Identification of interarea modes from an effectual impulse response of ringdown frequency data

In this paper, interarea modes are identified from ringdown frequency data acquired through wide-area measurement systems (WAMSs). These data contain not only an impulse response of interarea modes and noise but also a decaying dc component. The impulse response can be deformed by controlling the power system. An effectual impulse response is determined from a difference sequence between two sets of the data to remove the dc component and the deformation. A modal identification method is developed to minimize the noise of the effectual impulse response through singular value decomposition (SVD) with choice of rank thresholds. The developed method and a conventional Prony method are compared through simulations on the SNR. Kundur's test system is identified to verify the usefulness of the effectual impulse response. The developed method is applied to identify real power systems from Frequency Monitoring Network (FNET) data.