双极柔性直流电网短路电流暂态特性分析

Analysis on Transient Characteristics of Short-circuit Current for Bipolar VSC-based DC Grid

架空线柔性直流电网是实现大规模可再生能源广域协调互补和可靠送出的有效解决方案,是未来高压大容量柔性直流输电的重要应用方向。直流线路短路电流是柔性直流电网中换流阀、直流断路器及电抗器等关键主设备参数选取的重要依据之一。通过建立双极柔性直流电网单个换流站在直流线路不同短路故障类型下的等效电路数学模型,构建了故障时刻双极柔性直流电网等效电路网络模型,提出了一种适用于双极柔性直流电网的单极接地、单极接中性线及双极短路的暂态短路电流定量分析方法,实现了双极柔性直流电网直流线路任意故障类型、任意故障位置的暂态短路电流定量分析计算。最后,通过PSCAD/EMTDC仿真,验证了该分析方法的有效性和精确性。

Overhead transmission lines of VSC-based Directcurrent(DC) grid is an effective solution for the wide-area coordination, complementarity and reliable delivery of the largescale renewable energy sources, and therefore is an important application direction of VSC-HVDC charactered by highvoltage and large-capacity in the future. Short-circuit currentof DC lines is one of the important basis for the selection of the key equipment parameters such as converter valve, reactor and DC circuit breaker in DC grid. In this paper, the equivalent circuit model of a single converter station under different shortcircuit fault types is studied. Based on this, the equivalent circuit network model of VSC-based DC grid at fault time is established. Furthermore, a quantitative analysis method of transient short-circuit current for bipolar VSC-based DC grid under short-circuit faults including pole-to-ground, poleto-neutral line and pole-to-pole is proposed. As a result, thequantitative calculation of transient short-circuit current of any fault type and fault location for bipolar VSC-based DC grid is realized. Finally, the validity and accuracy of the proposed method is verified by PSCAD/EMTDC simulation.