用于燃料电池的三电平LLC谐振变换器的研究与设计

发布时间：2018-03-09 18:02

  本文选题：宽输入电压范围　切入点：三电平LLC　出处：《电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,燃料电池以其能量转换效率高、环境友好度高等方面的优势得到了快速发展,燃料电池分布式电源作为燃料电池的重要应用之一,对其能量转换系统的研究越来越关注。由于燃料电池随着负载电流的增加,输出电压下降率大,即输出电压范围较宽,并且燃料电池很难快速响应负载的突变,因此,对能够满足燃料电池输出电压范围并拥有较快的动态响应特性的直流变换器的研究与开发已成为一项重要的课题。针对燃料电池能量转换系统应用场合,本文以提高对宽输入电压范围适应性为目标,采用全桥三电平LLC谐振变换器拓扑,并研究了其工作原理和电路特性,具体从以下几方面开展了工作:首先,结合特定应用需求,对比研究了燃料电池能量转换系统中的多种直流变换器拓扑,选定了最为匹配的全桥三电平LLC谐振变换器拓扑。针对传统控制策略下谐振槽输入电压总谐波失真大的问题,本文提出一种改进型对称双移相控制策略,能够实现变换器三电平模式和两电平模式的切换,并且降低了谐振槽输入电压的总谐波失真。基于该控制策略,研究了LLC谐振网络的直流增益特性、软开关特性,并通过分析两种策略下谐振槽输入电压的总谐波失真随斩控角的变化,推导出改进型控制策略下的谐振槽输入电压总谐波失真小的结论,并仿真验证了理论分析的正确性。其次,根据燃料电池能量转换系统的具体设计要求,对全桥三电平LLC谐振变换器进行了详细的参数设计,重点开展了谐振网络的参数设计、高频变压器的设计,谐振电感设计等研究,并对数字控制器进行了优化设计。此外,在Saber仿真环境下,搭建了全桥三电平LLC谐振变换器的仿真模型,仿真验证了变换器对宽输入电压范围的适应性、软开关情况、输出电压纹波情况以及负载突变时系统的响应特性,最终验证了全桥三电平LLC谐振变换器及所设计控制策略的正确性。最后,根据设计指标的要求及仿真分析结果,搭建了全桥三电平LLC谐振变换器的300W实验样机,进行实验验证,实现了改进型对称双移相控制策略,并且宽输入电压范围适应性、软开关情况以及效率等指标达到了预期要求。
[Abstract]:In recent years, fuel cell has been developed rapidly because of its high energy conversion efficiency and high environmental friendliness. Distributed power supply for fuel cell is one of the important applications of fuel cell. More and more attention has been paid to the research of the energy conversion system. Because the output voltage of the fuel cell decreases greatly with the increase of the load current, that is, the output voltage range is wide, and the fuel cell is difficult to respond to the sudden change of the load quickly. The research and development of DC converters which can satisfy the output voltage range of fuel cells and have faster dynamic response characteristics have become an important subject. In order to improve the adaptability to wide input voltage range, the full-bridge three-level LLC resonant converter topology is adopted in this paper, and its working principle and circuit characteristics are studied. The work is carried out from the following aspects: firstly, combined with the specific application requirements, In this paper, a variety of DC / DC converter topologies in fuel cell energy conversion systems are compared, and the most matched full-bridge three-level LLC resonant converter topology is selected. The problem of large total harmonic distortion of resonant slot input voltage under traditional control strategy is discussed. In this paper, an improved symmetric double-phase shift control strategy is proposed, which can realize switching between three-level mode and two-level mode, and reduce the total harmonic distortion of resonant slot input voltage. The DC gain and soft switching characteristics of LLC resonant network are studied, and the variation of total harmonic distortion of resonant slot input voltage with chopping angle is analyzed. The conclusion that the total harmonic distortion of the resonant slot input voltage is small under the improved control strategy is deduced, and the correctness of the theoretical analysis is verified by simulation. Secondly, according to the specific design requirements of the fuel cell energy conversion system, The parameters of full-bridge three-level LLC resonant converter are designed in detail. The parameters of resonant network, the design of high-frequency transformer, the design of resonant inductor are studied, and the digital controller is optimized. In the Saber simulation environment, the simulation model of full-bridge three-level LLC resonant converter is built. The simulation results verify the adaptability of the converter to the wide input voltage range and the situation of soft switching. The output voltage ripple and the response characteristics of the system under the load abrupt change finally verify the correctness of the full-bridge three-level LLC resonant converter and the designed control strategy. Finally, according to the requirements of the design index and the results of simulation analysis, A 300W experimental prototype of a full-bridge three-level LLC resonant converter is built and verified by experiments. The improved symmetrical double-phase shift control strategy is realized. The parameters of wide input voltage range adaptability, soft switching and efficiency are achieved.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46;TM911.4
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本文编号：1589637