宽范围输入高效LLC谐振变换器的研究

发布时间：2018-07-06 10:36

本文选题：宽范围输入 + LLC谐振变换器　；参考：《陕西科技大学》2017年硕士论文

【摘要】：随着能源危机、环境污染问题的日益严重,充分利用可再生能源得到了人们的广泛关注。而可再生能源发电单元普遍存在输出电压范围较宽的特点,因此宽范围输入变换器被大量应用在可再生能源发电单元的后级。目前所采用的级联、串并联以及多模式类等结构的电路拓扑都较为复杂,且无法兼顾变换器的高效率和宽范围输入。论文针对此问题,以变换器对宽范围输入的适应性、高效性和高稳定性为目标,运用LLC电路的效率优势,采用将VFM(Variable Frequency Multiplier)技术与Burst控制模式相结合的方法,研制了一种能够满足宽范围输入,且任何负载下都可实现高效化的LLC谐振变换器。论文主要工作总结如下:(1)变换器的工作原理分析及实现宽范围输入的研究。针对LLC谐振变换器不能够满足宽范围输入,分析和研究了其拓扑结构,采用VFM技术,缩小了谐振回路的输入电压范围,使变换器能够实现宽范围输入,且在带有20%以上负载时效率较高;详细分析了变换器的工作原理,阐述了其增益特性、输入阻抗特性、ZVS条件及输入电容的电压平衡特性等。(2)变换器的主电路设计。通过分析电路的设计指标及结构,首先详细设计了变换器的主电路参数;其次对变换器所用到的元器件进行了设计与选择,主要包括功率开关管的选取,谐振电容、谐振电感以及励磁电感的设计与选择,变压器的设计,输出整流二极管、输出滤波电容等的选择。(3)变换器的控制系统设计。采用扩展描述函数法建立了变换器的小信号模型,推导了其传递函数,并根据不同的工作模态设计了对应的控制器,使系统能够满足动态响应要求。针对变换器轻载效率低的问题,采用了Burst控制模式,并进行了详细设计,使变换器工作在轻载时也能够达到较高的效率。(4)基于DSP的控制系统软硬件设计。采用数字控制方式,对控制系统的硬件电路进行了设计,主要包括:驱动电路、输出电压采样电路、输出电流保护电路、数字采样器等的设计。同时对变换器的主程序和子程序进行了设计,并根据离散化方法,完成了数字PI控制器的详细设计,实现了对变换器的数字控制。(5)电路仿真及验证。运用PSIM仿真软件对设计的电路做了仿真分析,仿真结果表明理论设计合理;研制了一台24V/1.5kW的实验样机,测试数据表明,该变换器可实现100V~400V的宽范围输入,当20%以上负载时效率可达到94.8%~96.5%,当5%~20%负载时效率能达到93.5%以上,当小于5%负载时效率能达到87.8%以上,验证了理论分析的可行性。论文研制的LLC谐振变换器可满足宽范围输入的要求,并且在任何负载下都可实现ZVS,效率较高,具有输出电压稳定、动态性能良好、控制精度高等优点,在新能源发电方面有较好的应用前景。
[Abstract]:With the energy crisis, the problem of environmental pollution is becoming more and more serious, and people pay more and more attention to the full use of renewable energy. Because of the wide output voltage range of renewable energy generation units, wide range input converters are widely used in the latter stage of renewable energy generation units. The circuit topology of cascaded, series-parallel and multi-mode classes is complex and can not take into account the high efficiency and wide range input of the converter. Aiming at this problem, aiming at the adaptability, high efficiency and high stability of the converter to wide range input, the paper uses the efficiency advantage of LLC circuit and combines VFM (variable Frequency multiplier) technology with burst control mode. A high efficiency LLC resonant converter is developed, which can satisfy the wide range input and achieve high efficiency under any load. The main work of this paper is summarized as follows: (1) Research on the principle of converter and wide range input. Aiming at the LLC resonant converter can not satisfy the wide range input, the topology structure is analyzed and studied. The VFM technique is used to reduce the input voltage range of the resonant circuit, so that the converter can realize the wide range input. The working principle of the converter is analyzed in detail, and the gain characteristic, the input impedance characteristic and the voltage balance characteristic of the input capacitance are expounded. (2) the main circuit design of the converter. By analyzing the design index and structure of the circuit, the main circuit parameters of the converter are designed in detail, and then the components used in the converter are designed and selected, including the selection of the power switch, the resonant capacitance, Design and selection of resonant inductor and excitation inductor, transformer design, output rectifier diode, output filter capacitance, etc. (3) Control system design of converter. The small signal model of the converter is established by using the extended description function method, and its transfer function is deduced. The corresponding controller is designed according to different working modes, so that the system can meet the requirement of dynamic response. In order to solve the problem of low light load efficiency, the burst control mode is adopted and the detailed design is carried out to make the converter work at low load to achieve higher efficiency. (4) the hardware and software design of the control system based on DSP. The hardware circuit of the control system is designed by using the digital control mode, including the design of the drive circuit, the output voltage sampling circuit, the output current protection circuit, the digital sampler and so on. At the same time, the main program and subroutine of the converter are designed. According to the discretization method, the detailed design of the digital Pi controller is completed, and the digital control of the converter is realized. (5) the circuit simulation and verification. The designed circuit is simulated and analyzed by PSIM software, and the simulation results show that the theoretical design is reasonable, and an experimental prototype of 24V / 1.5kW is developed. The test data show that the converter can achieve a wide range input of 100V / 400V. When the load is above 20%, the efficiency can reach 94.8%, when the load is 20%, the efficiency can reach 93.5%, and when the load is less than 5%, the efficiency can reach more than 87.8%, which proves the feasibility of theoretical analysis. The LLC resonant converter developed in this paper can meet the requirements of wide range input, and ZVSs can be realized under any load. The LLC resonant converter has the advantages of high efficiency, stable output voltage, good dynamic performance and high control precision. It has a good application prospect in the field of new energy generation.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM46

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