A model-predictive approach to emergency voltage control in electrical power systems

Recent blackouts have shown that traditional local protection against power system collapse is not always sufficient to arrest instabilities. This paper shows that centralized systems can perform better than traditional local protection, as well as outlining how the decision logic of such centralized systems can be implemented. We present a coordinated system protection scheme (SPS) against voltage collapse based on model predictive control and heuristic tree search. It coordinates dissimilar and discrete controls such as generator, tap changer and load shedding controls in presence of soft and hard constraints on controls as well as voltages and currents in the network. The response with the coordinated SPS is compared to an SPS based on local measurements using simulation of the Nordic 32 test system. In terms of the amount of load shedding required to restore voltage stability, the simulations indicate that load shedding based on local criteria is near optimal in the system studied. However, when also generator controls are considered as emergency controls, the coordinated scheme reduces the amount of required load shedding by 35% compared to the local scheme.