Abstract：Dual-active-bridge (DAB) converters are commonly adopted in large-capacity modular power electronic transformers (PET) due to their high-frequency galvanic isolation, symmetrical structure, and inherent soft switching performance. For renewable energy and energy storage equipment applications, the DAB converter operates in the wide input-to-output voltage range, requiring new modulation strategies with lower loss and lower current stress. Meanwhile, the nonideal issues, such as dead band effects, switching waveforms oscillation, and pulses delay, remain to be settled. For DAB converters operating in a wide voltage range, the existing multi- phase-shift modulation strategies still have large computation and discontinuous operating range problems. Moreover, the dead band effects need to be further analyzed, and the dead-time compensation strategies may not be suitable for the wide operating range. Therefore, this paper proposes a three-phase-shift (TPS) modulation strategy for a wide operating range and a dead-time compensation strategy. Firstly, the optimal algorithm of the wide voltage range TPS modulation strategy is presented, and its power transmission characteristic is evaluated. Based on the model of leakage inductance current, the electrical parameters of TPS modulation in full operating range could be obtained. The current stress characteristics are compared between the TPS modulation and single-phase-shift (SPS) modulation. The switching current model describes the soft switching characteristics in different switching modes. Secondly, considering the non-ideal factors, the dead band effects in different switching modes are elaborated, including phase-shift duty cycle loss, switching mode boundary change, soft switch performance failure, and voltage polarity reversal and voltage sag phenomena in the transformer primary side. Regarding the voltage distortion, by calculating the commutation process and switch states during the dead band, the boundary of voltage polarity reversal and voltage sag are derived. Thirdly, a dead-time compensation strategy based on switching pulses adjustment is proposed regarding the phase-shift duty cycle loss and soft switch performance failure. By adjusting the drive pulses of diagonal switches in the primary H-bridge, the inherent soft switch characteristics in mode 1 can be restored, and the switching loss and current stress of switches can be reduced. Finally, the theoretical analysis and the proposed strategy are verified by PLECS simulation and the 1.5 kW DAB converter experiment platform, where two 600 V IGBT half-bridge modules are applied. The following conclusions can be drawn from the simulation and experimental results: (1) The wide voltage range TPS modulation strategy adopted in this paper has full-range soft switching performance and can realize continuous regulation in the full power range. In switching mode 1, S2 and S4 are the hard turn-off and zero-voltage turn-on, and other switches are zero-current turn-on and -off. In mode 2, all switches are zero-voltage turn-on and hard turn-off. (2) The experimental waveforms in different working conditions can verify the correctness of the dead band effect boundary conditions in the whole operating range derived from the theoretical calculation. According to the experimental data, the phase-shift duty cycle loss and the voltage pulse loss caused by the dead band could be compensated by the proposed compensation strategy, restore the soft switching performance, and reduce the current stress and switching loss of switching devices. (3) In the wide voltage and full power range, the result shows that the proposed strategy can improve the converter’s efficiency in all working conditions of switching mode 1 and most working conditions of mode 2. At the same time, without changing the control architecture and modulation algorithm of the system, the proposed dead-time compensation strategy is easily implemented in engineering.
康薇, 肖飞, 任强, 王瑞田, 张新生. 双有源桥DC-DC变换器三移相调制及其死区效应分析和补偿[J]. 电工技术学报, 2024, 39(6): 1907-1922.
Kang Wei, Xiao Fei, Ren Qiang, Wang Ruitian, Zhang Xinsheng. Three-Phase-Shift Modulation and Its Dead Band Effect Analysis and Compensation of Dual-Active-Bridge DC-DC Converter. Transactions of China Electrotechnical Society, 2024, 39(6): 1907-1922.
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