Determination of static voltage collapse critical point based on load flow method with optimal multiplier

A new method for determination of static voltage collapse critical point based on Newton-Raphson load flow method with optimal multiplier is proposed. Different from continuation load flow and direct methods, this method starts from the infeasible region of load flow equations. It then approaches the desired critical point along the changing direction of injected power flow by making use of value of the optimal multiplier and the least square solution of load flow equations. All possible situations during the approaching process are analyzed and reactive power limits of generators are considered. The unified approach for identifying and calculating saddle node point and limit-induced bifurcation point is given. Convergence characteristic and computation complexity are analyzed. Tests in several systems show that the proposed method can converge at critical point after several iterations. The results are consistent with continuation load flow and direct methods.