Investigation on Critical Unstable Trajectory of Electric Power System Based on Non-Time Reference

A new approach is proposed in this paper to calculate the critical unstable trajectory of disturbed electric power system based on a non-time referenced variable. The critical unstable trajectory is obtained by calculating the unstable manifolds on CUEP through special linear and nonlinear transformation on a post-fault power system. The important thing is that there is no poly-value problem by the special set nonlinear transformation adopted in this paper, so the critical unstable trajectory is a simple beeline in Z-space if the CUEP is I-type. The proposed method is verified through a calculation example of New England electric power system. Compared the result of the proposed method with that of the step-by-step method, it shows that the critical unstable trajectory of a disturbed power system is correctly calculated in this paper. A four order nonlinear transformation is adopted in the formula and the precision is sufficient