Fast method for computing power system security margins to voltage collapse

The paper presents a simple, fast and reliable method for determining the distance in parameter (load) space from the system current operating point to the critical point for which voltage instability and even voltage collapse may occur. Sensitivity analysis is used to drive the system from the base case operating point to the vicinity of the critical point along a predefined load increase direction. In case the sensitivity analysis drives the system to the infeasible operating region, a special load flow method with step size optimisation is used so that relevant information can be obtained to restore the feasibility. Finally, the critical point is estimated from a certain number of conventional load flow calculations for different operating points in the vicinity of the critical point, by increasing the load along the predefined direction. The security margin to voltage collapse is obtained at a low computational cost. Simulation results for small and large power systems are shown to validate the effectiveness of the proposed method.