LLC谐振式变换器的滑模控制策略研究

发布时间：2018-06-10 03:30

本文选题：LLC谐振变换器 + 滑模控制　；参考：《浙江大学》2014年硕士论文

【摘要】：LLC谐振式变换器可以实现宽输入电压范围内原边开关管的零电压开通(ZVS)和副边整流二极管的零电流关断(ZCS),负载适应能力强,具有高效率、高功率密度、低电磁干扰等优点,在工业电源和消费电子领域都得到了广泛的应用。随着产品性能的不断提高,对于LLC变换器动态性能的要求也越来越高。然而,LLC谐振变换器存在动态特性漂移问题,同时光耦的时变寄生电容和自身非线性特性也对控制器的设计也带来了很大的挑战。本文提出了一种新颖的离散脉冲频率调制方式,成功地将滑模变结构控制应用于LLC谐振变换器,可以有效地增强系统鲁棒性,大幅度提高LLC变换器的动态性能。首先基于扩展描述函数方法对LLC谐振变换器进行小信号建模和分析,并给出详细的数学推导过程。通过理论计算和仿真结果比较,验证了扩展描述函数模型的稳态精度和动态跟踪性能。基于扩展描述函数模型,采用输入/输出反馈线性化方法设计系统滑模控制方程,可以实现特定的输出电压响应,并且能够得到包含输出电压变量的线性化子系统。利用传统线性系统的分析方法,验证系统的稳定性条件,给出了滑模控制参数的设计流程。最后分别搭建了基于滑模控制和PI控制的实验样机平台,验证滑模变结构控制方案的可行性,给出了系统的稳态运行波形和输出电压稳态精度。通过与PI控制实验样机对比,证明了滑模控制方案优良的动态响应性能。对于输出电压纹波要求较高的应用场合,提出了输出电压微分近似方法,有效地降低输出电压纹波,同时仍能够保持滑模控制的快速动态响应特性。 LLC变换器的滑模控制方案能够大幅度地提高系统的动态响应速度,适用于动态性能要求较高的应用场合,文中提出的模型、设计思路和控制方法对于LLC变换器动态性能的研究具有一定意义。
[Abstract]:LLC resonant converter can realize ZVS (ZVS) and ZCSS with zero current turn-off of side rectifier diode in wide input voltage range. It has the advantages of high load adaptability, high efficiency, high power density, low electromagnetic interference and so on. It has been widely used in the field of industrial power supply and consumer electronics. With the continuous improvement of product performance, the dynamic performance of LLC converter is becoming more and more demanding. However, the dynamic drift problem exists in LLC resonant converters, and the time-varying parasitic capacitance and nonlinear characteristics of optical coupling also pose a great challenge to the design of the controller. A novel discrete pulse frequency modulation scheme is proposed in this paper. The sliding mode variable structure control is successfully applied to the LLC resonant converter, which can effectively enhance the robustness of the system. The dynamic performance of the LLC converter is greatly improved. Firstly, the small signal modeling and analysis of the LLC resonant converter are carried out based on the extended description function method, and the detailed mathematical derivation process is given. The steady-state precision and dynamic tracking performance of the extended description function model are verified by theoretical calculation and simulation results. Based on the extended description function model, the sliding mode control equation is designed by the input / output feedback linearization method. The output voltage response can be achieved, and the linearized subsystem with output voltage variables can be obtained. Using the traditional linear system analysis method, the stability condition of the system is verified, and the design flow of the sliding mode control parameters is given. Finally, the experimental prototype platform based on sliding mode control and Pi control is built, respectively. The feasibility of the sliding mode variable structure control scheme is verified, and the steady-state operation waveform and output voltage steady-state precision of the system are given. By comparing with Pi control experimental prototype, it is proved that the sliding mode control scheme has excellent dynamic response performance. In order to reduce the ripple of output voltage effectively, a differential approximation method of output voltage is proposed for the application of high requirement of output voltage ripple. The sliding mode control scheme of LLC converter can greatly improve the dynamic response speed of the system, which is suitable for applications with high dynamic performance requirements. The design idea and control method have certain significance for the study of LLC converter's dynamic performance.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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