Optimal low-stator-frequency avoidance strategy to improve the performances of induction machine sensorless drives

This paper focuses on speed-sensorless drive of induction machine without signal injection. To ensure good performances of the speed observer without the disruptive effects of signal injection, it is possible to avoid the unobservable working points which lead to poor speed observation. To do so, the existing methods aim at avoiding the low stator frequencies. They are nonetheless difficult to use for real applications since they lack flexibility and do not take into account some industrial constraints. The approach presented in this paper consists in formulating all the working constraints in order to build a cost function. By minimizing this cost function, the proposed optimal avoidance strategy is more flexible and can be applied for any industrial application.