Transactions of China Electrotechnical Society  2024, Vol. 39 Issue (4): 1116-1131    DOI: 10.19595/j.cnki.1000-6753.tces.222091
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Transient Current Bias Suppression Strategy of Full Phase Shifting Dual Active Full Bridge DC Converter
Wu Chunhua, Chen Xiulin, Li Zhihua, Wang Fei
Shanghai Key Laboratory of Power Station Automation Technology Department of Electrical Engineering Shanghai University Shanghai 200444 China

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Abstract  The research on dual active full-bridge (DAB) converters mainly focuses on phase-shifting methods, topology, and dynamic response. Among them, phase shift methods include single phase shift, double phase shift, extended phase shift, and triple phase shift. These different phase-shifting methods correspond to different inductor current stress and reflux power, but the ultimate goal is to obtain higher transmission efficiency.
When the transmission power changes suddenly, the traditional phase shifting method will cause the circuit current to generate a DC bias. This biased current will increase the current stress of the inductor, and in severe cases, it will also cause the transformer to be biased. Therefore, a transition state is introduced to suppress the DC bias when the power changes suddenly. Firstly, the DAB converter based on full phase-shift modulation is taken as the research object. The current of the bridge arm on the low-voltage side of the DAB converter with this structure is reduced by half, and the voltage of the transformer on the secondary side is also reduced by half. Therefore, the conduction loss can be reduced, and the transmission efficiency can be improved. The global optimal solution of inductor current stress can be obtained by full phase shift modulation. The optimal solution is divided into four regions, and the sudden current change in each optimal region is analyzed. Two kinds of phase shifting states are divided, and each phase shifting state corresponds to a different relationship between the magnitude of the phase shifting angle. The sudden power change is discussed in the same direction and reverses sudden change in these two phase-shifting states. The corresponding current bias results can be obtained when the power changes suddenly in the full range. This result with a three-dimensional surface diagram fully reflects the magnitude of the inductor current bias generated when the power changes suddenly. Then, a new DC bias suppression strategy is proposed, which adopts a unified transition state introduction method for all power mutation situations. For all phase-shifting states, the pulse signals of the same group of switches are changed to facilitate the realization of unified modulation. Moreover, with the goal of no DC bias after power mutation, the transition-state phase shift angles corresponding to various sudden changes are calculated. It is shown that the same transition state results can be obtained by power mutation in different regions without changing the power mutation direction. Thus, the controller implementation is simplified, and fewer control chip resources are occupied while maintaining a fast dynamic response. Finally, a unified carrier modulation strategy is proposed. The applicability of the modulation strategy is analyzed, and the modulation method is applied to the experimental platform. During the experiment, the power is mutated in the same direction and reversed in the four optimal regions. The experimental results show that the method proposed can effectively suppress the DC bias when the power changes suddenly, and the dynamic response is relatively stable.
Through the above analysis and verification, the following conclusions can be obtained: (1) The traditional phase-shift modulation strategy will produce a current bias phenomenon when the power changes suddenly. In particular, the DC bias is more apparent when the power is suddenly changed across regions and reversed. (2) The proposed method of introducing a transition state can effectively solve the DC bias phenomenon. In addition, different phase shift states and working areas can obtain consistent results, simplifying the modulation process. A stable transition is achieved while ensuring the global optimum of the inductor current stress. (3) Switching pulses are generated by a new carrier modulation method. The suppression of the DC bias can be completed within one cycle, and no imbalance will occur. The experimental results are consistent with the theoretical analysis, which verifies the proposed method.
Key wordsDual active full bridge (DAB) converter      sudden change of power      transient DC bias suppression      full phase shift control      carrier modulation     
Received: 06 November 2022     
PACS: TM614  
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Wu Chunhua
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Wang Fei
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Wu Chunhua,Chen Xiulin,Li Zhihua等. Transient Current Bias Suppression Strategy of Full Phase Shifting Dual Active Full Bridge DC Converter[J]. Transactions of China Electrotechnical Society, 2024, 39(4): 1116-1131.
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https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.222091     OR     https://dgjsxb.ces-transaction.com/EN/Y2024/V39/I4/1116
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