A maximum likelihood based dynamic synchrophasor estimator for online purpose

Abstract

The dynamic of Phasor Measurement Units(PMUs) has directly bear on the research of dynamic characteristic, which is one of the research focus nowadays. Because of poor performance of finite-impulse response filters in analyzing dynamic signal, a new phasor measurement method based on maximum likelihood is proposed by this paper to improve accuracy of dynamic phasor estimation. A dynamic signal model in form of Taylor series is adopted to represent supply signal in power system. And the derivatives of Taylor, which are the representation of signal dynamics, are considered to be the variable to be estimated using maximum likelihood method. Finally, dynamic phasors can be attained by a new set of digital filter's coefficient determined by maximum likelihood method. With dramatic accuracy improvement, the calculation burden of the proposed method is the same as DFT algorithm with the same filter length. Therefore, it is convenient to employ this method for on-line purposes. Digital simulation and field data offline study let us make a conclusion that the method proposed by this paper has good performance under dynamic condition as well as in the presence of harmonics.