推挽正激三电平直流变换器及其控制策略

Push-pull Forward Three-level DC/DC Converter and Its Control Strategy

燃料电池输出电压变化范围很宽,使直流变换器的整流二极管选取极为困难。提出了一种适合于燃料电池的低压宽范围输入、高压输出场合的推挽正激三电平直流变换器。与常规的三电平直流变换器拓扑控制不同的是,该变换器的控制策略使整流电路输出电压为先低电平、后高电平的三电平波形,有效降低了整流二极管上的电压应力,同时减小了输出滤波器的体积和重量。分析该变换器的工作模态,讨论以0.5占空比工作的2个开关管实现零电压开通的条件,并对输出滤波器的设计进行分析。通过一个1kW的原理样机验证了该变换器及其控制策略的可行性。

The output voltage of fuel cell varies widely, leading to the difficulty of rectifier diodes selection. This paper proposes a push-pull forward three-level DC/DC converter topology which is suitable for the fuel cell with wide range and low input voltage and high output voltage applications. This paper proposed a novel control strategy different from the additional three-level control. The output voltage of rectifier circuit has low level first and high level later. The voltage stress and the volume of the output filter can be reduced. The operation modes of the converter were analyzed. The zero voltage switching conditions of the power devices that operated with 0.5 duty cycle were discussed and the design of the output filter was analyzed. The feasibility of the proposed converter and its control strategy were verified by the experimental results of a 1 kW principle prototype.