三电平LLC谐振变换器特性分析和控制策略研究

发布时间：2018-07-08 08:57

  本文选题：三电平半桥LLC谐振变换器 + 混合控制策略　； 参考：《山东大学》2017年硕士论文

【摘要】：LLC谐振变换器相对于PWM变换器具有开关频率高,开关损耗小,功率密度大,体积小,效率高等优点,因此在DC-DC电源、电动汽车充电等应用领域得到广泛关注和研究。与传统的谐振变换器相比,三电平LLC谐振变换器的开关管电压应力降为输入电压的一半,适合于电压输入较高的情况。且能够使原边开关管零电压开通(zero voltage switching,ZVS)和副边二极管零电流关断(zero current switching,ZCS),因此具有较高的变换效率。本文以三电平半桥LLC谐振变换器为拓扑,分析了传统的变频控制策略,给出了变频调制的工作过程和等效电路,通过基波近似法分析了输出电压增益与开关频率的关系,并指出了变频调节在输出电压调节范围上的不足。为了能够提高电压调节范围,本文在三电平半桥拓扑上引入了移相调制,分析了其工作过程、电压调节范围及软开关条件,导出了实现软开关的工作状态分界点,由此提出一种三电平半桥LLC谐振变换器移相和变频相结合的混合式调制策略,该策略根据软开关工作状态,切换移相调制和变频调制,以实现全程软开关和宽范围输出电压控制。小信号分析是闭环控制的必要环节。移相模式下由于开关频率保持恒定,利用状态空间平均法对LLC谐振变换器进行了小信号建模,推导出了其稳态模型和小信号模型,并设计了控制器;传统的状态空间法不适用于变频模式,本文采用了等效电路法对LLC谐振变换器进行小信号建模,并设计控制器。两种控制策略均通过闭环仿真进行了验证。最后,本文对三电平半桥LLC谐振变换器的硬件电路进行了设计,包括驱动电路,保护电路和采样调理电路等,利用数字化控制方案,采用TMS320F28335作为控制芯片,对混合式调制策略实现闭环控制。实验结果验证了理论分析的正确性和所提出的控制策略的可行性和有效性。
[Abstract]:Compared with PWM converters, LLC resonant converters have many advantages such as high switching frequency, low switching loss, large power density, small volume and high efficiency. Therefore, LLC resonant converters have been widely studied in the fields of DC-DC power supply, electric vehicle charging and so on. Compared with the conventional resonant converter, the switching voltage stress drop of the three-level LLC resonant converter is half of the input voltage, which is suitable for higher voltage input. The ZVS) and the ZVS (ZVS) can be switched off by the zero voltage of the primary side switch and the zero current of the auxiliary side diode (ZVS), so it has high conversion efficiency. In this paper, a three-level half-bridge LLC resonant converter is used as the topology, the traditional frequency conversion control strategy is analyzed, the working process and equivalent circuit of the frequency conversion modulation are given, and the relationship between the output voltage gain and the switching frequency is analyzed by the fundamental approximation method. And pointed out the frequency conversion regulation in the range of output voltage regulation. In order to improve the voltage regulation range, phase shift modulation is introduced into the three-level half-bridge topology. The working process, voltage regulation range and soft switching conditions are analyzed, and the working state dividing point is derived. A hybrid modulation strategy based on phase shift and frequency conversion for three-level half-bridge LLC resonant converter is proposed. The strategy switches phase shift modulation and frequency conversion modulation according to the soft switching state. In order to achieve the whole process of soft switching and wide range output voltage control. Small signal analysis is a necessary part of closed-loop control. Due to the constant switching frequency in phase-shifting mode, the small-signal model of LLC resonant converter is built by the state-space averaging method, the steady and small signal models are derived, and the controller is designed. The traditional state space method is not suitable for the frequency conversion mode. In this paper, the equivalent circuit method is used to model the LLC resonant converter with small signal, and the controller is designed. The two control strategies are verified by closed loop simulation. Finally, the hardware circuit of three-level half-bridge LLC resonant converter is designed, including drive circuit, protection circuit and sampling conditioning circuit. Using digital control scheme, TMS320F28335 is used as control chip. Closed loop control is realized for hybrid modulation strategy. The experimental results verify the correctness of the theoretical analysis and the feasibility and effectiveness of the proposed control strategy.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM46

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中国期刊全文数据库 前10条

1 孙孝峰;申彦峰;李午英;王宝诚;;交错并联双向Buck/Boost集成LLC谐振型三端口直流变换器[J];电工技术学报;2016年14期

2 江添洋;张军明;汪i裆，

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