A comparative study of linear and non-linear controller design and implementation for dc-dc buck converter

Abstract

Control applications of switched mode power supplies have been widely investigated. The main objective of research and development (R&D) in this field is always to find the most suitable control method to be implemented in various DC/DC converter topologies. In other words, the goal is to select a control method capable of improving the efficiency of the converter, reducing the effect of disturbances (line and load variation), lessening the effect of EMI (electro-magnetic interference), and being less effected by component variation. With the speed improvement and cost reduction of digital control, digital controller is becoming a trend for DC-DC converters in addition to existed digital monitoring and management technology. In this thesis, digital control is investigated for DC-DC converters applications. To deeply understand the whole control systems, DC-DC converter models are investigated based on averaged state-space modeling. Considering Buck DC-DC converter, the thesis takes it as an example for digital control modeling and implementation. In Chapter 3, unified steady-state DC models and small-signal models are developed for DC-DC buck converters. Based on the models, digital and analog controllers design is implemented. In Chapter 4, digital modeling platforms are established based on Matlab /Simulink, Digital and analog PID design and corresponding simulation results are provided. Also some critical issues and practical requirements are discussed. Chapter 5, describes in detail SMC (Sliding Mode Controller) and a briefly reviews the history of SMC. In the next section, a review of the theory of SMC is given, more particularly; the existence condition, the reaching condition, the system description in sliding mode, the chattering. The researches on and applications of SMC in electrical systems are shown. The SMC is implemented to the DC/DC Buck converter. The results are verified with the simulation results. Finally, the researches on and applications of the SMC for DC/DC converters are given in details. In Chapter 6, fuzzy logic control is introduced based on that knowledge an intelligent self- tuning fuzzy PID controller is proposed for the control of buck converter. The fuzzy logic control is used to tune the proportional, integral and derivative gain of the conventional PID controller. The compensated power converter is tested using the Simulink model in the presence of the disturbances, and it is shown that the self-tuning fuzzy controller is capable of keeping the power converter output voltage within the operating requirements, while improving system speed and stability. In Chapter 7, a DSP-based digital controller is implemented with the TI‗s DSP chip TMS320F2812. Related implementation methods and technologies are discussed.