Research And Design On The Harmonic Detector Of Power System Based On Arm

Along with the rapid increase of both power electronic devices and nonlinear loads in power systems, the harmonic components in power system voltage and current increasingly ascend, it makes power supply equipments and power utilization equipments overheating, power loss ascending, and evidently affects the secure, economic and stable operation of power system. Thus, it is of practical significance in the prevention of the harm from harmonics to measure harmonic contents in power system voltage and current in power system by real-time ways.To implement the real-time and accurate detection of harmonics in power system, firstly, the author compared and analyzed the existing harmonic detection methods published in periodicals and treatises; then the algorithm to be used for harmonic detection was decided; on this basis the design of a whole scheme of harmonic detector was finished. With the designed harmonic detector the harmonic contents existing in input voltage and current signals from three channels can be detected simultaneously, and the functions such as the display, statistics and storage of the detected data were equipped in this detector.In this paper, the research and design of a power system harmonic detector is presented. The study and selection of harmonic algorithm, the design of hardware and software system as well as the test of detection system are discoursed upon respectively. The concrete contents of this paper are as following:in the first part of this paper, the significance of the research on harmonic detection, the danger in power system caused by harmonics and the present situation of harmonic detection were expounded; in the second part, the concept of harmonics, the methods of harmonics detection were presented, and on the basis of analysis and research on several harmonic detection algorithms a fast Fourier transform (FFT) based windowed interpolation algorithm applied in the designed harmonic detector was determined; in the third part, the hardware design of this harmonic detection system was described, in which the advanced RISC machine (ARM) chip ARM7 was adopted as microprocessor and the design of such modules as main control, signal modulating, A/D sampling, data storage, real-time clock and liquid crystal display (LCD), as well as the anti-interference design for hardware were included; in the fourth part, the design of software for this harmonic detector was given, the system software consists of main program, analog-digital conversion, key processing and data processing, and the software was programmed by C language; the system test and error analysis were brought into the fifth part, after the analysis on the measured signals it was proved that both algorithm selection and the design of the detector can meet the requirement of accuracy; finally, above-mentioned research and design are summarized and the work to be carried out in the future was pointed out.