Based on the magnetic coupled resonance theory, a wireless power transfer (WPT) system features plate core structure is porposed to realize constant current charging for the variable load. The main factors that affect the transfer power, system efficiency and charging current are analyzed by the equivalent circuit model. Based on the dynamic characteristic of supercapacitor's equivalent load resistance during the constant current charging process, different values of power resistor are used to simulate its charging characteristic. Firstly, the regulation of charging current by the secondary side Buck converter is analyzed and the relationship between duty cycle and charging current is obtained. Then, constant current charging is achieved by PI control algorithm. Secondly, through the theoretical analysis and simulation, the parameters of the magnetic coupler are optimized and designed. Finally, the experimental setup is built to validate the system design method. When the transfer distance is 15cm and the range of load resistance is 0.5~5Ω, 29A constant charging current is achieved. Furthre, when load resistance is 3.2Ω, the designed system realizes 87.7% system efficiency and 2.58kW transfer power.%基于磁耦合共振原理,设计了一套采用平板磁心结构的变负载恒流充电无线电能传输系统.利用等效电路模型分析影响传输功率、系统效率和充电电流的主要因素.根据超级电容恒流充电过程中等效负载电阻动态变化规律,采用不同阻值的功率电阻模拟其充电特性.首先,分析二次侧Buck变换器对充电电流的调节作用,得到占空比与充电电流的关系,采用PI控制算法实现变负载的恒流充电;其次,通过理论分析和仿真实现磁耦合机构参数优化设计;最后,搭建系统实验平台对系统设计方法进行验证.在传输距离为15cm且负载电阻为0.5~5Ω 时,实现29A的恒流充电.当负载电阻为3.2Ω 时,系统效率和传输功率分别为87.7%和2.58kW.
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