| As the main structure of transmitting electric energy,power transmission line is an important part of power system.According to statistics,the parameter error of power transmission line is sometimes as high as 30%,which will seriously affect the results of power flow calculation,state estimation,security analysis and economic dispatch of power network,and will mislead energy management system to make wrong decisions,thus threatening the security of power network.Therefore,obtaining more accurate transmission line parameters will ensure safe and economical operation of the power system.Research on the measurement and estimation of power transmission line parameters has always been a hot trend.At present,most of the research focuses on the estimation of symmetric three-phase power transmission line parameters,and rarely involves the estimation of asymmetric three-phase power transmission line parameters.Asymmetric three-phase power transmission line is a kind of transmission line that without commutation or without complete commutation,which is ubiquitous in our power grid.Therefore,it is necessary to study the parameter estimation of the asymmetric three-phase power transmission line.According to the actual situation of power transmission and the equivalent model of power line,in this paper,two-port equivalent models and multi-time measurement equations of fully commutated and incompletely commutated three-phase power transmission line are established,and robust recursive least squares method is used to estimate parameters of fully commutated,and incompletely commutated three-phase power transmission line,which is used to update the wrong or missing transmission line parameters in the energy management system in time,and ensure the safe and economic operation of the power system.The main contents of this paper are summarized as follows:1.Simulation models of asymmetric three-phase power transmission line.Firstly,the equivalent models and network equations of single-phase and three-phase power transmission lines are studied in detail,and then the complete commutation and incomplete commutation three-phase power transmission line models including self-impedance,mutual impedance,self-admittance and mutual admittance parameters are established.Secondly,based on the complete commutation and incomplete commutation three-phase power transmission line models,a six-node five-branch power transmission line models are established by the forward and backward substitution method.Thirdly,the head current of each branch,the end current of each branch and the voltage of each node of the power network are simulated by MATLAB.2.Parameter estimation of fully commutated three-phase power transmission line.Firstly,the multi-time measurement equations of impedance and admittance parameters of fully commutated three-phase power transmission line are presented based on sliding window method.Secondly,based on phasor measurement unit measurements,recursive least squares and robust recursive least squares are presented to estimate parameters of fully commutated three-phase power transmission line.Thirdly,using MATLAB to simulate and compare the results of parameter estimation of each method.3.Parameter estimation of Incompletely commutated three-phase power transmission line.Firstly,according to the sliding window method,the multi-time measurement equations of the impedance and admittance parameters of the incomplete commutated three-phase power transmission line are presented.secondly,based on phasor measurement unit measurements,recursive least squares method and robust recursive least squares method are presented to estimate the parameters of incompletely commutated three-phase power transmission line.Thirdly,MATLAB is used for simulation and analysis of parameter estimation results of each method. |
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