Research On The Newton Method Power Flow For System With Small Impedance Branches

Power flow is the core and foundation of the power system’s analysis; it belongs to the steady-state analysis, and is widely used in power system’s planning, operation, automatic dispatching, analysis of security and reliability, and plan for optimal adjustment. However, with the increasing complexity of the modern power network, there are more and more ill-conditions in the power network, which often make the power flow without solution, or make the power flow divergent with the conventional methods. Therefore, the study on the convergence of power flow is particularly important and very meaningful.Small impedance branches are very common in the actual power systems. It is always one of the important tasks for steady-state analysis of power system to improve the convergence of Newton method for system with small impedance branches. Based on the analysis the influence of small impedance branches on Newton method in rectangular coordinates, a new varied-Jacobian Newton method is proposed to deal with systems with small impedance branches. Upon the modified equation of power flow, by analyzing the real part and imaginary part of voltage at both ends of small impedance branches in the iterative process, detailed analysis of the convergence properties of the improved algorithm is given. Compared with other three existing improved power flow algorithm, the proposed method which has less number of iterations indicates better convergence. In addition, the improved method can also converge while dealing with complicated power system.The existing improved algorithms which have been put forward already are mostly Newton power flow in polar coordinates for system with small reactance branches; there are rarely impedance types of small impedance for rectangular coordinate Newton power flow calculation. To solve this problem, a new improved method is proposed. The elements of the Jacobian use the bus injective current in the first iteration, which can improve the magnitude condition of the Jacobian matrix; while the elements of the Jacobian use the bus calculation current in the second iteration and later iterations. Not only the impedance type of small impedance for rectangular coordinate Newton power flow the new improved method can deal with, but also all kinds of small impedance branch system can acquire good convergence.