Research Of Modeling And Nonlinear Control Strategies For Buck Converter

DC-DC converter modeling analysis is the basis of researching switching power supply and it is of great importance in analysis and design of switching power supply. The differences between the traditional ideal model and the actual circuit model are an issue that can not be overlooked. On this issue, this paper analyses the modeling of Buck converter, and the modeling contributes to the improvement for the performance and efficiency of switching power supply.On the basis of analysing the present and future of DC/DC modeling, a state-space modeling method based on the non-ideal Buck converter is referred to. Taking the non-ideal Buck converter as an example, we elaborated on the modeling process of the continuous current mode and discontinuous current mode. To meet different requirements, the simulation models are established by using Matlab and Vissim respectively. For the requirements of frequency domain and time domain analysis,a small-signal modeling is also referred to based on the state-space model for Buck Converter, and the transfer function model is derived.In control methods, this paper first refers to the linear control method focusing on the PID control algorithm, and gives a detailed expression to the basic principles of commonly used methods of setting the control parameters, finally a PI controller based on the amplitude and phase margin method is designed and the closed loop simulation is carried out.After deeply understanding conventional PID control algorithm, we focus on nonlinear control methods. First, this paper introduces various nonlinear control methods, and then discusses the single-sliding and double sliding control methods. The sliding surface design and the equivalent sliding dynamic control are analyzed respectively, as well as ideal sliding surface accessibility and the invariance of the disturbance conditions. Moreover, this paper introduces back stepping and adaptive control methods. The controller is designed, and the simulation is carried out. By combining these nonlinear control algorithms, this paper designs the controller, and compares the simulation results with the ones above.At last, This paper designs a closed-loop control experiment platform for Buck Converter. According to the requirements of switch power design, the main circuit parameters selection is researched, and the voltage and current detection circuits are designed as well as the drive and photocoupler circuit. After designing the external hardware circuit, we discuss the control circuit using FPGA, introduce the design processes of VHDL (hardware description language) and SG (System Generator). Finally, the linear and nonlinear controllers are designed by combining VHDL and SG, and the simulations are given.