Research on boundary control with second-order switching surface for power electronic systems

Abstract

This thesis presents research results on boundary control with second-order switching surface for power electronics systems. The proposed switching surface can achieve near-optimum large-signal responses in power electronic systems with simple circuit implementation and does not require sensing extra state variables, as compared with the first-order switching surface. Converters can exhibit good steady-state and transient behaviors in both continuous and discontinuous conduction modes with the same control law. The proposed switching surface is not only capable of controlling buck converters, but also can be extended to various types of power electronics converters, such as dc/dc converters and dc/ac converters. The contents of this thesis are as follows. In Chapter 1, control methods of power electronic converters will be discussed. Then, some control issues, such the control performance versus control complexity and dynamic performances, will be discussed. Moreover, review and discussion on the boundary control and its practical issues will be given. In Chapter 2, the concept of second-order switching surface in boundary control for buck converters will be introduced. It is based on estimating the state trajectory movement after a switching action, resulting in a high state-trajectory velocity along the switching surface. This phenomenon accelerates the trajectory moving toward the target operating point. An implementation of the controller and experimental performance with a 120-W buck converter will be studied. In Chapter 3, a comparative study on the performance characteristics of buck converters with boundary control using the first-order switching surface in continuous conduction mode will be presented. Performance attributes include the average output voltage, output ripple voltage, switching frequency, and large-signal characteristics. Special emphases will be given to investigate the effects of the equivalent series resistance of the output capacitor on the above attributes, and the sensitivity of the output voltage against the variations of input voltage and circuit component values. Theoretical predictions will be verified with experimental results. In Chapter 4, the scope of Chapter 3 is extended. Major emphasis is given to converters operating in discontinuous conduction mode. In Chapter 5, a detailed examination of inverters using the proposed switching surface will be carried out. Dynamic responses of an inverter supplying to different kinds of loads, including resistive load, inductive load, and diode-capacitor rectifying circuit, will be studied. In Chapter 6, an overall conclusion of the research topics and some suggestions for further research will be given.

Date of Award	3 Oct 2005
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Shu Hung Henry CHUNG (Supervisor)