Abstract:The dual active bridge (DAB) DC-DC converter with voltage adjustment unit (VAU) is one of the solutions to reduce current stress in wide input voltage range. However, the impedance stability of the VAU-DAB cascade system is poor. This paper firstly deduces the output impedance model of the VAU and the input impedance model of the DAB, and analyzes the impedance ratio in the complex frequency domain according to the impedance stability criterion concept of the forbidden region. Because of the existing crossing point between the resonance peak of the VAU output impedance amplitude curve and DAB input impedance, the cascaded system is likely to cause system voltage oscillation instability due to impedance mismatch. Then, according to the impedance matching criteria, an impedance optimization controller based on lead-lag is proposed. By suppressing the convexity of the VAU output impedance, the cascade system meets the stability criterion, the system reliability is improved, and the current stress is reduced. Finally, the simulation verifies the proposed strategy.
农仁飚, 杨晓峰, 周兵凯, 李继成. 电压调整单元双有源桥级联系统的阻抗匹配优化设计[J]. 电工技术学报, 2021, 36(24): 5237-5249.
Nong Renbiao, Yang Xiaofeng, Zhou Bingkai, Li Jicheng. Optimal Design of Impedance Matching for Voltage Adjustment Unit-Dual Active Bridge Cascade System. Transactions of China Electrotechnical Society, 2021, 36(24): 5237-5249.
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