The Convergence Analysis Of Power Flow By Polar Newton Method Based On Compensation Method

The power flow is one of the most basic and important calculation methods in power system analysis.Its results reflect the operation state of power system,and serve as the basis for electric power operators to adjust the operation mode of power system and evaluate the reliability of power system.In the real life,with the power system network tends to be connected to the grid on a large scale,especially the incorporation of local small power grid,the complexity of the power grid is getting worse,the number of small impedance branch increases,resulting in the emergence of more and more ill conditioned networks,which seriously affects the analysis of the power system.As one of the most widely used power flow methods,the Newton method has the advantages of good convergence,high efficiency and moderate memory consumption.But in the actual calculation,for the power system with small impedance branches,the traditional Newton method can not guarantee the convergence of power flow.When the relevant parameters of the small impedance branches reach a certain condition,the convergence of the Newton power flow becomes poor.According to 'the characteristics of power system network,this thesis makes a theoretical analysis of Newton power flow.It is concluded that the bus types at both ends and impedance value of small impedance branches are important factors that affect the convergence of power flow.It is deduced that only two specific types of small impedance branches will lead to divergence of power flow,and other types of small impedance branches will not affect the convergence.The derived results are verified by an example.In view of the two kinds of small impedance branches which will lead to divergence of the Newton power flow,a polar Newton method power flow based on compensation method is proposed.Before the Newton power flow two kinds of small impedance branches that affect the convergence of power are selected for compensation,and a compensation branch is added,to make the branch become the combination of branches with normal impedance value,and there is no need to compensate all small impedance branches.After analysis,the two series compensation methods can solve the convergence problem 'of power flow with various types of small impedance branches.The method is applied to IEEE 14 system and 445 system of Northeast power grid.The results show that the two series compensation methods have good convergence when dealing with the power flow with various types of small impedance branches.At the same time,it reduces the memory and calculation time of power flow,which has high engineering practical value.