内嵌于MMC换流器的多端口直流潮流控制器

A Multiport Embedded DC Power Flow Controller for Modular Multilevel Converter

在柔性直流输配电系统中,由于直流系统易于通过多点馈入、多端成网以解决控制灵活及供电可靠的问题,环状及网状多端柔性直流输配电技术正获得越来越多的关注与研究。为解决柔性直流网络中潮流控制自由度不足问题,需要增加直流潮流控制器以实现潮流优化控制,达到输电走廊堵塞缓解及线损减少的目的。针对基于模块化多电平换流器(modular multilevel converter,MMC)的多端柔性直流网络,提出一种内嵌于MMC的多端口直流潮流控制器(embedded DC power flow controller,e-DCPFC),可实现同一电压等级环状或网状柔性直流电网的潮流控制。其通过对MMC拓扑的衍生实现,具有结构简单及易于多端口扩展的优势,且线路潮流双向可调。该文描述内嵌式直流潮流控制器的拓扑结构及工作原理,提出其与MMC的协同控制策略,在Matlab中搭建仿真模型,通过3种运行工况验证e-DCPFC的可行性及有效性。最后搭建e-DCPFC的原理样机进行实验验证,实验结果证明该直流潮流控制器在各种工况下直流网络潮流控制有效。

In flexible DC transmission and distribution systems,DC system is convenient to solve the problem of flexible control and reliable power supply through multi-point feed-in method and multi-terminal networks.Therefore,concerns and research about ring-type and mesh-type multi-terminal flexible DC transmission and distribution technology have been greatly increased.In order to solve the problem of low control degrees of freedom in flexible DC grids,it is necessary to add DC power flow controller(DCPFC)to realize optimal power flow control,so as to relieve the congestion of transmission corridor and reduce the line loss.Specific to multi-terminal flexible DC network with modular multilevel converter(MMC),this paper presented an embedded DC power flow controller(e-DCPFC)embedded in MMC,with which power flow control capability for ring-type and mesh-type flexible DC grids at the same voltage level can be realized.The controller implemented by derivation of MMC topology has advantages of simple topology structure,convenience for multi-port extension and bipolar regulating capacity.First,the topology of e-DCPFC and its embed method in MMC were presented.Second,based on the detailed analysis of the working principle of e-DCPFC,the coordinated control strategy for e-DCPFC and MMC was proposed.Then,a simulation model was built in Matlab to verify the feasibility and effectiveness of e-DCPFC through three operating conditions.Finally,a principle sample machine of e-DCPFC was built in the lab for experimental verification.The results show that the proposed controller can achieve effective control of power flow under various working conditions.