Co-ordination of emergency secondary-voltage control and load shedding to prevent voltage instability

The authors investigate emergency action in terms of secondary-voltage control and the system load shedding for prevention of voltage instability. Two modes of co-ordination of these control methods with corresponding models are proposed, and these are summarised into developed emergency-control algorithms. The emergency actions of the individual controls and of the proposed co-ordinated control modes are then simulated on a real multimachine power system. The results so obtained show the superiority of the proposed co-ordinated controls over a single control action in preventing voltage instability and system breakdown.