Research On Transient Power Quality Real-Time Monitoring And Data Compression Method

With the expanding of the power system, a variety of high-power nonlinear loadsbased on power electronic technology are increased, causing increasingly seriousproblem of power quality, accurate and reliable monitoring and analysis is the premiseand basis of improving power quality. The rapid extension of the power qualitymonitoring from the steady-state to real-time detection of transient disturbances, nolonger satisfied with making only limited to the steady power quality monitoringequipment needs. For this thesis focuses on the problems of power quality monitoring inthe transient detection and data compression, transient disturbance detection and powerquality data compression theory and realization carried out research work, and buildreal-time power quality monitoring and analysis system software platform in order toimprove the function of the modern power system power quality monitoring.①The paper presents a time positioning method of transient disturbance signalbased on the generalized S transform for the detection and realization of transient powerquality, moreover, automatic identification system of transient disturbance signals isconstructed by use of a rule-based decision tree. At first, modulus time-frequencymatrix is calculated by generalized S-transform, and then the disturbances’ start-stoptime is localized using the high frequency time-amplitude curve, moreover, fouridentification features are extracted according to maximum frequency spectrum curve,fundamental frequency amplitude curve and the localization results. At last, automaticclassification of disturbance signals is performed based on a rule-based decision tree.Simulation results show that the proposed time localization method is simple andintuitive, with high accuracy. The number of identification features is small and they areeffective with good classification results. The constructed automatic identification isoperator fast, small memory spending, suitable for real-time monitoring devices in thetransient power quality.②For mass data storage and transmission problems, the paper introduces theimage smoothing algorithm, and presents a compression scheme of the power qualityrecorded data based on two-dimensional wavelet transform with lifting scheme andimage SPIHT coding. In this program, the obtained one-dimensional power quality datais transformed to two-dimensional representation, in order to fully tap the power qualitycycle signals redundancy. The data based on image smoothing is more suitable for two-dimensional wavelet transform coding with lifting scheme, and image SPIHTcoding for the obtained wavelet coefficients can further improve the compressionperformance. The simulation results show that the proposed data compression schemehas good compression performance, has a higher signal to noise ration in thecompression ratio up to120times, while still better to keep the disturbance signalsmutation information, is a effective way to solution to power quality mass data storageand transmission problems.③Based on the proposed transient power quality detection method and datacompression method, the paper uses the LabVIEW development environment to designa real-time power quality monitoring and analysis system. This system enables thesteady state and transient power quality detection, is a intelligent multi-functionmonitoring system with data processing, display, transmission and storage, has flexiblescalability function, moreover, it can provide data support and theoretical basis forpower quality incidents analysis, with important practical applications.