模块化多电平换流器桥臂不平衡运行特性及冗余保护策略

发布时间：2018-05-08 04:41

本文选题：模块化多电平换流器 + 冗余保护　；参考：《南方电网技术》2016年11期

【摘要】：当模块化多电平换流器发生子模块故障时,换流器将运行在桥臂不对称的状态,会引发基频环流增大等一系列问题,进而影响换流器的运行特性。为此,综合考虑冗余子模块以及桥臂不对称运行的影响,对柔性直流系统数学模型、子模块开关函数以及环流产生机理进行了深入分析。在此基础上,提出了改进的换流器冗余保护策略。与传统策略不同,该策略在子模块故障发生后,无需切除非故障桥臂子模块,通过调整子模块电压基值降低桥臂不对称度。在电力系统仿真软件PSCAD/EMTDC中搭建了双端直流输电系统模型并进行了仿真验证,仿真结果证明所提出的策略可使换流器在桥臂不平衡状态下保持良好的运行特性,增强了换流器抵御子模块故障的能力。
[Abstract]:When the sub-module of the modularized multilevel converter fails, the converter will run in the asymmetric state of the bridge arm, which will lead to a series of problems such as the increase of the fundamental frequency circulation, which will affect the operation characteristics of the converter. Therefore, considering the influence of redundant submodules and asymmetric operation of the bridge arm, the mathematical model of flexible DC system, the switch function of the sub-module and the mechanism of circulation generation are analyzed in detail. On this basis, an improved redundancy protection strategy for converter is proposed. Different from the traditional strategy, this strategy can reduce the asymmetry of the arm by adjusting the voltage base of the sub-module without removing the non-fault submodule after the failure of the sub-module. In the power system simulation software PSCAD/EMTDC, a two-terminal DC transmission system model is built and verified by simulation. The simulation results show that the proposed strategy can make the converter maintain good operating characteristics in the unbalanced state of the bridge arm. The ability of converter to resist submodule failure is enhanced.
【作者单位】：国网浙江省电力公司经济技术研究院;浙江大学电气工程学院;
【分类号】：TM721.1;TM46

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