Abstract: Fundamental frequency modulation-based current source converter (FFM-CSC) does not require a submodule capacitor and many reactive compensation devices and filters. It is expected to become a better choice for offshore wind power DC transmission. However, the existing FFM-CSC offshore wind power delivery scheme has the following shortcomings: 1) The offshore gathering frequency is power frequency, and the light-weight effect is limited; 2) When centralized sending out, once the offshore gathering system fails, AC voltage cannot be established; 3) A lot of communication is required for CSC and wind turbine to coordinate AC voltage control. Therefore, the paper proposes a medium-frequency distributed long-distance offshore wind power HVDC system based on FFM-CSC. Firstly, the topology structure and mathematical model of the scheme are introduced. Then, the strategy of coordinating AC voltage control between offshore CSC and wind farm group without communication is proposed. To solve the DC overvoltage problem caused by the different wind speeds of wind farm stations, the two-terminal DC voltage cooperative control is proposed. A fault ride-through strategy of dual-end CSC cooperative bypass and DC-chopper inside fan is proposed to solve the fault of offshore system. Finally, the scheme is verified by simulation in PSCAD. The results demonstrate the feasibility of the proposed medium-frequency distributed offshore wind power HVDC system based on FFM-CSC and its control strategy.