一种适用于深远海全直流风电汇集网络的保护方法

随着海上风电向深远海发展，全直流型风电场由于不存在过电压问题等优点逐渐受到重视。针对全直流海上风电场的汇集线路继电保护问题，首先分析了直流汇集网络在不同故障类型及不同故障位置下的故障特征，计算对应故障情况下的故障电流，并与仿真值进行对比验证。根据故障特征提出一种利用汇集侧暂态电流变化率的单端量故障选线方案，利用区内外故障的故障暂态电流变化率极性和幅值差异，可在换流器过流闭锁前快速识别故障类型、故障线路及极性。通过在母线处设置附加选线流程，使线路末端高阻接地故障时也能准确选线。在PSCAD/EMTDC平台中搭建了全直流海上风电场模型，进行多种故障场景下的仿真分析，验证了所提故障选线方法的有效性。

A fault protection method of a DC collection network for an all-DC offshore wind farm

With the development of offshore wind farms to the deep sea, the all-DC wind farm is gradually coming into serious consideration because of its advantages such as no overvoltage problem. For relay protection for collection lines in an all-DC offshore wind farm, this paper first analyzes the fault characteristics with different fault types and location in the DC collection network. The corresponding fault currents are calculated and compared with the simulation values. A single-ended fault line selection method is proposed using the rate of change of transient current (ROCOTC) at the collection bus side, where the difference of the polarity and amplitude of the ROCOTC are used to identify fault type, line and polarity before overcurrent blocking of the converters. By setting an additional line selection process at the bus, even the fault line with a fault point at the end of the line and high grounding resistance can be accurately identified. A DC offshore wind farm simulation is built in PSCAD/EMTDC. A variety of simulation analyses of different fault scenarios is delivered, demonstrating the validity of the proposed fault line selection method.