| With the consumption of fossil energy,countries have set a time point to stop the use of fuel vehicles,which will gradually withdraw from the stage of history.But the development of new energy vehicles is still limited by the life of battery.The application of dynamic wireless power transmission(DWPT)technology to electric vehicles will realize "charging while running",which will further improve the endurance capacity of existing new energy vehicles,and also help to solve the problems such as the unsuitability of plug and the inconsistent charging interface.This paper studied the electric vehicle dynamic wireless power transmission using cascaded buck-boost converter,and analyzes in detail the characteristics of wireless charging system and thorny issues under the receiver characteristics of dynamic wireless charging system such as high input voltage,wide voltage range.Cascaded buck-boost converter circuit was introduced into the wireless power transmission(WPT)system.This paper proposed a model smooth switching strategy,which solved the smooth transition problem in wireless power transmission system.It completed a 42.56 k W power test at the same time and engineering suggestions were presented.First,the paper analyzed the wireless charging system in different kinds of power supply and different compensation network of the corresponding output characteristics and different DC-DC converter impedance transformation ability.It carried on the analytic calculation of single receiver system,frequency,and the size of the mutual inductance is studied,the influence of load impedance on the function characteristic.Based on system parameters,it simulated the four receiver system and got the dynamic running process single cycle efficiency extreme value point and average power.Secondly,in view of the value of receiving voltage and output power of WPT system,the influence of load impedance on output power of high frequency inverter is analyzed.The effects of mutual inductance fluctuation,self-inductance fluctuation,uncoupling of DQ coil and detuning on the voltage of receiving end are summarized and analyzed,which further illustrated the importance of wide input voltage range.At the same time,the resonant converter theory was introduced intothe WPT system to accurately explain the voltage sag phenomenon under series-series compensation and constant power load.Again,small signal model of DUAL mode was built to analyze the relationship between the right half plane zero and the dynamic charging voltage fluctuation frequency.The root cause of voltage and current spike in cascaded buck-boost converter mode switching was analyzed.It compared the single mode,the merits of the two models,three control strategies,and made improvement on this basis.A new control strategy was proposed,which added logical judgment to the three-mode control strategy and selected the master controller according to the future state of the switch.The simulation model of the whole system is built and the feasibility of the scheme is verified.Finally,the experimental prototype was designed and built,and the correctness of the proposed theory and the reliability of protection were verified through DC-DC separate experiments.In addition,joint debugging with high-frequency inverter,coupling mechanism and compensation network was completed.42.56 k W static parking charging and 10.64 k W dynamic charging were completed. |
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