张北柔直电网直流分压器二次电压测量异常引起误闭锁机理分析及改进措施

针对张北柔直电网试验示范工程某±500 kV换流站系统调试期间发现直流电压测量异常导致换流器误闭锁事件,通过对站内直流分压器结构及设计原理进行分析,研究了换流器误闭锁机理.发现直流分压器物理结构存在一定设计缺陷,直流分压器二次分压板二次测量电缆1路断线情况下,引起另外2路测量电压异常升高,达到柔直电网直流控制保护系统过电压保护定值,换流器误闭锁.针对存在的问题,分别从硬件和软件2个方面提出了改进措施并加以验证,有效地解决了直流分压器二次故障引起电压测量异常以致闭锁换流器的问题,为柔直电网中直流分压器的设计和选型提供了参考.

Mechanism analysis and improvement measures of error block caused by abnormal secondary voltage measurement of DC voltage divider in Zhangbei flexible DC grid

During the commissioning of a ±500 kV converter station in Zhangbei flexible DC grid test and demonstration project, it is found that the abnormal DC voltage measurement lead to the error block of the converter. By analyzing the structure and design principle of the DC voltage divider in the station, the error block mechanism of the converter is studied. It is found that the physical structure of the DC voltage divider has certain design defects. Under the condition that the secondary measurement cable of the secondary voltage divider of the DC voltage divider is disconnected in one line, the measured voltages of other two lines are abnormally increased, reaching the fixed value of overvoltage protection of the DC control and protection system of the flexible DC grid, and the converter is mistakenly locked. In view of the existing problems, the improvement measures are proposed and verified from both the hardware and software aspects, which effectively solves the problem of error block of the converter caused by the abnormal secondary voltage measurement. A reference for the design and selection of DC voltage divider in flexible DC grid is provided.