中文摘要：

直流电网已经成为柔性直流输电领域的研究热点之一。针对直流电网潮流控制自由度不足的问题,提出了一种基于模块化多电平换流器（modular multilevel converter,MMC）的新型直流潮流控制器（modular multilevel converterdirect current power flow controller,MMC-DCPFC）,其具有额定容量小、不需与外部电源连接和便于扩展等优点。首先,针对已有的直流潮流控制器的不足,提出了基于MMC的新型直流潮流控制器的拓扑结构及在直流系统中的安装方式;其次,通过对MMC-DCPFC的工作原理的分析,提出了满足系统要求的控制策略;最后,在PSCAD/EMTDC仿真平台搭建含有直流潮流控制器的三端直流输电系统,通过对3种工作方式的仿真实验,验证了该直流潮流控制器在控制直流系统潮流方面具有良好的可控性和有效性。

英文摘要：

DC power grid becomes a research hotspot of flexible HVDC system. In order to solve problem of low control degrees of freedom in DC power flow control, this paper presents a new type dc flow controller based on modular multilevel converter（MMC）. The controller has advantages of lower rated capacity, no external power connection and convenience for expansion. Aiming at shortcomings of existing dc current controller, topology and installation mode of MMC-direct current power flow controller（MMC-DCPFC） are presented. Control strategy meeting system requirements is put forward by analyzing MMC-DCPFC working principle. Finally, three-terminal HVDC system with DC power flow controller is established in PSCAD/EMTDC simulation platform to verify effectiveness and controllability of the MMC-DCPFC.