Abstract: The grid simulator can be used to test the reliability of power electronic grid-connected equipment, and in the process of designing its controller, due to the limitation of multi-controller collaborative processing, the system is complicated and the simulator cannot achieve the expected goal. This paper discusses a secondary control architecture for MMC type power grid simulator controller, which greatly reduces the number of controllers and optical fiber consumption, and meets the consistency and real-time design requirements of 10kHz operating frequency of power grid simulator. The optical fiber transmission system based on SFP and Aurora link layer protocol based on parallel communication based on external memory interface was designed, and a synchronization method based on double phase-locked loop module was proposed for multi-controller synchronization problem, and the corresponding hardware was built and experimental analysis and verification were completed.