A Speed Estimation Scheme Based on An Improved SOGI-FLL for Speed-Sensorless Control of Induction Motor Drives

With the aim to enhance the system reliability and reduce the system cost of induction motor drives, the speed-sensorless control, implemented by various speed estimation schemes, is demanded. The speed estimation provided by the second-order generalized integrator-frequency-locked loop (SOGI-FLL) is emerging as a promising method for speed-sensorless control. However, most of the existing SOGI-FLL schemes may undergo performance degradation during frequency ramps. Additionally, the SOGI-FLL scheme has an insufficient capability to reject disturbances, e.g., DC offsets. To address these issues, a speed estimation scheme based on an improved SOGI-FLL scheme for speed-sensorless control of induction motor drives is proposed. In this scheme, a new FLL is utilized as the speed estimator, which achieves accurate estimation with frequency ramps. Specifically, by employing a second-order SOGI-based flux observer, acceptable robustness of the proposed estimation scheme against DC offsets is obtained. Simulations are performed to investigate the performance of the proposed speed estimation scheme and a comparison with the conventional SOGI-FLL scheme is made.