Modal Damping Estimation: An Alternative for Hilbert Spectral Analysis

This paper proposes a novel approach for modal damping estimation from system oscillatory responses. It is well-known that the signal frequency can be estimated accurately by using time-frequency distributions. Accordingly, a dual function is defined based on the signal to be analyzed, whose frequency is the damping of the original signal. As the next step, Wigner-Ville Distribution (WVD) as the most prominent quadratic time-frequency distribution is applied for estimating the instantaneous frequency of the dual function which is equivalent to the damping factor of the original signal. The proposed method can be considered as a substitute for Hilbert Spectral Analysis (HSA). As will be seen, by rejecting the effect of fluctuations and noise on the mode amplitude, the proposed method provides an excellent estimate of damping. The effectiveness of the proposed method is illustrated using simulations in the Kundur test power system as well as by using real phasor measurement unit (PMU) data from the western power interconnection.