Security Evaluation under N-1 for Active Distribution Networks Coordinated with Transmission Grid

With the rapid development of smart grid technology, the distribution networks become more active, and the coordination between transmission and distribution grids becomes more significant. To achieve an accurate analysis for distribution grids considering the impact of transmission grids, this paper presents a practical security evaluation process under N-1 for active distribution networks (ADNs) coordinated with transmission grids. A linearized ADNs load restoration model is given to calculate the restored load after N-1. In order to consider the coordinated operation of transmission and distribution networks, the distributed global power flow (GPF) based on the master-slave-splitting method is used to calculate the power flow. The index for security evaluation of ADNs is established in power-lost load and voltage deviation aspects. The proposed evaluation process was tested in an integrated transmission and distribution test system. Results of numerical simulation showed the rationality of load restoration model and the validity of the proposed evaluation method.