Development of a new phasor measurement algorithm with decaying DC offset removal

Abstract

Current and voltage phasors remain the basis of most power system protection and automation functions. Most phasor measurement algorithms used for this purpose are derived from the discrete Fourier transform (DFT) method, which is justified by its relatively simple implementation and good harmonic rejection. Growing requirements for faster relay operation and higher accuracy impose new conditions, particularly the need for a shorter measurement window and immunity to a decaying DC (DDC) component. To address these demands, new solutions are emerging, often based on algorithms with an expanding measurement window and on assumed definitions of the proposed measurement model. The method presented in this paper combines the properties of the DFT with a suitably modified least squares (LS) method to meet the expected requirements, ensuring fast estimation of the phasor components of the fundamental-frequency component while remaining insensitive to the presence of the DDC component. The attached results of simulation studies show details of the application and some of the properties of the method proposed.