Fundamental current extraction using a sliding window technique for SAPF control

Oil and gas facilities use variable frequency drive (VFD) motors to boost energy efficiency, although the currents they generate cause harmonic distortion and faster equipment wear and aging. This study presents an advanced shunt active power filter (SAPF) controller based on a sliding-window discrete Fourier transform (SW-DFT) technique to accurately extract the fundamental current, thereby enhancing harmonic compensation performance. The proposed design eliminates the need for low-pass filters and a phase-locked loop (PLL) in harmonic identification, achieving faster dynamic response and simplified tuning. The controller is validated through controller hardware-in-the-loop (CHIL) experiments using a real-time digital simulator (RTDS), and demonstrates improved stability and superior harmonic mitigation. The experimental results indicate that the proposed controller reduces the total harmonic distortion (THD) by approximately 51% compared with the uncompensated case. Furthermore, a DIgSILENT model of an industrial oil and gas facility indicates that the incorporation of VFDs significantly increases harmonic distortion, reaching levels of 54.48% THD. The results confirm that the proposed SAPF controller significantly improves filter performance and contributes to more reliable, efficient power generation.