Research On Method Of Calculating Power Frequency Parameters Of Transmission Line By Using PMU Data

In recent years,with the continuous expansion of the power grid and the access of new energy sources,the operation mode of power system has become increasingly complex.Obtaining accurate line parameters is the basis of state estimation? current calculation? power network scheduling and fault analysis.Therefore,how to improve the accuracy of transmission line parameters and obtain a more accurate power grid model is crucial for the safe and stable operation of the power system.With the extensive use of synchronous phasor measurement in wide area measurement system,the PMU can obtain the voltage,current amplitude and phase angle of the fundamental frequency of each node of the power system by using the high precision timing signal of global positioning system GPS,Which provides favorable conditions for calculating accurate transmission line parameters.When the low frequency oscillation occurs in the power grid,since the fast Fourier algorithm used in the PMU cannot distinguish between the power frequency signal and the low frequency interference,the PMU collected data will contain the low frequency oscillation disturbance component,which will affect the correctness of the power system steady state analysis and calculation.Therefore,this paper presents a method to eliminate the low frequency interference components in the PMU data to obtain the power frequency component and then calculate the power frequency parameters of the transmission line.Theoretical analysis and simulation results verify the correctness of the proposed method,and the validity of the method is illustrated by the calculation of PMU measured data.In the measurement and calculation of high voltage transmission line parameters,the line parameters are considered as three-phase symmetry under normal circumstances,only use one of the phase or positive sequence components to measure and operation.However,due to various factors,the line parameters cannot achieve the ideal state of complete symmetry.Asymmetrical voltage and current generated by the asymmetric circuit parameters will not only make the energy in the transmission process to produce more losses,serious also endanger the generators ?transformers and other electrical equipment at the both ends of the line.In order to reduce the asymmetrical voltage on the high voltage transmission line and maintain the stable operation of the power grid,this paper proposes to use the Norton equivalent circuit of the three-phase high voltage transmission line,and regards the asymmetric line parameters as the equivalent admittance of the Norton equivalent circu it.Through regulating the amount of static compensator in the line,make the port voltage close to the three phase symmetry,so as to achieve the purpose of reducing the asymmetry on the line.The calculation results and Matlab simulation show that this method can effectively reduce the asymmetric voltage on the line.