Resolution of Frequency Domain Vector Applying for Inter-harmonics Detection

If the frequency difference between two components is less than one frequency resolution,it will cause serious main lobe interference on frequency domain.The discrete Fourier transform(DFT)method and its improvements failed to correct this error.Under the condition of ten fundamental periods of sampling window length,the reason of traditional DFT failed to detect two overlapping frequency components is first presented in this paper.Based on the phase property of the DFT spectrum line,it used the frequency domain method to calculate the frequency,amplitude and phase of each component that lead to main lobe interference.Simulation result illustrates that the correction method is simple and feasible.It can separate harmonics and inter-harmonics effectively and strongly restrain the spectral interruption,which has a desirable accuracy.