Circulation and Its Influence on Meshed Multiterminal DC Distribution System

The application demands of direct current distribution continue to increase owing to the development of DC transmission technologies and modern distribution systems. In netted multiterminal DC distribution systems, system circulating currents often occur because of the different positive and negative line parameters. In this study, the steady- state equivalent circuit model of four-terminal grid DC distribution system is established, and the mathematical expression of system circulation is theoretically derived. The variation characteristics of circulating currents caused by inconsistencies of positive and negative circuit parameters are quantitatively analyzed. The adverse effects of the system circulating currents on the operation and protection of the DC distribution system combined with the possible parameter changes in the actual power network are analyzed. On this basis, several feasible solutions are discussed, and the above- mentioned analyses are verified by MATLAB and PSCAD/EMTDC simulation.