一种基于内置变压器的高增益双向DC-DC变换器

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

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1 kW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。

In this paper,a bidirectional DC-DC converter(BDC)with high voltage-gain,low voltage stress,and wide soft-switching range is proposed for energy storage systems.By integrating a built-in transformer into a flying-clamped structure and two interleaved buck/boost structures,the high voltage-gain and reduced voltage stress can be realized simultaneously.The feature of the built-in transformer is that a balanced magnetic flux exists in the magnetic core to avoid magnetic saturation,which allows for a smaller size of magnetic core.The current ripple on the low-voltage side is significantly reduced by adopting an interleaved structure.Moreover,the voltage-matching on both sides of the built-in transformer is realized by adjusting the duty cycle,thus reducing the current loop.Meanwhile,by employing phase-shift control,the power transmission can be regulated monotonously.The soft-switching of all MOSFETs within a wide range of battery voltage is realized by reasonably configuring parameters.The operational principle and steady-state analysis were given in detail,and a prototype of 1 kW rated power was designed to verify the effectiveness of the proposed converter.It is found that the efficiencies of the prototype in boost and buck modes are similar,indicating that the conversion efficiency is not sensitive to the power flow direction.In addition,the efficiency is insensitive to the variation in voltage on the low-voltage side.Therefore,the proposed BDC is suitable for the energy storage system with high voltage gain and wide voltage range.