Chapter 21
Group Properties of Contingencies in Power Systems
21.1 INTRODUCTION
Group properties in general power networks will be explored in this chapter. The concept of a group of coherent contingencies will be formulated and demonstrated (Chiang et al., 2007, 2009; Tada and Chiang, 2008). The associated group properties for each group of coherent contingencies will be presented. These group properties include static group properties and dynamic group properties. These group properties will be explored and incorporated into the development of group-based BCU methods and will be presented in the next few chapters.
We define a group property with respect to a group containing several members. A group property is a property that every member of the group satisfies. To identify a group property, it is necessary to form a group of members. We will show that the boundary property is a group property provided that the group of contingencies is properly and accurately formed. Using group properties, we will show that it is not necessary to compute the boundary distance for every computed unstable equilibrium point (UEP) in a group of coherent contingencies. Instead, it is sufficient to compute the boundary distance of one UEP in a group of coherent contingencies in order to check the boundary property for all contingencies in that group. This exploration leads to a significant reduction in the computation and development of effective preventive control actions against a set of ...
