MMC-HVDC双极短路故障机理及暂态特性研究  

Research on Short Circuit Fault Mechanism and Transient Characteristics of MMC-HVDC Bipolar System

作　　者：张野 洪潮 李俊杰 张帆 杨健 ZHANG Ye;HONG Chao;LI Junjie;ZHANG Fan;YANG Jian(State Key Laboratory of HVDC,Electric Power Research Institute,CSG,Guangzhou 510663,China)

机构地区：[1]直流输电技术国家重点实验室(南方电网科学研究院),广州510663

出　　处：《南方电网技术》2018年第4期7-15,共9页Southern Power System Technology

摘　　要：MMC-HVDC输电系统直流线路的双极短路故障严重威胁系统的安全稳定运行,针对该问题研究了故障的暂态过程,并对故障特性进行了详细分析。首先,针对换流器闭锁前阶段,提出了反映MMC子模块动态投切过程的等值电路模型,仿真结果表明该等值电路模型可以准确有效地反映MMC子模块的高频投切过程,子模块电容的交替放电使直流侧故障电流上升更加迅速;其次,针对换流器闭锁后阶段,结合等效电路建立了数学描述方程,提出了换流器闭锁后的三阶段分析方法。分析表明换流器闭锁后,各桥臂电流中除闭锁前电容放电产生的非周期分量外,还存在闭锁瞬间桥臂电感上出现的非周期分量;直流侧出口故障时,故障电流峰值可能在换流器闭锁后出现。PSCAD/EMTDC模型仿真验证了所提理论分析结果的正确性。The bipolar short-circuit fault at DC line of MMC-HVDC transmission system is a serious threat to the safe and stable operation of the system.The transient process of the fault is studied and the fault characteristics are analyzed in detail.Firstly,an equivalent circuit model of MMC sub-module dynamic casting process is put forward for the pre-blocking stage of the converter.The simulation results show that the equivalent circuit model can accurately and effectively reflect the high-frequency switching process of the MMC sub-module.Alternating discharge of the sub-module capacitance makes the DC-side fault current rise more quickly.Secondly,a mathematical description equation is established with the equivalent circuit for the post-blocking stage of the converter,and a three-stage analysis method is proposed for the post-blocking stage of the converter.The analysis shows that after the inverter is blocked,in the currents of each bridge arm,there is a non-periodic component of the bridge arm inductance at the moment of blocking in addition to the non-periodic component of the capacitor discharge before the blocking;when the DC-side outlet fails,the peak value of the fault current may appear after the inverter is blocked.PSCAD/EMTDC model simulation verified that the theoretical analysis result is correct.

关 键 词：模块化多电平换流器 双极短路故障 子模块动态投切 等值电路模型 

分 类 号：TM721[电气工程—电力系统及自动化]