Research Of Embedded Harmonic Detection Based On Db Wavelet

In the recent years, along with the promotion of energy conservation technology and the automated technology, and the wide application of the electric power electronic installation such as variable current equipment, the frequency conversion equipment and so on, and the capacity expands day by day and the quantity increases day by day, the high harmonic became more and more serious, as a result the power quality drops and accident happen continually. Then how to restrain harmonics and improve electric power quality effectively became a research hotspot. Harmonic detection is the basis of the harmonic problem, is the core and springboard of harmonic research. Thus the analysis and measurement of harmonic one of the most crucial tasks in power system analysis and control.This paper introduces the concept of harmonic, harmonic mechanism of production, hazard of harmonic, harmonic source, the development of wavelet and embeded system; introduces the common wavelt and formation of db wavelet and their application and deficiency in electric power system, especially analyzes and simulate Db wavelet. This paper has studied a new method that combines the Fourier Transform with the Wavelet Transform for the reason that The FFT has the advantage to analyze steady harmonic, while the Wavelet Transformation has the advantage to analyze fluctuant and fast changing harmonic, and which can compensate with each other well. In this method the signals are put through binary wavelet transform into high frequency part and low frequency part. The high frequency part is analyzed to gain the transition characteristic through Wavelet transform; the low frequency is analyzed to gain the stable harmonics parameters through the Fourier transform, so we can not only obtain the stable harmonics parameters, but also determine sudden change signals. At last validity and feasibility of this method are proved by MATLAB simulation.Based on the algorithm, the paper applies 32digit ARM processor in the harmonic detection device, and transplants Embedded Real-Time Operation systemμC/OS- II in ARM processor; Make full use of the powerful control ability of ARM and powerful operation ability of DSP. The device can realize the real-time measurement, LCD display and communication with computer.At last, the paper combines Visual Basic with MATLAB programmed, designs computer software, constitutes an integrated power system harmonic detection system.