Research On Algorithm Of Inter-harmonic Detection Based On Spectrum Zoom In Power System

With the rapid construction of the global energy internet and the rapid development of smart grid technology,power electronics technology has been widely used.A large number of frequency control devices,industrial electric arc furnaces,wind turbines and other non-multiplied periodic loads are connected to the power grid.Lots of applications of similar devices cause irregular changes in voltage amplitude,phase,and waveform,and the generated harmonics and inter-harmonics cause serious pollution to the power signal.Inter-harmonics differ from harmonics due to their uncertainty,so traditional harmonic analysis methods cannot be fully used in inter-harmonics detection.The dense spectrum signal derived from inter-harmonics is more difficult to detect due to the presence of severe main-lobe interference.Therefore,this thesis has studied the problem of dense spectrum detection containing inter-harmonics.Based on the dense spectrum containing interharmonics,this thesis theoretically analyzes the spectrum interference between dense spectrum containing inter-harmonics.Using MATLAB software to simulate the three different cases of the inter-harmonic adjacent to the fundamental wave,the inter-harmonic adjacent to the harmonic,and the two adjacent inter-harmonics.The above analysis shows that the number of frequency components in the dense spectrum cannot be distinguished by the traditional spectrum analysis.Through the theory and simulation analysis of all-phase spectrum,it is proposed to use the energy centrobaric correction method to correct the frequency and amplitude detection of all-phase spectrum analysis,so as to improve the detection accuracy in non-dense spectral regions.According to the superiority of ZFFT algorithm based on complex analytical bandpass filter in dense spectrum detection,for engineering practicability,a improved ZFFT algorithm with adaptive function is proposed to calculate the dense spectral regions.This algorithm can effectively improve computing efficiency.Aiming at dense frequency signals containing inter-harmonics,an algorithm combining the all-phase energy centrobaric correction method and the improved ZFFT algorithm with adaptive function is proposed.Firstly,based on the characteristic of "phase invariance" of all-phase spectrum analysis,the criterion of dense spectral region is constructed.Secondly,the three-parameter of the signal non-dense spectrum region is directly obtained by the all-phase energy centrobaric correction method.Finally,the dense spectrum region is detected using a improved ZFFT algorithm with adaptive function.In summary,the proposed algorithm based on all-phase spectrum analysis and spectrum zoom can accurately detect dense spectral parameters containing inter-harmonics.And the accuracy and effectiveness of the algorithm are verified by simulation.