【摘要】 针对双极柔性高压直流系统阀交流侧接地故障产生的故障电流无过零点的问题，分析了故障端换流器闭锁后故障端和非故障端故障电流的特征，推导了解析表达式，得到了非故障端判断对侧接地故障的判据及保护方案。由于反向穿越零点的电弧电流有利于交流断路器弧隙介质绝缘能力的恢复，分析了故障后降低直流电压对阀交流侧故障电流反向穿越零点的影响，提出了非故障端退出运行后故障端直流侧非接地极经电阻接地的保护方案，推导了限流电阻与阀交流侧故障电流的表达式。最后在PSCAD/EMTDC平台上进行了仿真计算，结果表明，通过非接地极经电阻接地的方式不仅可以使换流变压器阀侧故障电流反向穿越零点，还可以避免换流变压器出现三相短路的情况。更多还原

【Abstract】 To address the issue that fault currents caused by grounding faults on the valve AC side of bipolar VSC-HVDC systems have no natural zero-crossing points, the characteristics of fault currents at both the faulty and healthy terminals after converter blocking at the faulty end are analyzed. Analytical expressions are derived, and a criterion and corresponding protection scheme for the healthy terminal to identify grounding faults on the opposite side are obtained. Since arc currents that reverse and pass through a zero crossing are beneficial for restoring the dielectric strength of the arc gap in AC circuit breakers, the impact of reducing DC voltage after a fault on the reverse zero-crossing behavior of valve AC-side fault currents is investigated. Based on this, a protection scheme is proposed in which, after the healthy terminal is taken out of operation, the non-grounded pole on the DC side of the faulty terminal is grounded through a resistor. The expressions for the current limiting resistor and the valve AC-side fault currents are derived. Finally, simulations are performed on the PSCAD/EMTDC platform. The results demonstrate that grounding the non-grounded pole through a resistor can not only enable reverse zero-crossing of valve-side fault current of the converter transformer, but also effectively prevent the occurrence of three-phase short circuits in the converter transformer.更多还原