Power Quality Analyzing System Based On LabWindows/CVI

Generator, transformer, circuitry, the non-linear or asymmetry of the consumers in system, as well as control means incomplete, outside interference and various failures is mainly responsible for system voltage unbalance and sine voltage distortion. So power quality problem arises. In view of the problem that the storage capacity is small, the display function is monotonous, measurement error of non-sinusoidal parameter is big and the data analyzing and processing is imperfect for traditional power quality analyzer, this paper introduce the design scheme of power quality analyzing system based on LabWindows/CVI.First, presents situation and analyzing measurement about power quality. Second, analyze the power quality indicators included define, causation and hazard. Third, present the mathematical analyses method about power quality which includes Fourier Transform, Window Function, Spectrum Aliasing and Spectrum Leakage. Fourth, detailedly depict the hardware and software design of power quality analyzing system. Adopt virtual instrument system basing on PXI to accomplish hardware setting up. In software, base on LabWindows/CVI platform to accomplish analyzing and processing of power quality indicators includes acquiring signal, analyzing signal, saving signal. Measure the frequency by Zero Cross Detection. Measure the amplitude and phase of fundamental and harmonious by Fast Fourier Transform. Obtain the phase deflection by correlation and the voltage fluctuation by comparison. Last, analyze the error of the measuring data and propose improving measure. Depict the shortage in this design, and make a prospect for the trend of power qualityanalyzing system.