Operating-Point Tracking Method for Sensorless Induction Motor Stability Enhancement in Low-Speed Regenerating Mode

Abstract

The stability of adaptive full-order observer (AFO) can be improved by feedback gain tuning and speed adaptive scheme modification for sensorless induction motor (IM) drives in low-speed regenerating mode. However, few research concern this problem with attention to IM operating point changes. To cope with this problem, this paper proposes an operating-point tracking method to design feedback gain and speed adaptive scheme for AFO. Compared with the existing approaches, lower synchronous speed can be accessible during step speed and load changes in low-speed regenerating mode without signal injection. Addressing the operating point changes, the estimated flux error is derived by adapting the projection of estimated current error with respect to speed and torque. The derivative estimated flux error with changing parameters is taken as an additional variable to design feedback gain. Meanwhile, the speed adaptive scheme is modified by the operating-point tracking expression. As a result, the proposed method acquires the capacity to track the operating point in real time. The experimental results on a 2.2-kW IM experimental setup confirm the effectiveness of the proposed method.