Study On High-accuracy Phasor Measurement Methods And Test Platform For PMU Calibration

Phasor measurement unit(PMU)has become one of the effective tools for monitoring power system because of its synchronization and rapidity.It can provide reliable and effective panoramic synchronized measurement data for the characteristic study of power-electronics-enable power systems.However,due to the lack of effective PMU laboratory and field test methods and technologies,there are about 30%of bad data in the actual PMU data,and even lead to wrong alarm and control command in serious cases.Therefore,this thesis focuses on the research and development of a high-accuracy synchrophasor measurement method and test platform for PMU calibration.The laboratory test method before PMU installation and the field test method after PMU operation are studied,and then the corresponding test platforms are developed to comprehensively ensure the data quality and measurement performance of PMUs.Main innovations of the thesis are as follows:(1)Existing PMU laboratory test adopting multiple nonlinear fitting models has the problem of cumbersome test and complex solution.To this end,a general nonlinear fitting model of fundamental signal is established to reduce the number of nonlinear unknowns.Then,the mathematical relationship between phasor fitting coefficients and frequency is deduced,and the iterative calculation method of phasor fitting parameters is proposed to realize the linear high-accuracy fitting of nonlinear time-varying parameters.A high-accuracy measurement method of frequency and rate-of-change-of-frequency based on the frequency domain characteristics of differentiator is further proposed.These methods provide reference values for PMU laboratory testing.(2)Due to the complexity of PMU field test signals,the signal and noise identification methods are required.An adaptive identification method of noise level based on the chi-square distribution of noise power spectrum is put forward,and then a threshold denoising method is proposed to reduce the measurement error of reference phasor caused by noise.In addition,the energy leakage characteristics of signal mutation and the relationship between singular value spectrum and amplitude spectrum of oscillation components are revealed.A nonlinear dynamic signal type identification method based on singular value time-varying curve and its attenuation characteristics is further proposed.This method provide a reference basis for the performance evaluation of field PMUs.(3)To solve the problem that the existing reference phasor time-domain fitting method relying on signal model is not applicable for the unknown field signal type,a general design framework of phasor measurement algorithm is established to transform phasor measurement from time-domain fitting to frequency-domain dynamic extraction.Then,the mathematical relationship between test requirements and feature frequency band filter parameters is deduced,which transfroms the requirements for algorithm characteristics into the requirements for filter parameter range.Finally,a field reference phasor measurement method based on complex feature frequency band filter is proposed,which provides reference values for PMU field testing.(4)The influence mechanism of timing errors and sampling errors on phasor accuracy is revealed,and then the hardware selection is carried out.A high-accuracy synchronized sampling method based on adaptive phase-locked frequency division technology is proposed.The reference PMU is thereby developed.Further,the PMU laboratory and field test platform software are developed to build the PMU automatic test platform based on the reference PMU.The test results show that the test platform can effectively realize the laboratory and field test of PMUs,and fill the gap in the field of PMU test technology based on the reference PMU in China.