柔性直流电网主动限流开断直流故障研究  

Research on DC Fault Isolation of MMC Based DC Grid Using the Active Current-limiting Approach

作　　者：周猛[1] 向往[1] 左文平[1] 文劲宇[1] 林卫星 ZHOU Meng;XIANG Wang;ZUO Wenping;WEN Jinyu;LIN Weixing(State Key Laboratory of Advanced Electromagnetic Engineering and Technology(Huazhong University of Science and Technology),Wuhan 430074,Hubei Province,China;TBEA China Xinjiang Sunoasis Co.,Ltd,Urumqi 830011,Xinjiang Uygur Autonomous Region,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 [2]特变电工新疆新能源股份有限公司,新疆维吾尔自治区乌鲁木齐830011

出　　处：《中国电机工程学报》2019年第23期6852-6866,共15页Proceedings of the CSEE

基　　金：国家自然科学基金项目(U1766211)~~

摘　　要：基于混合型模块化多电平变换器的柔性直流输电系统可通过主动控制来限制直流故障电流,即将在昆柳龙三端混合直流输电工程中应用。然而,关于混合型MMC的主动限流开断原理、故障电流演变特性、限流控制效果与影响因素尚缺少相关理论研究。针对上述问题,该文首先分析采用直流电压前馈的主动限流控制策略限流机理,研究计及延时后,换流器直流电压、电流在故障期间的演变特性。提出换流器与直流断路器协调控制策略,并分析采用不同协调控制策略时故障线路电流的动态演变过程。分析采用主动限流控制策略后的柔性直流电网对DCCB的开断电流大小需求。针对基于半桥MMC构建的直流电网和基于混合型MMC构建的直流电网2种技术方案,在DCCB开断电流需求、DCCB经济性以及直流电网故障特征等方面对二者进行对比分析。研究表明,与半桥MMC型直流电网相比,基于混合型MMC的直流电网在使用主动限流控制技术后,DCCB开断电流大小减小为原来的22%,使得DCCB的成本减小为原来的45%,故障后换流站直流功率最短时间恢复时间减小为原来的30%,故障后功率模块电容过电压减小为原来的33.3%。最后,通过仿真验证理论分析的合理性。The hybrid modular multilevel converter(MMC)based high voltage DC current(HVDC)system can limit the DC fault current through active control,which will be applied in the Kunliulong three-terminal hybrid HVDC project.However,there are few researches on the analysis of active current limiting mechanism,fault current evolution characteristics and impacts on current limiting control.To address the above problems,the mechanism of DC voltage feed-forward based current-limiting control was analyzed.The evolution mechanism of voltage and current of the converter during the fault was studied.The coordination control of converter and DC circuit breaker(DCCB)was proposed,and the dynamic process of fault current was analyzed when different coordination control strategies are adopted.The requirements of active current-limiting control for DCCB interruption current were analyzed.Taking the DC grid based on half-bridge MMC and the DC grid based on hybrid MMC as examples,the paper made a detailed comparative analysis of DCCB requirements and fault characteristics of DC grid.Study shows that the requirements for the interruption current of DCCB in DC grid based on hybrid MMC with active current-limiting control decreases to 22%,makes the DCCB cost reduced to 45%,the recovery time of DC power after fault reduced to 30%,the overvoltage of sub-module capacitors after fault decrease to 33.3%.Finally,the rationality of theoretical analysis was verified by simulation.

关 键 词：直流电网 柔性直流输电 混合型模块化多电平变换器 主动限流控制 直流断路器 

分 类 号：TM76[电气工程—电力系统及自动化]