在新能源的开发和利用中，燃料电池因其具备高工作效率和高功率密度，对环境不造成污染，应用也不受地域限制等诸多优点而得到广泛关注。但是燃料电池呈现出偏软的外特性，单体电池的输出电压仅在1V左右，而且受负载影响其动态特性很差，通常需要在其输出端加入一级DC/DC变换器改善工作性能。在交直流微电网的应用领域下，燃料电池DC/DC变换器则必须具备宽输入电压范围、大升压变比、高效率以及电气隔离的特点。针对以上功能要求，本文具体设计了一台用于交直流微电网系统的3kW燃料电池DC/DC变换器样机，在此基础上对其工作特性展开研究。本文主要工作内容如下：
首先明确3kW燃料电池DC/DC变换器的设计指标与要求，提出三种可适用的拓扑设计方案，经比较最终选定隔离升压全桥变换器即IBFBC的拓扑结构，进而分析了IBFBC电路的稳态工作机理。分别对IBFBC工作中存在的启动问题、变压器漏感问题以及升压电感磁复位问题展开研究，分析其成因并对解决方案进行比较分析。综合各方面确定采用带有源钳位的IBFBC主电路架构设计。
在主电路架构设计的基础上，根据指标要求对IBFBC的主电路中的功率MOS管和整流二极管进行选型设计，详细计算了高频变压器、升压电感以及其他无源功率器件的参数。进而设计了以DSP 28335为主控芯片的数字控制器的硬件电路，具体设计了PWM驱动电路、AD转换电路和通讯电路等，并详细分析了各电路的设计原理及参数选择依据。
在建立起IBFBC的状态空间平均模型和交流小信号模型基础上，借助于Matlab/Simulink仿真工具，从控制理论角度研究了IBFBC的动、静态特征，并采用PID校正控制改善系统性能。运用Saber仿真则验证了所设计的软启动控制算法的可行性和可操作性。进而进行了数字控制器的软件总体方案设计，分别对主程序、PWM、ADC进行软件设计。最终完成3kW燃料电池DC/DC变换器样机的搭建，并进行测试。实验结果表明，带有源钳位的IBFBC设计方案在理论与实践上都具有可行性，并且能够满足交直流微电网对燃料电池DC/DC变换器宽输入、大升压、高效隔离的性能要求。
关键词：燃料电池，宽输入，大升压，隔离升压全桥变换器，DSP
Abstract
In the Exploitation and Using of New-energy，Fuel cell have been widespread concerned because of its high efficiency, low environmental impact and scalability. However, fuel cell has its own defect to overcome, such as low output voltage, bad dynamic characteristics and soft output characteristics. A DC/DC converter is usually added to improve fuel cell’s performance. Applied to the hybrid ac/dc micro grid, fuel cell DC/DC converter should have the ability to accept wide input, get large step up ratio and high efficiency. Electric isolation also needs to be considered. This dissertation mainly studies and designs a 3kW fuel cell DCDC converter based on above requests. The main contents of this dissertation are as follows:
Given the design parameter of 3kW fuel cell DC/DC converter, three applicable converters are compared and IBFBC is chosen as the basic main circuit. Its working principle is analyzed and the start-up problem, the leakage inductance of the isolated transformer and magnetic reset of the input inductor are discussed respectively . Eventually, 3kW IBFBC is improved by active clamp technique.
According to the specific requirements, selection of devices for power MOSFET as switch and rectifier diodeParts selection is completed. Other passive components in main circuit, high-frequency transformer, boost inductor and capacitor, are presented and calculated specifically. Then based on DSP 28335, a digital controller’ circuit are designed in detail include PWM，ADC，SCI and CAN.
IBFBC’s State space average model and AC small-signal model are established. Its dynamic and static performance characteristics are studied with Matlab/Simulink and PID control is applied to improve the system. Soft-start is designed and verified in Saber. Based on DSP software develop platform CCS, the software control is designed and flow diagrams of main Program, PWM, ADC are given. The experiment and test are made on the 3kW IBFBC hardware platform. The results show that this IBFBC design for fuel cell successfully achieve high voltage step-up and wide input acceptance, and can be used to ac/dc micro grid with high efficiency.
Key Words: Fuel Cell, High Voltage Step-up, Wide Input, IBFBC, DSP
目 录
摘 要 I
Abstract II
目 录 III
1 绪论 1
1.1研究背景及意义 1
1.2燃料电池发电系统 3
1.2.1燃料电池的工作原理 3
1.2.2燃料电池DC/DC变换器的作用 6
1.3 燃料电池DC/DC变换器研究现状 8
1.3.1非隔离Boost变换器 8
1.3.2 LLC谐振变换器 10
1.3.3隔离PWM变换器 12
1.4主要研究工作 14
2 燃料电池DC/DC变换器方案设计 16
2.1设计指标与性能要求分析 16
2.2隔离升压全桥变换器的工作原理 17
2.3隔离升压全桥变换器的关键问题分析 22
2.3.1启动问题 22
2.3.2变压器漏感问题 24
2.3.3升压电感磁复位问题 30
2.4改进型隔离升压全桥变换器电路 31
2.5本章小结 31
3 隔离升压全桥变换器硬件电路设计 32
3.1隔离升压全桥变换器主电路设计 32
3.1.1高频变压器设计 32
3.1.2升压电感的设计 35
3.1.3有源钳位电容的设计 36
3.1.4功率开关管的选型 36
3.1.5整流二极管的选取 37
3.1.6输出滤波电容的设计 38
3.2数字控制器设计 38
3.2.1 DSP 28335概述 39
3.2.2驱动电路设计 40
3.2.3采样电路设计 42
3.2.4通讯电路设计 45
3.3本章小结 46
4 隔离升压全桥变换器建模分析与软件设计 47
4.1隔离升压全桥变换器建模 47
4.1.1状态空间平均模型 47
4.1.2交流小信号模型 48
4.2隔离升压全桥变换器控制算法设计 49
4.2.1 PID控制算法 49
4.2.2 PID控制器设计 51
4.2.3软启动控制设计 55
4.3隔离升压全桥变换器软件程序设计 56
4.3.1主程序 56
4.3.2中断服务程序 57
4.3.3 PI调节子程序 58
4.4样机性能测试与分析 60
4.5本章小结 63
5 总结与展望 64
5.1全文工作总结 64
5.2后续研究工作设想 64
参考文献 66
作者在攻读硕士学位期间发表的学术论文 69
致 谢 70
