采用余弦相似度的混合三端直流输电线路保护原理

Cosine Similarity-Based Protection of Hybrid Three-Terminal DC Transmission Line

为提高混合三端直流输电线路保护的可靠性、选择性、速动性和灵敏性,根据输电线路发生故障时电压和电流的变化差异,提出了一种基于余弦相似度算法的线路保护原理。该原理利用输电线路T区三端电流暂态分量构成故障区域选择判据;再将故障线路单端电流、电压故障分量进行数据标准化处理,利用两者余弦相似度的差异,完成区内、外故障及故障极识别。使用PSCAD/EMTDC搭建混合三端高压直流输电线路模型,运用Matlab对所提保护原理进行仿真验证。仿真结果表明:所提保护原理在不同故障情况下,均可在3 ms内识别故障,可靠性高、速动性好;可耐受500Ω过渡电阻,具有较强的耐过渡电阻能力;在20 dB噪声情况下,依旧可以识别故障,具有较强的抗噪声干扰能力。

To improve the protection reliability,selectivity,rapidness and sensitivity of the hybrid three-terminal DC transmission line,this paper proposes a line protection principle based on the cosine similarity algorithm according to the voltage and current fault characteristics of the transmission line.The principle uses the transient current components of three terminals in T-area to form the fault area selection criterion to realize fault area identification.Then data normalization is performed on the single-end current-voltage fault component of the fault line,and the difference in cosine similarity between the two is used to identify internal or external fault and fault pole.A hybrid three-terminal HVDC transmission line model is established in PSCAD/EMTDC,and the proposed protection principle is simulated and verified in MATLAB.The simulation results show that the proposed protection principle can identify faults within 3 ms under different fault conditions,with high reliability and good rapidity;it can withstand 500Ωtransition resistance,with strong resistance to transition resistance;it can still identify faults under 20 dB noise,with strong resistance to noise interference.