DFT-based recursive minimizing algorithm for power interharmonics analysis

The Discrete Fourier Transform (DFT) is still a widely-used tool for analyzing and measuring both stationary and transient signals in power system harmonics. However, the misapplications of DFT can lead to incorrect results caused by some problems such as aliasing effect, spectral leakage and picket-fence effect. A strategy of Recursive Group-harmonic Power Minimizing (RGPM) algorithm is developed for system-wide harmonic/inter-harmonic evaluation in power systems. The proposed algorithm can restore the dispersing spectral leakage energy caused by the DFT, and regain its harmonic/inter-harmonic magnitude and respective frequency. Every iteration loop for harmonic/interharmonic evaluation can guarantee to be convergent using the proposed Group-Harmonic Bin Power (GBP) algorithm. Consequently, not only high-precision in integer harmonic measurement can be retained, but also the inter-harmonics can be identified accurately, particularly under system frequency drift. The numerical example is presented to verify the proposed algorithm in term of robust, fast and precise performance.