The Research For Online Detecting Technology Of Three-phase Unbalance

Power plays an increasingly important role in modern society. The proportion ofpower in final energy consumption represents a country’s level of technologicaldevelopment. With more and more unbalanced loads in power system, three-phaseunbalance is getting worse. Three-phase unbalance not only affects the normaloperation of customer premise equipment, but also causes flickering and fluctuationsin supply voltage, increasing line losses, which seriously contaminates power quality.Power quality problems like three-phase imbalance have attracted much attention, anda number of power quality standards had been formulated at home and abroad.In order to achieve real-time detection of three-phase unbalance, this thesisdesigns a three-phase unbalance detection system with a DSP processorTMS320VC5502as the detection unit and an ARM processor Freescale K60as themanagement unit, which consists of multi-parameter analysis and a combination ofdisplay and storage of data. Based on powerful computing capabilities of DSP, thedetection system can calculate basic electrical parameters, and analyze three-phaseunbalanced event. With powerful management features of ARM, the detection systemcan achieve real-time display and data storage. The design has broad market prospectsbecause of simple structure, software portability, low cost, low power consumptionand high reliability.The thesis is made up of five parts. In the first chapter background knowledge ofpower quality, standards of power quality, the development of testing techniques areintroduced, last the research status of three-phase unbalance are summarized. Thesecond chapter details on the calculation methods of the power quality parameters,and proposes a fast three-phase unbalance vector calculation method. The thirdchapter details on the composition and working principle of the system, the overalldesign of the system and each module are introduced as well. The fourth chapterdetails on software system design, the software development platform and majorsoftware modules are introduced. In chapter five system debugging an d resultsanalysis are introduced, chapter five focuses on the analysis of the experimentalresults and error, the calibration of the fast three-phase unbalance vector calculationmethod. The last part concludes the thesis and point out the lack of the research.MATLAB simulation and DSP actual operation results show that the fast three-phase unbalance vector calculation method can achieve the same level ofprecision as the method recommended by the standards do, while much less clockcycles are required, which indicates its widely application in other systems. Testresults show that the system can meet the requirements of real-time online testing ofphase unbalance events, measurement of electrical parameters in DSP can meet thestandard’s requirements.