Research Of Application And Detection Method Of Power System Harmonic Based On Wavelet Transformation

Along with the rapid development of national economic, the problem ofelectrical energy quality brings to people's more and more attention. Thisproposed a higher demand to harmonic detection and compensation, and harmonicsdetection is not only the main basis of the research of harmonic, but also thecore link and the starting point of analyzing harmonics.The difficulty of electrical harmonics detection is the examination andanalysis of the sudden change, the transition condition, and the non-steadyperturbation signal. While the stable harmonic components are accuratelyattained, it also becomes essential to consider the real-time analysis andaccurate computation of the transition harmonics components. This will provideeffective basis to grasp the electrical energy quality condition as soon aspossible and reduce the breakdown. This paper has introduced the concept of theelectrical power system harmonics and the research value, elaborated the researchpresent situation of the domestic or foreign and the tradition analysis methodbriefly, and mainly analyzed characteristic and the insufficiency of the Fouriertransform and the Wavelet transform. This paper has also introduced the continualwavelet theories, concrete wavelet transform, Mallat algorithm, and Waveletpacket algorithm and so on. As a new tool, the Wavelet transform has good naturein the time domain and frequency range. It can capture the transition and unstablesignals. In this paper, the method of the combination Wavelet transform with theFourier transform has been proposed, and the principle of wavelet selection andthe computation method of harmonics parameters have been analyzed. The algorithmscheme is as follows: firstly put the signals through binary wavelet transforminto high frequency part and low frequency part. The high frequency part isanalyzed to gain the transition characteristic through Wavelet transform; thelow frequency is analyzed to gain the stable harmonics parameters through theFourier transform, so we can not only obtain the stable harmonics parameters,but also determine sudden change signals. In this way, the superiority of these two method has fully used.This paper has proposed a kind of design plan of harmonics detection andanalysis application. As the algorithm method which is based on the Wavelettransform and the Fourier transform needs large computation, double DSP are usedto realize the data processing and the control function. The main DSP chip isto complete the function of the control of the whole system and keyboard functionetc; the other DSP chip is to complete sample of data and the data processing.The two DSP chip will communicate with each other through double-mouth RAM.Finally, this paper has carried on the MATLAB simulation of the proposedmethod, and analyzed the simulation of the signal with sudden change. Throughthe simulation, the results have confirmed that the proposed method has goodanalysis ability to the unstable signal.