Cyber-physical assessment and comparison between centralized and distributed control mode in coordinated substation voltage control

The smart grid is a typical cyber-physical system (CPS) utilizing more advanced information and communication technologies (ICTs), in which hierarchical control system (HCS) plays an essential role. However, it should be noted that for the same control function, HCSs could have multiple modes for making control decisions. They may have different cyber structures and information flows, which could lead to different levels of system reliability under cyber contingency conditions. In this paper, we describe and compare two control modes of coordinated substation voltage control (CSVC), the centralized-control and distributed-execute (CCDE) mode and the distributed mode of centralized-coordinate and distributed-control (CCDC). We first introduce CSVC's control theory, as well as its two application modes. After generating quantitative node-branch cyber-physical models for each, we perform a cyber contingency assessment and compare the results. The computation result shows that distributed mode CCDC is more reliable against cyber contingencies. By comparing their cyber networks, we identify three possible reasons for their differences and propose a simple improvement plan for CCDC, which has proved to be helpful by cyber contingency assessment results.