基于MMC-HVDC并网风电系统的无功功率支撑研究

Study on Reactive Power Support of Grid Connected Wind Power System Based on MMC-HVDC

为研究柔性直流输电方式对并网双馈风力发电系统的无功功率支撑作用,在分析双馈风力发电并网系统、模块化多电平换流器(modular multilevel converter,MMC)高压直流输电系统工作原理的基础上,在实时数字仿真(real time digital simulator,RTDS)平台上进行系统建模研究,其中MMC-HVDC系统的整流侧换流站采取定有功和无功功率控制,逆变侧采用定直流电压控制。基于MMC-HVDC的并网双馈风力发电系统模型,研究交流电网处发生故障时,由风电系统内部"背靠背"换流器与MMC-HVDC系统两端换流器的协调交互控制维持直流电压的稳定,满足风电系统无功功率的需求。结果表明换流站间的协调控制策略较好地补偿风电系统的无功功率,同时验证了双端换流站所采取控制策略的有效性。

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.