A New Frequency Domain Filter for Precise Phasor Computation of Electrical Power Current

Abstract

Digital filters of electrical protective relays play primary roles in calculating the fundamental phasors of electrical power signals. In most fault cases, large amounts of decaying DC components are included in the current signals during the fault period. Decaying DC component significantly reduces the precision and convergence speed of all conventional frequency-domain filters such as Fourier and Walsh filters. In this investigation, this paper introduces a new frequency-domain filtering algorithm to remove the decaying DC components and accurately capture the fundamental power system phasors for digital protective relays. This is executed by means of a mathematical procedure using digital signal processing techniques. The proposed filter is tested for a wide variety of current signals during different fault conditions to assess its performance. The simulation results show that the proposed filtering algorithm has a superior performance at a wide range of decaying components.