Buck型功率变换器无抖振滑模控制器设计

Design of Chattering-free Sliding Mode Controller for Buck Converters

针对传统比例积分微分(PID)控制方法运用于直流Buck变换器时,在干扰较大的情况下,很难取得满意的控制效果问题,利用二阶滑模控制技术,提出了一种无抖振的滑模控制方法,以改善大扰动条件下Buck变换器的鲁棒性。将占空比变量的导数看作虚拟控制器,设计非连续的二阶滑模控制器;实际控制器则为非连续控制器的积分,从而避免了控制器的抖振。在此基础上,采用PWM定频控制方式将该算法运用在Buck电路上。通过和PID控制算法进行仿真和实验对比,验证了该滑模控制器的可靠性与优越性。结果表明:系统启动时间缩短了近50%;当突变负载和输入电压改变时,系统输出电压变化幅度明显减小。

Under the traditional proportional integral differential（ PID） controllers,it is usually not easy to obtain a satisfactory control performance for Buck converters subject to large disturbances. Aiming at this problem,a chattering-free control method based on the second order sliding mode control was proposed to improve the robustness of the Buck converters. Firstly,the average state-space model of Buck converter was established and the design of the chattering-free sliding mode controller was associated with controlling the output voltage of the Buck converter by selecting an appropriate sliding mode surface. The control design was accomplished by designing a discontinuous second order sliding mode controller where the derivative of the duty ratio was regarded as a virtual controller. The actual controller was the integration of the discontinuous second-order sliding mode controller,and thus the chattering problem can be avoided. On this basis,taking a direct discretization on the proposed algorithm by using Euler method,the chattering-free sliding mode controller can be implemented by the way of fixed-frequency PWM control technique based on a Lab VIEW platform. Finally,the reliability and superiority of the chattering-free sliding mode controller were verified by comparing PID controller through simulation and experimentation. It can be shown that： the system startup time can be shortened by nearly 50%; the variation range of system output voltage is significantly reduced under the conditions of load perturbation and input voltage change.