AN EXTERNAL NETWORK MODELING APPROACH FOR ONLINE SECURITY ANALYSIS

The model of the portions of the network that are not observable to the state estimator but affect the contingency analysis results plays an important role to the usefulness of the on-line security analysis functions. The advancement in the state estimation techniques inspires the use of state estimation for external network modeling. However, because of the large size of the interconnected network modeled, problems, such as numerical stability and Computational requirement, that do not show up in the small system might appear in the implementation of the large scale system. In order to use the state estimation for external network modeling the problems associated with the large scale state estimation shall be addressed. In this paper, an approach that combines the load flow and state estimation techniques is proposed. The proposed approach is designed to improve the numerical stability and provide an external network model for on-line security analysis. An initial load flow study that provides a preliminary solution for external network is followed by a state estimation using pseudo-measurements and proper weighting factors. Methods for handling multiple observable islands in the external network modeling process are described and simulation tests are carried out on a practical system with realistic complexity. © 1990 IEEE