Monitoring And Analysis On The Harmonics Of Power System Based On ARM7 Processor

Power electronic device is the most common source of harmonic in power grid. In recent years, because of rapid growth of power and electronic device, harmonic pollution in power system becomes more and more serious. It can produce harmful affection to all kinds of power device, communication equipment and wiring, even generate accident of power system so that directly affect safety production and normal running of lives. As a consequence, monitoring and studying power network harmonic is not only a premise to confine and eliminate harmonic ,but also a urgently demand to assure power supply system and other apparatus to run economically and safely. Howerver, people only pay more attention to improving these apparatus'quality to realize that goal, ignoring the affect of electric power quality on apparatus'safe and stable operation. In this case,it is necessary to monitor power quality in real-time. This paper will describe the principle and design of the power quality monitoring equipment.Referring to a great deal of literature,this paper put out the total design scheme and technique specifications of the power harmonic monitor instrument base on ARM7. Then according to these specifications, the electric circuits of the system are designed in detail, and the software of the data processing is written. As the core of the system-- microprocessor using LPC2132 , which is based on ARM7TDMI. And the AD convert chip uses AD73360. It is a new A/D converter promoted by AD company of USA, which is mainly used in power quality monitoring. By sampling voltage and current of the power system, the device can analyze the amplitude and phase of all times harmonics, the harmonic ratio and total harmonic distortion in power system. According to these, a new type of power harmonic tester is designed.The power system harmonic tester has a character of operation fast, precision high, simple structure, relatively cheap cost for fabrication, operation easily, strong display and so on. The paper are concentrated on discussing the design method of software and hardware about harmonic tester based on ARM7 processor:(1) Overall design of the system and function of circuit, (2) Hardware design include power circuit, A/D convertsion circuit, JTAG interface circuit, keystroke and liquid crystal display , data storage, real-time clock circuit and so on.(3) Design of system software including main program , the program of A/D conversion, the program of FFT with C language.(4) The system test and error analysis on the measured signals is proved that the design of the detector can meet the requirement of accuracy.