Modified Discrete Fourier Transform Algorithm for Parameter Estimation of Sinusoidal Signal with Decaying DC Offset

This paper proposes a modified discrete Fourier algorithm for parameter estimation of sinusoidal signal with decaying direct current (DC) offset. First, the sinusoidal signal parameter estimating error caused by the decaying DC offset in traditional Fourier algorithm is analyzed. Then, by carrying out discrete Fourier transform (DFT) twice every half a period on the sinusoidal signal which is affected by the decaying DC component, two estimating parameters of fundamental frequency component of the sinusoidal signal are gotten. Using the two estimating parameters, the fundamental frequency component parameters, which are immune to the effect of the DC offsets, are estimated without calculating the decaying DC component parameters. At last, the effectiveness and the feasibility of the algorithm are proved by the simulation results of both numerical simulation signal and ATP/EMTP simulated fault signal.