﻿ Buck型变换器固定时间自适应控制
 控制与决策  2020, Vol. 35 Issue (5): 1183-1190 0

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CHEN Qiang, QIAN Ning, NAN Yu-rong. Fixed-time adaptive control for Buck converters[J]. Control and Decision, 2020, 35(5): 1183-1190. DOI: 10.13195/j.kzyjc.2018.0847.
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Buck型变换器固定时间自适应控制

Fixed-time adaptive control for Buck converters
CHEN Qiang , QIAN Ning , NAN Yu-rong
College of Information Engineering, Zhejiang University of Technology, Hangzhou 310023, China
Abstract: A fixed-time adaptive control scheme is proposed for Buck DC / DC converters. Firstly, the fixed-time sliding mode surface and corresponding controller are developed for the system with known parameters to guarantee that the output voltage error converges to the equilibrium point within a fixed time, and the upper bound of the convergence time is independent of system initial states but determined by the control parameters. In the case that the value of some parameters including resistances and inductances is not precisely obtained under the effect of temperature and external disturbances, the adaptive update laws are designed for estimating all the unknown parameters of the Buck converters. Then, the fixed-time adaptive controller is proposed such that the output voltage error can converge to a small region around the equilibrium point within a fixed time. Simulation and experimental comparison results show the effectiveness of the proposed control scheme.
Keywords: fixed-time control    adaptive control    Buck converter    sliding mode control
0 引言

DC / DC变换器是一种实现直流电路电压转换的电力电子设备, 其基本拓扑可以分为Buck变换器、Boost变换器、Buck-Boost变换器等.其中Buck变换器又称降压变换器, 因其具有降压的特性以及结构简单、稳定性高、易于分析等特点而被广泛使用.随着电源变换器的性能要求日益提高, 越来越多非线性控制技术被应用于Buck变换器, 如反步法[1]、模糊控制[2]、神经网络[3]、自适应动态规划[4]、滑模控制[5-10]等.其中滑模控制方法具有稳定范围宽、动态响应快、鲁棒性强、控制实现简单等优点.文献[5]将滑模控制方法应用于Buck变换器, 并采用PWM调制方法, 以降低开关频率变化的影响; 文献[6]基于扩张状态观测器和滑模控制方法, 设计了一种基于扰动补偿的滑模控制律以提高系统抗干扰能力并实现系统渐近稳定; 文献[7-8]基于终端滑模理论设计了Buck变换器系统的有限时间控制器, 实现了变换器输出电压的快速跟踪控制; 文献[9-10]设计了有限时间自适应控制器, 用于解决Buck电路中系统不匹配干扰问题以及输出负载变化问题.然而, 文献[7-10]中系统收敛时间上界与系统初始状态变化有关, 即当系统初始状态变化时, 其收敛时间上界也随之发生变化. 2012年, 文献[11]提出了固定时间控制方法, 保证系统收敛时间一致有界, 且其时间上界与系统初始条件无关.目前, 固定时间控制方法已被应用于多智能体、电力系统、航天器等诸多领域[12-20], 但在DC / DC变换器控制领域尚未见报道.此外, Buck变换器中电阻、电感、电容受温度及外部干扰影响, 其参数值易发生变化且不易准确测得, 因此控制器设计需要考虑电容、电感等参数变化对控制器效果的影响.

1 系统描述及预备知识 1.1 Buck型DC / DC变换器模型描述

Buck型DC / DC变换器工作原理如图 1所示.

 图 1 Buck变换器电路图

 (1)

 (2)

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 (4)

1.2 预备知识

 (5)

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V(x)可以在固定时间内收敛到平衡点附近的邻域, 且该邻域可表示为

 (8)

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2 固定时间控制

 (12)

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3 固定时间自适应控制

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V2求导可得

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, 则式(36)改写为

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4 仿真分析

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4.1 系统参数设置

 图 2 输出电压误差x1
 图 3 控制器输出u
 图 4 输出电压误差x1(方法3和方法4)
 图 5 控制器输出u (方法3和方法4)
 图 6 参数估计
4.2 仿真实例1: Buck变换器(4)参数已知

4.3 仿真实例2: Buck变换器(4)参数未知

5 实验分析

 图 7 Buck变换器的实验测试系统
 图 8 负载突减时输出电压(上)和电流(下)
 图 9 负载突增时输出电压(上)与电流(下)

6 结论

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