光伏系统中LLC谐振变换器的研究
发布时间：2019-05-05 07:29
【摘要】：随着二次电源如超级电容等在光伏发电、高功率微波系统、不间断供电、电动汽车、通信电源以及航空电源等领域应用越来越广泛,双向DC-DC变换器应运而生,迅速的成为了人们关注的热点。高效高功率密度是现代电力电子技术发展的趋势,而软开关技术是提高电源工作频率和效率的关键,这样能大大减小电源的体积和重量,进一步提高功率密度。谐振型变换器有天然实现软开关的优势,近年来成为学者们研究的热点。本文以LLC谐振型变换器为基础,提出一种对称工作的双向LLC谐振型DC-DC变换器,验证能量双向流动对称性,并着重研究了在负载为容性负载时的变换器控制方法,优化调频控制区域,实现开关管的软开关。本文首先阐述了双向DC-DC变换器存在的意义,以光伏系统中二次电源为超级电容的应用为例对其在实际中的应用进行了较详细的介绍,对其研究现状和大致分类进行了总结。然后对软开关技术进行阐明,引出谐振型变换器存在的优点。对常规的三种谐振型变换器总结比较优缺点,引出本文研究的LLC谐振型变换器(LLC Resonant Converter,简称LLC-RC),以单向LLC-RC为例详细介绍了它的三种工作模态,并给出典型工作波形。利用基波近似等效法(Fundamental Harmonic Approximation,简称FHA)对LLC-R C建立稳态模型,给出电压增益曲线、电流值曲线以及ZVS实现条件。在双向L LC-R C中添加附加电感,利用FHA模型设计电路参数,建立双向LLC-RC仿真模型,验证能量双向流动的对称性以及软开关等特性,为后面将其应用在容性负载充电电源上提供依据。对容性负载的LLC-RC控制方法进行详细阐述,建立仿真模型,确定调频的控制方式,对FHA模型误差进行仿真分析,为选取调频工作区域提供理论依据。通过仿真验证误差非线性分析的正确性。为解决充电开始上涌电流过大的问题,改进了控制方法,采用两阶段PWM加调频的控制。设计建立容性负载的全桥LLC-RC仿真模型,实现了输入电压600V-300V变化范围内,输出电压均能实现额定60V输出,并且输出电流基本保持稳定,输入侧开关管基本全过程实现ZVS,在开关频率低于谐振频率的工作阶段,整流侧二极管无反向恢复电流的问题。最后,基于TI公司的TMS320F28027编写控制程序,根据实际计算设计电路参数,搭建验证容性负载LLC-RC实验平台,在输入电压为200V-100V范围内,输出最大电压均达到160V,增益调节范围为0.8-1.6。通过实验验证了选取工作区域的合理性以及PWM加调频控制方式的正确性,同时也验证了软开关实现的正确性。
[Abstract]:As the secondary power supply, such as supercapacitor, is widely used in photovoltaic power generation, high power microwave system, uninterrupted power supply, electric vehicle, communication power supply and aviation power supply, two-way DC-DC converters emerge as the times require. Quickly became the focus of people's attention. High efficiency and high power density is the development trend of modern power electronics technology, while soft switching technology is the key to improve the working frequency and efficiency of power supply, which can greatly reduce the volume and weight of the power supply and further improve the power density. Resonant converter has the advantage of natural soft-switching, and has become a hot research topic in recent years. In this paper, based on the LLC resonant converter, a symmetrical bidirectional LLC resonant DC-DC converter is proposed to verify the symmetry of two-way flow of energy, and the control method of the converter when the load is capacitive load is studied emphatically. The frequency modulation control area is optimized to realize the soft switch of the switch tube. In this paper, the significance of bi-directional DC-DC converter is described firstly. The application of secondary power supply as supercapacitor in photovoltaic system is introduced in detail, and its research status and general classification are summarized. Then the soft-switching technology is expounded, and the advantages of resonant converter are introduced. This paper summarizes and compares the advantages and disadvantages of the three conventional resonant converters, and introduces the LLC resonant converter (LLC Resonant Converter, (LLC-RC) studied in this paper. Taking one-way LLC-RC as an example, the three modes of its operation are introduced in detail. The typical working waveforms are given. The steady state model of LLC-R C is established by using fundamental equivalent method (Fundamental Harmonic Approximation, (FHA). The voltage gain curve, current value curve and ZVS realization condition are given. An additional inductor is added to the bi-directional LLC-RC, and the circuit parameters are designed by using the FHA model. The bi-directional LLC-RC simulation model is established to verify the symmetry of the two-way energy flow and the characteristics of the soft-switching. It can be used in capacitive load charging power supply. The LLC-RC control method of capacitive load is described in detail, the simulation model is established, the control mode of FM is determined, and the error of FHA model is simulated and analyzed, which provides the theoretical basis for selecting the working area of FM. The correctness of the error nonlinear analysis is verified by simulation. In order to solve the problem that the charging start surge current is too large, the control method is improved, and the two-stage PWM plus FM control is adopted. The full bridge LLC-RC simulation model of capacitive load is designed and established. Within the range of input voltage 600V-300V, the output voltage can be rated 60V and the output current is basically stable. The input side switch can realize ZVS, in the whole process. When the switching frequency is lower than the resonant frequency, the rectifier diode has no problem of reverse recovery current. Finally, based on the TMS320F28027 of TI Company, the control program is compiled. According to the actual circuit parameters, the capacitive load LLC-RC experimental platform is built. In the range of input voltage 200V-100V, the maximum output voltage reaches 160V. The gain adjustment range is 0. 8. 6. 6. 6. The rationality of selecting the working area and the correctness of the PWM plus FM control mode are verified by the experiments. At the same time, the correctness of the realization of the soft switch is also verified.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46
[Abstract]:As the secondary power supply, such as supercapacitor, is widely used in photovoltaic power generation, high power microwave system, uninterrupted power supply, electric vehicle, communication power supply and aviation power supply, two-way DC-DC converters emerge as the times require. Quickly became the focus of people's attention. High efficiency and high power density is the development trend of modern power electronics technology, while soft switching technology is the key to improve the working frequency and efficiency of power supply, which can greatly reduce the volume and weight of the power supply and further improve the power density. Resonant converter has the advantage of natural soft-switching, and has become a hot research topic in recent years. In this paper, based on the LLC resonant converter, a symmetrical bidirectional LLC resonant DC-DC converter is proposed to verify the symmetry of two-way flow of energy, and the control method of the converter when the load is capacitive load is studied emphatically. The frequency modulation control area is optimized to realize the soft switch of the switch tube. In this paper, the significance of bi-directional DC-DC converter is described firstly. The application of secondary power supply as supercapacitor in photovoltaic system is introduced in detail, and its research status and general classification are summarized. Then the soft-switching technology is expounded, and the advantages of resonant converter are introduced. This paper summarizes and compares the advantages and disadvantages of the three conventional resonant converters, and introduces the LLC resonant converter (LLC Resonant Converter, (LLC-RC) studied in this paper. Taking one-way LLC-RC as an example, the three modes of its operation are introduced in detail. The typical working waveforms are given. The steady state model of LLC-R C is established by using fundamental equivalent method (Fundamental Harmonic Approximation, (FHA). The voltage gain curve, current value curve and ZVS realization condition are given. An additional inductor is added to the bi-directional LLC-RC, and the circuit parameters are designed by using the FHA model. The bi-directional LLC-RC simulation model is established to verify the symmetry of the two-way energy flow and the characteristics of the soft-switching. It can be used in capacitive load charging power supply. The LLC-RC control method of capacitive load is described in detail, the simulation model is established, the control mode of FM is determined, and the error of FHA model is simulated and analyzed, which provides the theoretical basis for selecting the working area of FM. The correctness of the error nonlinear analysis is verified by simulation. In order to solve the problem that the charging start surge current is too large, the control method is improved, and the two-stage PWM plus FM control is adopted. The full bridge LLC-RC simulation model of capacitive load is designed and established. Within the range of input voltage 600V-300V, the output voltage can be rated 60V and the output current is basically stable. The input side switch can realize ZVS, in the whole process. When the switching frequency is lower than the resonant frequency, the rectifier diode has no problem of reverse recovery current. Finally, based on the TMS320F28027 of TI Company, the control program is compiled. According to the actual circuit parameters, the capacitive load LLC-RC experimental platform is built. In the range of input voltage 200V-100V, the maximum output voltage reaches 160V. The gain adjustment range is 0. 8. 6. 6. 6. The rationality of selecting the working area and the correctness of the PWM plus FM control mode are verified by the experiments. At the same time, the correctness of the realization of the soft switch is also verified.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46
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