Power system transient stability assessment based on quadratic approximation of stability region

This paper presents an approach to estimate the critical clearing time (CCT) of the multi-machine power systems based on the quadratic surface which approximates the boundary of stability region relating to the controlling unstable equilibrium point. While obtaining the coefficient matrix of the second order term of the quadratic approximation, we partition the coefficient matrix into four blocks to reduce the computation burden. The CCT is estimated by the crossing point of the quadratic approximation and the continuous faulted trajectory. Simulations in IEEE 9-bus and New England system show the effectiveness of the proposed approach.