This paper presents a topology of a DC grid with multi-voltage levels which is suitable for the system with large scale offshore and onshore distributed renewable generations in China. The advantages of the topology are analyzed. Control strategies for starting-up

fast power flow distribution

DC fault isolating and converter station tripping off are proposed. The simulation model of the DC grid is built using the PSCAD/EMTDC software tool. Simulation results validate the effectiveness of the proposed control strategies for flexible and reliable operation of the presented DC grid. This work is supported by National Natural Science Foundation of China (No. 51261130484) and State Grid Corporation of China (No. 2013-304).