As an important topic of power system protection, protection algorithm for transmission lines connecting modular multilevel converter (MMC)-based converter stations has attracted extensive attention. This article proposes a new time-domain pilot protection based on two-dimensional (2-D) space projection of dual differential currents for lines connecting converter stations. The dual differential currents, i.e., original and virtual differential currents, are projected into 2-D space. Subsequently, the dynamic trajectories of dual differential currents under various circumstances are elaborated. On this basis, the nonoperating zone and internal fault index are defined, whereby the criterion of pilot protection is developed. Afterwards, the operating characteristic of the proposed pilot protection is analyzed under various circumstances. The performance of proposed pilot protection is widely assessed using power systems computer aided design (PSCAD) and real time digital simulator (RTDS). The contribution of this article lies in a new time-domain pilot protection based current trajectory of dual differential currents, which exhibits exceptional performance in operating speed, sensitivity, complexity, tolerance to fault resistance, current transformer saturation and abnormal data, and adaptability to operation mode of MMC.

中文翻译：

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基于双差动电流二维空间投影的MMC-HVDC站连接线路先导保护

作为电力系统保护的重要课题，基于模块化多电平换流器（MMC）的换流站输电线路保护算法受到广泛关注。本文针对连接换流站的线路提出了一种基于双差动电流二维 (2-D) 空间投影的新型时域先导保护。双差分电流，即原始差分电流和虚拟差分电流，被投影到二维空间中。随后，详细阐述了双差分电流在各种情况下的动态轨迹。在此基础上，定义了非工作区和内部故障指标，从而制定了飞行员保护的判据。然后，分析了所提出的先导保护在各种情况下的动作特性。使用电力系统计算机辅助设计 (PSCAD) 和实时数字模拟器 (RTDS) 广泛评估建议的飞行员保护的性能。本文的贡献在于提出了一种新的基于双差动电流时域先导保护的电流轨迹，在动作速度、灵敏度、复杂度、故障电阻、电流互感器饱和和异常数据容忍度以及运行适应性方面表现出卓越的性能MMC模式。