Research on black start and collaborative control strategy of DRU-HVDC offshore wind farm system
With the shift of wind power development from onshore and inshore to distant offshore,the wind power integration scheme based on diode rectified DC transmission has become one of the research highligths due to its economic advantages.Due to the unidirectionality of diode power transmission,offshore wind farms cannot rely on onshore power grids for start-up.In this case,wind turbines adopt grid-forming control can realize the black start for the offshore wind farm.First,the structure and characteristics of the diode rectified DC transmission system for offshore wind power was analyzed,and then a control strategy for DFIG with the function of dual-mode switching which is suitable for this scenario was proposed.Next,the phase presynchronization strategy of wind turbines during process of grid connection was studied.On this basis,a black start strategy for offshore wind farms was proposed.Then,a layered control structure for offshore wind farms was designed,and a collaborative control strategy based on high-speed communication and mode switching was proposed considering the N-1 fault condition.At last,the simulation model of the offshore wind farm transmission system through diode rectification was established in matlab/simulink.The process of the offshore wind farm black start and the N-1 fault condition were simulated,the simulation results verify the effectiveness of the proposed black start strategy and collaborative control strategy for N-1 fault.
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