适用于直流电网的环流式线间直流潮流控制器

A Circulating Current Interline DC Power Flow Controller for DC Grid

针对直流电网潮流控制自由度不足的问题,提出一种线间直流潮流控制器(I-PFC)。I-PFC能够通过交流环流实现自身功率平衡,无需交流变压器作为内部的交流通路,且与现有线间直流潮流控制器相比,进一步降低了因单个电容充放电造成的电流波动,具有避免额外谐振、减小谐波、易拓展等优点。首先,提出I-PFC的拓扑结构,分析实现潮流控制的方法进而得到线路电流与串入电压的关系,并重点介绍了利用内部交流环流实现自身功率平衡的原理;其次,根据I-PFC的功率与能量,详细分析子模块电容电压的组成,其中主要包含直流、基频和二倍频分量,并设计包括直流潮流控制和功率平衡控制的I-PFC控制方法;最后在PSCAD/EMTDC仿真环境中搭建含有I-PFC的三端柔性直流环网,利用投入运行、反向调节和动态响应三个工况验证了该文所提出的I-PFC的可行性和有效性。

Aiming at the problem of insufficient free degree of power flow control in DC grid,this paper proposes a novel interline DC power flow controller(I-PFC).I-PFC can realize the power balance through the AC circulating current without AC transformer as AC internal pathway.Compared with the existing interline DC power flow controller,it further reduces the current fluctuation caused by charging and discharging of a single capacitor,and has the advantages of avoiding additional resonance,reducing harmonics and expanding easily.Firstly,the topology of I-PFC was proposed,and the method of power flow control was analyzed.Then the relationship between line current and series voltage was obtained,and the principle of power balance using internal AC circulating current was introduced.Secondly,according to the power and energy of I-PFC,the capacitor voltage of sub-module was analyzed in detail.It mainly consisted of DC,fundamental frequency and two frequency doubling components.The control strategy including DC power flow control and power balance control was designed.Finally,a three-terminal ring VSC-HVDC including I-PFC was built in PSCAD/EMTDC.The feasibility and effectiveness of the proposed I-PFC were verified by input operation,reverse regulation and dynamic response.