New precise measurement method of power harmonics based on FFT

Taking the rectangular window as an example, the summation in the expression of discrete Fourier transform is solved by the integral operation. Under the condition of asynchronous sampling, the long-range leakage and short-range leakage effects of the spectrum are explained. A new method, named multi-spectrum-line interpolation correction algorithm (MICA), is presented to correct the leakage effects. The difference between MICA and the previous windowed interpolation algorithm is analyzed. The simulation results show the measurement accuracy of MICA is very high and the long-range leakage effect can be corrected by applying not only the window with better spectral performances, but also the interpolation algorithm. MICA based on FFT can be applied to measure precisely the electrical harmonics and estimate the frequency offset in the orthogonal frequency diversion multiplexing (OFDM) communication system.