| Wireless power transfer(WPT)enables electric vehicle charging to be automated,and is perfectly combined with autonomous driving technology.It is an important basic technology to promote the popularization of electric vehicles and achieve the goal of "carbon neutrality".This article focuses on the realization,control and protection strategy of the wide coupling range of the medium and high power wireless charging system for electric vehicles,and the following main results have been obtained.Aiming at the series-series(SS)compensation WPT system’s power output problem caused by the frequency splitting characteristics in the strong coupling region,this article compares the misalignment characteristic of fixed-frequency symmetrical tuning,variable-frequency symmetrical tuning,and variable-frequency asymmetrical tuned SS WPT systems.The result reveals that the variable-frequency asymmetric tuning scheme can achieve rated power output in a smaller frequency range,and can achieve higher voltage gain.Then,this article mathematically modeled the coupling range,frequency range,output power,volt-ampere capacity,zero-voltage turn-on and other conditions in practical applications,and based on this,proposed a compensation design method for variable-frequency asymmetrically tuned SS WPT system.The system can meet the above five requirements at the same time.In order to solve the influence of the communication module of the wireless charging system on the stability of closed-loop control,this article proposes a nonbilateral communication control scheme.The secondary bridge controls the output through the phase shift of the bridge arm,and the primary bridge seeks the highest efficiency operating point of the system by introducing disturbance in the phase shift angle of the bridge arm.In addition,the secondary side transmits a simple signal to the primary side by adding the bypass output state to ensure that the primary side provides sufficient input.The simulation verification of the proposed non-bilateral communication control scheme is carried out through circuit simulation.Finally,for practical engineering applications,the overall working process of the wireless charging system and the required protection strategies are designed.A 3.3k W WPT prototype was made,and the compensation design method of the proposed variable-frequency asymmetrically tuned SS WPT system was experimentally verified.The experimental results show that the designed system can meet the five requirements of output power,coupling range,frequency range,volt-ampere capacity,and zerovoltage turn-on. |
