Identification of hunting frequency and equivalent transmission line impedance in a multi-machine system for stability applications

A generating unit in an interconnected power system often participates in both local and inter-area modes of oscillations. The spectral and temporal distributions of these modes are largely determined by the dynamics of the rest of the system. An adaptive stabilizer, capable of damping all modes of oscillation would require estimations of the dominant frequency of oscillation and the external equivalent line impedance as seen from the terminal of the machine concerned. The authors describe two new methods, one for identification of the external impedance and the other to obtain the power spectral density during hunting. The identified parameters are used in an adaptive PSS to evaluate it´s performance in a multi-machine system.