交流侧接地方式对多端柔性直流配电网保护配置的影响

  目的]  为了提高多端环形柔性直流配电网的供电可靠性，研究了交流侧不同接地方式下的故障特征及其对保护配置的影响。  方法]  首先确定了两电平、模块化多电平等不同类型换流设备的交直流故障等效通路，从故障过压、过流水平及故障恢复等方面分析了不同接地方式下交直流不对称故障对保护配置的影响。随后从保护原理配置、定值整定、出口方式及配合原则等方面，给出了多端环形柔性直流配电网典型保护配置方案。最后，在PSCAD/EMTDC仿真软件下搭建了三端柔性直流配电网的电磁暂态模型。  结果]  仿真结果表明:当交流侧采用高电阻接地方式时，通过合理的保护配置可提高交流不对称故障时系统的稳定性、实现直流不对称故障的零停电时间故障穿越。  结论]  研究成果为多端柔性直流配电网的接地方式设计、保护配置研究提供了一定参考。

Effect of AC-side Grounding Mode on Protection Configuration of Multi-terminal Flexible DC Distribution Network

  Introduction]  The paper aims to improve the reliability of the multi-terminal circular flexible DC distribution network, the characteristics of the fault in the different grounding mode of the AC side and its influence on the protection configuration are studied. The fault characteristics of multi-terminal circular flexible DC distribution network under different AC grounding modes were studied, and the impact on protection configuration had been given.  Method]  First of all, the equivalent AC/DC fault path of two-level and modular multi-level converter equipment was determined, and the influence of different grounding modes were analyzed from the aspects of fault overvoltage, overcurrent level and fault recovery. Then from the aspect of protection principle configuration, setting value setting, export mode and cooperation principle, the typical protection configuration scheme of multi-terminal circular flexible DC distribution network was given. Finally, the electromagnetic transient model of the three-terminal flexible DC distribution network was established under the PSCAD /EMTDC simulation software.  Result]  The simulation results show that when the AC side adopts a high resistance grounding mode, a reasonable protection configuration can improve the stability of the system when the AC asymmetrical fault occurs, and achieve zero interruption time fault ride through when the DC asymmetrical fault occurs.  Conclusion]  The research provides some reference for the design of grounding mode and the research on protection configuration of flexible multi-terminal DC distribution network.