Unified interpretation of indirect and direct vector control [of electric machines]

The vector control method can be classified into two groups, the indirect (the slip frequency controlled) vector control and the direct (the field oriented) vector control. The two control methods have been considered as the same methods uncertainly, but they are studied from quite different point of view for implementation. In the case of the direct type, modern control theory is applied to realize high performance. It has been known to be more robust that the indirect method against parameter deviations. In this paper, a unified interpretation of the two vector control methods is shown. From a comparison between them, a design method for the direct type is shown to be applicable to the indirect method. The authors show a new indirect vector control system which has the same robustness as the direct method.<>