A fast accurate method for direct assessment of transient stability

A direct stability assessment method that can act as a fast screening tool for determining retention or loss of stability is becoming of increasing interest in system planning, operation planning and on-line control center applications. In this paper, a fast, accurate method for determining retention or loss of stability without requiring time simulation for a particular fault, clearing time, clearing action, and operation condition is developed. This method is shown to require approximately the computation time of one or two decoupled load flow solutions. The method requires development of a linear or a nonlinear prediction of peak angle excursion after the transient. This linear peak angle predictor is developed based on a linearized power system model and a pulse acceleration model for the fault. This nonlinear predictor estimates the maximum angle excursion using a nonlinear power system model. The linear peak angle predictor is used to establish retention or loss of stability using an improved potential energy boundary surface (PEBS) method. Critical clearing times can be determined within maximum error of 4.5% compared to those calculated using a transient stability program on a 17 generator example system.