Research on the error of the fourier algorithm with DC filtering in fault current calculation of power system

DC filtering is commonly used together with Fourier algorithm in the calculation of root-mean-square (RMS) values of fault current of power system, so as to eliminate the errors produced by the decaying DC component in the fault current. In this paper, theoretical derivation was conducted, showing that errors of sampling values could be amplified by the DC filtering itself, which could lower the accuracy. So the effect of DC filtering should be comprehensively considered when applied in such circumstance. Numerical simulations concerning different number of sampling points and different initial phase angle of the fault current were also conducted to verify the conclusion. Results indicated that within a certain range of the initial phase angle, the amplification of the sampling error is maximized by the DC filtering, weakening the improvement in accuracy brought by the elimination of DC component, or even worsen the accuracy with too few sampling points for DC filtering calculation.