ABSTRACT
This chapter begins by covering some basic concepts from the theory of nonlinear system stability. It introduces the fundamental Lyapunov stability thought and the procedure of constructing Lyapunov stability function. The chapter deals with transient stability by a specific direct method mainly the transient energy function (TEF) method. In the actual operation of an electric power system, the parameters and loading conditions are quite different from those assumed at the planning stage. Asymptotic stability as judged from the linearized system is simple but of less practical use. Except for relying on experience, there is no systematic method to find the Lyapunov function as required by the theorem. Time-domain simulation is run up to the instant of fault clearing to obtain the angles and speeds of all the generators. The degree of conservatism introduced by the closest Unstable Equilibrium Point (UEP) approach is such that the results are usually of little practical value.
