Fast computation of security margins to voltage collapse based on sensitivity analysis

The paper presents a simple, robust, and efficient method for determining the maximum-loading point (MLP), and consequently the security margin to voltage collapse of electric-power systems. The computation procedure is based on a proper utilisation of sensitivity techniques. The load increments influence the behaviour of the reactive power injected by generators (slack and PV buses), thus making sensitivity analysis a very interesting tool for voltage-stability analysis and applications. The MLP is obtained accurately after a few load-change steps. Initially, load increments towards the MLP are defined through sensitivity analysis. If an overestimated load increment drives the system outside the feasible (stable) operating region, a very simple optimisation-based procedure aimed to minimising the power mismatches determines the load adjustment to drive the system back to the feasibility boundary. Simulation results for a range of system sizes are shown to validate the proposed method.