Abstract：The dual active bridge (DAB) has the advantages of bidirectional energy flow, low voltage and current stress of switching devices, input-output galvanic isolation, high power density, and soft switching. Thus, it is widely used in electric vehicles, DC distribution networks, microgrids, distributed energy, and other fields. When the input voltage changes or the load changes suddenly, the DAB converter will generate a transient DC bias current on the primary side of the transformer, leading to problems such as excessive primary current peak value and saturation of the transformer core. The improved triple phase shift (ITPS) control strategy based on direct power control is proposed to eliminate the DAB transient DC bias current. Firstly, the RMS optimization strategy based on multiple harmonic minimizations is reviewed, and the direct power control model of DAB under this strategy is deduced. Secondly, the transient DC bias current of different cases is analyzed, and the phase shift ratio combination scheme for suppressing the transient DC bias current is determined. When the DAB operation mode is changed, the duty cycle of the MOSFET in the transient period is adjusted to maintain the volt-second balance of the transformer. Then, when the DAB converter is used as a DC power supply, the transmission power and output voltage should be controlled. Since the relationship between the shift ratio and the transmission power is non-linear, the shift ratio cannot be directly determined by the voltage loop output. Therefore, combined with the power inner loop, the control method of the voltage outer loop based on the PI strategy is determined to realize the dual-loop control. Finally, a DAB converter prototype is built to verify the effectiveness of the proposed strategy. The experimental results show that when the transmission power steps within the heavy load range, the ITPS strategy shortens the transition time from six cycles to one cycle and reduces the peak value of transient current from 16 A to 11.5 A. When the transmission power steps from light load to heavy load, the ITPS strategy shortens the transition time from six cycles to one cycle and reduces the peak value of transient current from 19.7 A to 13.2 A. When the transmission power steps from heavy load to light load, there will be no current spike in the transient process, and the ITPS strategy shortens the transition time from four cycles to one cycle. In addition, compared with the SPS and FDM strategies, the ITPS strategy can reduce the RMS current by 18.5 % and effectively improves efficiency. The following conclusions can be drawn from the simulation and experimental results: (1) Compared with the traditional modulation strategy, the ITPS strategy can effectively suppress the transient bias current and shorten the transient process. (2) The ITPS strategy combines the dynamic performance of DAB with the optimization of steady-state performance, which can achieve a fast transient response while ensuring the optimization of the current RMS.
刘子薇, 孙兆龙, 刘宝龙, 郑伟. 基于直接功率控制的双有源桥暂态直流偏置抑制策略[J]. 电工技术学报, 2023, 38(12): 3234-3247.
Liu Ziwei, Sun Zhaolong, Liu Baolong, Zheng Wei. Transient DC Bias Suppression Strategy of Dual Active Bridge Based on Direct Power Control. Transactions of China Electrotechnical Society, 2023, 38(12): 3234-3247.
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2023, Vol. 38 
