具备高灵敏性与速动性的柔性直流输电系统纵联保护方案

多端柔性直流输电线路故障的快速识别对电网的安全稳定运行具有重大意义。目前,直流线路纵联差动保护未考虑电容电流的影响,其速动性的欠缺导致其仅用作后备保护。为解决该问题,提出了一种足够灵敏、且能够在超短时间窗内实现故障识别的纵联保护原理。首先,基于贝瑞隆模型,对电容电流进行有效补偿。其次,计及模型法对参数较为敏感这一不利因素,设计了保护浮动门槛。最后,基于区内/外故障情况下电流推演值与原始值间的Hausdorff距离存在差异性的特征,提出了一种多端柔性直流输电线路纵联保护原理。理论分析及仿真结果表明,所提的保护原理能灵敏、可靠地实现区内故障的识别,并且在速动性指标上能够满足柔性直流输电系统的要求。

A pilot protection scheme for an VSC-MTDC system with high sensitivity and rapidity

The rapid internal-fault identification capability of an VSC-MTDC is of great significance for the safety and stability of a power system. At present, DC line differential protection does not take the capacitive current into consideration, and the lack of speed makes it suitable only as a back-up protection. To solve this problem, a novel DC line differential current protection with high sensitivity is proposed. This can identify internal faults within a very short time window. First, the capacitive current is fully compensated based on the Bergeron model. Secondly, an adaptive threshold is set against the high sensitivity of the proposed method to the parameters of the system. Finally, based on the difference of Hausdorff distance between the original measurement and the deduced measurement, a novel DC current differential protection adaptive to the characteristics of the VSC-MTDC is put forward. Theoretical analysis and simulation results indicate that the proposed protection can identify internal fault sensitively and reliably, and the speed is high enough to meet the requirements for fault-isolation of VSC-MTDC systems.This work is supported by the Science and Technology Project of State Grid Corporation of China (No. 5100-201999331A-0-0-00) and National Natural Science Foundation of China (No. 51907069).