Study Of Harmonic Analysis Of Power System Based On Combination Window Function

In order to improve the stability of the power system,the power electronic arrangement such as capacitors,which are widely used,interact with the nonlinear load in the system,causing the steady waveform distorted of the AC voltage or current,which has brought the harmonic pollution and reduced the power quality.Accordingly,the harmonic detection and elimination is used to constructe a healthy power system which has becoming an important issue.Nowadays,the Fast Fourier Transform(FFT)has been the most widely used method for harmonic detection.However,the usual method was used to improve FFT algorithm according to window function and digital interpolation,owing to the spectrum aliasing and the fence effecting produced from the non-integer period truncation and the asynchronous sampling in the practical application.Based on refining for the traditional FFT algorithm,this paper proposed a series of combination window functions and interpolation FFT algorithm.Initially,this paper introduced the principle of the Fast Fourier Transform,which was used to analyze the cause of spectrum aliasing and fence effect,and discussed the spectrum characteristics of the basic window function from three aspects of the main lobe width,the peak side lobe level and the minimum attenuation of stop-band,Meanwhile the formula of the double spectrum line interpolation has been used to derive in this paper.Then the most basic window function of Hanning window,Hamming window and Blackman window were used to select in the paper,which constructed the window function such as self-multiplication,mutual-multiplication,self-convolution,unequal self-convolution,mutual-convolution,unequal mutual-convolution and mixed window separately,according to operation combination of the basic window function by the mathematical operation principle of multiplication and convolution.What's more,in order to verify the feasibility of the spectrum characteristics of the basic window function,the algorithm of double-spectrum-line interpolation FFT was deduced based on the combination window function.Meanwhile the simulation test was used to operate by using the classical harmonic signal.In this paper,the validity of the simulation result was used to verify that the accuracy of combined window function was better than the basic window function.Finally,the effectiveness of the algorithm of this paper in practical application was used to prove according to the test of the harmonic analyze by the actual current and voltage data of the EAST power system.