Highly reliable transient stability solution method using energy function

Power system stability is usually determined by solving nonlinear differential equations numerically, for instance, by the Runge Kutta method. P.D. Aylett applied the energy function method to the power system stability problem. This paper discusses the Kakimoto method and PEBS method (Potential Energy Boundary method) proposed by T. Athay. It is pointed out that overly optimistic solutions are obtained due to the presence of second swing and decelerating step-out. This paper proposes a new method to determine the stability limit. Kakimoto's method gives an incorrect solution when the solution trajectory does not reach the critical energy curve and his method also fails to give the stability limit curve on the phase plane. A disadvantage of Athay's method is that the stability limit curve is approximated by PEBS method. The method proposed gives a clearly defined stability limit curve.