Speed-Sensorless Control of Induction Motor Drives with A Delay-Based Frequency Estimation Method

With the presence of speed sensors, challenges, including deteriorated system reliability but increased system cost, have been imposed on induction motor drives. Hence, speed-sensorless control techniques are required in high-performance induction motor drives. Distinctive advantages, e.g., structural and control simplicity and acceptable performance, have pushed the closed -loop synchronization (CLS)-based estimation schemes popular for motor drives. However, in most of the existing CLS-based schemes, their performance may be degraded during acceleration and deceleration processes. To address this, a delay-based frequency estimation (DLL) scheme is explored for speed-sensorless control of induction motor drives in this paper. Disturbances like DC offsets will adversely affect speed estimation, and hence, a closed-loop flux observer is introduced in the implementation of the proposed DEE scheme. The performance of the proposed DLL scheme is investigated by extensive experiments.