A Phasor Estimation Algorithm to Eliminate the Impact of Decaying DC Component

Fundamental phasor plays a prominent role in fault identification, location, and clearance. However, because of the transient process of fault transmission line and current transformer (CT), the fault current trends to contain decaying dc component (DDC). This makes it difficult for the precision of phasor estimation algorithm to meet the requirements of advanced applications based on fundamental phasor. In order to eliminate the adverse effects of DDC, a Full-cycle DFT(FCDFT)-based phasor estimation algorithm is proposed in this paper. The sum of four quarter-cycle samples at interval combinations are utilized to extract and remove frequency domain error terms introduced by DDC into the fundamental phasor. The algorithm is compared with existing techniques in MATLAB environment. The comparison results reveal the proposed technique can eliminate DDC interference with any decay time constant under noise with a small amount of additional computation based on traditional DFT. Moreover, the proposed algorithm has strong robustness to interferences.