PMU-based Modal Analysis of Two RTE Oscillation Events

Abstract

This paper presents an analysis of two recent major oscillation events in the RTE power system. Data from Phasor Measurement Units (PMUs) collected during the events are analyzed by using ambient and ringdown modal estimation tools. Fast Frequency Domain Decomposition (FFDD) and Covariance-based Fast Stochastic Subspace Identification (FSSI-Cov) are applied for ambient modal analysis. In the first event, we show that the frequency of an inter-area mode changed dramatically after a system topology change while its damping also decreased. The second event may be related to the emergence of an unknown sustained oscillation whose frequency was close to that of a system inter-area mode. Analysis of these two events shows the relative strengths and weaknesses of different oscillation monitoring algorithms and their usefulness in measurement-based modal analysis of large system events. Furthermore, the paper will also discuss the computational burden and other challenges in implementing the algorithms in real-time applications.