Measurement Study, Based On Instantaneous Reactive Power And Harmonic Wavelet Transform

In recent years, the electrical harmonic pollution is getting more and more serious with the far-ranging of power electronics technologies. It has become a curse to power system, which deteriorates the quality of electric energy. Harmonic detection is the important part of harmonic issue and harmonic detection method is the key of harmonic detection. This paper primarily studies the harmonic detection methods.The theory of instantaneous reactive power has been applied in many fields since it was proposed in 1980's. Based on this theory, one harmonic real time detection method can be applied in active power filter. On the analysis of the theory of instantaneous reactive power, the paper brings forward a new harmonic detection method based on multiple frequency transform. The detection theory of positive sequence harmonic and negative sequence harmonic is respectively proved in detail. The correlative concepts are defined and the simulation validates the feasibility of this method.Due to the excellent time-frequency characteristic, wavelet transform has been applied in harmonic detection in recent years. Compared with the Fourier transform and short time Fourier transform, this paper explains the advantages of wavelet transform in time-frequency analysis. By simulation, the selection of wavelet function and wavelet scale is discussed. Through analyzing the shortages of existing wavelet functions, new wavelet functions which have concentrated energy and good frequency domain localization nature are proposed. Compared with the existing wavelet functions, the new wavelet functions are proved to be better harmonic detection capability. The new wavelet functions have superiority in time varying harmonic compared with the Fourier transform that the break point can be exactly detected. Finally, the application value of new wavelet function is discussed in harmonic detection by using wavelet packet mathematics.