【作者】 张帆；

【导师】 伍小杰；

【作者基本信息】 中国矿业大学 ， 电气工程（专业学位）， 2019， 硕士

【摘要】 随着人类社会对能源需求的增长和传统化石能源的枯竭,作为新能源的主要形式之一,光伏发电得到了广泛的关注和发展。多电平、易拓展的模块化光伏并网系统可以同时实现分布式发电和独立的最大功率点追踪,是理想的大规模光伏发电系统形式。本文将高效率的三端口交错并联Boost LLC谐振变换器作为模块化光伏直流并网系统的基本变换器单元,将变换器的双向端口通过一条低压直流母线相连,以解决系统中各模块输出功率不均衡及电压振荡的问题。首先,分析了三端口交错并联Boost LLC谐振变换器的工作原理,列出了主要电压和电流参数的时域表达式,在此基础上推导了变换器的增益特性。分析了变换器中半导体器件实现软开关的理论约束条件,并推导了实际中的软开关工作范围。将变换器的交错并联Boost结构与普通Boost变换器对比,研究了变换器输入电流的纹波特性。其次,介绍了基于三端口DC/DC变换器的模块化光伏直流并网系统,并分析了该系统的工作原理,阐述了单个模块接入和退出系统的方法。将三端口交错并联Boost LLC谐振变换器作为系统的基本变换器单元,研究了系统在MPPT运行模式和恒功率运行模式下的控制策略。分析了系统所用控制策略的输出端口均压误差。再次,结合三端口交错并联Boost LLC谐振变换器的特性,给出了变换器的器件参数设计流程,并根据流程设计了变换器各个器件的参数。给出了变换器中半导体器件、磁性元件和电容的损耗计算方法并建立了主要器件的损耗模型,为变换器的优化设计奠定了基础。最后,搭建了基于三端口交错并联Boost LLC谐振变换器的模块化光伏直流并网系统仿真和实验平台。通过仿真和实验验证了交错并联Boost LLC谐振变换器的工作原理和特性,也验证了模块化光伏直流并网系统及其均压控制策略的合理性与有效性。更多还原

【Abstract】 With the growth of human society’s demand for energy and the exhaustion of traditional fossil energy,as one of the main forms of new energy,photovoltaic power generation has been widely concerned and developed.Multi-level,easy-to-expand modular grid-connected photovoltaic systems can achieve both distributed generation and independent maximum power point tracking,which is an ideal form of large-scale photovoltaic power generation system.In this thesis,an efficient three-port interleaved boost LLC resonant converter is used as the basic converter unit of modular DC gridconnected photovoltaic system.The bi-directional port of the converters are connected through a low voltage DC bus to solve the problem of unbalanced output power and voltage oscillation of each module in the system.Firstly,the operational principles of three-port interleaved boost LLC resonant converter are analyzed,and the time-domain expressions of main voltage and current parameters are listed.On this basis,the gain characteristics of the converter are derived.The theoretical constraints of soft-switching for semiconductor devices in converter are analyzed,and the operating range of soft-switching in practice is deduced.The interleaved parallel boost structure of the converter is compared with the conventional boost converter,and the ripple characteristics of the input current of the converter are studied.Secondly,the modular DC grid-connected photovoltaic system based on three-port DC/DC converter is introduced.The operational principles of the system are analyzed,and the method of single module accessing and exiting the system is expounded.The three-port interleaved boost LLC resonant converter is used as the basic converter unit of the system.The control strategies of the system in MPPT mode and constant power mode are studied.The output voltage sharing error of the control strategy used in the system is analyzed.Thirdly,according to the characteristics of three-port interleaved boost LLC resonant converter,the design flow of device parameters of the converter is given,and the parameters of each device of the converter are designed according to the flow.The loss calculation methods of semiconductor devices,magnetic components and capacitors in converter are given,and the loss models of the main devices are established,which lays a foundation for the optimal design of the converter.Finally,the simulation and experiment platform of modular DC grid-connected photovoltaic system based on three-port interleaved boost LLC resonant converters is built.The operational principles and characteristics of interleaved boost LLC resonant converter are verified by simulation and experiment.The rationality and effectiveness of modular DC grid-connected photovoltaic system and its voltage sharing control strategy are also verified.更多还原