INTERHARMONICS ANALYSIS BASED ON INTERPOLATION FFT ALGORITHM

Inter-harmonics is a kind of the harmonics which are not an integer of the fundamental frequency component. The inter-harmonics, same as the integer harmonics, have serious impacts on the design of harmonics compensation equipments, so it is important to measure inter-harmonics accurately. The interharmonics cannot be achieved accurately by using FFT for an unsynchronized sample sequence analysis because of large errors in such cases. To reduce the errors caused by using FFT for an unsynchronized sample sequence analysis and to improve the measuring precision of interharmonics in electric power system, an interharmonics estimation based on interpolation FFT algorithm is proposed. The estimation algorithm based on Rife-Vincent (Ⅲ) window for the interharmonics parameters is given. This algorithm can make the analysis accuracy improved significantly. Simulation results demonstrate that the estimation interharmonics frequency, amplitude and phase are highly accurate using the improved algorithm for the unsynchronized sample sequence analysis.