直流双极闭锁故障下送端系统暂态过电压计算方法

针对特高压直流输电系统闭锁引起的暂态过电压严重威胁系统安全运行的问题,推导建立了直流双极闭锁后换流母线暂态电压的解析表达式。在此基础上,建立了送端交流系统电力网络等值模型,推导出了直流双极闭锁后送端交流系统内任一关键节点暂态过电压的计算方法。为判断送端新能源节点面临高压穿越问题的严重程度、提前发现系统薄弱环节,提出用阻抗比来表征节点的暂态过电压程度。在直流双极闭锁后节点暂态电压压升值随着阻抗比增大而呈现线性升高的趋势。基于DIgSILENT仿真平台,搭建了CIGRE直流输电标准测试系统和吉泉±1100 kV高压直流送端系统,验证了送端系统暂态过电压计算方法及结论的正确性。

Transient overvoltage calculation method of HVDC sending-end system under DC bipolar blocking

A U-HVDC system’s transient overvoltage caused by DC blocking will threaten the safe operation of a system.Thus an analytic formula calculating transient voltage of the commutation bus after DC bipolar blocking is derived.Based on this,the equivalent model of the power network of the sending-end system is established,and the transient overvoltage calculation method of any key node of the AC system is derived.In order to judge the severity of the high voltage crossing problem faced by the new energy node and find the weak link of the system in advance,the impedance ratio is proposed to represent the transient overvoltage degree of the node.The voltage rise value of the node transient voltage increases linearly with the increase of the impedance ratio after DC bipolar blocking.Finally,the CIGRE HVDC standard test system and the Jiquan±1100 kV DC transmission sending system are set up in the DIgSILENT simulation platform to verify the correctness of the transient overvoltage calculation method of HVDC sending-end system.