Abstract
This paper proposes an analytical criterion for stability boundaries of non-autonomous systems. The criterion can analytically enlarge the conservative stability limits obtained by the classical Lyapunov's direct method almost up to the exact stability boundaries even for non-autonomous systems. It is based on the Melnikov's method which estimates homoclinic intersections in the dynamical systems theory. The definition of the criterion has strong advantages in its easy and quick estimation of the stability, compared with the numerical integration of the non-autonomous systems. The effectiveness is confirmed in its application to an electric power system with dc transmission under periodic swing.
