An Improved Harmonics Detection Method Based on Sliding Disrete Fourier Transform for Three-phase Grid-tie Inverter System

Abstract

Harmonic currents in a grid-tie inverter system not only increase the inverter loss but also reduce the inverter efficiency. Harmonic detection is the precondition of harmonic control.Among the various methods, sliding discrete Fourier transform (SDFT) based algorithms has found wide and popular applications due to advantages like simplicity and excellent selectively filtering properties. However, SDFT suffers from disadvantages like slow dynamics and large memory occupation.In order to alleviate these drawbacks, an improved SDFT is proposed to detect the system harmonics.The proposed SDFT not only maintains the advantages of simplicity and selectively filtering properties but also features fast transients, around 1/6 fundamental cycle for typical harmonics in three-phase application, which is much shorter than the one-cycle settling time of the conventional SDFT.Simulation and experimental results show the validate effectiveness of the proposed method.