计及换流站控制响应的多端混合直流线路后备保护设计

多端混合直流系统故障暂态过程受直流控制响应的影响较大，针对其线路故障特征的分析和保护原理的研究，应当充分计及直流控制特性的影响。为此，根据多端混合直流系统的特点，计及故障后不同换流站的控制响应过程，对其直流线路故障暂态电流的变化趋势关系进行研究分析。并基于此提出了基于滑窗均值电流的多端混合直流线路区内、区外故障识别判据，给出了具体的保护方案。通过PSCAD/EMTDC对所提保护方案的可行性进行了仿真验证。仿真结果表明，所提方案能够可靠识别包含T接汇流母线在内的各种直流线路故障，天然具有故障选极能力，耐受故障过渡电阻能力和抗噪声干扰能力强，且无需数据同步，可作为多端混合直流线路的快速后备保护。

Backup protection design for multi-terminal hybrid HVDC lines considering control response

The fault transient process of a multi-terminal hybrid HVDC system is affected greatly by DC control response. The impact of DC control characteristics should be taken into consideration in the analysis of line fault features and research on the protection principle. Based on the characteristics of this type of HVDC system and the control response of different converter stations, the variation tendency relationship between fault transient currents after a DC line fault occurs is studied and analyzed. Then the fault identification criterion based on the sliding mean currents to identify the DC characteristics of internal and external line fault is proposed, and a specific protection scheme is presented. The validity of the proposed protection scheme is verified by PSCAD/EMTDC simulation. The results show that the proposed scheme can quickly and correctly identify line faults including on the T-junction DC bus. It can be implemented with superior performance for a fault transition resitance and with noise interference. Synchronous data is not needed. With fault pole selection capability, the proposed scheme qualifies as fast backup protection for multi-terminal hybrid HVDC transmission lines. This paper is supported by the National Natural Science Foundation of China (No. 52077082).