UHVDC换相失败对差动保护的影响及解决方法

The Impact of Differential Protection during UHVDC Commutation Failure and Its Solution

交直流混联系统中,交流系统发生故障时导致直流系统侧发生换相失败,交流侧在故障工况下的电气特征发生较大差异,使得交流输电线路差动保护的动作量和制动量均受到影响,可导致保护的误动作.通过分析换相失败时直流侧电流馈入交流系统引发的电流相角差差异较大这一故障特征,提出一种改进的差动保护新算法.通过故障分析和PSCAD/EMTDC仿真验证,改进的差动保护在各种故障情况下均能正确动作.

In the AC/DC hybrid system,the failure of the AC system will cause the commutation failure of the DC system,resulting in a large variation in the electrical characteristics of the fault conditions.It is making the amount of action and amount of brake of differential protection misoperation in the AC transmission line.In this paper,differential protection operation characteristics of hybrid system is analyzed,and compared with the traditional differential protection criterion.An improved traditional differential protection algorithm is proposed,by using the current phase angle quite different characteristics of the fault when the DC system causes the commutation failure with DC current feed,so that protection an correctly distinguish between internal and external failures.Through failure analysis and EMTDC/PSCAD simulation,improved differential protection in all kinds of fault conditions can operate correctly.