Coherency and area identification

Abstract

We have proposed a coherency criterion which requires the states to be coherent with respect to only a selected set of modes. This criterion results in disturbance-independent coherent groups. For dynamic networks, the coherent groups found according to this criterion form aggregable areas, which verifies the heretofore heuristic coherency-based aggregation technique used in power system analysis. For models of real systems, we have developed a grou** algorithm to identify near-coherent states which form near-aggregable areas. The algorithm is efficient and has shown to be applicable to large scale power systems with as many as 400 machines and 1700 buses.

In this chapter, we have dealt with coherency with respect to a selected set of modes. In the next chapter, we examine coherency with respect to the slowest modes. As will be shown, this leads to areas that are weakly connected.