Control strategies against voltage collapse considering undesired relay operations

Control strategies as countermeasures against voltage collapse considering undesired relay operations are mainly discussed here. In the experiences of blackouts, undesired relay operations have played a very important role in cascading events leading to a voltage collapse. An algorithm for quick identification of critical relays is first depicted, the operations of which may significantly deteriorate the systems in terms of voltage stability. Then, the proposed approach determines a control strategy satisfying a relay margin criterion. For this purpose, a combinatorial optimisation formulation with a utility function evaluated by a quasi-steady-state simulation is used, and a local search algorithm to deal with binary control variables in the formulation is employed. The methodology is demonstrated with the modified New England 39-bus system.