Research On Sliding Mode Control And Performance Improment Of Buck Converter

The structure of the Buck converter system changes periodically with the on/off of the switching tube.A reasonable control strategy is the basis for ensuring the good performance of the system.This paper mainly studies the application of sliding mode control theory in converters.Firstly,based on the Kirchhoff circuit law,by introducing the control quantity,the unified differential equation of the Buck converter system is established according to the on-off state of the switching tube,and the Buck converter linear sliding mode controller and terminal sliding mode controller are designed.Non-singular terminal sliding mode controller,and derive stable voltage regulation conditions under different switching states.The mechanism research on the stability,switching frequency and controller parameter setting problems is studied,and the mathematical influence relationship between the nonlinear links of the control system is revealed.Secondly,based on the Buck converter equivalent control closed-loop system,the phase trajectory characteristics of the non-singular terminal sliding mode control system are studied.In the phase plane,the phase trajectories of the system state under the influence of different initial states of the system and their distribution laws are considered,and the equations of the critical surfaces are given.The relationship between the initial state of the system and the arrival time of the sliding surface is analyzed.The estimation algorithm of the maximum arrival time is proposed,and the mathematical expression of the output response time of the Buck converter is derived.Then,for the Buck converter non-singular terminal sliding mode control system,a single value improvement strategy is proposed.By setting the constraints and limiting the high-order variable symbols of the sliding surface,only the positive values of the higher-order variables are preserved during the sliding mode and system variable convergence,which simplifies the system operation and improves the response speed and robustness of the system.Sex.The stability proof is given,and the simulation and experimental analysis are carried out under four conditions: rated condition,input voltage disturbance,load disturbance and reference voltage periodic variation,which verifies the effectiveness of the improved strategy..Finally,the full-step sliding mode control method is applied to solve the problems of differential and high-frequency chattering in the existing sliding mode control,and the controller is improved.A new full-step sliding surface and robust control law are designed for the second-order Buck converter control system,and the stability proof is given.System performance is improved by eliminating control amount chattering.The Buck full-scale sliding mode controller is improved based on the single value improvement strategy,and the output quality of the Buck converter is improved.