Speed sensorless control performance improvement of induction motor drive using uncertainty cancellation

An improved speed estimator using parameter uncertainty cancellation and its application to an indirect field-oriented induction motor drive are presented. First, the speed estimation errors of a V-I model-based adaptive speed observer due to parameter variations are analysed. Then, accordingly, a novel compensation scheme is developed to cancel the effects of parameter variations on the estimated speed performance; A variable structure system controller, with the detected error signal as its input, is employed to realise the proposed compensation scheme. Finally, the robust speed control with quantitative control performance considering the effect of dead-time enlargement due to the feedback of estimated speed is presented. Theoretic bases of the proposed speed estimator and the robust speed controller are derived in detail, and their validities are demonstrated by some simulation and measured results.