Fast estimation of transient stability limits by combining direct method with least squares technique

This paper proposes a novel method for calculating transient stability limits by combining the direct method with the least squares technique. In this paper, the nonlinear relationship between the transient energy margin (Delta V) and the generator mechanical power input (P-m) at different fault clearing times (T-cl) has been studied. The functional relation of Delta V=f(P-m,T-cl) has been established by using the least squares technique. In this way, the transient stability limits at different fault clearing times under a given large disturbance can be quickly obtained. In order to make the proposed method suitable for handling large scale power systems, dynamic equivalent technique has also been used. The proposed method has then been tested on the 59-machine Northeast China power system, and the results have been compared with other methods. (C) 1998 Elsevier Science S.A. All rights reserved.