Transient stability limit assessment by modified signal energy approach

Signal energy method is a time-domain simulation based method for rapid determination of power system transient stability limits. It is based on the observation that the signal energy of the transient voltage response to a given contingency rises asymptotically with the increasing power to its limit. The power transfer limit could be estimated directly from the signal energies calculated using the simulation results obtained on various power levels once the signal energy function can be formulated in terms of power transfer. In this paper, two new analytical approximations, namely the first and third order approximations, are proposed for the signal energy function formulation. The validity and the effectiveness of the proposed approximations have been verified on the 10-machine New England system and the 47-machine SiChuan and ChongQing power network in China. Comparisons with the original signal energy method showed that the proposed approaches are more effective and adaptive. In particular, the first order approximation approach is capable to determine the system transient stability limit efficiently with high accuracy.