Study On Virtual Instrument Based On-line Monitoring And Measurement Technique Of Power Quality

In this paper, the virtual instrument technique is used in the study of the power quality in electric power system. Why power quality questions are attracting attention increasingly has three chief reasons: the electricity load structure occurs the great change in the modern power system; Very sensitive to power quality control equipment and the electronic installation service based on the computer system of large numbers have been used; In the power market under the operating mechanism, power is as the commodity, and users certainly puts forward the more and more higher requirement to the commodity quality. At present, our country power quality national standard was chiefly stipulated five quotas: frequency, harmonic and voltage deviation, three-phase unbalance and the voltage fluctuation and flicker. The objective of this paper is using the newest technology of the field of measurement and control now --the virtual instrument technique to which mentioned above five power quality standards. Its real time monitoring is able to go deep into analysis to the monitoring and then the influence of harmonic to the measurement of electric energy is studied. It also can provide the detailed power quality monitoring analysis and results for the power department.The virtual instrument is follow-on product outcome of software and hardware of computer technique, and it is replacing traditional electronic instrumentation step by step, and is the development direction of modern electrician's electronic measurement instrument. The virtual instrument technique is mainly used in measurement, control and emulation. Leading the virtual instrument technique to the power system possesses the most vast application foreground. LabVIEW of American nation instrument company development system is the outstanding representative of virtual instrument in the research and development at present. The key part of the technology of on-line monitoring and measurement of power quality in this paper is using LabVIEW and its DAQ(data acquisition card to develop. "The software is the instrument" is the major characteristic of virtual instrument technology. In this paper, LabVIEW graph software is adapted to realize a series of functions such as FFT, avoiding frequency spectrum leakage and interleaving etc that are realized by hardware realization originally. The hardware uses a industry control computer based on PCI bus and a signal converter. The industry control computer is make up of LCD, hard disk, face pattern keyboard and net cards and modem etc, and can monitor waveform and data on the spot, and data can be passed to monitor center far away to be analyzed further by way of local area network and public telephone net.The harmonic is the important aspect of power quality question, and under the circumstances that the harmonic exists. At present, a large number of Watt-hour meter are still using and their accuracy suffers the influence. In this paper, except the research of on-line monitoring and measurement of power quality, the influence of harmonic to the measurement of power was thoroughly analyzed. This paper puts forward and realized a method of separating the measurement of harmonic power and the base wave power. which provides fixed quantity data of the harmonic power and its influence for the power department.