Research Of Embedded Power Harmonic Detection System Based On Wavelet Transform

Along with rapid growth of non-linear loads in the power system, the component of power system harmonics becomes increasingly complex. It threats the safe of power system and electrical equipment, and causes serious damage to the equipment, even the accident. So the development of power harmonic detection system is significative for restraining power networking harmonics.This paper discusses the mechanism of harmonic, through simply summarizeing and compareing the application of the several common methods of harmonic analysis, determines this paper adopts the harmonic analysis method-wavelet analysis. The paper discusses the characteristic of wavelet funciton and the basic principle of wavelet transform, and analyzes emphatically the physical essence of aliasing in discrete wavelet, then thoroughly studies the the new method which could suppress discrete wavelet frequency aliasing through adding odd extraction process. MATLAB simulation proves that it can analyze the local characters of signals exactly while effectively eliminating aliasing, improving the precision of harmonics analysis. Based on this algorithm, the paper constructs a power system harmonic detection system based on LPC2478platform. This system inputs data of the power network by the Synchronizing circuit, subsequently completes wavelet analysis adding odd extraction process by software, and achieves the detection and analysis for the harmonic of three-phase voltage and current.The paper analyzes the working principle of harmonic detecting system detailedly and nails down the function requirements. It designs every module for the system, transplants Embedded Operation system μC/OS-Ⅱto LPC2478microprocessor, and writes the device driver and applications with C language. It includes the main program, harmonic detecting procedures, and communication procedures and so on. Finally, through the overall test, results show that the power harmonic detection system designed in this paper and combined with embedded control, high efficient data processing, network communication, and providing friendly human interface can achieve detect and analyze the work harmonic content of the power net precisely and reliably.