A Full- and Half-Cycle DFT-based technique for fault current filtering

Decaying DC components in fault currents will make the digital filter to obtain inaccurate phasors and cause the false operations of a relay system. Many studies have put their focuses for removing the decaying DC components from fault currents. Generally, they need extra samples or phasors to obtain the parameters of the decaying DC component. In order to accelerate the filter response, this paper presents a new Discrete Fourier Transform (DFT)-based algorithm which does not need extra sample to remove the decaying DC component. To achieve this, the samples used for a traditional DFT computation are split to four groups. Both the Full-Cycle DFT (FCDFT) and the Half-Cycle DFT (HCDFT)-based computations have been developed in this paper. The proposed algorithm is evaluated by MATLAB/SIMULINK generated data to show its effectiveness.