一种超宽电压范围隔离型DC-DC变流器研究

Research on Extra-wide-voltage-range Isolated DC-DC Converter

针对不同规格电动汽车的统一充电系统需求,研究2倍以上宽输出电压范围隔离型DC-DC变流器已成为该领域的热点。提出了一种隔离型的LLC串-并联模式变换拓扑及其设计方法,实现0.5~3.0倍的宽输出电压范围,且所有功率器件满足软开关运行。首先,利用半桥变模态控制,获得1.0倍以下电压增益;然后,利用PWM脉冲180°移相实现串-并联快速切换,实现1.0倍或2.0倍电压增益的转换;最后,通过变频结合PWM整流器直流电压调压功能,实现0.5~3.0倍宽电压增益的调节。样机实验结果表明:所提变流器利用上述策略,达到了预期的0.5~3.0倍增益,且实现软开关运行;此外,并联至串联切换过程时间非常短,仅300μs,串联至并联切换过程稍长,但也仅4.5 ms,适用于对电压增益范围要求较宽的应用场合。

Recently,due to the demand of a uniform charging system for electric vehicles(EVs)of different specifi-cations,the isolated DC-DC converter with a wide output voltage range and a voltage gain higher than 2 has become a hot research topic.In this paper,an isolated LLC series-to-parallel conversion topology and its design methodology are proposed,which has a voltage gain of 0.5~3.0.In addition,the operation of soft switching is achieved for all power de-vices.Firstly,this converter can produce a gain of less than 1 under half-bridge mode-switching control.Secondly,it can transform from parallel to series and from series to parallel connection by 180°phase shift through PWM pulse,thus ob-taining a voltage gain between 1.0 and 2.0.Finally,by taking advantage of the variable-frequency control and the DC voltage regulation of PWM rectifier,a wide voltage gain of 0.5~3.0 can be achieved.The experimental results of a proto-type show that the expected voltage gain of 0.5~3.0 can be achieved under the proposed strategy.Meanwhile,all power devices can be operated in soft-switching mode.Furthermore,the transition time between parallel and series mode was very short,i.e.,merely 300μs.Although a little longer time was taken to transform from series to parallel mode,the spe-cific time cost was only 4.5 ms.It is concluded that the novel converter is suitable for application scenarios that require a wide voltage gain range.