An Extended Speed Adaptive Observer with Auxiliary Variables for Sensorless Induction Motor Low-Speed Operation

This paper proposed an extended speed adaptive observer (ESAO) with auxiliary variables to improve the stability of sensorless induction motor (IM) low-speed operation. The mathematical model of IM is reconstructed by introducing an auxiliary variable. On this basis, an ESAO is designed with a novel speed adaption law. Compared with the conventional adaptive full-order observer (AFO), the proposed ESAO can reduce the unstable region in low-speed operation without without complex feedback gain design. Experimental results show the effectiveness of the proposed method.