This letter analyzes the mechanism of commutation failures (CFs) caused by sending end AC faults. It is founded that the dc impulse current after fault clearance is the direct reason of CF occurring under nonserious sending end AC faults, and the controller interaction is the main reason of CF occurring under severe sending end AC faults. Moreover, a prevention strategy is proposed based on the revealed mechanism, and the validity is verified by the simulation results.

中文翻译：

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发送端交流故障导致LCC-HVDC换相失败的机理及预防

这封信分析了由发送端AC故障引起的换向故障（CF）的机制。研究发现，故障清除后的直流冲击电流是CF在非严重发送端AC故障下发生的直接原因，控制器的相互作用是CF在严重发送端AC故障下发生的主要原因。此外，基于所揭示的机制提出了一种预防策略，并通过仿真结果验证了其有效性。