Study On Chaos In PWM DC/DC Converters

Chaos is a kind of seemingly random, chance or irregular movement, which appears in a definiteness system. It is a property token of non-linear system. It will be widely applied to engineering. A switched-mode DC/DC converter is a high non-linear control system, which has intrinsic non-linear. Under certain conditions, the converter may have seemingly random chaos without repetition. So analyzing chaos from the angle of linear theory and definiteness theory can not meet the increasing requirement to control performance of DC/DC converters. Recently, people attach more and more importance to the research of chaos in the DC/DC converters. In order to improve the control performance of converters, it is significant and helpful to further analyze the intrinsic irregular movement in DC/DC converters under the guidance of nonlinear dynamics theory. This dissertation studies chaos mechanism and chaos control in PWM DC/DC converters.Chapter one (introduction) introduces the brief history of chaos research and mathematical mechanism of chaos, discusses the development and orientation of nonlinear research in power electronics circuits both at home and abroad, and presents the research purpose and content of this dissertation.Chapter two (preliminary knowledge) first introduces in detail some mathematics notions and conclusions which are most critical and most closely related to the content of this dissertation. These theories include basic notions of chaos and bifurcation theory in nonlinear dynamics theory, basic notions of dynamic system of modern control theory and stability theory. Secondly, this dissertation introduces basic content of PWM DC/DC converters, discusses the basic methods of research on chaos in DC/DC converters. The author puts forward the thought of analyzing bifurcation and chaos in DC/DC converters with the theories of nonlinear dynamics, and the thought of controlling nonlinear problems with linear controlling methods of modern control theory.Chapter three (research on bifurcation and chaos in PWM DC/DC converters) first theoretically analyzes and emulates period-doubling bifurcation of PWM DC/DC converters with the "inverse" piecewise numerical emulation. Then the author analyzes in detail the sampled-data model, the mathematical model, which is suitable to the nonlinear research of DC/DC converters. The author introduces the possibility that there are Neimark bifurcation and saddle-node bifurcation in DC/DC converters. Finally, through circuit experiment, the author proves that when circuit parameters change, DC/DC converters will experience the evolution from bifurcation of a series of period-doubling to chaos. The author offers analysis and conclusion of output performance of DC/DC converters in chaotic state.Chapter four (research on chaos control in PWM DC/DC converters) first introduces the research background, purpose and physics mechanism of chaos control, as well as some basic problems which are worth attention in the design of chaos control system. Secondly, the author discusses the basic principle of OGY method and problems that are worth attention in the circuit experiment. Finally, based on modem control theory and OGY method, the author puts forward some chaos control schemes, conducts emulation and circuit experiment, and proves the feasibility of chaos control in DC/DC converters.Chapter five (conclusion of the whole dissertation) mentions the research fruit of the dissertation again, and points out some aspects which need further research.