基于交直流保护协同配合的交直流碰线保护新方案

交直流混联电网迅速发展，交直流碰线故障成为其特有故障类型。以不同类型交直流碰线故障为研究对象，着眼于故障隔离至线路重合/重启全过程，揭示了现有交直流两系统相关保护出口动作逻辑存在的不足及风险，并进一步提出在交流侧设计并新增交直流碰线保护方案的新思路，通过构造一种可以反映直流系统等值阻抗相角特性的保护算法，实现交直流碰线故障识别。基于此，通过优化交流侧新增的交直流碰线保护和直流侧已配置的交直流碰线保护间的动作时序和逻辑配合关系，实现了交直流碰线故障下直流系统的自适应重启，避免了交流侧重合于永久性故障场景下直流线路首末端发生工频过电压的风险。在PSCAD/EMTDC平台中搭建交直流碰线故障的仿真模型并进行大量仿真实验，仿真结果验证了所提交直流碰线保护新方案的可行性。

A Novel Protection Scheme of AC and DC Line-Touching Based on Coordination of AC and DC Protection

The AC/DC hybrid grid is developing rapidly, and the AC-DC line-touching fault has become an unique fault type. By taking different types of AC and DC line touching faults as the research object, and focusing on the whole process from fault isolation to line reclosing/restarting, the paper explores the deficiencies and risks of existing AC and DC systems in relevant protection outlet action logic, and proposes a new idea for designing and adding a AC-DC line-touching protection scheme on the AC side. By constructing a protection algorithm that can reflect the phase angle characteristics of the DC system equivalent impedance, the AC-DC line touching fault identification is realized. Through optimizing the action sequence and logical coordination relationship between the newly added AC-DC line-touching protection on the AC side and the AC-DC line-touching protection placed on the DC side, the adaptive restart of the DC system is realized under the AC-DC line-touching fault, which avoids the risk of power frequency overvoltage at the head and end terminals of the DC line under the scenario of AC side permanent fault. A simulation model of AC-DC line-touching fault is built in the PSCAD/EMTDC platform, and a large number of simulation experiments are carried out. The simulation results verify the feasibility of the proposed new AC-DC line-touching protection scheme.