| With the increasing awareness of energy conservation and environmental protection,more and more attention has been paid to electric vehicles,and the key of related research is how to realize safe and convenient battery charging of electric vehicle.Wireless charging stands out among various charging methods due to its advantages of safety,stability and convenient maintenance.However,in practical application,the hard switching state of the high-frequency switch tube will cause switching losses,and changes of parameters,sunch as load and mutual inductance,will affect the performance of charging voltage and transmission efficiency.Therefore,in order to solve the above problems,the voltage regulating methods of transmitting terminal and receiving terminal are analyzed with the ZVS technology,and the the voltage transmission ratio is controlled to realize the efficiency optimization of the whole system.The main research contents of this paper are as follows:Firstly,the mutual inductance equivalent model of the system is established,and the resonant compensation topology is introduced to solve the problem of low transmission capacity caused by inductance in the coupling mechanism.By comparing the research on the compensation characteristics of different topologies,the series-series topology is selected as the research object,and its output characteristics are analyzed.Finally,the influencing parameters of the system’s output performance are analyzed with simulation,which lays a theoretical foundation for the efficiency optimization in the following paper.Secondly,to deal with the switch loss caused by the high frequency of the inverter circuit,a ZVS inverter circuit is designed with the auxiliary branch of LR,which can provide additional discharging current for parasitic capacitance to realize the ZVS.Then,the working state,voltage regulation principles and ZVS implementation conditions of phase shift pulse width modulation(PSPWM)and improved pulse density modulation(PDM)are introduced.In order to solve the problem of large auxiliary current of PSPWM and the current fluctuation of improved PDM,a hybrid modulation is used at low pulse density,and the improved PDM is used in the other cases.Thirdly,to deal with the problem of voltage output instability caused by the changes of load and mutual inductance,an enhanced PDM is used to achieve the voltage stabilization by combining the working modes of the semi-bridgeless active rectifier circuit.By the analysis of the principle of PDM under the different combinations of modes,the realization method of enhanced PDM is given and the expressions of load voltage and output power are derived.Then,the voltage stabilization control of the semi-bridgeless active rectifier is combined with the control of ZVS inverter circuit,and the voltage transmission ratio is controlled to realize the efficiency optimization of the whole system.The effectiveness of the control strategy is verified by the simulation of PSIM.Finally,the experimental platform of wireless charging system for electric vehicle based on DSP is designed,and the main parts of its software and hardware are introduced.Then,the proposed control strategies in this paper are verified by experiments.The ZVS of the inverter circuit can be realized with the auxiliary current,and the load voltage can be stabilized at 100 V with lower voltage ripples,also,transfer efficiency is improved. |
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