Research And Design On High Precision Multi-Function Power Quality Monitoring Instrument

With the development of national economy and the establishment of the system of market economy, people begin to put more attention to the specialcommodity------power energy. Since 1970s, the nonlinear, the instability and theunbalance of the voltage have become more and more serious due to the electronic device and other nonlinear load in power network. By the on-line and real-time monitoring, recording and analysis, the scientific evidence can be provided to improve the power quality, to formulate the policy of bringing the power quality under control as well as to supply the important data for later power quality control and the technical parameters setting for controlling device.First, the author gives an introduction to the study of power quality home and abroad, then gives a classification to the problems of power quality in detail. The author also gives a complete explanation to the regular power quality indices according to The International Standards, i.e. voltage deviation, frequency deviation, three-phase voltage unbalance factor, harmonics, fluctuation and flicker of voltage and so on. According to the IEC or the National Standards, the author summarizes the different monitoring theories and calculating methods in power quality indices, which give necessary theoretical support and calculating methods to the developing of the monitoring instrument.Second, the author gives a study to the hardware design of the monitoring instrument. The advanced upper and lower computer hardware framework is adopted to achieve the high accuracy and multi-function power quality detecting and analytical functions. The upper computer is based on the PC104 bus embedded industrial control computer to achieve the functions of statistical analysis, parameters setting, storing, displaying and communicating. The lower computer is based on a 32bit high speed floating-point DSP and a 250kHz, 16-bit, 6-channel simultaneous sampling ADC to achieve the functions of high speed and high precision data acquisition, the arithmetics of the related indexes in power quality and the high speed data communication with the upper computer.Third, the author gives an introduction to the software design to the monitoring instrument. During the design of the monitoring instrument, the author adopts the embedded Linux operation system and the QT/Embedded GUI developing platform to achieve the functions of statistical analysis, storing, communicating, displaying andtouch screen operation and so on. The whole operating interface of the monitoring instrument is friendly, good-looking and practical. What's more, the program design is full of high flexibility and transplantation.The author gives a full introduction to the results of the function test of the monitoring instrument at the end of the thesis. The test data proves that the arithmetics methods are correct and reasonable and the design of the hardware and the software achieve the desired requirementsThe monitoring instrument with high precision and multi-function has passed the technical appraisement organized by the Science and Technology Department of HuNan Province. It has reached the international level. As an effective way to detect power quality, the monitoring instrument is working well in many large steel enterprises and power departments.