Harmonic detection algorithm based on recursive filter

Due to the problems of Fourier algorithm and wavelet algorithm on harmonic detection, proposed harmonic detection algorithm based on a recursive filter in this paper. Unlike a wavelet, the central frequency and frequency window radius of the recursive filter can be adjusted separately, the magnitude frequency property (MFP) of its real part and imaginary part is identical, symmetrical and no side lobes, moreover has no relative to the central frequency. By virtue of these attributes, it can overcome frequency spectrum leakage and fence effect of FFT, eliminate frequency bank aliasing of wavelet transform, and realize accurately detection of harmonic and interharmonic in power system. Further, a recursive algorithm is adopted that updates current output only using several previous sample values and filtering outputs. Thus, this recursive algorithm is highly desirable for real-time applications. The simulation results show that the method is able to identify numbers of harmonic and interharmonic accurately, and has highly detecting accuracy to amplitude and frequency.