Research On High-accuracy Harmonic Detection Algorithm Based On Window And Interpolation

The harmonic pollution in the power grid is becoming more and more serious,which causes the distortion of voltage and current waveform and threatens the safe operation of the power grid.The accurate detection of harmonic parameters is an important prerequisite for accurate treatment.This paper will focus on the high-accuracy harmonic detection algorithm based on window and interpolation.First of all,through the analysis of the advantages and disadvantages of several kinds of harmonic detection algorithms,it is found that the Fast Fourier Transform(FFT)algorithm is the most suitable algorithm in harmonic detection.Secondly,two main problems of FFT algorithm are studied.The first problem is the spectral leakage caused by the truncated sampling signal,the phenomenon and reasons of spectrum leakage are analyzed.The window function which can effectively suppress the spectrum leakage is studied and the selection criteria of window function is analyzed,several common windows are also introduced;The second problem is the fence effect caused by the asynchronous sampling,the phenomenon of fence effect is analyzed and the interpolation algorithm which can reduce the error of the fence effect is studied.The correction formula of common window function for different interpolation algorithms are calculated by using the cftool toolbox in MATLAB.Then,window and interpolation FFT algorithm is fully studied by conbine window function with interpolation algorithm.Thirdly,a harmonic detection algorithm based on the five-term Maximum-Sidelobe-Decay(MSD)window and triple-spectrum-line interpolation FFT is proposed.The time domain and frequency domain characteristics of five-term MSD window are analyzed,and a complete harmonic detection algorithm is formed with the triple-spectrum-line interpolation algorithm.The program of the algorithm is compiled by the MATLAB,the simulation results of the algorithm and other window and interpolation algorithms for harmonic detection under various conditions show that the algorithm has high detection accuracy in all harmonic environment,the algorithm can also effectively observe the full spectrum information of signals which is convenient for further analysis of other components in the signal.Then,a harmonic detection algorithm based on five-term MSD and triple-spectrum-line interpolation improved Goertzel is proposed.The Goertzel algorithm and the improvement of the algorithm is studied,and a complete harmonic detection algorithm is formed with five-term MSD window and triple-spectrum-line interpolation algorithm.The implementation of the algorithm is studied,the algorithm save computing time by calculating the only three spectrum line required in triple-spectrum-line interpolation algorithm.Through the MATLAB,comparing the simulation result of harmonic detection algorithm based on the five-term MSD and triple-spectrum-line interpolation FFT,it shows that the algorithm has the same high detection accuracy as five-term MSD window and triple-spectrum-line interpolation FFT algorithm,the calculation speed of the algorithm is improved in the absence of full spectrum information.It is appropriate for the conventional harmonic environment requiring high detection accuracy and real-time requirements.Finally,the experimental platform is built to generate the experimental harmonic discrete signals for analysis.Through the detection results of the two algorithms and the other algorithm,it shows that both of the two algorithms proposed in this paper have high detection accuracy,and they have their own characteristics in detecting function and speed.