Finite-time Output Feedback Method For Second-order Uncertain Systems And Its Application In Converters

In industrial systems,nonlinear structures similar to second-order uncertain systems can be found everywhere,so it is of theoretical and practical significance to study the control problem of second-order uncertain systems.For example,the controller design of second-order nonlinear system can be applied to common converter systems,such as buck type DC/DC converter,DC/AC converter system.Due to the time-varying and uncertain characteristics of such system structure,the controller design is very challenging.The finite-time control technology is a new nonlinear control method with fast convergence and strong disturbance rejection performance which can effectively improve the control performance of the closed-loop system.This dissertation is based on the finite-time control problem of second-order uncertain systems.In this dissertation,the second order uncertain system,finite time theory and converter control technology are reviewed.Then the research significance of the second-order uncertain system is analyzed and the problems to be solved in this dissertation are introduced.Based on the second-order uncertain system,a finite-time state feedback controller is designed by using the backstepping method,and the stability of the closed-loop system is proved.Then,considering the unknown state of the actual system,a finite-time output feedback controller based on observer is designed,and the stability of the closed-loop system is proved by using the principle of non-separation.Then,the theoretical results are applied to buck type DC/DC converter and DC/AC converter system.First of all,the model and working principle of buck type DC/DC converter is analyzed,and finite-time output feedback controller based on buck type DC/DC converter system is designed.Matlab/M file is used for simulation verification,and a semi-physical simulation experiment platform based on dSPACE is built to verify finite-time output feedback controller.Verification results show that,compared with PI control and linear output feedback,the finite-time output feedback control method based on buck converter can not only effectively improve the convergence rate of the closed-loop system,but also have better disturbance rejection performance.Then,the model and working principle of DC/AC converter are analyzed,and the finite-time output feedback controller based on the DC/AC converter system is designed.Matlab/Simulink module is used for simulation verification,and a semi-physical simulation experiment platform based on dSPACE is built to verify the finite-time output feedback.Verification results show that the finite-time output feedback control method based on DC/AC converter has better control performance than PI control.