Observation of Security Region Boundary for Smart Distribution Grid

This paper observes the boundary of distribution system security region (DSSR). DSSR is defined as a set of all the operating points satisfying N-1 security constraints. First, the basic concepts of N-1 security are introduced for distribution system under smart grid background. Then, the dividing phenomenon of operating points security is reported, which indicates that DSSR boundary of a given distribution network exists. Moreover, an approximation method based on N-1 simulation is proposed in order to find DSSR boundary. Then, the observation results of the DSSR boundary are presented for the expanded reliability Busbar test system BUS4 case. The topological characteristics of DSSR boundary are further summarized, which show that the DSSR is a dense set and its boundary is approximately linear. This paper indicates the existence of DSSR and gives a method to observe it. Finally, the benefit of DSSR is illustrated by its typical applications.