Improvement of AFO for Sensorless IM at Zero and Very Low-Speed

In the speed-sensorless induction motor (IM) drive system adopting the adaptive full-order observe (AFO) method, the capability of drive is poor at low-speed range. To solve the problem, a novel method is proposed based on the principle of minimum magnetizing current error, and the feedback gains are designed accordingly. On the basis, the magnetizing current error is used in the speed estimation and then suitable weighting factor is introduce, and enhanced speed estimation method. Through Lyapunov's theorem and Routh-Hurwib criteria, the stability of proposed method is proved. Finally, the feasibility of the proposed scheme was verified by the experiments.