Fast Transient Harmonic Selective Extraction Based on Modulation-CDSC-SDFT

The fast harmonic compensation ability of active power filter (APF) is limited by the transient time of harmonic extraction method. The frequency-domain extraction method based on Discrete Fourier Transform (DFT) suffers from the disadvantage of one fundamental cycle transient time. Therefore, this paper proposes a selective harmonic extraction method based on Modulation-CDSC-SDFT, which improves the fundamental analysis frequency of Sliding DFT (SDFT) by modulation and Cascaded Delayed Signal Cancellation (CDSC) operations in advance to shorten the transient time significantly. Aiming at the harmonic compensation case of finite odd and even harmonics generated by an electric arc furnace, the configuration process and simulation results are given. The fundamental detection transient time can be as short as 0.23 cycle when the modulation frequency is set to 20th order. Moreover, faster transient can be obtained with a higher modulation frequency.