arXiv:2611.13558v1 Announce Type: new Abstract: Decaying DC (DDC) offsets severely compromise the accurate estimation of current phasors immediately following power grid fault occurrence. Consequently, conventional full-cycle discrete Fourier transform (FCDFT) algorithms experience decaying oscillatory magnitude errors, potentially causing distance relays to malfunction. This paper introduces a modulation-assisted technique designed to precisely eliminate the DDC components from fault current signals. By multiplying the fault signal with a high-frequency carrier and applying consecutive sliding Fourier projections, the proposed method effectively isolates the DDC signal while entirely rejecting higher-order harmonic interference. It utilizes a direct algebraic solution derived from a robust forward-difference operation across just three sequential projections to estimate and extract the DDC parameters. Furthermore, the algorithm seamlessly processes both single and multiple DDC components by dynamically tracking them as one equivalent first-order mode. Extensive evaluations are conducted to validate the proposed method accuracy. The proposed algorithm limits the maximum overshoot (MO) to 0.62% (0.59% for $k \geq 8$) for the evaluated DDC cases, and to 2.47% (0.95% at 20 dB for $k = 8$) under noisy conditions.