±500 kV双端柔性直流架空输电系统中混合式直流断路器重合闸操作暂态特性

Transient Operation Characteristics for Reclosing of the Hybrid DCCB in a± 500 kV Two-Terminal MMC-HVDC Transmission System

±500 kV柔性直流输电系统采用架空线路输电方案时,输电线路出现暂时性短路事故的概率激增,需采用断路器实施重合闸以保障系统的可靠运行,目前直流断路器(DC circuit breaker,DCCB)重合闸时的暂态操作特性尚不清楚。本文建立了含换流站关键设备和混合式高压直流断路器在内的双端±500 kV伪双极柔性直流架空输电系统模型,研究了柔性直流输电系统单极暂时性对地短路故障发生后,混合式直流断路器开断至重合闸过程的电磁暂态特性以及直流断路器关键参数对其开断和重合闸特性的影响。仿真分析表明直流断路器能够在5 ms内切断该故障;由于换流阀不闭锁,断路器开断后换流变阀侧电流未降至0。150 ms故障去游离时间后断路器可在4 ms内重合闸,换流变阀侧电流和极线电压将在200 ms内振荡上升至额定运行工况。此外,随着RCD支路电容C增大,断路器关断性能降低,而断路器重合时固态开关支路与机械支路电流转移速率则与RCD支路的电容C无关。研究成果可为±500 kV柔性直流架空输电线路断路器性能校验提供相应的数据参考。

Temporary short-circuit accidents of transmission lines will increase greatly in ± 500 k V MMC-HVDC overhead transmission system,which need the DC circuit breakers（ DCCBs） reclose to ensure the reliability of power supply. How ever,the transient operation characteristics for reclosing of DCCB are not yet clear. A ± 500 k V pseudo bipolar MMC-HVDC overhead transmission system model is established,which includes the key equipment of converter station and the hybrid DCCB. The impact of the electromagnetic transient characteristics and key parameters of hybrid DCCB on the breaking and reclosing characteristics during the breaking and reclosing process is studied when a single pole occurs short circuit fault to ground. The simulation results show that the hybrid DCCBs could cut off the fault in a short time（ less than 5 ms）. Because the converter valve is not locked,the current of valve side of converter transformer would not reduce to 0 after the breaking of DCCB. After 150 ms of fault deionization,the current of valve side of converter transformer and the pole voltage would rise to the rated operating condition in 200 ms with oscillating condition. In addition,the breaking performance of DCCB reduces with the increasing of the capacitance of RCD branch,w hile the current transfer rate of solid branch and mechanical branch is not related to the capacitance of RCD branch. The results of this paper can provide the corresponding data reference for the performance check of circuit breaker of ± 500 k V MMC-HVDC overhead transmission lines.