A Composite Detection Method Based on FFT for Wideband Harmonics in Power System

Harmonics of the power system are becoming complex and wideband along with the high penetration level of renewable energy system. Aiming at the low detection accuracy of wideband harmonics containing components closing at frequency, a composite detection method based on FFT is proposed. First, the component region with close frequencies is discriminated according to the phase spectrum of the windowed signal. Then, the accurate estimations of harmonic frequency and amplitude can be obtained by two algorithms. Respectively, the multiple modulation zoom FFT algorithm is applied in the region above, and the windowed interpolation FFT algorithm is applied in remaining regions. The accurate estimation of harmonic phase can be obtained by the all-phase FFT algorithm. Finally, the results of simulation demonstrate that the proposed method is effective in identifying the harmonics containing components with close frequencies in a wide frequency range by all the circumstances. Compared with the traditional methods, the proposed composite detection method has less computation and high detection accuracy.