| With the increase in electric vehicles,charging facilities are also rapidly building,and the safety of the charging process was got more attention.The operation stability of the power electronic charging circuit is one aspect that affects the charging.However,when the circuit goes out of control,it will inevitably have an impact on the life span of the power battery,at the same time it will affect equipment safety and personnel safety.In addition,the nonlinear characteristics of power electronic circuits are the current research hotspots.Previous researchers have paid more attention to low-order circuits such as buck and boost.There are few researches on high-order circuits in China and abroad.The main reason is that high-order circuits are more complicated and have more modalities,and the mathematical models are more difficult to be set up.However,higher-order circuits in the industry are now being used more and more widely because of some of their characteristics superior to lower-order circuits,such as the three-level LLC resonant circuit.Therefore,it is necessary to study the nonlinear characteristics of it.In this thesis,three-level LLC resonant circuit is the research object,from the basic principles,parametric design,mathematical modeling,chaos simulation analysis,chaos suppression methods and so on.First,the whole work process of the circuit is described in detail.Based on this,the parameters are mainly designed for the resonant network,and an effective control algorithm is proposed,and the validity of the parameter design and the operation stability of the circuit are verified.Using the established circuit model,it sets parameters of the circuit(DC power supply voltage,the proportion of control parameters,the reference value of the charging current)and the dependent variable(charge current).The independent variable is changed by a certain step,and the strobe sampling diagram of independent variable and dependent variable is obtained,which is used to analyze the occurrence of the chaotic phenomenon in the circuit.The chaos of the three-level LLC resonant circuit has been found.At last,the control strategy of the chaotic phenomenon based on parametric resonance perturbation method is proposed for the chaos of the circuit.The effectiveness of the method is verified by simulation.In summary,this thesis studies the process of chaos phenomenon in the resonant circuit of three-level LLC,and provides the basis for the parameter design of practical industrial circuits.It also controls the chaos phenomenon to reduce the harm of the chaos phenomenon. |
