基于变频重构S/SP拓扑的无线电能传输系统恒流恒压研究

Research on Constant Current and Constant Voltage of WPT System Based on Variable Frequency Reconfiguration S/SP Topology

针对电动汽车无线充电系统耦合系数和负载变化导致系统输出电流和电压剧烈波动的问题,提出一种由交错叠放式线圈结构和变频重构控制策略组成的无线电能传输系统,通过重构补偿拓扑,并切换工作频率,实现了系统的恒流恒压输出。首先,分析了拓扑重构前后系统的恒流、恒压输出特性和零相角特性,对比恒流恒压工作模式下补偿电容的大小,给出了系统参数调整方法。其次,剖析了交错叠放式线圈结构模型,提出基于耦合系数波动最小原则的线圈结构优化策略。所提出的系统补偿元件较少,两个工作频率点符合国际标准。最后,搭建一套500 W的实验样机,验证系统的可行性和有效性。实验结果表明,交错叠放式线圈在X轴方向偏移发射线圈外径的55%(187mm)或Y轴方向偏移120mm时,耦合系数波动率小于5%。系统在恒流模式下电流波动率为3.58%,在恒压模式下电压波动率为4.83%,满足无线充电系统恒流恒压需求。

Wireless power transfer(WPT)technology achieves contactless power transfer through the media,such as electromagnetic fields,which provides a new,feasible way to solve safety and convenience problems in traditional contact charging.In the wireless charging of electric vehicles,the WPT system must have a constant current and constant voltage output and reduce output current and voltage fluctuations to prolong the service life of the battery.However,in practice,the output of the WPT system is affected by the coupling coefficient between the coils and the load variation.This paper proposes a WPT system comprising a staggered stacked coil structure and variable frequency reconfiguration S/SP compensation.The system's anti-offset performance is improved by optimizing the coil structure,and fluctuations in constant current and constant voltage outputs are suppressed by reconfiguring the compensation topology and switching the operating frequency.Firstly,a variable frequency reconfiguration control strategy combined with topology reconfiguration and frequency switching is proposed.The characteristics of constant current output,constant voltage output,and zero phase angle of the variable frequency reconfiguration S/SP compensation system are analyzed.The size of the compensation capacitors in the constant current and constant voltage operating modes is compared,and a method for system parameter adjustment is given,which effectively solves the problems of complex system design and wide frequency switching range.Secondly,the magnetic field superposition theorem is applied to analyze coils.An isotropic series compensation coil is introduced at the edges of the rectangular coil to compensate for the coupling coefficient at the edges of the main coil,which forms an SSC structure with good anti-offset properties.Finally,a 500 W experimental prototype was built to verify the anti-offset performance.The experimental results show that the fluctuation rate of the coupling coefficient of the staggered stacked coil is less than 5%when the X-axis direction is offset by 55%(187 mm)of the outer diameter of the transmitting coil or the Y-axis direction is offset by 120 mm.The error between the simulation and experiment is not greater than 5%,and the error between the theoretical value and experiment does not exceed 5%.The output current of the system in constant current mode is 6.3 A with a current fluctuation rate of 3.58%,and the output voltage in constant voltage mode is 74 V with a voltage fluctuation rate of 4.83%,which meets the constant current and voltage requirements of the wireless charging system.In future research,switching between the two operating modes of constant current and constant voltage will be considered to achieve automatic switching.