For studying the reactive power support of flexible DC transmission mode to the grid connected doubly fed wind power generation system

the study of system modeling is performed on the real time digital simulation（RTDS） platform on the basis of operating principle of HVDC system of modular multilevel converter（MMC）

in which the converter station at the rectifier side of MMC-HVDC system adopts the active and reactive power control. The inverter adopts constant DC voltage control. On the basis of grid connected double feed wind power generation system model of MMC-HVDC

the coordination control of"back to back"converter and inside the wind power system and converter at both ends of MMC-HVDC system in case of fault at the AC grid is studied so to maintain DC voltage stability and meet the requirement of reactive power of wind power system. It is shown by the result that the coordination control strategy between converter stations can compensate better the reactive power of the wind power system and

at the same time

the effectiveness of the control strategy adopted for the two end converter stations is verified.