基于架空线路简化模型的柔性直流电网双极短路故障定位法

在模块化多电平换流器(MMC)组建的多端柔性直流输电系统中,准确定位直流侧双极短路故障位置是确保快速功率恢复的重要举措。针对目前故障测距存在的问题及获取架空线路参数的困难,文中提出了一种基于架空线路简化R-L模型的柔性直流电网双极短路故障定位方法。通过预设双极短路故障试验可反推出架空线路故障态下的单位电阻和电感值,从而得到R-L线路模型。在此模型的基础上推导故障定位公式,代入故障线路两端的实测电压和电流数据即可较为准确地计算出故障位置。通过PSCAD/EMTDC中的四端柔性直流系统验证了所提定位算法的有效性。仿真结果表明,所提定位算法具有很高的精度和可靠性,几乎不受过渡电阻和系统传输功率的影响,同时这也证明了简化R-L模型具有很高的精度。

Location Method of Pole-to-pole Short-circuit Fault for Flexible DC Grid Based on Simplified Model of Overhead Line

Accurately locating pole-to-pole short-circuit faults on DC side of multi-terminal flexible DC transmission system with modular multilevel converters (MMCs) is a key measure to ensure fast power recovery. In view of the problems of distance measurement for fault location and difficulties in obtaining the parameters of overhead lines, this paper proposes a location method of pole-to-pole short-circuit fault for the flexible DC grid based on a simplified R-L model of overhead lines. The unit resistance and inductance values in the fault state of overhead lines can be deduced through the presetting pole-to-pole short-circuit fault tests, so the R-L line model is obtained. Based on the model, the fault location formulas are derived, and the fault location can be calculated more accurately by using the measured voltage and current data from both ends of the short-circuit line. A four-terminal flexible DC system based on PSCAD/EMTDC is used to verify the effectiveness of the proposed location algorithm. The simulation results show that the proposed location algorithm has high precision and reliability, which is almost immune to the transition resistance and the transmission power of the system. At the same time, it also proves that the simplified R-L model has high precision.