Design Of Power Quality Disturbances Identification System Based On Fuzzy Nearness

With the development of electric power industry and the innovation ofscience and technology, some equipments with loads of nonlinearity, impact andunbalance, which are sensitive to electric power, have poured in the electricalpower system, causing serious pollution to power grid, and leading to the declineof power quality. Therefore, people have increasingly realized the importance ofpower quality. To monitor and identify the power quality disturbances quicklyand efficiently is the precondition of managing and guarantying the power qualityof the grid, and is also the important content of the study of power quality.The paper intensively studies several methods which are applied to identifythe power quality disturbances of the grid, such as Fourier transform, wavelettransform, HHT transform, S transform, dq conversion, instantaneous reactivepower theory and fractal method and so on. Based on the comparison betweentheir advantages and disadvantages, and by introducing the theory of fuzzynearness in fuzzy mathematics to the power quality disturbances identification,the paper puts forward an identification method upon fuzzy nearness, anddevelops a disturbance identification system used to validate the method based onvirtual instrument technology.The paper introduces the background and significance of the subject, thebasic concepts of power quality, and overseas and domestic research status ofpower quality disturbances identification, and proposes a disturbancesidentification method of power quality upon fuzzy nearness, and focuss on dqconversion, the basic theory of the wavelet transform, the choice of wavelet baseand the theory of fuzzy nearness. The paper analyzes the disturbancesidentification algorithm, designs the process to identify disturbance signals andprograms to synthesize waveforms of the studied disturbance signals which are made the simulation analysis of dq conversion and wavelet transform energydistribution to analyze the feasibility of the method under Matlab simulationenvironment. The paper designs a hardware system solution which uses theindustrial motherboard for core, builds a conditioning circuit that is entirelyconstituted by analog circuits for the grid voltage and current signalsconditioning, and uses TI’s ADS1178chip as the analog-to-digital converter. Thepaper designs a software architecture based on LabVIEW in which Matlab iscalled and two programming software of LabVIEW and Matlab are combined toachieve complementary advantages and to improve the efficiency ofprogramming, and at the same time does experiments for the system combinedwith the designed hardware platform and analyzes the experimental results.The paper completes the combination of fuzzy mathematical theory andalgorithm of power quality disturbances identification. The algorithm has theadvantages of fast response and high accuracy, and the effectiveness of themethod is proved by the software simulation and experiments of the system. Thesystem can be used as the foundation for on-line identifying and controllingpower quality disturbances.