Mode initialization for on-line estimation of power system electromechanical modes

Measurement-based mode-estimation methods are utilized to estimate electromechanical modes of a power system using phasor measurement units (PMU) data. These methods need to extract a certain amount of information before they can provide a useful mode estimation. Traditionally, the information is gathered solely from measurement data. A priori mode information from other resources (e.g. model eigenvalue analysis, engineering knowledge) are not fully utilized. For real-time applications, this means that the mode estimation takes time to converge. By adding a mode regularization term in the objective function, this paper proposes a mode initialization method to include a priori mode information in a regularized robust recursive least squares (R3LS) algorithm for on-line mode estimation. The proposed method is tested using a simple model, a 17 machine model and is shown to be able to shorten the convergence period of the R3LS algorithm. The proposed method is also applied on the measurement data recorded right before a major power outage in the western North American Grid on August 10^th 1996 to show its potential application in detecting an approaching small signal stability problem.