Mode shape estimation and mode identification for inter-area oscillations utilizing correlation analysis techniques

This paper presents a new algorithm for rapid estimating inter-area oscillation(IAO) mode shapes and corresponding modes using correlation analysis(CA). It firstly extracts a weak damping component strongly associated with objective mode from each tie-line active power signal came from WAMS(Wide Area Measurement System), through a low-pass or band-pass filter which is designed by a priori modal knowledge obtained from off-line calculation. Then the self-correlation and cross-correlation coefficients resulted from CA of these time-domain signals are used to determine a inter-area mode shape of tie-line power deviation and equivalent speed deviation which is always able to correspond to a mode. Finally, the results about IAO features are checked with the modal form(MF) from off-line calculation and on-line correction in order to confirm the dominant mode and its mode shape at current state. Two pairs of stationary and non-stationary synthetic signals are utilized to verify the applicability of CA. The case studies have been carried out on a 4-area and 9-bus system and a planning case in East China Power Grid(ECPG), and the results show that the proposed algorithm is efficient and effective, and also indicate the potential practicability for WAMS of bulk power system.