Modular multilevel converter based high voltage direct current transmission system (MMC-HVDC) is one of the most promising solutions to integrate large amount of offshore wind power. However

the power variation range of offshore wind power is large

and the transmitting end is a system with high degree of power electronics. Therefore

the system is prone to small-signal oscillation instability. This paper proposes a stable control strategy and parameter optimization method for the offshore wind farm connected MMC-HVDC system

taking into account both small-signal stability and voltage control capability within the full power range. Firstly

a small-signal model for the offshore wind farm connected MMC is established. Based on modal analysis and participation factor method

the oscillation modes and the related dominant factors of the system are analyzed. Secondly

this paper proposes an AC voltage proportional control strategy suitable for the wind farm connected MMC to ensure the system small-signal stability within the full power range. Then

an optimization design method for control parameters is discussed to ensure the voltage deviation at the grid connection points meets the system requirements within the full power range. Finally

the effectiveness of the proposed AC voltage proportional control strategy and parameter optimization method are validated by simulation.