Framework for Identification of Power System Operating Security Regions

Power system operation aims, in principle, at maintaining reliable and secure supply of electricity while minimizing the total cost of operation. In theory, there are two main objectives that could be considered, namely the maximization of system security and the minimization of total operating cost of supplying energy. In practice, however, the security requirements are included as constraints rather than formulating the problem as a security maximization mandate. The system security constraints are in fact boundaries that surround all possible operating modes (scenarios) of the power system. In other words, these boundaries form the feasible operating domain in the parameter space spanned by various operating variables within which the system can safely be operated. For a given operating scenario, the associated security level is measured by the "distance" (for example, the Euclidean norm) of the operating point from the security region boundary. This paper presents a novel framework for identification and representation of operating security regions in power systems as well as evaluation of security levels associated with different operating scenarios. While the concepts and principles presented are general, the work of this the paper is confined to the interpretation of the security boundary in terms of system stability criteria. Of course, the framework presented is applicable quite as well to other criteria that may be considered.