风电场送出线等传变距离保护

分析了具备低电压穿越(LVRT)能力的双馈式风电场送出线路故障暂态特性。风电送出线路风场侧保护测得的电压与电流主要频率分量不一致,致使传统的依据工频电压、电流相量的距离保护元件动作性能受到严重影响,无法正常工作。基于输电线路时域模型的解微分方程算法不涉及信号的频域信息,可以克服送出线电压、电流主频不同带来的影响,但受高频分量的影响较大。等传变距离保护相较传统的解微分方程算法,增加了低通滤波及故障点电压重构两个环节,显著改善了算法的测距性能。PSCAD/EMTDC仿真结果表明,线路不同位置处发生不同类型故障时,等传变距离保护算法均可以实现快速、准确测距。

Equal transfer process-based distance protection for wind farm outgoing transmission line

The fault features of outgoing transmission line in DFIG-based wind plant with the capacity of low-voltage ride-through (LVRT) are analyzed. The main frequency inconsistency between voltage and current of wind farm outgoing transmission line leads a serious impact on the action performance of traditional distance protection element based on power frequency voltage and current phasor. The differential equation algorithm based on the time-domain differential equation model of transmission line does not involve the frequency-domain information of the signal, thus it is unaffected by the main frequency inconsistency between voltage and current of wind farm outgoing transmission line. But the high-frequency characteristic of the differential equation algorithm is poor. Compared with the traditional differential equation algorithm, two processes are gained in the equal transfer process-based distance protection, low-pass filtering and re-structuring of the voltage at the fault point, which significantly improves the performance of the algorithm. The PSCAD/EMTDC simulation results show that the distance element which employs the equal transfer process-based distance protection algorithm can trip correctly and quickly while unaffected by the wind power transient voltage and current no matter what kind of fault occurs in the protection scope.