LAUSR

Flux estimator (FE) is critical for achieving high-performance sensorless drive of induction motors. A voltage model (VM) is an excellent candidate for a FE since it does not require speed information and has a simple structure. A VM using a closed-loop style has excellent sensorless drive capability over a wide speed range. However, it is limited by the uncertainties such as offset and parameter mismatch. This paper presents an improved a closed-loop style FE. To overcome the problems inherent in the conventional FE, a hybrid strategy for the changeover between control modes is applied. In the setting of the FE’s cutoff frequency (CF), the influences of the offset and parameter mismatch are analyzed. The phase distortion and acquisition of the back electromotive force are also analyzed. From this analysis, a vector compensation strategy for the flux linkage is applied. This strategy facilitates the CF setting, which improves the robustness against both the offset and parameter mismatch. Finally, the effectiveness of the proposed FE in a sensorless driven induction motor is verified using simulations and experiments under various conditions.