| This thesis was supported by Natural Science Foundation of Chongqing(CSTC2009BB6190) and independent research project of State Key Laboratory of PowerTransmission Equipment&System Security and New Technology(2007DA10512711209).With the development of power network interconnection and the grid operatingenvironment getting more and more complicated, It’s urgent to develop newtechnologies for stability monitoring and control of power system. Wide AreaMeasurement System (WAMS) based on synchronized phasor measurement technologycan monitor and analyze the running state of power system. WAMS has importantsignificance for reinforcing the reliability of power system. Phasor Measurement Unit(PMU) is the core of the WAMS, and the accuracy and real-time of the phasormeasurement algorithm is directly related to measurement accuracy and operating speedof PMU. What’s more, the accuracy of measurement has direct bear on the efficiency ofapplications of WAMS, such as statc estimation, power flow calculation and wide areaprotection etc. Therefore, it’s necessary to study synchronized phasor measurementalgorithm, which can improve performance of WAMS and security and stability ofpower system. A new synchronized phasor measurement algorithm and a newsynchronized phase measurement algorithm according to different application and itsimplementation are proposed in this thesis. The main contents are as follows:The influence of input signal frequency deviation on the result of discrete Fouriertransform is analyzed. Because the window length can’t include complete signal periodafter periodic extension for intercepted signal, the discrete Fourier transform afterfixed-interval-sampling may cause fence effect and spectrum leakage. The geometricrelation between phasor measurement estimated value and true value when frequency ofinput signal deviates from the nominal value is discussed.This thesis proposes a new phasor measurement algorithm based on the interpolatorquadrature formula and the linear interpolation in the discrete time-domain. Thecompound Simpson’s formula is chosen to accomplish Fourier coefficient equivalencefor improving precision. The principle of linear interpolation is researched, which canbe utilized to solve the window length error when used discrete Fourier transform. Themeasuring accuracy and noise immunity comparison between the proposed and common DFT compensation algorithm is made by MATLAB simulation.According to measurement requirements for phase angle, a new phase anglemeasurement algorithm based on virtual α-β stationary coordinate is proposed. Theformula about frequency deviation and phasor angle calculation error of DFT is deduced.Two forms of positive sequence component expression under α-β stationary coordinateare discussed, and the mathematical model of virtual α-β stationary coordinatecontained two reversed-phase β axis is constructed. Based on the DFT error mechanism,the presented method could greatly eliminate the sinusoidal error of the conventionalDFT algorithm with different proportion summed of three DFT result. After compensatethe fixed offset, we can get the precise phase angle measurement result. The simulationsfor measuring accuracy and noise immunity of the proposed algorithm compared withquasi positive sequence DFT and corrected DFT are made in MATLAB.A synchronized phasor measurement unit based on multi-CPU structure is designedand realized. The design of hardware includes mainly that synchronized clock cell,acquisition unit, digital input unit, digital output unit, ARM9data management unit andpower unit. The design of software includes mainly that DSP software design, digitalinput/output software design, ARM7software design and ARM9software design.Detailed anti-interference measures are presented to ensure safe and stable operation ofthe measurement unit. |
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