Accurate transmission line parameters are the basis of power system calculations. Aiming at obtaining accuracy online transmission line parameters in the case of large random noises even bad data in Phasor Measurement Unit (PMU) measurements, which occurs frequently in the practice, a new adaptive robust identification method combining adaptive linear neuron (ADALINE) and traditional robust IGG (Institute of Geodesy & Geophysics, Chinese Academy of Sciences) method is proposed. In detail, first, the identification model of transmission line parameters is presented based on the multi-period PMU measurements at both ends of the transmission line. Then, a parameter solving model based on ADALINE is established. Furthermore, to fully use measurement information, the adaptive robust ADALINE (ARA) are proposed, which applies the robust IGG weight function (Scheme I) to ADALINE to realize "three segments" robust identification. In addition, to improve the robustness, the expectation and variance of the equation residual sequence are estimated adaptively with the median principle to adjust the threshold for the IGG function to assure robustness (TAR), which is independent of the known information for the error of the measurement equipment. The cases based on PSCAD simulated data and measured data show the effectiveness and engineering practicality of the proposed method.
Phasor measurement unit (PMU), which could provide high-frequency phasors including the amplitude and phase angle synchronized with Global Positioning System (GPS)/BeiDou Navigation Satellite System (BDS) signal, plays a vital role in dynamic monitoring of power systems. However, if the GPS/BDS signal could not be received, the time of PMU, which depends on the crystal oscillator (CO), would cause measurement deviation due to frequency shifts of CO, and then the PMU data would engage deviations and deteriorate the relevant applications. In recognizing the above problems, this paper proposes a method to detect the frequency deviation of the crystal oscillator (FDCO) based on the correlation coefficient, according to its relation with the characteristic of the voltage phase angle difference(VPAD) between the two ends of the line. In detail, firstly, the quality of the VPAD of PMU between the two ends of the line is analyzed and the related problem is stated. Secondly, the characteristics of PMU data, when FDCO exists, are derived and analyzed, especially the VPAD between the line, and the suitability of the data for detecting the FDCO is discussed. Thirdly, the ideas and specific methods of detecting the FDCO in case of malfunction of GPS/BDS signal are proposed. Furthermore, the validity of the proposed method with simulation data and modified measured data is presented. Finally, the conjectures on the reasons for the approximately constant VPAD deviation in the previous section are discussed.
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