Design Of Power Quality Monitoring System Based On Virtual Instrument

The paper is about the power quality monitoring system designed and researched. Thepaper introduces the researching general situation of problem’s power quality, the researchfocus at home and abroad, harm’s of the power quality problem, as well as the sense ofresearch the problem of electric energy quality. In power quality problems, harmonic problemis most important, the article also elaborated the generation of harmonic, harmonic harm, aswell as on harmonics suppression researching.The paper also presents the index of power quality problem and its algorithm. The steadystate indicators of power quality problem includes: voltage deviation, frequency deviation,voltage three-phase unbalance, voltage fluctuation and flicker, and harmonics. In order toenhance the quality of electric energy management, the electricity sector promulgated thepower quality indicators of national standards. The algorithm of power quality mainly hasthe time-domain simulation method, frequency domain analysis methods and methods basedon transform, time-domain simulation method is researched the transient phenomena in thesystem,which uses of various time-domain simulation program; frequency domainsimulation method researches the steady problem of the power quality; There is a variety ofmethods of based on the transformation, and the paper mainly introduces the FFT, theartificial neural network and wavelet transform.The monitoring system designed is based on virtual instrument monitoring system, andthe paper introduces the virtual instrument profiles, and the advantage compared withtraditional instrument. The data acquisition part of the monitoring system comprises asensor, a signal conditioning circuit and data acquisition card，and it introduces the selectionand configuration. It is the main task of the monitoring system monitoring which is softwaredesign, including the frequency deviation measurement module, voltage effective valuemeasurement module, active power, reactive power, power factor measurement module,three-phase unbalance degree measurement module, harmonic measurement module. In thefrequency measurement, introduces the selection of frequency measurement algorithm, thesystem is used the FFT and its improved algorithm, and introduce the FFT algorithm further;in harmonic measurement, the harmonic characteristics are introduced in detail, the harmonicdistortion of waveform processing, and introduced the wavelet transform, in the harmonicmeasurement module, needs to use the window function to reduce leakage, this selection is aHanning window.The paper also was verified the software monitor module using the actual acquisition ofpower quality data, and analysis the data processing results and possible error. Finally, it has made a conclusion in the place of improved to the design of system, pointout the further research work and prospects.