Wide-Speed Range Stability Improvement of Speed-Sensorless Induction Motor Drives Based on Orthogonality Voltage-Model Observer

The stability in both low-speed range and high-speed range are one of the major challenges of sensorless induction motor drives. This article proposes the wide-speed range stability solution from the perspective of the orthogonality voltage-model (VM). First, the mathematical expression of VM is reconstructed by considering the orthogonality of rotor flux, and an extended state observer is established on this basis for stator current estimation. After ensuring the effectiveness of current estimation, the extended state variable is adopted as the feedback term for rotor flux estimation. Finally, the operation speed is extracted from the rotor flux estimation by a phase-locked loop. By studying the observer stability in both continuous-domain and discrete-domain, the observer gains are designed to guarantee the stable operation in both low-speed range and high-speed range. The verification experiments are conducted on a 3.7 kW induction motor test bench, and the results can confirm the validness of the proposed sensorless method.