Research On Local Harmonic Detection Method Based On Wavelet Transform

Electric energy is the important foundation of modern social survival. with thedevelopment of industry and information technology modernization, electric equipment ismore sensitive to power quality. the impact of electrical power quality caused by theeconomic loss is more prominent. With the development of modern industry, equipmentcapacity of various nonlinear growth rate exceeded the equipment capacity of powergeneration growth rates, a large number of power electronic load, electric arc furnace, electriclocomotives and other sources of interference device connected to the grid, these devices inoperation on power quality caused serious pollution, resulting in safety electrical equipmentitself to reduce the additional loss, resulting in the power grid and electrical equipment, bringabout waste of energy. This paper focuses on how to reduce the harmonic local grid throughthe method of wavelet transform.According to the characteristics of harmonic detection of the local power grid, from theNyquist sampling theorem, the frequency characteristics of wavelet transform decompositionlayers, sampling is detected under different number of harmonic frequency decompositionmethod, and lays the foundation for the harmonic detection of power system of local powernetwork. Combined with the request of high harmonic detection of power system transientand accuracy, from the mathematical analysis of the Mallat algorithm for frequency mixingcauses the stack, and the corresponding physical significance, and proposes a new algorithmfor inserting odd extraction branch in the basic links in the existing three, and compares theanti-aliasing algorithm, to solve the aliasing frequency in Mallat algorithm was put forwardtheoretically, and keep the characteristic of the algorithm is high efficiency. This paper alsopresents alternative basis functions for the detection of harmonic of the local power grid,based on the analysis of wavelet transform of each basis function characteristics, select the appropriate basis functions, and use of computer software, the algorithm of anti-aliasing effectis simulated, the other with the local power grid110kV bus line of35kV6kV industrial useelectric instantaneous voltage detection data, the wavelet transform in the odd extractionbranch in the basic links in the algorithm was analyzed, found in the new algorithm, wavelettransform anti-aliasing effect is improved obviously, and can satisfy the requirement ofefficiency, and has a certain practical value.