“…E-mail: masa_hojo@tokushima-u.ac.jp *State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049, China **Department of Electrical and Electronic Engineering, Tokushima University, 2-1 Minami-josanjima Tokushima 770-8506, Japan of generator coherency under different disturbances, which is, however, inconsistent with practical cases. The measurement-based methods identify the generator coherency based on the hierarchical clustering method [11], independent component analysis [12,13], spectral clustering method [14,15], wavelet phase difference [16], robust principal component analysis [17], Koopman mode analysis [18], graph theory [19,20], and intelligent method [21,22]. These methods can adapt to various operation conditions, topology changes, and different disturbances by using the real-time measurement data because all the influences of these factors are reflected in the transient response of the power system.…”