宽增益高效率CLLLC变换器的变频双移相调制策略

Variable-Frequency Dual-Phase-Shift Modulation Strategy for CLLLC Converter with Wide Voltage Gain and High Efficiency

在输入电压宽范围变化时,变频调制CLLLC变换器存在开关频率变化范围宽的问题,而移相调制CLLLC变换器难以实现宽范围零电压导通(ZVS)。为了实现宽输入电压CLLLC变换器的高效率,该文提出一种变频双移相调制方法。通过同时调节开关频率、一次侧全桥和二次侧全桥之间的移相角,拓宽CLLLC变换器的增益并提高其效率。采用时域分析法求解变频双移相调制CLLLC变换器的电压增益与谐振电感电流有效值,并分析频率以及移相角对电压增益和谐振电感电流有效值的影响。最后,通过搭建一台100~300 V输入、48 V/400 W输出的实验样机,验证了理论分析的正确性。

In the DC microgrid,a bidirectional isolated DC-DC converter with a wide range of input voltage is required to ensure the safety and efficiency of power conversion.The CLLLC converter was selected by discussing the advantages and disadvantages of various DC-DC converters.Aiming at the problem of large secondary switch loss and limited step-down range of variable-frequency phase-shift modulated CLLLC converter,this paper proposes a variable-frequency dual-phase-shift(VF-DPS)modulation strategy.The proposed VF-DPS modulation strategy can enhance the voltage gain and efficiency of the CLLLC converter by simultaneously adjusting the switching frequency,phase-shift angle in the primary side full bridge,and phase-shift angle between the primary and secondary sides.The proposed strategy operates in two modes:the buck mode and the boost mode.In the buck mode,when the input voltage exceeds the rated input voltage,adjustments in the phase-shift angle in the primary side full bridge achieve a voltage gain of less than 1.In the boost mode,when the input voltage is below the rated input voltage,adjustments in the phase-shift angle in the secondary side full bridge result in a voltage gain greater than 1.According to these two modes,VF-DPS modulation is adopted for the CLLLC converter.The waveform shapes of the resonant inductor current and excitation inductor current are changed by VF-DPS modulation,achieving zero voltage switching(ZVS)for all switches.The modal analysis of the VF-DPS modulated CLLLC converter is conducted.Time domain analysis method is used to solve the voltage gain and resonant inductor current.Furthermore,the influence of different frequencies and phase-shift angles on the voltage gain and root mean square of the resonant inductor current is analyzed.An experimental prototype was designed with an input voltage of 100~300 V and an output of 400 W/48V.The experiments tested the wide input range,working mode,soft switching,and efficiency of the CLLLC converter.The peak efficiency is 95.1%in the buck mode and 94.4%in the boost mode,confirming soft switching in both operating modes.The VF-DPS modulated CLLLC converter has a wider gain range and higher efficiency than the variable-frequency phase-shift modulation.The proposed VF-DPS modulated CLLLC converter addresses challenges of wide switching frequency variations and ZVS losses in the wide input voltage of the variable-frequency modulated CLLLC converter and the phase-shift modulated CLLLC converter,respectively.The VF-DPS modulated CLLLC converter realizes the soft switching of all switches.Moreover,the converter achieves a voltage gain range of 3 times and a peak efficiency of 95.1%.Future research will focus on integrated magnetic design to further enhance efficiency and reduce the volume of the converter.