A Hybrid Multiplexing MMC Topology with Wide Operating Range and Energy Balance Control Strategy
Wang Rui1, Wang Yi1, Yang Hanfei1, Gao Yuhua1, Su Zimeng1, Ma Junchao2
1. Hebei Key Laboratory of Distributed Energy Storage and Micro-Grid North China Electric Power University Baoding 071003 China; 2. State Grid Zhejiang Electric Power Co. Ltd Research Institute Hangzhou 310000 China
Abstract：The modular multilevel converter (MMC) faces challenges due to the excessive number of submodules, which causes disadvantages such as a large area, heavyweight, and high cost of the converter station. A hybrid multiplexing modular multilevel converter (HM-MMC) is proposed to address this issue. On the AC side, HM-MMC achieves full-cycle multiplexing of the bridge arms through the alternating conduction of switch groups. Thus, the number of submodules in HM-MMC is reduced. An energy exchange circuit is established between the bridge arm and the DC side on the DC side, which balances energy in the bridge arms and facilitates wide-range voltage regulation. Firstly, by applying the coordination of switch groups, two MMCs' bridge arms at each phase are changed into a single multiplexed bridge arm in HM-MMC, reducing submodules and capacitors for lightweight construction. The topology features positive and negative guided operation modes that alternate every half cycle, allowing the multiplexing of bridge arms. These arms are designed to output a sinusoidal half-wave under two guided operation modes. With the help of switch groups, the HM-MMC achieves half-wave inversion, thereby generating a full sinusoidal wave on the AC side. Furthermore, a controlled energy exchange circuit is constructed using the DC side unit in each cycle, with the bridge arm directly connected to the DC side capacitor. This circuit allows surplus or missing energy from the bridge arms to charge or discharge the capacitor on the DC side, ensuring the voltage stability of submodules. Due to the structure and control strategy of HM-MMC, a slight increase in the number of submodules extends the energy exchange time, thereby removing limitations on the modulation ratio. Through simulation and experimental results, the following conclusions can be drawn: (1) Through the cooperation of the switch groups, the full-cycle multiplexing of the bridge arm submodules is realized. The number of submodules is reduced by about 72% compared to conventional MMC. Besides, the operating frequency of the multiplexing switch groups is the power frequency or triple power frequency. There are no high-frequency switching actions during the operation of HM-MMC, which reduces the requirements for dynamic voltage balancing and switching consistency of the series insulated gate bipolar transistors (IGBTs). (2) HM-MMC establishes an energy exchange circuit for the bridge arms by multiplexing DC side units. Accordingly, the submodules in arms can carry out controlled charge or discharge to maintain capacitor voltage stability, and the modulation range of HM-MMC is extended to [0, 4/π]. In addition, due to the coordination of the DC unit and the switch groups, when more submodules are required at a low modulation ratio, the exchange time of the bridge arm is extended. The average number of submodules per phase of HM-MMC is 0.567N. (3) The proposed energy balance, current control, hybrid multiplexing operation modes, and time-sharing modulation strategy form a comprehensive control strategy of HM-MMC. This strategy achieves a controllable energy balance based on lightweight MMC and avoids the influence on the output AC voltage of the phase unit.
王锐, 王毅, 杨晗菲, 高玉华, 苏子萌, 马骏超. 具有宽运行范围的混合复用型模块化多电平拓扑及其能量均衡控制策略[J]. 电工技术学报, 2025, 40(15): 4740-4754.
Wang Rui, Wang Yi, Yang Hanfei, Gao Yuhua, Su Zimeng, Ma Junchao. A Hybrid Multiplexing MMC Topology with Wide Operating Range and Energy Balance Control Strategy. Transactions of China Electrotechnical Society, 2025, 40(15): 4740-4754.
[1] 刘欣, 袁易, 王利桐, 等. 柔性直流输电系统三端口混合参数建模及其稳定性分析[J]. 电工技术学报, 2024, 39(16): 4968-4984. Liu Xin, Yuan Yi, Wang Litong, et al.Three-port hybrid parameter modeling and stability analysis of MMC-HVDC system[J]. Transactions of China Elec- trotechnical Society, 2024, 39(16): 4968-4984. [2] 武鸿, 王跃, 刘熠, 等. 基于广义电容电压不平衡度的MMC子模块开路故障诊断策略[J]. 电工技术学报, 2023, 38(14): 3909-3922. Wu Hong, Wang Yue, Liu Yi, et al.Open circuit fault diagnosis strategy of MMC sub-module based on generalized capacitor voltage unbalance[J]. Transa- ctions of China Electrotechnical Society, 2023, 38(14): 3909-3922. [3] 侯玉超, 郭祺, 涂春鸣, 等. 面向输出性能优化的高低频混合型模块化多电平变换器及其调控策略[J]. 电工技术学报, 2024, 39(14): 4467-4479. Tu Chunming, Wang Xin, Wang Ying, et al.A high and low frequency hybrid modular multilevel converter for output performance optimization and its control strategy[J]. Transactions of China Electro- technical Society, 2024, 39(14): 4467-4479. [4] Rao N P, Shukla A.Analysis of capacitor voltage unbalance in hybrid MMC and its novel operation with reduced submodule capacitance[J]. IEEE Journal of Emerging and Selected Topics in Power Elec- tronics, 2022, 10(6): 7271-7284. [5] 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. [6] 王琛, 陶建业, 王毅, 等. 桥臂复用型模块化多电平换流器的拓扑及控制研究[J]. 中国电机工程学报, 2022, 42(9): 3373-3385. Wang Chen, Tao Jianye, Wang Yi, et al.Research on topology and control of arm multiplexing modular multilevel converter[J]. Proceedings of the CSEE, 2022, 42(9): 3373-3385. [7] 李宇薇, 王毅, 高玉华, 等. 桥臂复用模块化多电平变流器单极接地故障无闭锁穿越及能量均衡[J]. 电工技术学报, 2025, 40(1): 190-202. Li Yuwei, Wang Yi, Gao Yuhua, et al.Pole-to-ground fault riding-through and energy balance of arm- multiplexing modular multilevel converter[J]. Transa- ctions of China Electrotechnical Society, 2025, 40(1): 190-202. [8] Merlin M M C, Green T C, Mitcheson P D, et al. The alternate arm converter: a new hybrid multilevel converter with DC-fault blocking capability[J]. IEEE Transactions on Power Delivery, 2014, 29(1): 310-317. [9] Farr E, Feldman R, Watson A, et al.A sub-module capacitor voltage balancing scheme for the alternate arm converter (AAC)[C]//2013 15th European Con- ference on Power Electronics and Applications (EPE), Lille, France, 2013: 1-10. [10] Wickramasinghe H R, Sun Pingyang, Konstantinou G.A hybrid VSC-HVDC system based on modular multilevel converter and alternate arm converter[C]// IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society, Singapore, Singapore, 2020: 4141-4146. [11] 高玉华, 王琛, 王毅, 等. 基于半波交替的轻型化MMC拓扑及控制策略[J]. 电力系统自动化, 2023, 47(17): 149-159. Gao Yuhua, Wang Chen, Wang Yi, et al.Topology and control strategy of light-weight modular multi- level converter with half-wave alternating[J]. Auto- mation of Electric Power Systems, 2023, 47(17): 149-159. [12] 范世源, 杨贺雅, 杨欢, 等. 具有故障穿越能力的T型桥臂交替多电平换流器及其调制策略[J]. 电力系统自动化, 2021, 45(8): 41-50. Fan Shiyuan, Yang Heya, Yang Huan, et al.T-type alternate arm multilevel converter with fault ride- through capability and its modulation strategy[J]. Automation of Electric Power Systems, 2021, 45(8): 41-50. [13] 任鹏, 涂春鸣, 侯玉超, 等. 基于Si和SiC器件的混合型级联多电平变换器及其调控优化方法[J]. 电工技术学报, 2023, 38(18): 5017-5028. Ren Peng, Tu Chunming, Hou Yuchao, et al.Research on a hybrid cascaded multilevel converter based on Si and SiC device and its control optimization method[J]. Transactions of China Electrotechnical Society, 2023, 38(18): 5017-5028. [14] 薛英林, 徐政, 王峰. 基于三次谐波电流注入的AAMC电容电压均衡策略[J]. 电工技术学报, 2013, 28(9): 104-111. Xue Yinglin, Xu Zheng, Wang Feng.Capacitor voltage balancing strategy base on third harmonic current injection for the alternate-arm multilevel converter[J]. Transactions of China Electrotechnical Society, 2013, 28(9): 104-111. [15] 王顺亮, 廖鑫, 张芮, 等. 基于三次谐波注入的桥臂交替换流器子模块电容优化方法[J]. 电力系统自动化, 2024, 48(12): 165-176. Wang Shunliang, Liao Xin, Zhang Rui, et al.Submodule capacitance optimization method for alternate arm converter based on third harmonic injection[J]. Automation of Electric Power Systems, 2024, 48(12): 165-176. [16] Reddy G A, Karaka N R, Shukla A.Constant overlap-time based SMS capacitor voltage balancing scheme for alternate arm converter[C]//2021 IEEE Energy Conversion Congress and Exposition (ECCE), Vancouver, BC, Canada, 2021: 2595-2600. [17] Yang Heya, Qu Qiannan, Chen Cong, et al.Sub- module capacitor voltage control for alternate arm converter with current commutation modulation[J]. IEEE Transactions on Power Delivery, 2024, 39(1): 635-646. [18] Farr E M, Feldman R, Clare J C, et al.The alternate arm converter (AAC): “short-overlap” mode operation: analysis and design parameter selection[J]. IEEE Transactions on Power Electronics, 2018, 33(7): 5641-5659. [19] Wickramasinghe H R, Konstantinou G, Pou J.Gradient-based energy balancing and current control for alternate arm converters[J]. IEEE Transactions on Power Delivery, 2018, 33(3): 1459-1468. [20] Farr E M, Feldman R, Clare J C, et al.The alternate arm converter “extended-overlap” mode: AC faults[J]. IEEE Transactions on Power Electronics, 2021, 36(5): 5371-5388. [21] Merlin M M C, Soto-Sanchez D, Judge P D, et al. The extended overlap alternate arm converter: a voltage- source converter with DC fault ride-through capa- bility and a compact design[J]. IEEE Transactions on Power Electronics, 2018, 33(5): 3898-3910. [22] Liu Shenquan, Saeedifard M, Wang Xifan.Zero- current switching control of the alternate arm HVDC converter station with an extended overlap period[J]. IEEE Transactions on Industrial Electronics, 2019, 66(3): 2355-2365. [23] Zhang Rui, Wang Shunliang, Ma Junpeng, et al.Capacitor voltage balancing for alternate arm converter based on conduction angle and zero- sequence voltage[J]. IEEE Transactions on Power Electronics, 2023, 38(3): 3268-3280. [24] Chivite-Zabalza J, Trainer D R, Nicholls J C, et al.Balancing algorithm for a self-powered high-voltage switch using series-connected IGBTs for HVDC applications[J]. IEEE Transactions on Power Elec- tronics, 2019, 34(9): 8481-8490. [25] Wickramasinghe H R, Konstantinou G, Ceballos S, et al.Alternate arm converter energy balancing under parameter variation[J]. IEEE Transactions on Power Electronics, 2019, 34(4): 2996-3000.
2025, Vol. 40 
