Identification of coherent generators by spectrum analysis

A new method of identifying the coherency of a group of generators using spectrum analysis technique is presented. First, the rotor angles of generators in the early part of the transients are predicted by the Taylor series expansion of the power system model. The values obtained are taken as sample data for the spectrum analysis with an FFT algorithm. The coherency criteria based on the spectra are presented and the coherent groups of generators can be quickly identified. A 34-bus 9-machine power system is used to illustrate that the proposed method is a fast and practical one.