Buck三电平直流变换器的双闭环控制设计

发布时间：2018-05-06 18:00

本文选题：Buck三电平直流变换器 + 飞跨电容　；参考：《重庆大学》2014年硕士论文

【摘要】：在高输入/输出电压的功率变换场合，选取具有合适耐压值的功率开关器件往往比较困难。多电平变换器利用飞跨电容使得输入电压在串联的各开关管之间均分，不但能降低开关管电压应力和减小输出滤波器体积，还能提高动态特性，所以在输入/输出电压较高的中大功率变换场合具有广泛的应用前景。但是，多电平变换器的输出电压与各飞跨电容电压之间存在耦合的关系，是一个强耦合的非线性系统，所以需要将其解耦成多个单输入输出系统，以对飞跨电容电压和输出电压进行独立的控制。随着对开关变换器的动态特性和稳定性要求不断提高，一些非线性的控制方法被应用到开关变换器之中。滑模控制具有动态响应快、鲁棒性强等特点，，是所有用于开关变换器的控制策略中鲁棒性最强的控制策略之一。与其他控制方法相比，滑模控制对开关变换器的非线性特征具有天然的适用性。模糊控制不依赖于被控对象的数学模型、对被控对象的非线性具有自适应能力，但稳态控制精度不高。PID控制具有原理简单、稳定精度高、可靠性好等特点，可是要获得满意的控制效果就需要对PID控制器的参数不断地进行在线调整。因此，把模糊控制与PID控制结合起来，利用模糊控制器对PID控制器的参数进行调节，可充分发挥它们各自的优点，以使控制效果更加完美。本文详细分析了Buck三电平直流变换器的基本工作原理，针对飞跨电容电压闭环与输出电压闭环耦合的特点，对其进行解耦，以实现对输出电压和飞跨电容电压进行独立的控制，并建立了Buck三电平直流变换器的数学模型。针对Buck三电平直流变换器工作模态复杂的特点，介绍了滑模控制及其在开关变换器中的常用分析方法，设计出基于等效控制理论的定频滑模控制器对输出电压进行控制，并结合传统PID控制与模糊控制的优点，设计出自整定模糊PID控制器对飞跨电容电压进行控制。在理论研究的基础上，对所设计的Buck三电平直流变换器双闭环控制系统进行仿真试验，仿真结果表明了理论分析的正确性和所设计控制器的优越性。
[Abstract]:In the case of high input / output voltage power conversion, it is difficult to select the power switch with suitable voltage value. The multilevel converter makes use of the flying capacitance to divide the input voltage equally among the switches in series, which can not only reduce the voltage stress and the output filter volume, but also improve the dynamic characteristics. Therefore, it has a wide application prospect in the field of medium and large power conversion with high input / output voltage. However, the output voltage of the multilevel converter is coupled with the voltage of each flyover capacitor, and it is a strongly coupled nonlinear system, so it is necessary to decouple it into a number of single-input and output systems. Independent control of flyover capacitor voltage and output voltage. With the increasing demand for dynamic characteristics and stability of switching converters, some nonlinear control methods have been applied to switching converters. Sliding mode control is one of the most robust control strategies for switching converters because of its fast dynamic response and strong robustness. Compared with other control methods, sliding mode control has a natural applicability to the nonlinear characteristics of switching converter. Fuzzy control does not depend on the mathematical model of the controlled object, and has adaptive ability to the nonlinearity of the controlled object. However, the steady-state control precision is not high. Pid control has the characteristics of simple principle, high stability precision, good reliability and so on. However, in order to obtain satisfactory control effect, the parameters of PID controller need to be continuously adjusted on line. Therefore, the combination of fuzzy control and PID control, the use of fuzzy controller to adjust the parameters of PID controller, can give full play to their respective advantages, in order to make the control effect more perfect. In this paper, the basic working principle of Buck three-level DC / DC converter is analyzed in detail. Aiming at the characteristics of the coupling between the flyover capacitor voltage closed-loop and the output voltage closed-loop, the decoupling is carried out to realize the independent control of the output voltage and the flyover capacitor voltage. The mathematical model of Buck three level DC / DC converter is established. Aiming at the complex mode of Buck three-level DC / DC converter, this paper introduces the sliding mode control and its common analysis method in switching converter, and designs a constant frequency sliding mode controller based on equivalent control theory to control the output voltage. Combined with the advantages of traditional PID control and fuzzy control, a fuzzy PID controller is designed to control the transcapacitor voltage. On the basis of theoretical research, the simulation experiment of the designed Buck three-level DC / DC converter dual-closed-loop control system is carried out. The simulation results show the correctness of the theoretical analysis and the superiority of the designed controller.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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