Preventive and Emergency Transient Stability Control

A unified approach to transient stability closed-loop control is presented. It relies on the general transient stability method called SIME, from which the Preventive and the Emergency SIMEs are derived. The Preventive SIME uses time-domain simulations of plausible contingencies prior to their occurrence, for the online power system monitoring from the control room. The Emergency SIME, on the other hand, uses real-time measurements, acquired on the system power plants after the actual occurrence of a contingency in order to appraise and trigger countermeasures indispensable for the system integrity. Despite fundamental differences in their design and objectives, the two approaches have also common features. This paper highlights main differences and similarities, and illustrates them on a realistic, large power system. The tradeoff between on-line preventive control and real-time emergency control is also assessed in terms of size of the involved countermeasures.