Research On Control Strategy Of Offshore Wind Farm Integration Via VSC-HVDC

For the limitation of large capacity and long distance, the offshore wind farm is usually connected with system by the flexible DC. For doubly fed wind machine connected to grid via flexible HVDC system, the 3 control systems of wind machine, send side converter station, side converter station system need coordination. Power output from doubly fed wind machine affected by wind speed change, however, the traditional constant ac voltage/constant active power control can not realize the maximum power transmission. Ry comparing operating characteristics of system under infinity control mode, constant ac voltage/constant active power control, and ac voltage dq component control, infinite control mode as the most suitable for wind power grid system is put forward. it is concluded that the infinity control method, is able to ensure the voltage stability of wind farms export,and at the same time, wind farm power are transmitted through the dc system as much as possible.With the increase of wind power penetration, in order to improve the security and stability of the power grid, research on low voltage ride through control strategy emerge in endlessly, however, there are few works on systematic summary and comparison of various methods. For wind farm system connected to grid through flexible DC, the problem that how to select a low voltage ride through strategy is followed. Through the simulation analysis of various low voltage ride through strategy control effect on the Matlab/Simulink platform, their strengths and weaknesses are analyzed and evaluated from six aspects, such as dc voltage rise during the fault, pressure on wind turbines, ride-through reliability, stability returns time of transmission power by the receiving end converter, investment size, and adaptive wind turbines type, so as to provide a reference for the selection of the low voltage ride through strategy of the wind farm connected to grid through the flexible HVDC system.