Research On Initial Jacobian Matrix Of Cartesian Coordinate Newton Method Power Flow

As an important means of power system analysis,power flow is widely used in system planning,power grid monitoring and scheme optimization.With the merger of domestic regional power grids and UHV construction,the operating state of power systems is often ill-conditioned.Power flow in ill-conditioned systems tend to cause power flow divergence or unsolvable power flow,and the existence of small impedance branches in the system is generally the cause of ill-conditioned power flow the reason.Therefore,the research on the power flow of power system with small impedance branches has practical significance.The Newton method is widely used as one of the mainstream algorithms for power flow.The advantage of the Newton method compared to other power flow algorithms is that it can handle some ill-conditioned power flow problems;however,the Newton method has poor convergence The existence of the small impedance branches makes the value of the node current phasor calculated in the system very large,which leads to a large condition number of the Jacobian matrix in the Newton method power flow,which has a morbid effect on the jacobian matrix.According to the processing effect of the existing algorithm on the small impedance branches and the effect of the small impedance branches on the jacobian matrix,this paper proposes a two-stage iterative Newton method in cartesian coordinates:in the first stage iteration,the real and imaginary parts of the current are set to zero to participate in the calculation;in the second stage iteration,the real and imaginary parts of the node current phasor in the elements of the jacobian matrix are retained,that is,the traditional Newton method is used to calculate.Theoretical derivation proves that the method in this paper can solve the convergence proble of power flow calculation with small impedance branches.Since the real and imaginary parts of the node current are set to zero,the effect of small impedance parameters is eliminated,and a benign jacobian matrix is constructed;at the same time,the reactive power in the PV nodes is not adversely affected by the inaccuracy of the given value,thereby ensuring power flow converges reliably to further improve convergence.Taking the modified IEEE 30-bus system and 445-bus system of northeast power grid as examples,the first iteration is determined as the best solution for the convergence of the first-stage power flow in this method;it is verified that the method in this paper deals with different types of small impedance branches They all achieve good convergence effect,have no adverse effects on conventional branches,and have good adaptability;comparison with existing methods shows that:the method in this paper guarantees the convergence of power flow with small impedance branches while requiring fewer iterations,the convergence effect is better.