Power Quality Harmonic Detection And Disturbance Analysis Based On Fourier Transform And Wavelet Transform

With the increasing demand for electricity,the topological structure of power grid is becoming more and more complex,and the load is becoming more and more diverse.The problem of power quality has attracted much attention.Among them,harmonic analysis is an important research basis of power quality;and the identification of transient disturbance has gradually become a difficulty in the analysis of power quality.In order to ensure the stable operation of the power system,accurate analysis of the power grid signal has become the primary task to improve the power quality.This paper describes the concept and classification of power quality,briefly introduces the research status of power quality detection,common analysis methods and problems in the analysis process.Aiming at the problems of asynchronous sampling,spectrum leakage and fence effect,this paper uses FFT and wavelet transform to analyze the steady-state and transient components of the signal accurately and improve the detection accuracy.The specific scheme is: use Newton interpolation to quasi synchronize the original sampling sequence to achieve the same sampling period as the actual period;use wavelet modulus maxima to detect whether there is transient disturbance in the original signal;if there is mutation,use wavelet Mallat algorithm to reconstruct high-frequency information and extract interference components;if there is only steady-state signal,use windowed interpolation FFT algorithm to analyze The parameters of amplitude and phase of each harmonic are obtained.In this way,combined with the analysis advantages of Fourier transform and wavelet transform,different components of the signal are analyzed to improve the detection effect.Through the theoretical analysis of quasi synchronous detection,wavelet transform,Fourier transform and hybrid algorithm,the power network signal model is established to simulate each algorithm respectively.The results show that: quasi synchronous can correct the collected signal accurately,restore and have a high degree of synchronization;the improved windowed interpolation FFT has a detection accuracy of 0.3% for the steady-state harmonic;the wavelet can be divided into frequency bands,which is beneficial to the detection of steady-state harmonic Using wavelet modulus maxima to detect signal singularity and extract transient disturbance signal accurately,the accuracy is 0.6%;similarly,for complex power signal,the hybrid algorithm can also meet the actual engineering needs after analysis.Finally,the key points of hardware and software in the power quality detection system are described.The design of data acquisition,processing and communication modules is emphasized,and the harmonic analysis and transient identification of power system signals are realized.