基于改进相对距离偏差系数的海上风电柔性低频送出线路时域纵联保护OA

The fault response characteristics of offshore flexible low-frequency AC transmission systems differ significantly from those of traditional synchronous generator based power systems,which may cause malfunction of conventional current differential protection.To address this issue,this paper conducts an in-depth analysis of the current curve characteristics formed by the currents at both ends of a flexible low-frequency transmission line,and proposes a relative distance deviation coefficient-based pilot protection(RDDC-PP)method.The proposed method can accurately identify internal faults and exhibits inherent robustness against abnormal data and current transformer(CT)measurement errors.Furthermore,the Lorentz transformation is employed to improve the current trajectories,and an improved relative distance deviation coefficient-based time-domain pilot protection(IRDDC-PP)method is developed.An adaptive parameter α is also designed to enhance the robustness of IRDDC-PP to disturbances such as synchronization errors and Gaussian white noise.The proposed method is validated using a digital-physical co-simulation platform.Simulation results demonstrate that the proposed method operates accurately under various fault resistances,fault locations,fault types,and sampling frequencies.In addition,it exhibits strong robustness against disturbances such as CT measurement errors,abnormal data,noise,and synchronization errors.Compared with existing methods,the proposed approach achieves superior performance in terms of speed,sensitivity,dependability,and security.