DC circuit breaker (DCCB) is one of the most promising solutions for handling DC fault in half-bridge modular multilevel converter (MMC)-based DC grid. Generally after fault isolation, DCCBs are required to have the ability to quickly reclose so as to restore power transmission. However, the traditional simultaneous reclosing scheme may make the whole system suffer from secondary strikes such as overvoltage and overcurrent in the event of permanent faults. To solve this problem, many adaptive reclosing schemes have been proposed. Among them, the sequential reclosing scheme can achieve rapid recovery without laying any burden on the sampling and protection system. Unfortunately, secondary strikes under a reclosing failure still exist though they can be suppressed. Due to this, this paper illustrates that the overcurrent protection-based fault identification method is not able to identify the fault in time, and thus the secondary strikes are generated during the second tripping. Optimal configuration of DCCBs' parameters can reduce these adverse impacts but cannot avoid them. Based on this, an adaptive reclosing scheme is proposed. Permanent and temporary faults are recognised according to the voltage characteristics at the beginning of the fault line as soon as the arresters are conducted. Extensive simulations on a four-terminal DC grid in PSCAD/EMTDC show that the proposed method can eliminate the potential adverse impacts and is robust to fault resistance.

中文翻译：

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基于MMC的直流电网中混合高压直流断路器的自适应顺序重合闸策略

直流断路器 (DCCB) 是处理基于半桥模块化多电平转换器 (MMC) 的直流电网中直流故障的最有前途的解决方案之一。一般在故障隔离后，要求直流断路器具有快速重合闸的能力，以恢复输电。然而，传统的同时重合闸方案在发生永久性故障时可能会使整个系统遭受二次冲击，例如过压和过流。为了解决这个问题，已经提出了许多自适应重合闸方案。其中，顺序重合闸方案可以实现快速恢复，而不会给采样和保护系统增加任何负担。不幸的是，重合闸故障下的二次冲击仍然存在，尽管它们可以被抑制。由于此，本文说明基于过流保护的故障识别方法不能及时识别故障，从而在二次脱扣时产生二次雷击。DCCBs参数的优化配置可以减少这些不利影响，但不能避免它们。在此基础上，提出了一种自适应重合闸方案。避雷器导通后，根据故障线开始处的电压特性识别永久性和暂时性故障。在 PSCAD/EMTDC 中对四端直流电网进行的大量仿真表明，所提出的方法可以消除潜在的不利影响，并且对故障电阻具有鲁棒性。DCCBs参数的优化配置可以减少这些不利影响，但不能避免它们。在此基础上，提出了一种自适应重合闸方案。避雷器导通后，根据故障线开始处的电压特性识别永久性和暂时性故障。在 PSCAD/EMTDC 中对四端直流电网进行的大量仿真表明，所提出的方法可以消除潜在的不利影响，并且对故障电阻具有鲁棒性。DCCBs参数的优化配置可以减少这些不利影响，但不能避免它们。在此基础上，提出了一种自适应重合闸方案。避雷器导通后，根据故障线开始处的电压特性识别永久性和暂时性故障。在 PSCAD/EMTDC 中对四端直流电网进行的大量仿真表明，所提出的方法可以消除潜在的不利影响，并且对故障电阻具有鲁棒性。