A novel analytical method for DC offset mitigation enhancing DFT phasor estimation

•A novel fully analytical method for DC offset current mitigation.•A simple and implementable method enhancing DFT calculation in distance protection systems.•A robust approach against noise and harmonics disturbances.•A fully online method which uses a minimum amount of data in its algorithm.•Multiple DC offset signals are attenuated effectively through a simple analytical approach. This paper introduces a new technique to remove DC offset (DCO) in fault current based on current second-order derivation to enhance the phasor estimation process. In this method, adding the (fault current) FC and a given coefficient of second-order derivative (SOD) of FC yield to calculate DC offset quantity in a simple analytic approach. Discrete Fourier transform (DFT) is only able to determine harmonics with a specific frequency, not with wide range variation like DCO. In this paper, a simple method is proposed to filter DCO from the main signal and prepare pure sinusoidal input for the DFT function. This pre-processing method prepares a signal without DCO for accurate phasor estimation in discrete Fourier transform (DFT) which is widely used for frequency estimation in protection systems. A set of different scenarios were considered to evaluate the proposed method with other practical methods. The results with computer-generated and simulation-based signals show that the proposed method is simple and more accurate to calculate DCO.