Application of integral manifold theory in large scale power system stability analysis

Near identity coordinate transformations are used to decouple the stability problem for a class of non-linear two time scale systems into a stability problem for slow variables and a stability problem for fast variables only. This facilitates the computation of the region of attraction in the slow subspace of much lower dimension. In this paper we describe a technique to decouple the slow dynamics of the system from its fast components. This is the nonlinear counterpart of the decoupling transformation for linear systems existing in the literature. The results are applied to a three-machine power system having strong and weak connections to compute the critical clearing times.