Concavity-convexity of distribution system security region. Part I: Observation results and mechanism

Abstract

This paper observes the concavity-convexity of the distribution system security region (DSSR) and explains the observation results. Firstly, DSSR is observed in 2D space, and more complex 2D images are newly discovered. Secondly, to explain how the new images are formed, the concave regions are observed in 3D space, and their inner space and surface characteristics are discovered by convex decomposition. There are two kinds of concave regions, i.e., simple-concave regions and complex-concave regions. The former is only a backup region, while the latter also contains a sectional region covering the surface of the backup region, partially compensating for the dent of the former. Thirdly, based on the load transfer after an N-1 contingency, the mechanisms of the concave regions and new images are revealed. It is found that a concave region is generated by the union of sub-regions formed from multiple load transfer paths. Finally, the observation results and mechanisms are tested on an expanded IEEE RBTS-Bus4 case. This paper is the first in a two-part series on the concavity-convexity of DSSR. It reveals the concave-convex characteristics and mechanisms of DSSR through direct observation, which lays a theoretical foundation for security assessment and optimal control based on DSSR. Part Ⅱ will reveal the concave-convex principle of DSSR through mathematical deduction.