Research On Harmonic Detection Method Of Large Scale Photovoltaic Grid Connected

Looking for new clean and renewable energy has become the main energy development direction of our government.Meanwhile,driven by carbon emission reduction and environmental protection policies Under the circumstance,photovoltaic power generation technology is gradually mature and widely used in various industries,which provides a new way to solve the energy crisis in China.However,the grid connected inverter must be used in grid connected rectification,which leads to the increase of harmonic content in photovoltaic grid connection.Therefore,it is of great significance to study harmonic detection of large-scale photovoltaic grid connected power generation for safe and stable operation of power grid.The main contents of this paper include:(1)In view of the problems of the power quality and operation stability of the grid caused by complex the grid connected system of large-scale photovoltaic power generation,and focuses on the analysis of the working principle of two components of harmonic source,namely photovoltaic array and grid connected inverter,and then model of photovoltaic grid connected system is integrated.In this model,the generating mechanism of harmonic voltage of photovoltaic grid connected system is discussed and analyzed in detail.(2)In view of the problem that a large number of inverters are needed in photovoltaic power generation,which leads to the increase of the inherent odd harmonic content of the grid,a targeted detection method of odd harmonic in photovoltaic grid connection is proposed.Based on the six cosine windows,the side lobe performance is optimized and the new window function is optimized.The three spectral line interpolation is proposed for fence effect.The interpolation process in frequency domain is analyzed.At the same time,the system of the correction formula for harmonic detection is obtained by polynomial fitting approximation.The results of the algorithm of odd harmonic detection in different environments are studied by Matlab simulation software.(3)In order to solve the complex intensive spectrum and inter harmonic problems in the grid caused by the use of power electronics in large-scale photovoltaic grid connection,the window function with narrow main lobe is optimized,and the phase invariant characteristics of the full phase inter phase harmonic detection are used to determine the phase of the inter grid harmonic detection.At the same time,the three spectral lines near the intermediate frequency point including the most inter harmonic information are analyzed in frequency domain The weighted processing improves the accuracy of harmonic parameter detection between grid connection.Through Matlab simulation,the simulation and comparison experiments with traditional windowed bispectral line interpolation FFT algorithm verify that the proposed algorithm has verified the accuracy and effectiveness of the new algorithm in the aspects of dense spectrum analysis,high precision detection of harmonic and inter harmonic and overcoming white noise pollution.