New modified fourier algorithm to eliminate the effect of the DC offset on phasor estimation using DFT

This paper proposes a new modified Fourier algorithm to eliminate the adverse influence of a decaying dc offset when Discrete Fourier transform (DFT) is used to estimate the phasor of the fundamental frequency component. The proposed algorithm decomposes the DFT process into even sample set DFT and odd sample set DFT. The effect of the dc offset is eliminated by using the recursive relationship between the outputs of even sample set DFT and odd sample set DFT. The performance of the algorithm is evaluated by using computer- simulated signals and EMTP-generated signals. The evaluation results indicate that the proposed algorithm can estimate the accurate phasor of the fundamental frequency component regardless of not only the primary decaying dc offset but also the secondary decaying dc offset caused by CT circuit itself including its burden.