A technique for estimating security margin to voltage instability using multiple load flow solutions

A technique is presented for estimating the security margin for voltage instability in electric power systems. The margin is represented as an index of closeness of a pair of multiple load flow solutions. This approach is based on the fact that the number of multiple load flow solutions becomes two as power systems get heavily loaded. The objective of this study is to reduce computational effort by avoiding the exhaustive search in evaluating the closest solution to a feasible solution. An efficient method for selecting the initial value in evaluating the closest solution is presented. The proposed method allows implementation of the index as an online tracking measure for voltage instability