Study Of Nonlinear Behavior And Chaotic Control In Two DC/DC Converters

Switching power supply is a kind of high-frequency power conversion device.It is an indispensable power source form in the rapid development of electronic informational industry.DC-DC converter belongs to the core part of switching power supply.The performance of the converter has a great influence on the performance of the switching power supply.When some circuit parameters change slightly,the DC-DC converter will exhibit rich nonlinear dynamic behavior.Such as bifurcation and chaos,and these phenomena will make the circuit system oscillate violently in the process of operation,make the system unstable,and even lead to the system collapse.With the rapid development of modern power electronics technology,the performance of switching power supply is becoming more and more important in various industries,so it is very important for the nonlinear analysis of DC-DC converter and the chaos control strategy to control it.In this paper,the non-isolated Buck converter and the isolated Buck converter(forward converter)are taken as examples to study the nonlinear dynamic behavior,and the stability of the system is analyzed.Then,the chaotic state of the system is controlled from the chaotic state to the stable periodic state.The main work of this paper is as follows:(1)The working principle of Buck converter is analyzed,and the discrete mathematical model of the converter is deduced,on the basis of which,with the help of the mathematical modeling method of power transformer,the relationship between the initial voltage and the secondary voltage of the transformer is obtained.The discrete mathematical model of forward converter is derived.(2)With input voltage and filter capacitor as bifurcation parameters,the bifurcation diagram and time-domain waveform diagram of Buck converter are given by means of MATLAB simulation software,and the evolution process from stable state to chaotic state is discussed.When the input voltage between 20 V and 40 V increases,the system becomes more unstable with the increase of the voltage,and when the filter capacitance between10 ?F and 47 ?F is smaller,the system becomes more unstable;the load resistance and the magnifying factor are used as the bifurcation parameters.The nonlinear dynamic behaviorof forward converter in parameter space is studied by numerical method.According to its bifurcation diagram and Poincare section diagram,the simulation of the converter from stable state to chaotic state is discussed.When the load resistance between 20 ? and 100 ?increases or the magnification factor between 3 and 6.5 is smaller,the system becomes more unstable.(3)The discrete mathematical model of Buck converter and forward converter is established by using the state space averaging method.The stability of the system is studied by the combination of analytical and numerical simulation,and the stable working interval of Buck converter and forward converter is obtained.(4)In this paper,the chaos control methods of several common nonlinear systems are briefly analyzed,and the Buck converter is controlled by using the improved COGY method of OGY,which makes the system return to the stable 1-period state from the chaotic state.This control extends the stable range of the input voltage of the system and proves the feasibility of the improved chaos control strategy.