Research On The Influence Of Jacobian Matrix On The Convergence Of Cartesian Coordinates Newton Method Power Flow Calculation

As one of the most basic methods of power system analysis,power flow calculation plays an irreplaceable role in power network operation planning and steady-state analysis.With the improvement of the national economic level,the power network structure is becoming more and more complex,making more and more small impedance branches appear in the power system structure.Although the conventional Newton method power flow calculation can deal with some ill-conditioned problems,it often fails to converge when the power system contains small impedance branches.Therefore,it is of great research significance to find a method that can make the power flow calculation converge.After studying the characteristics of the small impedance branch and the correction equation of the power flow calculation,it is found that when a small impedance branch appears in the power network,the value of the bus current in the power flow calculation tends to become very large.The deterioration of bus current data conditions will cause the established Jacobian matrix to be no longer suitable for power flow calculation,which leads to one of the important reasons for the divergence of the final calculation results;another reason is that the initial voltage value selection does not meet the requirements.After continuous development,when there are not many small impedance branches in the power grid,many improved algorithms can get a convergent solution.However,when there are more small impedance branches,the problem of more iterations of power flow calculation will occur.On the basis of existing research algorithms,power flow calculation can handle smaller impedance branches,and a new and improved algorithm is proposed.Starting from the bus type at both ends of the small impedance branch,when the end point is a PQ bus,the injection current algorithm is used to modify the Jacobian matrix elements,and this method has been used in subsequent iterative calculations;When the end point is a PV bus,the calculation current algorithm is used to modify the Jacobian matrix elements,and this method has been used in subsequent iterative calculations.The PQ bus adopts the injection current calculation method to reduce the bus current,and a smaller bus current can effectively improve the Jacobian matrix elements.By establishing a good Jacobian matrix,the convergence of the power flow calculation can be improved.The reactive power of the PV bus is uncertain,and the method of calculating the current by the bus can reduce the influence of the indefinite reactive power.The calculation example verifies that the improved Cartesian Newton method guarantees the convergence of the power flow calculation,and at the same time has fewer iteration calculations.