Research On Linear Power Flow Calculation And Sensitivity Analysis Of Distribution Network

With the large-scale access of clean energy to distribution network,the complexity of distribution network is intensified and the difficulties of power flow calculation increase.In order to respond to the demand of rapid analysis of distribution network,this paper studies the linear power flow calculation of distribution network with distributed generation(DG),the linear interval power flow calculation based on affine arithmetic,and the sensitivity calculation of node voltage and network loss of distribution network.According to the characteristics of the distribution network itself,Taylor series expansion technology is used to perform a linear approximation of the non-linear terms of the node power equations in the form of polar coordinates,and the property of the admittance matrix is used to sort the node power equations to derive a linearity.In order to make the linear power flow equations applicable to distribution network with DG,the expression of reactive power generated by non-PV type DG is simplified into a quadratic function of voltage magnitude by using Taylor series expansion technique,that is,the simplified power flow model of DG.Combining the simplified power flow calculation model with the linear node power equation,a linear power flow calculation method for distribution network with distributed generation is proposed.The proposed method can handle not only PV-type DG and PQ-type DG,but also PI-type DG and PQ(V)-type DG,which has strong versatility.Finally,based on the Newton-Raphson method power flow calculation results as a benchmark,the typical test system shows that the proposed method has higher calculation accuracy and greater versatility than existing linear power flow calculation methods,and can be used as a rapid analysis method for distribution network.By combining affine arithmetic with linear power flow model,an interval linear power flow model based on affine arithmetic is established.When the interval power flow is calculated by the proposed model,there is no need for iteration,which significantly enhances calculation efficiency.Example shows that the proposed model based on afine arithmetic can represent the correlation between variables,which overcomes the defect that the interval iteration results are too conservative.According to the characteristics that distribution network has rather small branches loss,it is assumed that no branches loss will occur due to the change of node injection power.The upstream node set,downstream node set,and upstream branch node set are defined.According to the variation of the node injection power,the variation value of the power of each branch is deduced.Based on the variation of the branch power,a sensitivity calculation method of node voltage and network loss is proposed.The proposed method does not need Jacobian matrix,admittance matrix or complex matrix operation,but only needs to traverse the network.The practicability and rationality of the proposed method are verified by example analysis.