| With the development of modern information technology, switching power supply is becoming more and more widely used because of its high conversion efficiency, low power consumption, small-size and so on. However, the increasing diversity and complicationof electrical equipment has put towards a high request on the performance of switching power supply. The linear control method used in the traditional switching power supply is hard to meet the constantly renewed requirements. In order to seek a better control scheme, more and more scholars dedicated themselves to study the design of simple structure and easy implemented controllers with stronger anti-disturbance ability.This paper mainly introduces three kinds of control methods to improve the anti-disturbance ability of Buck converters. The first method is to combine the variable parameter PI controller with disturbance observer. The new method not only has the advantage of easy implementation, but also possesses stronger anti-disturbance ability than traditional PI controllers. Considering that the Buck converter is a typical variable structure system, this paper then proposes a new discontinuous second order sliding mode control method. This control strategy is based on a mathematics model which is more close to the actual case, so as to eliminate the negative influence caused by nonlinear characteristics of Buck converters. Finally, combining with the fixed frequency sliding mode technology, this paper also proposes a quasi-continuous second order sliding mode control method which will solve the unfixed switching frequency problem in practice. The main content of the thesis can be summarized as follows.(1) A composite control strategy which combines the variable-parameter PI control and disturbance observer(DOB) is presented. Firstly, the mathematical model of Buck converters in frequency domain by State-Space Averaging Method has been built. On this basis, a composite controller is constructed by combining thevariable-parameter PI controller and disturbance observer(DOB). The disturbance rejection analysis of the composite controller is given by rigorous mathematical proof.Finally, the discretization of the composite controller is given for the implementation by LabVIEW software.(2) A discontinuous second order sliding mode control strategy is presented.Firstly, taking the disturbances into account, the mathematical model of Buck converters in state space is proposed. Secondly, by applying the modified version of the adding a power integrator technique, the second order sliding mode controller can be constructed recursively by means of a step-by-step design procedure. Under the new second order sliding mode controller, it can be proved that the closed-loop system of Buck converter is finite-time Lyapunov stable rather than only finite-time convergent. Finally, a detailed way on how to design and implement the new second order sliding mode controller for buck converters is proposed.(3) A quasi-continuous second order sliding mode control strategy is presented.Base on the mathematical model of Buck converters, a second order sliding mode controller which is continuous almost everywhere can be designed by using the geometric method. In addition, the finite-time Lyapunov stability analysis for the closed-loop system of Buck converters is given by using a contradiction method.Finally, combining PWM technique, a fixed frequency PWM-based implementation method for the quasi-continuous second order sliding mode controller can be obtained.(4) In order to demonstrate the performance of the proposed algorithms, the closed-loop buck converter system under above controllers is tested by using MATLAB. Meanwhile, this paper also designs experiment platforms based on LabVIEW and DSP chip, respectively. The effectiveness of the proposed algorithms has been verified by using these experiment platforms.The conclusion and future research is finally given in the last chapter.
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