A Reiterative DFT to Damp Decaying DC and Subsynchronous Frequency Components in Fault Current

This work presents a reiterative discrete Fourier transform (DFT) algorithm for fault current filtering. First, the short-windows DFT (SWDFT)-based mimic filter is developed to damp the measurement. Then, a reiterative scheme is proposed to reconstruct the damped measurement for further damping. The proposed algorithm can sufficiently damp the decaying dc as well as the subsynchronous frequency components. Thus, the proposed algorithm is appropriate to the filtering design on both the conventional and series-compensated transmission lines. Meanwhile, the recursive form is developed to reduce the computational burden. The simulation results illustrate that the algorithm significantly reduces the time to obtain the accurate fundamental phasor and that it has a better performance than the conventional DFT algorithm.