| In recent years,environmental degradation and energy shortage have become increasingly prominent.It is a trend to accelerate the promotion of clean and environment-friendly Electric Vehicle(EV).Compared with wired charging,wireless charging has many advantages,such as no physical contact,avoiding plugging and contact wear,safety and reliability,and taking up little space.In this paper,based on inductive wireless power transfer technology,the maximum DC tracking frequency modulation resonance method is studied to optimize the output energy efficiency.Based on the output characteristics of the Secondary side chopper circuit and compensation circuit,the Secondary side predictive output control is studied to stabilize the output of the system.The specific research contents are as follows:Firstly,the research background and significance are described.Combined with the current EV charging methods,the wireless power transfer technology is reviewed,and the key research points to promote the progress of wireless charging technology are listed and analyzed.Secondly,taking S/S topology as an example,the mutual inductance and T model of loosely coupled transformer is established.The input and output characteristics of S/S,S/P and S/SP resonant compensation circuit are analyzed,and the comparative analysis is made under different load conditions.It is concluded that S/SP compensation is superior to the other two topologies.In addition,the relationship between energy efficiency and load and frequency of S/SP compensation topology is deduced and analyzed to provide a theoretical basis for the establishment of control strategy.Thirdly,the reason of compensating topology detuning of inductive wireless power transfer is analyzed,the relationship between the change of primary and secondary leakage inductanceThirdly,the reason of compensating topology detuning of inductive wireless power transfer is analyzed,the relationship between the change of primary and secondary leakage inductance and transfer efficiency is deduced,and the necessity of resonance adjustment is expounded.The determination basis of maximum DC current tracking resonance is deduced by formula,and the frequency modulation resonance method of maximum DC current tracking is studied.The simulation results show that this method can improve the transfer efficiency under the condition of detuningThen,the relationship between the transformer coupling coefficient,Buck-Boost duty ratio and the output voltage and efficiency of S/SP compensation circuit is deduced.The coupling transformer output voltage and transfer energy efficiency can be stabilized within a certain range of coupling coefficient by adjusting duty ratio.According to the output characteristics of the circuit,the predicted output control of the backside Buck-Boost chopper circuit is studied to ensure that the output voltage and current of Buck-Boost are constant when the coupling coefficient changes.Simulation results show that the predictive output control is effective.Finally,the effectiveness of the method is verified by experiments,which can improve the transfer efficiency in the state of excessive compensation or under compensation for leakage inductance in the state of detuning.It is also verified that the predicted output control can achieve constant output voltage and current when the output power fluctuates and the coupling coefficient of loose-coupling transformer changes. |
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