Power System Security Corridors Concept and Computation

This paper introduces a novel scheme for the region-wise predictive security assessment. The proposed scheme is based on the concept of the security corridor, which assumes that the normal range of operating points can be restricted to the neighborhood of the system\´s predicted (or nominal) trajectory. Our scheme tries to characterize this neighborhood by a number of ellipsoids overlapping along the system\´s predicted trajectory. The intersection of these ellipsoids with the system\´s steady-state security region defines a security corridor which is characterizable by a relatively small number of constraints. Each ellipsoid covers a specific operating time interval, so the time of operation serves as a localizing parameter in this scheme. The small number of constraints needed to describe the secure part of an ellipsoid allows the efficient use of the security corridors in a variety of power system operation and planning applications. For on-line security monitoring, for instance, as long as the actual trajectory stays within the "width" of the security corridor - which can be verified rather trivially - the system security is guaranteed. The effort involved in constructing a security corridor is explained through a discussion on some computational aspects of the scheme, and by presenting the results of some numerical studies performed on a sample system.