Control Strategy Based on the Energy Balance for Reducing Sub-Module Capacitor Voltage Fluctuation of Modular Multilevel Converter
Li Kai1, Zhao Zhengming1, Yuan Liqiang1, Lu Sizhao2
1. State Key Lab of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China; 2. Kunming University of Science and Technology Kunming 650504 China
Abstract：Capacitors are the key elements in the sub-modules of the modular multilevel converter (MMC). Reducing sub-module capacitor voltage fluctuation is a dual requirement to improve capacitor reliability and reduce converter costs. Firstly, the influence of different circulating currents to the capacitor voltage fluctuation is analyzed in this paper. It is shown that injecting the typical 2nd order circulating current can reduce the capacitor voltage fluctuation greatly without increasing too much loss. Secondly, after introducing the existing energy-balance based control strategy with the line-cycle time scale, the control strategy with the control-cycle time scale is proposed. It can reduce the capacitor voltage fluctuation by injecting the 2nd order circulating current and improve the transient performance at the same time. Compared with the traditional proportional-integral controller, the proposed energy-balance based control strategy avoids the complicated adjusting process of parameters, which can be used in various conditions. Finally, both simulation and experimental results verify the proposed control strategy.
李凯, 赵争鸣, 袁立强, 鲁思兆. 基于能量平衡的降低模块化多电平变换器子模块电容电压波动控制策略[J]. 电工技术学报, 2017, 32(14): 17-26.
Li Kai, Zhao Zhengming, Yuan Liqiang, Lu Sizhao. Control Strategy Based on the Energy Balance for Reducing Sub-Module Capacitor Voltage Fluctuation of Modular Multilevel Converter. Transactions of China Electrotechnical Society, 2017, 32(14): 17-26.
[1] Marquardt R. Stromrichterschaltungen mit verteilten energiespeichern: Germany, DE 10103033031A1[P]. 2001-1-24. [2] 童时中. 模块化理论和方法是现代工业大生产的基础[J]. 水利电力机械, 1997(2): 22-25. Tong Shizhong. Modularization theory & method is the base of modern industry large-scale production[J]. Water Conservancy & Electric Power Machinery, 1997(2): 22-24. [3] Debnath S, Jiangchao Q, Bahrani B, et al. Operation, control and applications of the modular multilevel converter: a review[J]. IEEE Transactions on Power Electronics, 2015, 30(1): 37-53. [4] 黄守道, 彭也伦, 廖武. 模块化多电平型变流器电容电压波动及其抑制策略研究[J]. 电工技术学报, 2015, 30(7): 62-71. Huang Shoudao, Peng Yelun, Liao Wu. Study of capacitor voltage fluctuation and its suppression for modular multilevel converter[J]. Transactions of China Electrotechnical Society, 2015, 30(7): 62-71. [5] Deng F, Chen Z, Khan M R, et al. Fault detection and localization method for modular multilevel con- verters[J]. IEEE Transactions on Power Electronics, 2015, 30(5): 2721-2732. [6] Ilves K, Norrga S, Harnefors L, et al. On energy storage requirements in modular multilevel con- verters[J]. IEEE Transactions on Power Electronics, 2014, 29(1): 77-88. [7] Engel S P, De Doncker R W. Control of the modular multi-level converter for minimized cell capacitance[C]// Proceedings of European Conference on Power Electronics and Applications (EPE), Birmingham, UK, 2011: 1-10. [8] Picas R, Pou J, Ceballos S, et al. Optimal injection of harmonics in circulating currents of modular multi- level converters for capacitor voltage ripple mini- mization[C]//Proceedings of IEEE Energy Conversion Congress and Exposition Asia Downunder, Melbourne, Australia, 2013: 318-324. [9] Pou J, Ceballos S, Konstantinou G, et al. Circulating current injection methods based on instantaneous information for the modular multilevel converter[J]. IEEE Transactions on Industrial Electronics, 2015, 62(2): 777-788. [10] Vasiladiotis M, Cherix N, Rufer A. Accurate capacitor voltage ripple estimation and current control considerations for grid-connected modular multilevel converters[J]. IEEE Transactions on Power Electronics, 2014, 29(9): 4568-4579. [11] Bergna G, Berne E, Egrot P, et al. An energy-based controller for HVDC modular multilevel converter in decoupled double synchronous reference frame for voltage oscillation reduction[J]. IEEE Transactions on Industrial Electronics, 2013, 60(6): 2360-2371. [12] Li B, Zhang Y, Wang G, et al. A modified modular multilevel converter with reduced capacitor voltage fluctuation[J]. IEEE Transactions on Industrial Electronics, 2015, 62(10): 6108-6119. [13] Lu S, Yuan L, Zhao Z, et al. An energy-based multi- loops control strategy for MMC[C]//Proceedings of International Conference on Electrical Machines and Systems, Pattaya, Thailand, 2015: 553-558. [14] Li K, Li C, Lee F C, et al. Precise control law of MMC and its application in reducing capacitor voltage ripple by injecting circulating current[C]// Proceedings of International Conference on Electrical Machines and Systems (ICEMS), Pattaya, Thailand, 2015: 371-377. [15] Hagiwara M, Maeda R, Akagi H. Control and analysis of the modular multilevel cascade converter based on double-star chopper-cells (MMCC-DSCC)[J]. IEEE Transactions on Power Electronics, 2011, 26(6): 1649-1658. [16] Li Binbin, Xu Dandan, Xu Dianguo. Circulating current harmonics suppression for modular multilevel converters based on repetitive control[J]. Journal of Power Electronics, 2014, 14(6): 1100-1108. [17] Marzoughi A, Burgos R, Boroyevich D, et al. Analysis of capacitor voltage ripple minimization in modular multilevel converter based on average model[C]//IEEE Workshop on Control and Modeling for Power Electronics (COMPEL), British Columbia, Canada, 2015: 1-7. [18] Yin L, Zhao Z, Lu T, et al. An improved DC-link voltage fast control scheme for a PWM rectifier- inverter system[J]. IEEE Transactions on Industrial Applications, 2014, 50(1): 462-473. （编辑 陈 诚）
2017, Vol. 32 
