并联型多端直流输电金属回线运行方式*

并联型多端直流输电系统换流器故障后,采用金属回线运行可减小接地极引线电流。与两端直流输电不同的是,并联型多端直流输电系统的金属回线运行方式非常多。以四端并联型多端直流为例,按1～3个换流器故障分类,分别介绍各金属回线运行方式。分析金属回线运行时电流流向。提出在并入开关站的换流站之间采用3根输电线路设计,使得任一换流器故障后均有金属回线运行方式。分析多端系统中换流站共用接地极线的金属回线电流情况,对金属回线电流测点的配置进行建议。

Metallic Return Modes in Parallel Type Multi-terminal HVDC Transmission

When a fault occurred in the converter of a parallel type multi-terminal HVDC (MTHVDC), a metallic return mode (MRM) is usually used to decrease the current of electrode line. Different from the two-terminal HVDC, there are many MRMs in the parallel type MTHVDC. Taking a four-terninal shunt HVDC as an example, this paper introduces its MRMs in the cases where one to three of the converters are faulted, and analyzes the current in the metallic return. A design of three transmission lines adopted between two stations is proposed in order to ensure a MRM available for the system when any converter is faulted. This paper also discusses the current of metallic return for the common electrode line in a MTHVDC system, and puts forward suggestions for the position of current measurement in the metallic return, and puts forward suggestions for the configuration of current test points in the metallic return.