Research On The Cartesian Coordinate Newton Method Power Flow With Variable Jacobian Of Considering About Bus Type

The most basic and important calculation in power system analysis is power flow.With the increasing scale of Power grids,ill-conditioned systems in power systems are increasing,and small impedance tributary systems are common in morbid systems.Conventional Power Flow often fail to reliably when solving a modified equation with a small impedance branch in a power system.Therefore,the research on the convergence of power flow has important theoretical significance and practical significance.Through the study of the modified equation of the power flow,since the impedance value of the small impedance branch is very small and the admittance value is very large,the calculated real and imaginary values of the bus calculation current are large.Resulting in a worse numerical condition of the Jacobian matrix.According to this,an improved algorithm is proposed to solve this problem,and a detailed proof of the improved power flow algorithm for reliable convergence with small impedance branches is derived.The existing improved algorithm based on Cartesian coord:inate Newton has better convergence for systems with less impedance-type small impedance branches.However,when the system contains many impedance-type small impedance branches,the power flow will have more iterations and less convergence.In order to solve this problem,this paper improves the existing improved algorithm and proposes a new improved algorithm:the Cartesian Newton method for modifying the Jacobian matrix elements with iteration and bus type.In the first iteration,the PQ bus calculates the Jacobian matrix elements from the real and imaginary parts of the bus injection current calculated by the given active power and reactive Power,the PV bus and all bus subsequent iterations the Jacobian matrix elements are calculated by bus for current calculation.Since the Jacobian matrix element of the PQ bus uses the bus injection current in the first iteration,the value of the Jacobian matrix element is relatively small,which makes the power system reliably converge when the power flow is performed with the small impedance branch.The example analysis of the IEEE30 bus and the 445-bus system of the Northeast Power Grid is carried out,and the convergence of the improved algorithm for the reactance,resistance and impedance small impedance branches is analyzed.Compared with the existing improved algorithms,the improved algorithm has fewer iterations and better convergence.