Modular Multilevel Converter Sub-Module Fault Characteristics Analysis and Decoupling Control Strategy
Fan Zhihua1,2, Miao Shihong1,2, Liu Zhiwen1,2, Chao Kaiyun1,2, Kang Yilong1,2
1. State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan 430074 China; 2. Hubei Electric Power Security and High Efficiency Key Laboratory Huazhong University of Science and Technology Wuhan 430074 China
Abstract：Focusing on the situation that modular multilevel converter (MMC) with asymmetrical sub-module (SM) numbers of arms caused by sub-module fault, a mathematic model of arms under asymmetric operation based on the switch function is established. It is revealed that the inconsistent switching functions of upper and lower arm submodules are the cause of the asymmetric operation. By means of compensating impedance to counteract the asymmetry component caused by the unequal number of arm sub-modules, the unsymmetrical operating mode under the sub-module fault is transformed into the quasi symmetrical operating mode without sub-module fault, and then the coupling equivalent circuit among AC current, DC current and AC circulation is established under asymmetric conditions. The influence of coupling relationship among currents of the equivalent circuit on the internal operating characteristics of arms is studied. The analysis shows that the fundamental frequency current will appear in arm current, and the AC current will also introduce the DC current component and the double frequency current component. Finally, the mapping relationship between the current and voltage of arms at different frequencies is constructed, and the arms current control strategy with SM fault-tolerant ability is further proposed. Simulation verifies the effectiveness of proposed control strategy.
[1] 徐政, 薛英林, 张哲任. 大容量架空线柔性直流输电关键技术及前景展望[J]. 中国电机工程学报, 2014, 34(29): 1-12. Xu Zheng, Xue Yinglin, Zhang Zheren.On VSC- HVDC technology suitable for bulk power overhead line transmission[J]. Proceedings of the CSEE, 2014, 34(29): 1-12. [2] 李善颖, 吴涛, 任彬,等. 基于模块化多电平变换器的储能系统综述[J]. 电力系统保护与控制, 2015, 43(16): 139-146. Li Shanying, Wu Tao, Ren Bin, et al.Review of energy storage system based on modular multilevel converter[J]. Power System Protection and Control, 2015, 43(16): 139-146. [3] Perez M A, Bernet S, Rodriguez J, et al.Circuit topologies, modeling, control schemes, and applications of modular multilevel converters[J]. IEEE Transa- ctions on Power Electronics, 2014, 30(1): 4-17. [4] Zeng R, Xu L, Yao L, et al.Design and operation of a hybrid modular multilevel converter[J]. IEEE Transactions on Power Electronics, 2014, 30(3): 1137-1146. [5] 徐殿国, 李彬彬, 周少泽. 模块化多电平高压变频技术研究综述[J]. 电工技术学报, 2017, 32(20): 104-116. Xu Dianguo, Li Binbin, Zhou Shaoze.Overview of the modular multilevel converter based high voltage motor drive[J]. Transactions of China Electro- technical Society, 2017, 32(20): 104-116. [6] 王浩, 刘进军, 梅桂华. 一种串联侧三相解耦型统一电能质量控制器[J]. 电工技术学报, 2016, 31(2): 215-220. Wang Hao, Liu Jinjun, Mei Guihua.A unified power quality conditioner with three-phase decoupling in series section[J]. Transactions of China Electro- technical Society, 2016, 31(2): 215-220. [7] 李凯, 赵争鸣, 袁立强. 模块化多电平变换器上、下桥臂不对称运行环流重复控制[J]. 电工技术学报, 2016, 31(20): 122-129. Li Kai, Zhao Zhengming, Yuan Liqiang.Repetitive control of circulating current in MMC with asymmetrical operation of upper and lower arms[J]. Transactions of China Electrotechnical Society, 2016, 31(20): 122-129. [8] Konstantinou G, Pou J, Ceballos S, et al.Active redundant submodule configuration in modular multilevel converters[J]. IEEE Transactions on Power Delivery, 2013, 28(4): 2333-2341. [9] Wang J, Ma H, Bai Z.A submodule fault ride- through strategy for modular multilevel converters with nearest level modulation[J]. IEEE Transactions on Power Electronics, 2018, 33(2): 1597-1608. [10] 李探, 赵成勇, 李路遥, 等. MMC-HVDC子模块故障诊断与就地保护策略[J]. 中国电机工程学报, 2014, 34(10): 1641-1649. Li Tan, Zhao Chengyong, Li Luyao, et al.Sub- module fault diagnosis and the local protection scheme for MMC-HVDC System[J]. Proceedings of the CSEE, 2014, 34(10): 1641-1649. [11] Liu H, Loh P C, Blaabjerg F.Review of fault diagnosis and fault-tolerant control for modular multilevel converter of HVDC[C]//39th Annual Conference of the IEEE Industrial Electronics Society (IECON 2013), Vienna, Austria, 2014: 1242-1247. [12] 殷实, 谭国俊. 一种基于扩展卡尔曼滤波算法的MMC系统故障诊断策略[J]. 电工技术学报, 2016, 31(19): 74-84. Yin Shi, Tan Guojun.A novel fault diagnosis strategy of MMC system based on EKFA[J]. Transactions of China Electrotechnical Society, 2016, 31(19): 74-84. [13] Hu P, Jiang D, Zhou Y, et al.Energy-balancing control strategy for modular multilevel converters under submodule fault conditions[J]. IEEE Transa- ctions on Power Electronics, 2014, 29(9): 5021-5030. [14] 李探, 赵成勇. MMC子模块故障下桥臂不对称运行特性分析与故障容错控制[J]. 中国电机工程学报, 2015, 35(15): 3921-3928. Li Tan, Zhao Chengyong.Operation characteristics of the MMC with asymmetrical arms under sub-module faults and the fault-tolerant control[J]. Proceedings of the CSEE, 2015, 35(15): 3921-3928. [15] 江丽丽, 马文忠, 李林欢, 等. 模块化多电平换流器的容错控制策略[J]. 电网技术, 2014, 38(9): 2497-2503. Jiang Lili, Ma Wenzhong, Li Linhuan, et al.A fault-tolerant control strategy of modular multi-level converters[J]. Power System Technology, 2014, 38(9): 2497-2503. [16] Deng F, Tian Y, Zhu R, et al.Fault-tolerant approach for modular multilevel converters under submodule faults[J]. IEEE Transactions on Industrial Electronics, 2016, 63(11): 7253-7263. [17] 黄守道, 廖武, 高剑, 等. 基于改进均压算法的模块化多电平变流器开关频率分析[J]. 电工技术学报, 2016, 31(13): 36-45. Huang Shoudao, Liao Wu, Gao Jian, et al.Switching frequency analysis of modular multilevel converter based on the improved capacitor voltage balancing algorithm[J]. Transactions of China Electrotechnical Society, 2016, 31(13): 36-45. [18] 王姗姗, 周孝信, 汤广福, 等. 模块化多电平电压源换流器的数学模型[J]. 中国电机工程学报, 2011, 31(24): 1-8. Wang Shanshan, Zhou Xiaoxin, Tang Guangfu, et al.Modeling of modular multi-level voltage source converter[J]. Proceedings of the CSEE, 2011, 31(24): 1-8. [19] Pérez M A, Ricardo L F, Rodríguez J.Decoupled current control of modular multilevel converter for HVDC applications[C]//IEEE International Sympo- sium on Industrial Electronics, Hangzhou, China, 2012: 1979-1984. [20] Zeng R, Xu L, Yao L, et al.Analysis and control of modular multilevel converters under asymmetric arm impedance conditions[J]. IEEE Transactions on Industrial Electronics, 2016, 63(1): 71-81. [21] 刘国伟, 赵宇明, 袁志昌, 等. 深圳柔性直流配电示范工程技术方案研究[J]. 南方电网技术, 2016, 10(4): 1-7. Liu Guowei, Zhao Yuming, Yuan Zhichang,et al.Study on demonstration project technical scheme of VSC-DC distribution system in Shenzhen[J]. Southern Power System Technology, 2016, 10(4): 1-7.
2018, Vol. 33 
