Different approaches for estimation of dampings and frequencies of electromechanical modes from PMU ambient data

Small signal stability of power systems is one of the most crucially important issues, since the electrical demand is increasing at a galloping rate and power systems are expanding day by day. In this regard, estimation of dampings and frequencies of electromechanical modes through the analysis of field measurements has become a heated study topic for electrical power system researchers in recent years. There have been several methods to analyze different types of Phasor Measurement Units (PMUs) signals i.e., transient, ambient, and probing. Among the proposed techniques, those which are capable of analyzing ambient data seems to be more practical, since this type of data can be achieved under the normal operating condition of power systems. In this paper, several methodologies are investigated so as to estimate the dampings and frequencies of electromechanical modes from analyzing the ambient data of a multi-area power system. In general, these methods are categorized into block-processing and online approaches. The authors apply the approaches to the simulated data achieved from PMUs implemented in the 5-area New England- New York power system which operates under the normal condition. The results are discussed and compared with each other and advantages, disadvantages, and practical application of each one are explained. By doing so, power system operators and planners are made capable of selecting the pertinent and applicable approach according to their desire, analysis tools, and system operating condition.