Transient dynamics in electric power system with DC transmission: fractal growth in stability boundary.

This article discusses the effects of DC power flow on the transient dynamics of an AC/DC power system, based on a non-symmetrical swing equation system. The non-symmetry implies a unidirectional component of external forcing, which corresponds to both DC power and exciting power swing. The dynamical behavior when affected by a DC external force, however, has not been solved for these systems, although some studies on the Duffing equation with unsymmetrical force were reported. The dynamical behavior now remains an open problem in power system dynamics and also in nonlinear oscillation theory. As an important aspect of the dynamical behavior, one consider a stability boundary and its qualitative change in the swing equation system.