Research On Harmonic Detection Methods Based On FFT And FFT IP Core

Harmonic has great influence on the safety,stability and economic operation of electric power system,it is significant to study the harmonic problems of electric power system,and harmonic detection is the starting point and main basis for the study of harmonic problems.Among the methods of harmonic detection,FFT is popular because of its ease of implementation,but due to the influence of spectrum leakage and fence effect,FFT will produce a large error in harmonic detection,therefore,it is of great significance to study the improved algorithm of FFT and implement of FFT using hardware.This thesis first analyzes the FFT algorithm of windowed double line interpolation and windowed three line interpolation,and presents methods of harmonic detection based on FFT algorithm of 4 items 5 steps Nuttall windowed double line interpolation and 4 items 5 steps Nuttall windowed three line interpolation,furthermore,this thesis derives the algorithm principles of double line interpolation and three line interpolation separately and makes simulation analysis of complex harmonic signal,and the two cases of fundamental frequency variation and white noise are considered.The analysis of simulation results show that the proposed algorithms can improve the accuracy of harmonic detection and effectively overcome the influence of fundamental frequency variation and white noise of different signal-to-noise ratio on harmonic parameters detection.Secondly,this thesis analyzes the FFT algorithm of windowed phase difference,and presents a method of harmonic detection based on FFT algorithm of 4 items 5 steps Nuttall windowed phase difference,what’s more,this thesis derives the algorithm principle of phase difference and makes simulation analysis of complex harmonic signal,and the fundamental frequency variation,white noise and interharmonics are considered.The analysis of simulation results show effectiveness and strong anti-interference ability of the proposed algorithm.In the end,this thesis analyzes the preparation of schematic diagram’s each module and makes the ModelSim simulation of given input data using FFT IP core,and the accuracy of ModelSim simulation results of FFT IP core is verified combined with the simulation results of MATLAB.The accuracy of the simulation amplitude results is high,and on average,it can reach more than 80%.Especially when the amplitude is large,the relative error of amplitude results is less than 5%,and the correctness of the designed schematic diagram is verified.The FFT IP core achieves the function of FFT operation,and within a certain range of error,accurate detection of harmonic amplitude parameters can be realized by FFT IP core.