具有自均压功能的新型高增益LLC谐振变换器

A New High Gain LLC Resonant Converter with Self Voltage Equalization Capability

LLC谐振变换器具有开关损耗低、运行效率高的优势,但电压增益调节范围受开关频率与变压器匝比限制,无法满足光伏微网系统应用场景的需要。为此,文章提出一种采用变频控制的高增益LLC谐振变换器。该变换器通过改变传统全桥LLC的整流网络结构,使其具有更高的升压能力,并使高压侧器件电压应力降低为输出电压的一半,更好地适应高电压场合。文章首先详细分析了该变换器工作在欠谐振模式下的工作原理及自均压原理;其次,推导变换器电压增益及器件电压应力;再次,通过变换器的小信号模型设计闭环控制器,实现了电压闭环;最后,通过搭建一台650 W的实验样机,验证理论分析的正确性。

LLC resonant converters have the advantages of low switching losses and high operating efficiency,but the voltage gain adjustment range is limited by the switching frequency and transformer turn ratio,which cannot meet the needs of application scenarios of photovoltaic microgrid systems.For this reason,this paper proposes a high gain LLC resonant converter with frequency conversion control.This converter changes the rectification network structure of the traditional full bridge LLC to make it have higher boosting ability and reduces the voltage stress of the high-voltage side device to half of the output voltage,better adapting to high voltage situations.It firstly provides a detailed analysis of the working principle and self voltage equalization principle of the converter operating in under-resonant mode.Secondly,it derives the voltage gain of the converter and the voltage stress of the device.In addition,a closed-loop controller is designed using the small signal model of the converter to achieve voltage closed-loop.Finally,it builds a 650 W experimental prototype,and the correctness of the theoretical analysis is verified.