摘要
Traditionally, the discrete Fourier transform (DFT) has been widely recognized as an effective tool for digital delay in power systems protection, specifically for estimating the fundamental phasor. However, faulted waveforms in power systems often contain an exponentially decaying direct current (DDC) component. Unlike harmonics, the DDC component does not correspond to a specific frequency but spans a broad range of low frequencies, causing undesirable oscillations in the conventional DFT output. To address this issue, this digest presents an enhanced DFT-based algorithm designed to accurately estimate frequency and phasor in faulted signals, even under off-nominal frequency conditions. Since only a few additional operations are added to the DFT, it remains efficient for real-time digital relay applications. Numerical experiments are performed to validate the effectiveness of the proposed method.