LAUSR

For wide-speed range operation of speed sensorless induction motor drives (SSIMD), the stable operation at low synchronous speed range (including zero synchronous speed) is a great challenge. Virtual voltage injection method is found efficient to overcome this challenge. However, the injected virtual voltage into observer results in the estimated speed error, it is reasonable to rely upon this method only when the performance of traditional SSIMD is poor, i.e., at low speed range. At middle and high speed ranges, virtual voltage injection method cannot meet the high-accuracy requirement of speed estimation in industrial application. For wide-speed range operation of SSIMD, a necessary switching system is proposed in this article to meet the stability requirement and accuracy requirement at the same time. The input-state stability theory is adopted to verify the stability of switching method, because the switching system is a nonlinear and strong coupling system. Then the switching trajectory is optimized for smooth and fast switching transition. Finally, the effectiveness and feasibility of the proposed method are verified by experimental results.