基于开关函数的晶闸管整流器差动保护新方法

A New Differential Protection Method of Thyristor Converter in Rectifier Station Based on Wwitching Function

高压直流输电系统中,针对传统换流器直流差动保护在交流侧发生接地故障时保护范围模糊的问题,文中以整流器为研究对象,提出了一种基于开关函数的整流站晶闸管换流器差动保护新方法。首先,分析了基于换流阀导通特性的开关函数模型,建立了交流三相电流和直流电流的平衡关系,以区分换流器的内部和外部故障;然后,利用交流侧电流互感器两侧接地故障时零序电流的差异,明确了换流器保护的交流侧边界。最后,通过PSCAD仿真将该保护和传统直流差动保护进行了比较,结果表明:该保护可有效解决传统直流差动保护拒动于区内相间短路故障及误动于变压器引出线接地故障的问题。

The HVDC transmission system consists of the DC side high-voltage terminal current and the non-neutral terminal current,which form the protective concept of conventional converter differential protection.It can act solely on a ground failure,but can be induced by an accident of a ground failure.Therefore,this paper considers the rectifier as a topic of research and provides a new technique of current diff erential protection for thyristor transformers.The first is to examine the converter's conduction properti es.The balance between AC 3-phase current and DC is formed based on the modulating models to iden tify internal and external failures of the converter,and the protection limit when the AC side of the conv erter is founded is not obvious.The converter's alternating current(AC)side is not visible.The difference between zero sequence currents on both sides of the AC side current transformer is used to define the AC side of the converter in order to validate the AC side of the converter security.Lastly,the PSCAD simulation co mpares protection with classical protection for the DC differential.The results indicate that the protectio n is capable of solving the issue that the classic DC differential protection cannot work properly on the short-circuit failure phase-to-phase and the main transformer wire ground failure.