Abstract As the core component of the modular multilevel converter (MMC) systemsub-module (SM), the capacitoris one of the most fragile components due to its long-term working environment of high-frequency and high-power. Therefore, real-time monitoring of capacitor status is very important to ensure the reliable operation of the MMC system. In this paper, an online monitoring method for SM capacitance in MMC based on Haar wavelet transform reconstruction switch sequence is proposed. Firstly, the input and excision switch sequence of submodule is reconstructed by Haar wavelet transform on the capacitor voltage signal of the MMC system. Secondly, the voltage signal during charging period of the capacitor is selected based on the reconstructed switching sequence, and the capacitance value is monitored online combined with the bridge current signal. Finally, the accuracy and effectiveness of proposed method are verified by the MMC system working condition simulation platform. The proposed method can evaluate the capacitance through the capacitor voltage and arm current signals from the control system, which greatly reduces the difficulty of monitoring by removing the need for switching signals. It provides theoretical and method support for capacitor condition monitoring and active operation and maintenance of the MMC system.
Luo Dan,Chen Minyou,Lai Wei等. Online Monitoring Method for Sub-Module Capacitance in Modular Multilevel Converter Based on Haar Wavelet Transform Reconstruction Switch Sequence[J]. Transactions of China Electrotechnical Society, 2022, 37(20): 5278-5289.
[1] Li Bo, Ma Ziming, Hidalyo-Gonzalez P, et al.Modeling the impact of EVs in the Chinese power system: pathways for implementing emissions reduction commitments in the power and trans-portation sectors[J]. Energy Policy, 2021, 149: 111962. [2] 茆美琴, 程德健, 袁敏, 等. 基于暂态能量流的模块化多电平高压直流电网接地优化配置[J]. 电工技术学报, 2022, 37(3): 739-749. Mao Meiqin, Cheng Dejian, Yuan Min, et al.Optimal allocation of grounding system in high voltage direct current grid with modular multi-level converters based on transient energy flow[J]. Transactions of China Electrotechnical Society, 2022, 37(3): 739-749. [3] 张志文, 雷诗婕, 翟承达, 等. 高压直流输电系统吸收与并联电容换相换流器特性分析[J]. 电工技术学报, 2019, 34(增刊2): 684-691. Zhang Zhiwen, Lei Shijie, Zhai Chengda, et al.The characteristic analysis of HVDC system with absorp-tion and shunt capacitance commutated converter[J]. Transactions of China Electrotechnical Society, 2019, 34(S2): 684-691. [4] 曹帅, 向往, 左文平, 等. 风电经柔性直流电网外送系统的交流故障诊断与穿越控制策略[J]. 中国电机工程学报, 2021, 41(4): 1295-1306. Cao Shuai, Xiang Wang, Zuo Wenping, et al.AC fault diagnosis and ride-trough control strategy for the wind power delivery system via HVDC grid[J]. Pro-ceedings of the CSEE, 2021, 41(4): 1295-1306. [5] 刘浔, 戴迪, 饶洪林, 等. 直流系统换流阀常见故障及处理方法[J]. 电子世界, 2015(21): 115-117. Liu Xun, Dai Di, Rao Honglin, et al.Common faults and treatment methods of converter valve in DC system[J]. Electronics World, 2015(21): 115-117. [6] Yang Shaoyong, Xiang Dawei, Bryant A, et al.Condition monitoring for device reliability in power electronic converters: a review[J]. IEEE Transactions on Power Electronics, 2010, 25(11): 2734-2752. [7] 许建中, 李钰, 陆锋, 等. 降低MMC子模块电容电压纹波幅值的方法综述[J]. 中国电机工程学报, 2019, 39(2): 571-584, 654. Xu Jianzhong, Li Yu, Lu Feng, et al.A review of suppression methods for sub-module capacitor voltage ripple amplitudes in modular multilevel converters[J]. Proceedings of the CSEE, 2019, 39(2): 571-584, 654. [8] 贾科, 赵其娟, 冯涛, 等. 柔性直流配电系统高频突变量距离保护[J]. 电工技术学报, 2020, 35(2): 383-394. Jia Ke, Zhao Qijuan, Feng Tao, et al.High-frequency fault component distance protection for flexible DC distribution system[J]. Transactions of China Electro-technical Society, 2020, 35(2): 383-394. [9] 付华, 陈浩轩, 李秀菊, 等. 含边界元件的MMC-MTDC直流侧单端量故障辨识方法[J]. 电工技术学报, 2021, 36(1): 215-226. Fu Hua, Chen Haoxuan, Li Xiuju, et al.MMC-MTDC DC side single-ended quantity fault identification method with boundary elements[J]. Transactions of China Electrotechnical Society, 2021, 36(1): 215-226. [10] 束洪春, 代月, 安娜, 等. 基于交叉重叠差分变换的MMC-HVDC线路故障识别方法[J]. 电工技术学报, 2021, 36(1): 203-214, 226. Shu Hongchun, Dai Yue, An Na, et al.Fault identi-fication method of MMC-HVDC line based on sequential overlapping derivative transform[J]. Transa-ctions of China Electrotechnical Society, 2021, 36(1): 203-214, 226. [11] 王希平, 李志刚, 姚芳. MMC系统功率器件基频结温波动快速计算方法[J]. 中国电机工程学报, 2020, 40(18): 5805-5815. Wang Xiping, Li Zhigang, Yao Fang.Simplified estimation of the fundamental frequency junction temperature fluctuation for IGBTs in modular multi-level converters[J]. Proceedings of the CSEE, 2020, 40(18): 5805-5815. [12] Ronanki D, Williamson S S.Failure prediction of submodule capacitors in modular multilevel converter by monitoring the intrinsic capacitor voltage fluctu-ations[J]. IEEE Transactions on Industrial Electronics, 2020, 67(4): 2585-2594. [13] Abushafa O, Atkinson D, Gadoue S, et al.A new scheme for monitoring submodule capacitance in modular multilevel converter[C]//8th IET Inter-national Conference on Power Electronics, Machines and Drives (PEMD 2016), Glasgow, UK, 2016: 1-6. [14] Sun Yuting, Wang Mingyu, Ran Li.Capacitance monitoring method for metallized polypropylene film capacitor in MMC[C]//2019 IEEE Sustainable Power and Energy Conference (iSPEC), Beijing, China, 2019: 2431-2436. [15] Deng Fujin, Qian Heng, Liu Chengkai, et al.Capa-citor ESR and C monitoring in modular multilevel converters[J]. IEEE Transactions on Power Electro-nics, 2020, 35(4): 4063-4075. [16] Liu Chengkai, Deng Fujin, Yu Qiang, et al.Sub-module capacitance monitoring strategy for phase-shifted carrier pulse-width modulation based modular multilevel converters[J]. IEEE Transactions on Industrial Electronics, 2021, 68(9): 8753-8767. [17] Jo Y J, Nguyen T H, Lee D C.Condition monitoring of submodule capacitors in modular multilevel con-verters[C]//Energy Conversion Congress & Exposition, Pittsburgh, PA, USA, 2014: 2121-2126. [18] 辛熙锴, 马柯, 蔡旭. 工频周期四点电压采样的MMC子模块电容值在线监测方法[J]. 中国电机工程学报, 2021, 41(11): 3896-3903. Xin Xikai, Ma Ke, Cai Xu.Online monitoring for sub-module capacitance in modular multilevel converter with four sampling points of capacitor voltage[J]. Proceedings of the CSEE, 2021, 41(11): 3896-3903. [19] Wang Zhongxu, Zhang Yi, Wang Huai, et al.Capa-citor condition monitoring based on the DC-side start-up of modular multilevel converters[J]. IEEE Transactions on Power Electronics, 2020, 35(6): 5589-5593. [20] Wang Hanyu, Wang Huai, Wang Zhongxu, et al.Condition monitoring for submodule capacitors in modular multilevel converters[J]. IEEE Transactions on Power Electronics, 2019, 34(11): 10403-10407. [21] Xia Hongjian, Zhang Yi, Wang Huai, et al.Condition monitoring for capacitors in modular multilevel converter based on high-frequency transient analysis[C]//2021 IEEE Energy Conversion Congress and Expo-sition (ECCE), Vancouver, BC, Canada, 2021: 5342-5347. [22] 夏宏鉴, 陈民铀, 赖伟, 等. 基于频带能量的模块化多电平换流阀中金属化薄膜电容器失效检测方法[J]. 中国电机工程学报, 2021, 41(22): 7782-7792. Xia Hongjian, Chen Minyou, Lai Wei, et al.Failure detection method for metalized polypropylene film capacitor in modular multilevel converter based on band energy[J]. Proceedings of the CSEE, 2021, 41(22): 7782-7792. [23] 徐政. 柔性直流输电系统[M]. 北京: 机械工业出版社, 2013. [24] Yen G G, Lin K C.Wavelet packet feature extraction for vibration monitoring[J]. IEEE Transactions on Industrial Electronics, 2000, 47(3): 650-667. [25] Rauber T W, de Assis Boldt F, Varejao F M. Hetero-geneous feature models and feature selection applied to bearing fault diagnosis[J]. IEEE Transactions on Industrial Electronics, 2015, 62(1): 637-646. [26] Youssef O A S. A wavelet-based technique for discrimination between faults and magnetizing inrush currents in transformers[J]. IEEE Transactions on Power Delivery, 2003, 18(1): 170-176. [27] 朱柏寒, 陈羽, 马金杰. 基于波前陡度的输电线路单端行波故障测距[J]. 电力系统自动化, 2021, 45(9): 130-135. Zhu Baihan, Chen Yu, Ma Jinjie.Wavefront steepness based single-ended traveling wave fault location for transmission lines[J]. Automation of Electric Power Systems, 2021, 45(9): 130-135. [28] 姜涛, 李孟豪, 李雪, 等. 电力系统强迫振荡源的时频域定位方法[J]. 电力系统自动化, 2021, 45(9): 98-106. Jiang Tao, Li Menghao, Li Xue, et al.Time-frequency domain location method for forced oscillation source in power system[J]. Automation of Electric Power Systems, 2021, 45(9): 98-106. [29] 苏燕, 徐艳华. 基于单片机的激光测距系统设计[J]. 激光杂志, 2017, 38(9): 128-131. Su Yan, Xu Yanhua.Design of laser range system based on single chip microcomputer[J]. Laser Journal, 2017, 38(9): 128-131. [30] 李恩溢, 马柯, 蔡旭. 模块化多电平变流器的子模块工况模拟测试方法[J]. 电力系统自动化, 2022, 46(4): 132-142. Li Enyi, Ma Ke, Cai Xu.Operating condition simulation test method for sub-modules of modular multilevel converter[J]. Automation of Electric Power Systems, 2022, 46(4): 132-142. [31] Tang Yuan, Ran Li, Alatise O, et al.Improved testing capability of the model-assisted testing scheme for a modular multilevel converter[J]. IEEE Transactions on Power Electronics, 2016, 31(11): 7823-7836. [32] 王希东, 宋剑波, 任伟. 失真信号采样技术研究[J]. 电子测量与仪器学报, 2006, 20(1): 85-88. Wang Xidong, Song Jianbo, Ren Wei.Study of the technique for acquiring the distorted signal[J]. Journal of Electronic Measurement and Instrument, 2006, 20(1): 85-88. [33] 崔忠奎. 电测信号数据采集误差与采样频率确定[J]. 佳木斯工学院学报, 1988, 6(2): 26-30. Cui Zhongkui.Data acquisition error and sampling frequency determination of electrical measurement signal[J]. Journal of Jiamusi University (Natural Science Edition), 1988, 6(2): 26-30.
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