High-frequency voltage oscillation occurs at the initial stage of DC short-circuit fault in the modular multilevel converter (MMC)-based high-voltage direct-current systems, which directly threatens the reliable operation of the secondary equipment in DC circuit breakers (DCCBs). Therefore, this paper focusses on the voltage oscillation characteristic at DCCB terminals, considered the stray parameters of connecting lines, the parasitic parameters of main equipment and the impedance of grounding grid, established equivalent circuit models of MMC-HVDC converter station at the initial stage of pole-to-pole and pole-to-ground fault, and obtained the analytical formula for the voltage oscillation frequency. Then, the comparison with the DC short-circuit test data of ±200 kV MMC-HVDC converter station verified the validity of the models and revealed the mechanism of voltage oscillation. Finally, the influence of the parameters of the converter station on the oscillation characteristics was discussed. It was proposed to install the DCCB at the MMC valve's terminal near the DC side, and the oscillation frequency is about 10–60 kHz, which is more than 5 times lower than that at the DC reactor's terminal near the DC pole bus, and the disturbance of oscillation to DCCB was alleviated.

中文翻译：

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直流故障暂态过程中直流断路器端子电压振荡的分析与抑制

基于模块化多电平换流器（MMC）的高压直流系统直流短路故障初期会出现高频电压振荡，直接威胁直流断路器（DCCB）二次设备的可靠运行). 因此，本文着眼于DCCB端电压振荡特性，考虑连接线路杂散参数、主设备寄生参数和接地网阻抗，建立了MMC-HVDC换流站初期等效电路模型。极对极和极对地故障，得到电压振荡频率的解析公式。然后，与±200 kV MMC-HVDC换流站直流短路试验数据对比，验证了模型的有效性，揭示了电压振荡机理。最后讨论了换流站参数对振荡特性的影响。建议在靠近直流侧的MMC阀端安装DCCB，其振荡频率约为10~60 kHz，比靠近直流极母线的直流电抗器端低5倍以上，且减轻了对 DCCB 的振荡干扰。