Research On Parameter Estimation Method Of Two-port Interconnected Grid External Network Static Equivalent Parameter On The Basis Of Internal Network Measured Information

Traditional static equivalent methods of power system is presented on the basis of knowing external all model information. However,in the power market,interconnected subsystem represents the different interest group usually,the grid data of every group is regarded as a secret of business value.The real-time data can not exchange between the interconnected subsystem,then,the independent power simulation's error of subsystem is very big, affecting the security and stability of interconnected system. Therefore,in the case of lacking all external model and state information,and traditional static equivalent methods can not use,how to achieve the effective estimation of external static equivalent parameters,which is a critical problem of guaranting veracity of the subsystem independent power simulation.Aiming to the problems above, the contents presented in the paper are as follows:â‘ On the basis of Ward and power source equivalent theory,this paper presents a Extended voltage-source-branch Ward-equivalent-circuit Model (EWM) of external network and it's equivalent parameters's two-stage estimation method. First stage, regarded the equivalent injections at the boundary busses and equivalent admittance between the boundary busses as the equivalent parameters, establish the simplified ward equivalent circuit of two-port external network and build N-time least squares estimation model of equivalent parameters. Second stage, use voltage source connected the series impedance equivalent branch instead of the equivalent injections at the boundary busses, form the EWM. Then establish least squares estimation model of EWM's parameters, considering the relations of the two equivalent circuit parameters. Finally, use Gauss-Newton method to get the equivalent parameters of the first and second stage equivalent parameters, and make the latter as the equivalent parameters of the external network. Owing to the restriction effect of the first stage equivalent parameters, the coupling effect among the EWM parameters decreases and the accuracy of equivalent parameter estimations is guaranteed as well.â‘¡On the basis of two-stage estimation method,this paper presents a external static equivalent parameter estimation method with considering measurement errors.In the two-stage model,considering the physics constrained of static equivalent parameters,and adding to state variable and it's measurement equation,then take it's estimation value as the second related variable's true value. This paper use fmincon of MATLAB optimization tool box's function to get the equivalent parameters of two stage equivalent parameters,and make the latter as the equivalent parameters of the external network. This method decrease the random measurement error's influence,and increase the robustness of parameter results.â‘¢According to the above two external static equivalent parameter methods. This paper use IEEE 39-bus modified system and IEEE 118-bus modified system,and Guang dong power grid to simulate and analysis the model and algorithm. The results of the simulation indicate that the external static equivalent parameter methods in this paper is valid.