基于新型子模块拓扑的MMC-HVDC故障阻断特性研究

发布时间：2018-04-28 04:21

  本文选题：模块化多电平换流器 + 新型子模块　； 参考：《东北电力大学》2017年硕士论文

【摘要】：模块化多电平换流器(MMC)凭借诸多优点在柔性直流输电领域发展十分迅速。当应用于远距离高压直流输电时,由半桥型子模块(HBSM)构成的传统MMC在直流侧发生故障时虽然可以闭锁所有绝缘栅双极型晶体管(IGBT)实现对器件的保护,然而因为IGBT并联续流二极管,造成短路电流不能被闭锁,从而使其不具备直流侧故障清除能力。针对传统半桥型子模块无法清除直流侧故障的问题,许多具备直流故障阻断功能的新型子模块相继被提出,相比半桥型子模块,这些新型子模块增加了额外的阻断器件,从而在电平数较多的情况下增加了换流器的损耗。本文首先对MMC的基本原理做了简要介绍,其次,在研究了现有的具备直流故障自动清除能力的新型MMC子模块之后,对其做了改进,提出了一种具备三电平输出能力且具备较强故障阻断功能的新型子模块,并将新型子模块拓扑结构与传统半桥子模块结合构成桥臂混合子模块式换流器,以降低由新型子模块构成的换流器所带来的额外损耗问题。并分析了混合式换流器的调制策略以及交流电压阶梯波的谐波特性,且通过PSCAD/EMT DC仿真平台进行了仿真验证。针对基于循环嵌套机理的MMC(NLMMC)的优越性,本文提出了一种具备直流故障阻断能力且损耗较低的混合子模块,应用到基于循环嵌套机理的MMC之后,使新型换流器在具有直流侧故障阻断能力的基础上,提高了电平输出能力,从而间接地减少了换流器的损耗。文章从该拓扑结构的工作原理入手,对新型换流器的故障阻断机理和调制策略进行了分析,提出了分层电压平衡控制策略。最后通过PSCAD/EMTDC仿真平台搭建了仿真模型,对换流器的电平输出能力以及故障阻断能力进行了仿真验证。
[Abstract]:Modularized multilevel converter (MMC) is developing rapidly in the field of flexible DC transmission by virtue of many advantages. When it is applied to long distance HVDC transmission, the traditional MMC composed of half bridge module (HBSM) can protect the device even though it can lock all insulated gate bipolar transistors (IGBT) when the DC side fails. However, the short circuit current can not be locked because of the IGBT parallel current diode, so it does not have DC side fault clearance capability. In view of the problem that the traditional semi-bridge sub-module can not clear the DC side fault, many new sub-modules with DC fault blocking function have been proposed one after another. Compared with the half-bridge sub-module, these new sub-modules have added additional blocking devices. Thus, the loss of converter is increased when the number of level is more. In this paper, the basic principle of MMC is introduced briefly. Secondly, after studying the existing new MMC submodule with DC fault automatic clearing capability, the paper improves it. A new type of sub-module with three-level output capability and strong fault blocking function is proposed. The topology of the new sub-module is combined with the traditional half-bridge sub-module to form a hybrid sub-module converter. To reduce the extra loss caused by the converter made up of new submodules. The modulation strategy of the hybrid converter and the harmonic characteristics of the AC voltage step wave are analyzed, and the simulation results are verified by the PSCAD/EMT DC simulation platform. Aiming at the superiority of MMC based on cyclic nesting mechanism, this paper presents a hybrid submodule with DC fault blocking capability and low loss, which is applied to MMC based on cyclic nesting mechanism. On the basis of DC side fault blocking capability, the new converter can improve the level output ability, thus indirectly reducing the converter loss. Based on the working principle of the topology, this paper analyzes the fault blocking mechanism and modulation strategy of the new converter, and puts forward a layered voltage balance control strategy. Finally, the simulation model is built on the PSCAD/EMTDC simulation platform, and the level output capability and the fault blocking ability of the converter are verified by simulation.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM721.1;TM46

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