Breaking Power Flow Fast Calculation Based On Constant Jacobian Matrix

This paper discusses the equivalent breaking power flow calculation method based on the fast decoupling method with constant Jacobian matrix.This method can approximately be subdivided into the direct method and the iterative method.Among them,the direct method is to add injection power compensation to the branch nodes of the breaking branch to equal the variation of the power after the branch is disconnected.In this way,the distribution of power and power variables can be calculated accurately by identifying the type of point nodes on the basis of the original power flow and the internal connection between the original active power and the power variables derived from the Taylor expansion of active power.The iteration rule directly corrects the voltage and phase angle variables before the iteration begins.The calculation principle of the iterative method is simple,the solution process is decoupled and the calculation speed is fast.However,the calculation precision will be affected by the overlook of the disconnection branch to the ground admittance in the calculation.Then the constant Jacobian breaking power flow calculation method based on fast decoupling method is proposed.This method simulates the outage state of the branch by the branch opening function and the Taylor expansion formula of the voltage to calculate the distribution of the power flow after the fault.The power flow calculation results of IEEE standard system confirm the feasibility of the method.In this paper,a power flow algorithm based on the constant Jacobian matrix using the modified coefficient matrix function is proposed based on the Newton-Ralphson power flow algorithm preserving nonlinear term.In the whole iterative process,only one Jacobian matrix is needed to be calculated in the Newton-Ralphson power flow algorithm preserving nonlinear term while the Jacobian matrix must be repeated during the iterative process of the Newton-Ralphson flow algorithm.In order to ensure faster computing speed of the algorithm and avoid that the calculation results are not convergent due to the change of network structure,the simplified version of Newton-Ralphson power flow algorithm retaining nonlinear flow is used as the basis of calculation.The calculation speed of breaking power flow is improved under the condition of sacrificing some precision.On the basis of the improved calculation of the power flow,the branch opening function is used to simulate the branch opening,and the modified coefficient matrix functionA_km???is derived by analyzing its influence on the admittance matrix and the original Jacobi matrix in the flow calculation.The simulation example based on IEEE standard node system verifies the accuracy and rapidity of the algorithm.To sum up,a new method of quantitative calculation and analysis for static safety analysis of power system is provided in this paper,which combines the power flow algorithm with the retention of nonlinear term and the open power flow calculation method of the modified coefficient matrix functionA_km???.