Research On Chaos And Chaotic Control Of PWM DC/DC Converter

Chaos is a kind of internal random movement, which appears in non-linearsystems. In recent 20 years, it has been paid great attention as a property token ofnon-linear system. A switched-mode DC/DC converter is a high non-linear controlsystem, which can produce chaotic phenomenon under certain parameters. Soanalyzing the phenomenon of unstable action and subharmonic of DC/DC converterfrom the angle of linear theory and definiteness theory can not meet the increasingrequirement of control performance of DC/DC converter. Under some specialconditions, explaining unstable phenomenon of DC/DC converter from chaotic theorycan be more reasonable and easily accepted. Based on chaotic theory, researching anddesigning corresponding control method can give great help to increase controlperformance of DC/DC converter. This dissertation makes more studies on chaosmechanism and chaotic control of PWM DC/DC converters. Theoretically analyzes and emulates chaos and period-doubling bifurcation ofBuck and Boost converters with piecewise linear numerical emulation. Performancesof the output ripples of DC/DC converter from stable state to chaotic state areanalyzed in time domain and frequency domain respectively. Aim at identifying chaosof DC/DC converter, the method of using Fourier Descriptor to extract output signalscharacteristics is put forward, based on which an improved BP neural network is thenused to identify the output signals of DC/DC converter. Finally, the testing resultindicates the identification rate of the output signals of DC/DC converter using thisBP neural network can reach to 100%. Based on theoretical research, an experimentis done to exhibit chaos and evolution from stable state to chaotic state of DC/DCconverter, which validate the correctness of theoretical analysis. Study the features of DC/DC converter in chaotic state, OGY method, outsideforce feedback control method and delay feedback control method are usedrespectively to control chaos in DC/DC converter. Then features, effects andlimitations of every control method are analyzed and compared one another.According to the principle of outside force feedback control method, a chaotic controlcircuit is designed to control chaos in DC/DC converter. The result of experimentvalidates the feasibility of chaotic control in DC/DC converter. Apply the technology of chaotic anti-control to DC/DC converter. Externalnoise driving method, delay feedback control method and chaotic signal drivingmethod are used respectively to give a chaotic anti-control over DC/DC converter inunstable or chaotic state in order to make it come into a new chaotic state. Analyzethe feature of chaotic attractor in phase space of DC/DC converter before and afteranti-control from the angle of geometry. Define two structure parameters of chaoticattractor in order to reflect the trait of output ripples of DC/DC converter according tothe change of these two structure parameters, so the quality of the output performanceof DC/DC converter can be estimated quantificationally.