Study Of Chaotic Anti-control And Its Application In Buck Converter

The DC-DC switching converters are the core part of modern power electronics system and their operation directly affect the working performance of power electronics system. Due to the non-linear characteristic of their devices and the fast switching of the power switch, the switching converters perform as a strongly nonlinear and time-varying system, which consequentially exist abundant non-linear phenomena, such as bifurcation and chaos, etc. With the increasing scale of power electronics system, the nonlinear characterstics are more and more obvious, under certain conditions, chaos will appear in the converter, which will bring some endanger to the stable operation of the system or enhance its operation.The voltage-mode controlled Buck converter is the main object in this paper, we studied the bifurcation and chaotic behavior in it, studied and simulated deeply in the aspect of modeling, operation procession, bifurcation behavior. We did some research and concluded of chaos anti-control methods or strategies from the perspective of reducing converter's EMI, and proposed the method of using resonant parametric perturbation to reduce the EMI level.The main works in this dissertation are as follows:(1)Reviewes the development history and present situation of chaos, in particular the nonlinear phenomena and the development and current situation of their control and anti-control in power electronic circuits, points out the significance of the relative research topics, then brings forward the goal and content of this paper.(2)Introduces the definition and characteristics about chaos, analyze the chaos dynamic characteristics and typical roads of periodic route to chaos, and gives the difference and connection between the chaos signal and random signal.(3)Summarizes on some kinds of switching converters, focuses on the voltage-mode control Buck converter, explains its relative operation principle, and use the theory analysis combine with the computer simulation to describe and characterize the chaotic regime in different ways and means. Then simply introduces some chaos control and anti-control methods and strategies, proposes two ways of chaotic switching modulation and chaotic parameter control to reduce EMI level.(4)Simply introduces traditional methods of reducing EMI and improving EMC, put forward the advantages of chaotic switching modulation method, chaotic switching signal obtained from the famous "Chua's circuit" was used to control Buck converter. Through the analysis of its output voltage power spectrum show that chaotic switching modulations have good effect on spreading power spectrum, which can be used to reduce the level of EMI.(5)Establishs Buck converter under resonant parametric perturbation, analyzes its circuit, derives its dynamic equation, obtains the bifurcation diagram under different parameters by changing the parameters of the system, and obtains the characteristic multipliers by calculation of Jacobian matrix. Through the analysis of these phenomena and the output voltage power spectrum, it is show that the chaotic parameter control is the better choice in reducing EMI of switching converters.