Desynchronized Processing Technique for Harmonic and Interharmonic Analysis

A new desynchronized processing technique for harmonic and interharmonic analysis that has general validity and results fully compatible with the IEC standard is presented. This technique is based on a double-stage signal processing procedure: In the first stage, the harmonic components are accurately estimated via interpolations in frequency domain and filtered away from the original signal so that in the second stage, interharmonics can be evaluated without the spectral leakage due to harmonic tones. Since the procedure does not require synchronization, it allows adopting a fixed sampling frequency and, at the same time, the direct use of fast Fourier transform on the acquired samples, thereby reducing the computational burden. The procedure is successfully applied to both numerical tests and on field measurements. The obtained results are as accurate as those of synchronized techniques.