一种基于内置变压器的高增益双向DC-DC变换器

提出一种应用在储能系统的双向DC-DC变换器,其具有电压增益高、电压应力小和软开关范围宽的优势。通过将内置变压器集成在飞跨电容结构和2个交错的Buck/Boost结构中,可以同时实现电压增益高和电压应力小。内置变压器结构的特点是磁芯中的磁通可以相互抵消,避免了磁饱和,从而有效地减小磁性器件的体积。通过采用交错的结构,低压侧的电流纹波明显减少;通过调节占空比,实现变压器原、副两边的电压匹配,从而减少环流;同时,通过采用移相控制,可以单调地调节传输功率;合理设置参数后,所有MOSFET可以实现宽范围的软开关。详细给出了工作原理和稳态分析,并设计了额定功率为1kW的实验样机,以验证所述变换器的可行性。样机的效率在升压模式和降压模式下是相似的,这表明该变换器的效率是不受功率传输的方向影响的;在低压侧电压变化时,该变换器的效率变化不大。因此,所提变换器适用于需要高电压增益、宽电压侧电压范围的储能系统。

High Voltage-gain Bidirectional DC-DC Converter Based on Built-in Transformer

In this paper, a soft-switching bidirectional dc-dc converter (BDC) with high voltage-gain and low voltage stress is proposed for battery energy storage system. A built-in transformer is integrated into two-phase half-bridge BDC and flying-clamped structure to achieve high voltage-gain and reduced voltage stresses simultaneously. The feature of built-in transformer is that the balanced magnetic flux exists in the magnetic core, which allows for a small size of magnetic core. The current ripple in the battery side is reduced by adopting the interleaved structure. Moreover, the voltage-matching on both sides of the BT is realized by the adjustment of the duty cycle. As a result, the transformer always operates under the highest-efficiency condition. Besides, by employing phase-shift control, power flow can be regulated monotonously. Soft-switching of all the switches within a wide range of battery voltage is obtained by employing the optimal design. The operational principle and steady-state analysis are provided in detail. Experimental results from a prototype of 1-kW verify the effectiveness. It can be found that the efficiencies of the boost mode and buck mode are very close to each other. It can be concluded the power flow direction is not sensitive to the conversion efficiency. Moreover, the efficiency is insensitive to the variation of the low voltage side voltage. Therefore, the proposed BDC is a good candidate for the interface between the energy storage system with a wide voltage range and the high-voltage dc bus in dc microgrid.