Development of interharmonics identification using enhanced-FFT algorithm

摘要

The fast Fourier transform (FFT) is a mostly used tool to measure power system harmonics. FFT, however, is not applicable to analyse interharmonics due to spectral leakage effect. Although International Electrotechnical Commission (IEC) standard is recommended for interharmonic measurement, the individual interharmonic frequency and respective amplitude cannot be worked out under this framework. For this reason, this paper proposes an enhanced-FFT model to build up the relationship between interharmonic frequency and dispersed leakage energy. The mathematical equation is thus established to find actual value of interharmonic frequency. Moreover, the true interharmonic amplitude can be retrieved from the dispersed energy collection. In other words, the sampling window length is no longer required to match the interharmonic period and the correct measurement results can be achieved. The proposed model is developed using a simple arithmetic equation so that it is feasible for more efficient calculation for interharmonic analysis. Performance results verify that the proposed scheme can achieve accurate, rapid and reliable outcomes.