response. Fourth, sensitivity to machine's parameter variations is studied; the robust stability property is enhanced by the observer's feedback gain; and the robust sensitivity to inductance variation is strengthened by the adjustment of mutual inductance with stator voltage accordingly. Experiment is conducted with a 4-kW DFIM drive system to verify the validation of the proposed theoretical concepts.