半桥MMC型柔性直流电网自适应限流控制研究  

Research on Adaptive-current-limiting Control of VSC-HVDC Grid Based on Half-bridge MMC

作　　者：倪斌业 向往[1] 周猛[1] 左文平[1] 蔡普成 文劲宇[1] NI Binye;XIANG Wang;ZHOU Meng;ZUO Wenping;CAI Pucheng;WEN Jinyu(State Key Laboratory of Advanced Electromagnetic Engineering and Technology(Huazhong University of Science and Technology),Wuhan 430074,Hubei Province,China)

机构地区：[1]强电磁工程与新技术国家重点实验室(华中科技大学),湖北省武汉市430074

出　　处：《中国电机工程学报》2020年第17期5609-5619,共11页Proceedings of the CSEE

基　　金：国家自然科学基金项目(U1766211,51807071);中国博士后科学基金项目(2018M642840)。

摘　　要：柔性直流电网直流故障短路电流具有上升速度快、峰值高等特点。当前,尚不成熟的故障电流抑制技术在一定程度上阻碍了柔性直流电网的大规模建设和发展。已有学者通过在直流电网中增加直流限流器或改进换流器拓扑的方式来抑制直流故障电流。然而上述技术方案会增加直流电网的建设成本。该文通过充分挖掘半桥型模块化多电平变换器(modular multilevel converter,MMC)的控制潜力,提出一种适用于半桥型MMC的自适应限流控制策略。该控制策略通过在直流故障期间快速改变投入的子模块数量,从而快速降低换流器直流电压达到抑制故障电流的目的。首先介绍限流控制的基本原理以及控制器结构,分析并推导半桥型MMC的直流故障电流和桥臂故障电流的计算方程,进一步仿真验证限流控制作用下故障电流的计算方程,最后在基于半桥型MMC的四端柔性直流电网中对限流控制策略的有效性进行仿真验证。仿真结果表明:限流控制使得直流断路器((DC circuit breaker,DCCB)的开断电流减小4.92k A(46.95%),耗散能量减小26.1MJ(67.93%),并且减小故障期间桥臂电流的峰值,降低了换流器过流闭锁的风险。The VSC-HVDC grid has characteristics of fast rising rate and high peak value of DC fault current.At present,the immaturity of fault current suppression technology hampers the development and construction of the VSC-HVDC grid.Many researches use the DC current limiter or improve the converter topology to decrease the fault current.However,the above schemes also suffer from the additional investment of the DC grid.This paper proposed an adaptive-current-limiting control scheme of the half-bridge modular multilevel converter(MMC).This scheme could effectively reduce the fault current of the DC grid,without adding any equipment.The principle of the current-limiting control,together with the structure of the controller,were firstly introduced.The calculating equations of DC current and arm currents of the half-bridge MMC were derived.The calculating equations of fault currents under current-limiting control were further derived and verified.Eventually,the four-terminal DC grid based on half-bridge MMC was simulated to verify the effectiveness of the current-limiting control.The simulation results shown that the proposed current-limiting control could not only reduce breaking current and absorbed energy of the DC circuit breaker(DCCB)by 4.29 k A(40.74%)and 23.4 MJ(60.47%),respectively,but also could decrease the peak arm currents and the risk of converter block.

关 键 词：直流电网 柔性直流输电 半桥型模块化多电平变换器 自适应限流控制 直流断路器(DCCB) 

分 类 号：TM76[电气工程—电力系统及自动化]