With the growing demands for flexible power supply, dc grids outstand with the advantages of simple structure, high efficiency and large capacity. However, the dc fault protection is one of the most critical issues in restriction of dc grids. The fault current interruption time of the existing dc circuit breakers (DCCBs) rises along with the increase of fault distance and a vast amount of energy would be dissipated in the DCCBs. To overcome these problems, this brief proposes a multiterminal active resonance circuit breaker (MAR-CB), which contains a converter-side breaker (CSB) for each modular multilevel converter (MMC) as well as multiple line-side breakers (LSBs) and ultra-fast disconnectors (UFDs) for dc lines. During the dc fault interruption, a reverse current is generated by the resonance of the CSB and LSB to extinguish the UFD arc. Afterwards, the converter-side current is interrupted by the CSB, while the line-side current is interrupted by the LSB. The proposed MAR-CB can handle the dc fault with the advantages of short interruption time, reduced energy dissipation, low conduction loss and absence of additional pre-charge dc source. A four terminal dc grid is simulated with PSCAD/EMTDC to verify the effectiveness of the MAR-CB and a down-scale prototype experimentally confirms the performance of fault interruption.

中文翻译：

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基于模块化多电平换流器的直流电网的多端有源谐振断路器

随着对灵活供电需求的日益增长，直流电网以其结构简单、效率高、容量大等优点脱颖而出。然而，直流故障保护是直流电网限制中最关键的问题之一。现有直流断路器（DCCB）的故障电流中断时间随着故障距离的增加而增加，大量的能量会在DCCB中耗散。为了克服这些问题，本简报提出了一种多端有源谐振断路器 (MAR-CB)，其中包含用于每个模块化多电平转换器 (MMC) 的转换器侧断路器 (CSB) 以及多个线路侧断路器 (LSB) 和用于直流线路的超快速隔离开关 (UFD)。在直流故障中断期间，CSB和LSB的谐振产生反向电流以熄灭UFD电弧。之后，转换器侧电流被 CSB 中断，而线路侧电流被 LSB 中断。所提出的 MAR-CB 可以处理直流故障，具有中断时间短、能量耗散减少、传导损耗低和不需要额外的预充电直流电源等优点。使用 PSCAD/EMTDC 模拟四端直流电网以验证 MAR-CB 的有效性，并通过缩小规模的原型实验确认故障中断的性能。