The Accurate Calculation and Analysis of Overcurrent under Modular Multilevel Converter DC Fault
Cai Yang1,2,3, Guo Wenyong1,2, Zhao Chuang1,2,3, Sang Wenjun1,2,3
1. Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China; 2. Key Laboratory of Applied Superconductivity Chinese Academy of Sciences Beijing 100190 China; 3. University of Chinese Academy of Sciences Beijing 100049 China
Abstract The modular multilevel converter (MMC) is vulnerable to DC fault. Significant overcurrent will occur on the converter after the fault, which has a serious impact on the reliability of MMC. The accurate calculation of fault transient current is crucial to evaluate the overcurrent. This paper presents an precise method to calculate MMC fault overcurrent. The proposed calculation method considers both the influence of grid voltage and DC capacitor discharging. The equivalent model of MMC is established and analyzed, it can be concluded that the differential of arm voltage to time should be composed of capacitance term and submodule switch function term. Based on the method, the numerical solution of the fault current under the DC fault was calculated. Maximum and minimum possible overcurrent was derived. The precision of calculation method was verified by the electromagnetic transient (EMT) simulation results. Finally, the proposed approach was further compared with the two conventional calculation methods. It is verified that the proposed approach has significantly higher accuracy than the conventional methods. The proposed approaches provide a numerical evaluation tool for the design of MMC and DC fault protection.
Cai Yang,Guo Wenyong,Zhao Chuang等. The Accurate Calculation and Analysis of Overcurrent under Modular Multilevel Converter DC Fault[J]. Transactions of China Electrotechnical Society, 2021, 36(7): 1526-1536.
[1] 彭浩, 邓焰, 王莹, 等. 模块化多电平变换器模型及稳态特性研究[J]. 电工技术学报, 2015, 30(12): 120-127. Peng Hao, Deng Yan, Wang Ying, et al.Research about the model and steady-state performance for modular multilevel converter[J]. Transactions of China Electrotechnical Society, 2015, 30(12): 120-127. [2] 苏见燊, 郭敬东, 金涛. 柔性直流电网中直流故障特性分析及线路故障重启策略[J]. 电工技术学报, 2019, 34(增刊1): 352-359. Su Jianshen, Guo Jingdong, Jin Tao.DC fault characteristics and line fault recovery strategy in flexible DC power network[J]. Transactions of China Electrotechnical Society, 2019, 34(S1): 352-359. [3] 许建中, 王乐, 武董一, 等. 采用子模块相关性坐标变换解耦的混合模块化多电平换流器可靠性建模[J]. 电工技术学报, 2019, 34(18): 3821-3830. Xu Jianzhong, Wang Le, Wu Dongyi, et al.Reliability modeling of hybrid modular multilevel converter using coordinate transformation based on decoupled sub-module correlations[J]. Transactions of China Electrotechnical Society, 2019, 34(18): 3821-3830. [4] 郝瑞祥, 杨晓峰, 薛尧, 等. 一种具有直流故障限流能力的模块化多电平换流器[J]. 电工技术学报, 2017, 32(6): 172-180. Hao Ruixiang, Yang Xiaofeng, Xue Yao, et al.A novel modular multilevel converter with DC fault current limiting capability[J]. Transactions of China Electrotechnical Society, 2017, 32(6): 172-180. [5] 罗永捷, 蒲羿, 宋勇辉, 等. 混合型模块化多电平换流器启动冲击电流特性分析及控制策略[J]. 电工技术学报, 2020, 35(增刊1): 49-59. Luo Yongjie, Pu Yi, Song yonghui, et al. The inrush current characteristics and control strategies of hybrid modular multilevel converter systems during start-up processes[J]. Transactions of China Electrotechnical Society, 2020, 35(S1): 49-59. [6] 张国驹, 祁新春, 陈瑶, 等. 模块化多电平换流器直流双极短路特性分析[J]. 电力系统自动化, 2016, 40(12): 151-157. Zhang Guoju, Qi Xinchun, Chen Yao, et al.Characteristic analysis of modular multilevel converter under DC pole-to-pole short-circuit fault[J]. Automation of Electric Power Systems, 2016, 40(12): 151-157. [7] 孙吉波, 王宇, 刘崇茹, 等. 基于MMC的多端直流电网双极短路故障电流计算[J]. 电力自动化设备, 2018, 38(11): 72-78. Sun Jibo, Wang Yu, Liu Chongru, et al.Pole-to-pole short circuit current calculation of multi-terminal DC grid based on MMC[J]. Electric Power Automation Equipment, 2018, 38(11): 72-78. [8] 尹太元, 王跃, 段国朝, 等. 基于零直流电压控制的混合型MMC-HVDC直流短路故障穿越策略[J]. 电工技术学报, 2019, 34(增刊1): 343-351. Yin Taiyuan, Wang Yue, Duan Guozhao, et al.Zero DC voltage control based DC fault ride-through strategy for hybrid modular multilevel converter in HVDC[J]. Transactions of China Electrotechnical Society, 2019, 34(S1): 343-351. [9] Nguyen T H, Khalifa H A H, El Moursi M. Alternating submodule configuration based MMCs with carrier-phase-shift modulation in HVDC systems for DC fault ride-through capability[J]. IEEE Transactions on Industrial Informatics, 2019, 15(9): 5214-5224. [10] 周光阳, 李妍, 何大瑞, 等. 含限流器的多端柔直系统故障保护策略[J]. 电工技术学报, 2020, 35(7): 1432-1443. Zhou Guangyang, Li Yan, He Darui, er al. Protection scheme for VSC-MTDC system with fault current limiter[J]. Transactions of China Electrotechnical Society, 2020, 35(7): 1432-1443. [11] 王姗姗, 周孝信, 汤广福, 等. 模块化多电平换流器HVDC直流双极短路子模块过电流分析[J]. 中国电机工程学报, 2011, 31(1): 1-7. Wang Shanshan, Zhou Xiaoxin, Tang Guangfu, et al.Analysis of submodule overcurrent caused by DC pole-to-pole fault in modular multilevel converter HVDC system[J]. Proceedings of the CSEE, 2011, 31(1): 1-7. [12] Wang Weihua, Zhu Jin, Li Wei, et al.Analysis and hardware-in-the-loop simulation of a pole-to-pole DC fault in MMC-based HVDC systems[C]//13th Brazilian Power Electronics Conference and 1st Southern Power Electronics Conference (COBEP/ SPEC), Fortaleza, 2015: 1-5. [13] Jiang Bin, Gong Yanfeng, Cao Jun, et al.Fault current analysis of MMC based HVDC system under DC pole-to-pole fault condition[C]//International Conference on Renewable Power Generation (RPG 2015), Beijing, 2015: 1-5. [14] 段国朝, 王跃, 尹太元, 等. 模块化多电平变流器直流短路故障电流计算[J]. 电网技术, 2018, 42(7): 2145-2152. Duan Guozhao, Wang Yue, Yin Taiyuan, et al.DC short circuit current calculation for modular multilevel converter[J]. Power System Technology, 2018, 42(7): 2145-2152. [15] 马焕, 姚为正, 吴金龙, 等. 含桥臂阻尼的MMC-HVDC直流双极短路故障机理分析[J]. 电网技术, 2017, 41(7): 2099-2106. Ma Huan, Yao Weizheng, Wu Jinlong, et al.Analysis of DC pole-to-pole short circuit fault behavior in MMC-HVDC transmission systems with bridge arm damper[J]. Power System Technology, 2017, 41(7): 2099-2106. [16] Li Bin, He Jiawei, Tian Jie, et al.DC fault analysis for modular multilevel converter-based system[J]. Journal of Modern Power Systems and Clean Energy, 2017, 5(2): 275-282. [17] Leterme W, Beerten J, Hertem D V.Equivalent circuit for half-bridge MMC DC fault current contribution[C]//IEEE International Energy Conference, Leuven, 2016: 1-6. [18] 王威儒, 贺之渊, 李国庆, 等. 含交流影响的MMC-HVDC直流故障电流递推计算方法[J]. 中国电机工程学报, 2019, 39(增刊1): 313-320. Wang Weiru, He Zhiyuan, Li Guoqing, et al.Recursive calculation method of MMC-HVDC DC fault current with AC effect[J]. Proceedings of the CSEE, 2019, 39(S1): 313-320. [19] Langwasser M, De Carne G, Liserre M, et al.Fault current estimation in multi-terminal HVDC grids considering MMC control[J]. IEEE Transactions on Power Systems, 2019, 34(3): 2179-2189. [20] 徐政, 刘高任, 张哲任. 柔性直流输电网的故障保护原理研究[J]. 高电压技术, 2017, 43(1): 1-8. Xu Zheng, Liu Gaoren, Zhang Zheren.Research on fault protection principle of DC grids[J]. High Voltage Engineering, 2017, 43(1): 1-8. [21] 李斌, 何佳伟, 李晔, 等. 多端柔性直流系统直流故障保护方案[J]. 中国电机工程学报, 2016, 36(17): 4627-4637. Li Bin, He Jiawei, Li Ye, et al.DC fault protection strategy for the flexible multi-terminal DC system[J]. Proceedings of the CSEE, 2016, 36(17): 4627-4637. [22] Wang M, Beerten J, Van Hertem D.Frequency domain based DC fault analysis for bipolar HVDC grids[J]. Journal of Modern Power Systems and Clean Energy, 2017, 5(4): 548-559. [23] 徐政. 柔性直流输电系统[M]. 北京: 机械工业出版社, 2012. [24] Ahmed N, Angquist L, Norrga S, et al.A computationally efficient continuous model for the modular multilevel converter[J]. IEEE Journal on Emerging and Selected Topics in Circuits and Systems, 2014, 2(4): 1139-1148.
2021, Vol. 36 
