Fast computation of voltage stability security margins using nonlinear programming techniques

This paper presents a simple, fast, and efficient method for determining the maximum loading point (MLP) and the voltage stability security margin of electric power systems. The proposed method is based on nonlinear programming techniques. The MLP is accurately obtained after a few load change steps. The computational procedure involves two kinds of load changes. Initially, load increases toward the MLP are defined for minimizing an objective function based on sensitivities. In case an overestimated load increase drives the system outside the feasible (stable) operating region, another very simple optimization-based procedure aimed to minimize the power mismatches determines the load adjustment (curtailment) to pull the system back onto the feasibility boundary. Simulation results for small test to large realistic systems are shown to validate the proposed method.