Application Research For Buck Converter On Variable Structure Control

Application of sliding mode control theory to the Buck Converter and design of practical sliding mode controller are studied in this thesis. It focuses on the design of several practical sliding mode controls. The state observer and load identification are designed based on the variable structure for Buck converter to increase robustness under the condition of internal parameters variations and external disturbances, and to improve dynamic characteristics.First, the sliding mode control theory and its application in converter control are discussed. Based on the analysis of research around the world, several issues and their solutions of current sliding mode control switch are presented. Sliding mode controller based on the index trading law is designed and its frequency and general features are analyzed. Comparing with the traditional PWM switch Converter of proportional-integral control, it shows the advantages of sliding mode control.The chattering of sliding mode algorithm can't be avoided completely. In order to reduce chattering, the path of speed is associated with the distance of the sliding surface and trajectory. The sliding mode controller based on the adaptive trending law is designed. Two different trending laws are used in the process of reaching sliding surface and in the sliding surface. Then the sliding mode controller based on the adaptive trading law is designed. The simulation results show that the two controllers can reduce chattering effectively.Because the state variables and load feedback is necessary in controller, design of state observer is the key to the controller. Output voltage is reconstructed with the induction current by the method of integral reconstruction. The method based on sliding mode state observer and Buck Converter state observer is designed with the principle of equivalence in sliding mode control. And Buck converter load is identified on-line by sliding mode theory. The simulation results show that the method can track the system load effectivelyFinally through the feedback from state variables and the load to the controller, we get the sliding mode controller with state observer and load identification and apply it into the Buck Converter. The simulation results, with a variety of input voltage and load mutations, show the Controllers have good effect in reducing the system's chattering, response rate and achieving stable state time.