Abstract：When the bipolar DC microgrid is operated with various loads, voltage unbalance occurs between the positive and negative buses. A bipolar voltage balancer is required to balance the bipolar output voltage. This paper proposes an asymmetrically modulated three-level dual-active-bridge (DAB) bipolar voltage balancer that can operate in unipolar mode even if a fault occurs in one of the DC poles. The neutral-point-clamped (NPC) circuit serves as the secondary circuit of the DAB, with its two output capacitors connected to the positive and negative buses. The switching state [PN] and [NP] affect the total output power, while [PO] and [NO] affect the output power of both ports. Dd is the difference between the duty ratios of [PO] and [NO]. The differential power ΔPb is adjusted by changing Dd. The total power Pob is changed by D0, the shift ratio between the primary and secondary sides. Pob and ΔPb are also affected by D3 and Dc, where D3 is the duty ratio of [PN] or [NP], Dc is the average duty ratios of [PO] and [NO]. The waveform of inductor current iL is asymmetric when Dd≠0, and the average value of iL is zero. The mathematical model of Pob and ΔPb is established. Under the bipolar operation mode, D0 and Dd are used to adjust Pob and ΔPb. To reduce the peak-to-peak value of the inductor current and avoid failure of the single PI, the condition ∂Pob/∂D0<0 should be satisfied. To increase the range of differential power and avoid failure of a single PI, the condition ∂ΔPb/∂Dd<0 should be satisfied. The values of Dc and D3 affect the constraints of D0 and Dd, as well as the maximum value of Pob and ΔPb. The constraint ranges for D0 and Dd, with combination [D3, Dc], are established. The maximum values of Pob and ΔPb are analyzed. Taking the peak-to-peak value of the inductor current as the optimization goal, the Dc and D3 values under the optimal working point are obtained under the condition that [Pob, ΔPb] meets the given value. In unipolar operation mode, the output power at one port is zero; the converter only needs to supply energy to the other output port. It is equivalent to the traditional two-level DAB. The driving signal and steady-state waveforms of the converter operating in unipolar mode are shown. Finally, experimental waveforms for the DC 100 V/±DC 160 V converter prototype operating in bipolar and unipolar modes are presented, thereby verifying the effectiveness of the control strategy. The highest efficiency under the bipolar operation mode is 93.2%. Besides, when Pob remains constant, the conversion efficiency decreases as |ΔPb| increases. The following conclusions can be drawn. (1) ΔPb is mirror-symmetric with Dd about the zero point, which is beneficial to the bidirectional adjustment of ΔPb. (2) To avoid failure of the single PI controller and get better performance, the constraints ∂ΔPb/∂Dd<0 and ∂ΔPb/∂Dd should be satisfied. (3) Under the bipolar operation mode, the maximum of Pob is 0.75. With the increase of |ΔPb|, the maximum value of Pob is decreased. That means ΔPb is provided at the expense of Pob. (4) Under the unipolar operation mode, the maximum of Pob is 0.5. (5) The efficiency is highest in the medium output power range. Meanwhile, as |ΔPb| increases, the efficiency decreases.
陈艳慧, 戴伟成. 基于非对称调制的三电平双有源桥型双极电压平衡器[J]. 电工技术学报, 2026, 41(20): 6989-7005.
Chen Yanhui, Dai Weicheng. Three-Level Dual Active Bridge Bipolar Voltage Balancer Based on Asymmetric Modulation. Transactions of China Electrotechnical Society, 2026, 41(20): 6989-7005.
[1] 杨鸣, 汪小丰, 司马文霞, 等. 基于模型预测与复合占空比的双有源全桥变换器电压电流暂稳态调控方法[J]. 电工技术学报, 2025, 40(4): 1203-1220. Yang Ming, Wang Xiaofeng, Sima Wenxia, et al.Transient-and steady-state optimization of voltage and current for dual active bridge converters based on model predictive control and composite duty modu-lation[J]. Transactions of China Electrotechnical Society, 2025, 40(4): 1203-1220. [2] 李海波, 赵宇明, 刘国伟, 等. 基于时序仿真的商业楼宇交流与直流配电系统能效对比[J]. 电工技术学报, 2020, 35(19): 4194-4206. Li Haibo, Zhao Yuming, Liu Guowei, et al.The time sequential simulation based energy efficiency com-parison of AC and DC distribution power system in commercial buildings[J]. Transactions of China Electrotechnical Society, 2020, 35(19): 4194-4206. [3] 刘赞, 沙金, 邱高峰, 等. 多级离散扩展移相控制双有源桥DC-DC变换器的原理、参数设计与性能[J]. 电工技术学报, 2024, 39(12): 3761-3773. Liu Zan, Sha Jin, Qiu Gaofeng, et al.Principle, parameters design and performance of multistage discrete extended-phase-shift control dual active bridge DC-DC converters[J]. Transactions of China Electrotechnical Society, 2024, 39(12): 3761-3773. [4] 周念成, 范炳昕, 廖建权, 等. 计及直流变压器控制模式切换的直流配电网优化运行策略[J]. 电力系统自动化, 2025, 49(6): 176-186. Zhou Niancheng, Fan Bingxin, Liao Jianquan, et al.Optimal operation strategy for DC distribution net-work considering control mode switching of DC transformer[J]. Automation of Electric Power Systems, 2025, 49(6): 176-186. [5] Rivera S, Wu Bin, Kouro S, et al.Electric vehicle charging station using a neutral point clamped converter with bipolar DC bus[J]. IEEE Transactions on Industrial Electronics, 2015, 62(4): 1999-2009. [6] 周明珠, 刘超, 庄一展, 等. 一种非隔离型双极性输出DC-DC变换器合成方法[J]. 电工技术学报, 2025, 40(12): 3953-3963. Zhou Mingzhu, Liu Chao, Zhuang Yizhan, et al.A synthesis method for non-isolated DC-DC converters with bipolar outputs[J]. Transactions of China Elec-trotechnical Society, 2025, 40(12): 3953-3963. [7] 李霞林, 郭力, 王成山, 等. 直流微电网关键技术研究综述[J]. 中国电机工程学报, 2016, 36(1): 2-17. Li Xialin, Guo Li, Wang Chengshan, et al.Key technologies of DC microgrids: an overview[J]. Pro-ceedings of the CSEE, 2016, 36(1): 2-17. [8] 汪飞, 雷志方, 徐新蔚. 面向直流微电网的电压平衡器拓扑结构研究[J]. 中国电机工程学报, 2016, 36(6): 1604-1612. Wang Fei, Lei Zhifang, Xu Xinwei.Research on topologies of voltage balancers applied in DC micro-grid[J]. Proceedings of the CSEE, 2016, 36(6): 1604-1612. [9] Pires V F, Cordeiro A, Roncero-Clemente C, et al.DC-DC converters for bipolar microgrid voltage balancing: a comprehensive review of architectures and topologies[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2023, 11(1): 981-998. [10] 张来勇, 涂春鸣, 肖凡, 等. 双有源桥变换器电流应力的本征规律分析及其优化控制[J]. 电工技术学报, 2025, 40(12): 3977-3993. Zhang Laiyong, Tu Chunming, Xiao Fan, et al.Intrinsic law analysis and optimization control of current stress in dual active bridge converter[J]. Transactions of China Electrotechnical Society, 2025, 40(12): 3977-3993. [11] 尹政, 邓富金, 王青松, 等. 双有源桥变换器移动离散控制集无模型预测电压控制策略[J]. 电工技术学报, 2025, 40(6): 1853-1863. Yin Zheng, Deng Fujin, Wang Qingsong, et al.Model-free predictive voltage control with moving-discrete-control-set for dual active bridge con-verters[J]. Transactions of China Electrotechnical Society, 2025, 40(6): 1853-1863. [12] Kim K, Cha H.Dual-active-half-bridge converter with output voltage balancing scheme for bipolar DC distribution system[J]. IEEE Transactions on Indu-strial Electronics, 2022, 69(7): 6850-6858. [13] Lee J Y, Kim H S, Jung J H.Enhanced dual-active-bridge DC-DC converter for balancing bipolar voltage level of DC distribution system[J]. IEEE Transactions on Industrial Electronics, 2020, 67(12): 10399-10409. [14] Lin Yuchen, Zhou Feng, Xu Guo, et al.Bipolar current-fed DC-DC converter with automatic voltage balance and full range ZVS for bipolar DC system[J]. IEEE Transactions on Power Electronics, 2024, 39(4): 4248-4259. [15] Lee M, Choi D, Chae J, et al.Voltage-balancing dual-active-bridge (VB-DAB) converter for bipolar DC distribution system[J]. IEEE Transactions on Industrial Electronics, 2023, 70(3): 2461-2471. [16] Tian Qingxin, Zhang Xin, Zhou Guohua, et al.A family of symmetrical bipolar output converters based on voltage-multiplying rectifiers for interfacing renewable energy with bipolar DC microgrid[J]. IEEE Transactions on Power Electronics, 2023, 38(7): 9157-9172. [17] Van den Broeck G, Martinez W, Dalla Vecchia M, et al. Conversion efficiency of the buck three-level DC-DC converter in unbalanced bipolar DC microgrids[J]. IEEE Transactions on Power Electronics, 2020, 35(9): 9306-9319. [18] Zhang Xianjin, Gong Chunying.Dual-Buck half-bridge voltage balancer[J]. IEEE Transactions on Industrial Electronics, 2013, 60(8): 3157-3164. [19] Zhang Xianjin, Gong Chunying, Yao Zhilei.Three-level DC converter for balancing DC 800-V voltage[J]. IEEE Transactions on Power Electronics, 2015, 30(7): 3499-3507. [20] Lee J Y, Jung J H.Modified three-port DAB converter employing voltage balancing capability for bipolar DC distribution system[J]. IEEE Transactions on Industrial Electronics, 2022, 69(7): 6710-6721. [21] Byun H J, Kim S H, Lee Y S, et al.Control strategy of triple-active-bridge converter for bipolar DC micro-grid[J]. IEEE Transactions on Industrial Electronics, 2024, 71(9): 10658-10668. [22] 滕百川, 马建军, 朱淼, 等. 具备故障重构能力的双极直流接口变换器最优运行区域[J]. 中国电机工程学报, 2024, 44(10): 3998-4012. Teng Baichuan, Ma Jianjun, Zhu Miao, et al.Optimal working zone of DC-DC interface converter for bipolar DC distribution system with fault-tolerant capability[J]. Proceedings of the CSEE, 2024, 44(10): 3998-4012. [23] Naseem N, Cha H.Triple-active-bridge converter with automatic voltage balancing for bipolar DC distribution[J]. IEEE Transactions on Power Elec-tronics, 2022, 37(7): 8640-8648. [24] Lee J Y, Cho Y P, Jung J H.Single-stage voltage balancer with high-frequency isolation for bipolar LVDC distribution system[J]. IEEE Transactions on Industrial Electronics, 2020, 67(5): 3596-3606. [25] 安峰, 宋文胜, 杨柯欣. 基于扩展相移的双有源全桥DC-DC变换器多目标优化控制方法[J]. 中国电机工程学报, 2019, 39(3): 822-831, 961. An Feng, Song Wensheng, Yang Kexin.Multi-objective optimization control scheme based on extended phase-shift of dual-active-bridge DC-DC converters[J]. Proceedings of the CSEE, 2019, 39(3): 822-831, 961.
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