A Level Multiplication MMC Topology and Modulation Strategy for Medium Voltage DC System

doi:10.12204/j.issn.1000-7229.2022.05.005

Abstract

Abstract:

Since the level number of modular multi-level converters (MMC) used in medium voltage DC systems is small, it is difficult to operate with lower operating losses and higher voltage quality. Thus, a level multiplication MMC (LM-MMC) topology and level multiplication modulation (LMM) strategy is designed. By introducing B-submodules with capability of parallel output non-integer level, the output level of LM-MMC can be multiplicated. Secondly, the operation mode of submodule is rotated according to the sorting result, which can effectively balance the capacitor voltages. In addition, when the LMM strategy is applied to the LM-MMC topology, the sum of output level in the upper and lower arms is constant, and the circulating current of the converter is lower. Finally, according to the simulation and physical experiment results, the operating loss of LMM strategy applied to the LM-MMC topology is lower, and the output waveform quality is higher.

Key words: level multiplication modular multilevel converter(LM-MMC), level multiplication modulation (LMM), voltage quality, circulation current, power loss

CLC Number:

TM46

XU Tong, WANG Chen, TAO Jianye, WANG Yi, LIU Fei, WANG Shibin, TIAN Xu, LIU Liantao. A Level Multiplication MMC Topology and Modulation Strategy for Medium Voltage DC System[J]. ELECTRIC POWER CONSTRUCTION, 2022, 43(5): 40-49.

Figures/Tables 18

Fig.1 Topology of traditional three-phase MMC

Fig.2 Schematic diagram of traditional NLM

Fig.3 Schematic diagram of CPS-PWM

Fig.4 Topology of LM-MMC

Fig.5 Topology and working model of B-SM(d=2)

Fig.6 Topology and working model of B-SM(d=3)

Fig.7 Inrush current suppression strategy

Fig.8 Principle of LMM

Fig.9 Principle of capacitor voltage ranking

Fig.10 Process of working mode determination

Fig.11 Simulation model

Table 1 Simulation parameters

Fig.12 Simulation results comparison of four modulation strategies

Fig.13 Power loss of four modulation strategies

Fig.14 Simulation results when d=3

Fig.15 Experiment system

Table 2 Experiment parameters

Fig.16 Experiment results

References 24

[1]	胡鹏飞, 朱乃璇, 江道灼, 等. 柔性互联智能配电网关键技术研究进展与展望[J]. 电力系统自动化, 2021, 45(8): 2-12.
	HU Pengfei, ZHU Naixuan, JIANG Daozhuo, et al. Research progress and prospects of key technologies of flexible interconnected smart distribution network[J]. Automation of Electric Power Systems, 2021, 45(8): 2-12.
[2]	周月宾, 宋强, 杨柳, 等. 模块化多电平换流器电容用量的标幺化分析与设计方法[J]. 电力建设, 2021, 42(11): 1-12.
	ZHOU Yuebin, SONG Qiang, YANG Liu, et al. Design and analysis for energy storage requirements of modular multilevel converter applying per-unit model[J]. Electric Power Construction, 2021, 42(11): 1-12.
[3]	苏麟, 朱鹏飞, 闫安心, 等. 苏州中压直流配电工程设计方案及仿真验证[J]. 中国电力, 2021, 54(1): 78-88.
	SU Lin, ZHU Pengfei, YAN Anxin, et al. Design scheme and simulation verification of Suzhou medium voltage DC distribution project[J]. Electric Power, 2021, 54(1): 78-88.
[4]	熊雄, 季宇, 李蕊, 等. 直流配用电系统关键技术及应用示范综述[J]. 中国电机工程学报, 2018, 38(23): 6802-6813.
	XIONG Xiong, JI Yu, LI Rui, et al. An overview of key technology and demonstration application of DC distribution and consumption system[J]. Proceedings of the CSEE, 2018, 38(23): 6802-6813.
[5]	魏志文, 罗煜, 曾远方, 等. 中压配电网柔性互联示范工程技术方案设计[J]. 电力建设, 2022, 43(3): 1-11.
	WEI Zhiwen, LUO Yu, ZENG Yuanfang, et al. Technical scheme design of an MVAC distribution network project for demonstration with MVDC flexible interconnection[J]. Electric Power Construction, 2022, 43(3): 1-11.
[6]	张爽, 李宏强, 王峰, 等. 基于电压源换流器的多端柔性直流输电系统拟交流最优潮流[J]. 电力系统保护与控制, 2020, 48(13): 31-37.
	ZHANG Shuang, LI Hongqiang, WANG Feng, et al. Quasi-AC optimal power flow for voltage source converter-based multi-terminal DC system[J]. Power System Protection and Control, 2020, 48(13):31-37.
[7]	王威儒, 辛业春, 丛佳琦, 等. 模块化多电平换流器混合调制策略[J]. 电力建设, 2018, 39(3): 77-82.
	WANG Weiru, XIN Yechun, CONG Jiaqi, et al. Hybrid modulation strategy of modular multilevel converter[J]. Electric Power Construction, 2018, 39(3): 77-82.
[8]	胡灿, 付超, 王毅. 直流配电网中MMC的谐波分析与调制方法设计[J]. 电力建设, 2018, 39(7): 81-88.
	HU Can, FU Chao, WANG Yi. Harmonic analysis and modulation design of MMC in DC distribution network[J]. Electric Power Construction, 2018, 39(7): 81-88.
[9]	罗永捷, 宋勇辉, 熊小伏, 等. 高压大容量MMC换流阀损耗精确计算[J]. 中国电机工程学报, 2020, 40(23): 7730-7742.
	LUO Yongjie, SONG Yonghui, XIONG Xiaofu, et al. Accurate loss calculation method for bulk-power MMCs[J]. Proceedings of the CSEE, 2020, 40(23): 7730-7742.
[10]	蔡信健, 吴振兴, 孙乐, 等. 直流电压不均衡的级联H桥多电平变频器载波移相PWM调制策略的设计[J]. 电工技术学报, 2016, 31(1): 119-127.
	CAI Xinjian, WU Zhenxing, SUN Le, et al. Design for phase-shifted carrier pulse width modulation of cascaded H-bridge multi-level inverters with non-equal DC voltages[J]. Transactions of China Electrotechnical Society, 2016, 31(1): 119-127.
[11]	王坤, 刘开培, 王思茹, 等. 基于排序算法的MMC电容电压均衡策略对比研究[J]. 电力建设, 2017, 38(11): 9-18.
	WANG Kun, LIU Kaipei, WANG Siru, et al. Comparative analysis on MMC capacitor voltage balancing strategy based on sorting algorithm[J]. Electric Power Construction, 2017, 38(11): 9-18.
[12]	李笑倩, 宋强, 刘文华, 等. 采用载波移相调制的模块化多电平换流器电容电压平衡控制[J]. 中国电机工程学报, 2012, 32(9): 49-55.
	LI Xiaoqian, SONG Qiang, LIU Wenhua, et al. Capacitor voltage balancing control by using carrier phase-shift modulation of modular multilevel converters[J]. Proceedings of the CSEE, 2012, 32(9): 49-55.
[13]	马信乔, 程启明, 江畅, 等. 基于双载波调制策略的模块化多电平矩阵变换器的优化电平方法[J]. 高电压技术, 2021, 47(3): 963-971.
	MA Xinqiao, CHENG Qiming, JIANG Chang, et al. Optimized level method for modular multilevel matrix converter based on dual-carrier modulation strategy[J]. High Voltage Engineering, 2021, 47(3): 963-971.
[14]	DARUS R, POU J, KONSTANTINOU G, et al. A modified voltage balancing algorithm for the modular multilevel converter: Evaluation for staircase and phase-disposition PWM[J]. IEEE Transactions on Power Electronics, 2015, 30(8): 4119-4127. doi: 10.1109/TPEL.2014.2359005 URL
[15]	PEREZ-BASANTE A, CEBALLOS S, KONSTANTINOU G, et al. Circulating current control for modular multilevel converters with (N+1) selective harmonic elimination:PWM[J]. IEEE Transactions on Power Electronics, 2020, 35(8): 8712-8725. doi: 10.1109/TPEL.2020.2964522 URL
[16]	PANDA K P, LEE S S, PANDA G. Reduced switch cascaded multilevel inverter with new selective harmonic elimination control for standalone renewable energy system[J]. IEEE Transactions on Industry Applications, 2019, 55(6): 7561-7574. doi: 10.1109/TIA.2019.2904923 URL
[17]	王琛, 许同, 王毅, 等. 一种适用于少子模块MMC的等效电平调制策略[J]. 中国电机工程学报, 2021, 41(14): 4954-4964.
	WANG Chen, XU Tong, WANG Yi, et al. An equivalent level modulation strategy for MMC with small quantities of submodules[J]. Proceedings of the CSEE, 2021, 41(14): 4954-4964.
[18]	LIN L, LIN Y Z, HE Z, et al. Improved nearest-level modulation for a modular multilevel converter with a lower submodule number[J]. IEEE Transactions on Power Electronics, 2016, 31(8): 5369-5377. doi: 10.1109/TPEL.2016.2521059 URL
[19]	CHEN X X, LIU J J, SONG S G, et al. Circulating harmonic currents suppression of level-increased NLM based modular multilevel converter with deadbeat control[J]. IEEE Transactions on Power Electronics, 2020, 35(11): 11418-11429. doi: 10.1109/TPEL.2020.2982781 URL
[20]	WANG Y, HU C, DING R Y, et al. A nearest level PWM method for the MMC in DC distribution grids[J]. IEEE Transactions on Power Electronics, 2018, 33(11): 9209-9218. doi: 10.1109/TPEL.2018.2792148 URL
[21]	许仪勋, 冯紫妍, 张建浩, 等. 一种适用于少子模块MMC全电平模式混合调制策略[J]. 华北电力大学学报(自然科学版), 2021, 48(6): 14-23.
	XU Yixun, FENG Ziyan, ZHANG Jianhao, et al. An equivalent level modulation strategy for MMC with small quantities of submodules in DC distribution grid[J]. Journal of North China Electric Power University (Natural Science Edition), 2021, 48(6): 14-23.
[22]	ILVES K, TAFFNER F, NORRGA S, et al. A submodule implementation for parallel connection of capacitors in modular multilevel converters[C]// 2013 15th European Conference on Power Electronics and Applications (EPE). 2013: 1-10.
[23]	ABB Group. Insulated gate bipolar transistor (IGBT) and diode modules with SPT and SPT+chips[EB/OL]. ABB Press, 2017. (2017-03-02)[2021-05-03]. http://new.abb.com/semiconductors/igbt-and-diode-modules.
[24]	王琛, 许同, 王毅, 等. 具备阻断直流故障电流能力的MMC钳位双电容子模块[J]. 高电压技术, 2021, 47(5): 1729-1739.
	WANG Chen, XU Tong, WANG Yi, et al. A clamp dual capacitor submodule of MMC with DC fault current blocking capability[J]. High Voltage Engineering, 2021, 47(5): 1729-1739.