Future Research Issues

Abstract

In this chapter we briefly survey what has been accomplished in this field so far and indicate new areas of research for further investigation. The history of using direct methods in power system stability is a long one of nearly four decades following the equal area criterion by Kimbark. Although there was a relative lull in the 60’s and early 70’s, the work being limited only to the aca-demia, the late 70’s and the 80’s have seen a big upsurge in terms of research publications. There have been the breakthrough concepts of the controlling u.e.p and the potential energy boundary surface. The two are not irreconcilable concepts as suspected earlier. The characterization of the region of stability boundary in the multi-dimensional space has helped the development of hybrid techniques which combine the best features of both the controlling u.e.p and the PEBS methods. As systems became larger, consistency regarding accurate determination of critical clearing time or energy margin were matters of concern. Here the concept of grouping of machines following a fault has been helpful. This concept can be used either in a multimachine context by correcting the K.E and identifying the grouping through normalized P.E margin or reduce the system to a single machine infinite bus system by assuming coherency in the two groups. Extensions to multi-area energy functions have been made. If coherency is not to be assumed then corrections to the potential energy portion of the energy function associated with centers of inertia (slow energy function) are needed.