Research On The Detection Of Metal Foreign Objects For Magnetically Coupled Resonant Wireless Power Transfer

Magnetically-Coupled Resonant Wireless Power Transfer(MCR-WPT)has gained significant attention from both academia and industry due to its ability to maintain high transmission efficiency over medium to long distances.However,the large air gap between the coupled coils in MCR-WPT systems makes it susceptible to foreign object intrusion.When metal objects intervene in the wireless power transfer area,they can quickly heat up due to the high-frequency magnetic field,posing a fire hazard.Therefore,the efficient and cost-effective detection of metal foreign objects that may enter the MCR-WPT system is the focus of this thesis.Firstly,this thesis investigates the interaction between metal foreign objects and the MCR-WPT system.It analyzes the effects of eddy currents and magnetic effects generated by metals in high-frequency magnetic fields on the parameters of the MCRWPT system.An equivalent circuit model is established and validated through finite element simulations and experiments.Furthermore,based on the established equivalent circuit model,the detection principle of metallic foreign objects based on electromagnetic characteristics is elucidated within a unified framework,providing theoretical guidance for the proposed metallic foreign object detection scheme.Secondly,this thesis proposes a detection coil array that is suitable for active metallic foreign object detection.It features low cost,easy scalability,and high detection sensitivity.Adjacent detection coils are arranged in a matrix pattern and are coupled through a bottom layer of ferrite to enable co-planar wireless power transfer.The detection coils,in conjunction with compensation capacitors,form resonant circuits.The presence of metallic foreign objects causes a shift in the resonance point,resulting in a significant change in the circuit current and high sensitivity.The central coil only requires power supply,reducing the complexity of the driving circuit and minimizing system costs.The structure and parameters of the matrix-style detection coil are further optimized through finite element simulations.Finally,a metal foreign object detection experimental platform is built to validate the proposed detection scheme.Experimental results show that the detection prototype achieves a high sensitivity with current variations ranging from 15.1% to 77.4% for aluminum and iron plates with a radius of 30 mm,depending on their relative positions.Additionally,the impact of this detection device on the coupling magnetic field,electrical parameters,and transmission performance of the MCR-WPT system is explored through simulations and verified through the experimental platform.The results demonstrate that the installation of the detection device causes a slight decrease of 3.6% in the transmission efficiency of the MCR-WPT system,indicating that the proposed metallic foreign object detection scheme has a minimal impact on the system’s transmission performance.