(1. Global Energy Interconnection Research Institute, Beijing 102211, China; 2. State Key Laboratory of Advanced Power Transmission Technology, Beijing 102211, China; 3. Beijing Key Laboratory of DC Grid Technology & Simulation, Beijing 102211, China)

First, the basic control strategy of a modular multilevel converter(MMC)based high voltage direct current(MMC-HVDC)transmission system is studied. Then, the characteristics of the back-to-back MMC-HVDC transmission system is analyzed, which can provide synchronous control signal sharing between sending and receiving ends so as to realize delay-free sharing of control signal at two sides of the converter. On this basis, according to the application requirements of MMC based back-to-back high voltage direct current transmission system, a control strategy is proposed. Finally, the effectiveness of the control strategy is verified by digital simulation via PSCAD/EMTDC. This work is supported by State Grid Corporation of China(No. 2014GW-05).