| FFT is a most-used and basic method of harmonic measurement in electric power network. The existing methods of spectrum correction fall short of the requirement for fast, precise measurement. Correction errors of single frequency signals mainly come from interferences of adjacent negative frequency components. Precise correction of single ultralow frequency would be realized by calculating determinant of the coefficient. For signals of single frequency adjacent to Nyquist frequency, their precise-correcting formula may be deducted similarly. Correction errors of harmonic spectrum mainly rise from interferences between different frequency components. The paper puts forth a successive correction method based on the magnitude of amplitude values, and thus improving identification capabilities of harmonic signals as well as correction precision. By analyzing noise errors of the successive correction methodology, the author puts forward an error-estimating formula, which proves to be valid through simulated calculations and actually-measured data.
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