A numerical method to evaluate power system global stability determined by limit cycle

This paper presents a method to investigate a global stability in a multi-machine power system with multiple dominant power oscillation modes. The global stability boundary formed by an unstable limit cycle is predicted by means of Hopf bifurcation theory. The authors have investigated a numerical method to analyze the nonlinear characteristics in power systems by acquiring the power swing data where the coefficients of nonlinear polynomial terms are determined by the least squares method. A modified method has been also developed for the application to large-scale multi-machine power systems with longitudinally interconnected configuration. Numerical examples illustrate that the influence of the modal interaction on the nonlinear structure of the power system as well as the Hopf bifurcation characteristics can be evaluated by the proposed method.