Research On Distribution Network State Estimation Based On Load Model

With the rapid development of intelligent distribution network technology and the increasing power demand of users,the power quality and stability of users need to be further improved.As an important part of distribution management system,distribution network state estimation is the basis of advanced application and safe and stable operation of distribution system.Therefore,how to improve the accuracy of state estimation has become the research focus of distribution network state estimation.This thesis is taken the distribution network state estimation considering the load model as the main research content,and carries out research work from the basic algorithm of distribution network state estimation,distribution network comprehensive load model,photovoltaic power generation grid connected system model and load model including photovoltaic power generation.Firstly,this thesis introduces the distribution network state estimation,including the mathematical description of measurement system and distribution network parameters,and expounds the weighted least square method and distribution network state estimation method based on node voltage.The two processing methods of virtual quantity measurement are simulated and analyzed,which provides a theoretical basis for the subsequent distribution network state estimation considering the load model.Secondly,considering the high proportion of induction motor load in distribution network load,a distribution network state estimation method considering comprehensive load model is proposed on the basis of static load model.Taking the potential node in the induction motor as a new node in the distribution network,the expressions of the virtual measurement function and Jacobian matrix of the load node are derived.Based on the measured data,the virtual measurement is added,and the IEEE-33 bus system and 141 bus system are used to simulate and analyze the method.The results show that the comprehensive load model is helpful to improve the accuracy of state estimation results.Finally,in view of the increasing penetration of new energy in the power grid and the change of load properties,the mathematical models of photovoltaic cells,DC / DC converters and inverters in photovoltaic grid connected system are established.Based on the comprehensive load model,the photovoltaic power generation grid connected system is further considered,the distribution network state estimation method considering the comprehensive load model is improved,the state variables of photovoltaic grid connected system are combined with the state variables of state estimation,and the expression of measurement function and Jacobian matrix are improved.The simulation results of IEEE-33 bus system and 141 bus system show that the accuracy of the state estimation results of this method is further improved.