Improvements in operation of vector controlled induction machines by application of modified machine models

The theory of induction machine vector control is based on constant parameter induction machine d-q axis model that neglects all the parameter variations, flux saturation and iron core loss. Due to inevitable variation of parameters during operation of the drive, actual performance may significantly deteriorate from ideal. In general, two approaches may be identified as being available to combat the problem of parameter variations. The first approach relies on modern control techniques and attempts to increase the robustness of the drive while still relying on the same basic constant parameter d-q axis model of the machine. The second approach attempts to improve the accuracy of orientation and thus performance of the drive by using modified d-q axis models of induction machines. The modified models account for one or more sources of parameter variations and thus essentially provide an open-loop adaptation for the specific parameter(s) in question. The paper is devoted to this second approach and its purpose is to discuss some of the modified models that enable improved operation of vector controlled induction machines. The emphasis is placed on main flux saturation and iron core loss