A Comparative Analysis of MDSC-Based Phasor Estimation Technique for Digital Relays in Power System Protection

Decaying DC offset frequently emerges as a major issue in power systems, especially under fault conditions. This leads to a distortion in the current waveform associated with the fault, which could significantly challenge protective and control mechanisms, possibly leading to their malfunction or breakdown. These decaying DC components (DDCs) complicate the extraction of critical parameters such as the current magnitude and phase angle of the fundamental frequency component from fault signals, which is crucial for the accurate operation of protective relays. Discrete Fourier Transform (DFT)-based algorithms are frequently used for phasor estimation, but their accuracy suffers when confronted with decaying DC components (DDCs) in power system fault currents. The low sampling rate further exacerbates the inaccuracy of DFT-based estimations, leading to inaccurate fault detection by protective relays. This paper comprehensively reviews three innovative methods that leverage the Multiple Delayed Signal Cancellation (MDSC) filter to overcome these limitations. The MDSC-based phasor estimation effectively attenuates the DDC component, enabling precise and rapid phasor estimation, benefiting from its higher sampling rate, and enhancing accuracy in relaying applications. The theoretical foundations of each method are analyzed, with an emphasis on their unique advantages and potential applications in digital relaying and power system protection. This review provides valuable insights into the latest advancements in DDC elimination, offering a pathway to more reliable and efficient fault analysis in power systems. Numerical and simulation tests unequivocally demonstrated the effectiveness of the proposed approach by showcasing its superior performance compared to four other phasor estimation methods. The proposed methods demonstrated exceptional performance in conditions plagued by multiple DDCs, harmonics, noise, and off-nominal frequencies, achieving fast and precise phasor estimation.