Early Prevention Method for Power System Instability

This paper presents a method to determine suitable countermeasures against emerging aperiodic small disturbance rotor angle (ASD) instability. The method utilizes stability indicators, computed in real time, to define a criterion for ASD stability. Sensitivities of these stability i ndicators are then determined and used to identify the most in fl uential nodes for counter measures. To increase the computational speed, only nodes visited by a self-propagating graph, rooted at the vulnerable generator, will have their sensitivities calculated. The steady state voltages after a given counter measure are then determined, using a grid transformation coefficient (GTC) and a numerical, iterative solution to an equation system. The stability criteriacan then be assessed to evaluate the sufficiency of a suggested counter measure. The method is demonstrated on a synthetic 8-bus network and a 464-bus model of the Western Denm ark transmission grid. The method successfully demonstrates its ability to efficiently identify and evaluate counter measures for a large, practical system.