Research On Foreign Object Detection Of Wireless Power Transfer System In Seawater

The underwater electromechanical equipment uses traditional wired methods for charging,which is cumbersome and has poor safety,which greatly limits the range of activities of underwater equipment.Using magnetic resonance coupling wireless power transfer（MRCWPT）technology to charge electromechanical equipment in the ocean can effectively solve the above problems.However,in practical applications,due to the complex marine environment,the WPT system is inevitably affected by marine garbage and marine organisms.Especially when the metal foreign objects in marine garbage enter the coupling area of the WPT system,it will not only affect the electromagnetic parameters of the system,reduce the efficiency of the system,and even damage the electromechanical equipment;when marine organisms adhere to the coil gap for a long time,the marine fouling will affect the normal connection and charging of underwater electromechanical equipment.Otherwise,the electromagnetic radiation generated by the coupling mechanism may also pose a threat to the lives of marine organisms.Therefore,in order to ensure the safety of electromechanical equipment in the ocean,it is of great significance to study the detection of foreign matter in the WPT system in seawater.In this paper,the detection of metal foreign objects and marine biological foreign objects in WPT system in seawater medium is studied,the major researches are as follows:（1）Based on the theoretical basis of MRC-WPT technology,the influence of seawater medium on wireless charging system is analyzed,and the equivalent circuit analysis model of MRC-WPT system in seawater medium is established.On this basis,the influence of seawater medium on the coupling mechanism is further analyzed from the electromagnetic field theory,and the energy attenuation characteristics of different media at different frequencies are simulated.In order to solve the problem of mutual inductance instability caused by oceancurrent disturbances during charging,a high-order resonant compensation network is used to simulate and study the transmission characteristics of the system.（2）The effects of different types of foreign objects on the MRC-WPT system in seawater were studied by classifying foreign objects.The WPT system in the seawater medium is modeled by finite element method.The influence of foreign objects of different types,sizes and locations on the system and the influence of charging system on organisms are analyzed.It has been studied that the differences in the influence of different types of foreign objects on the system are mainly the electrical conductivity and permeability of foreign objects.（3）On the basis of the previous article,combined with the principle of the influence of different foreign objects on the system,a foreign objects detection method based on the external detection coil is designed,and the output voltage change of the detection coil in different media is studied and simulated,and the sensitivity of the detection coil in the seawater medium is found to be reduced.In order to effectively improve the sensitivity and accuracy of the foreign object detection,the coil is optimized from the parameters of the foreign object detection coil such as structure,line-space,turns,and combination mode,and the resonant circuit of the foreign object detection coil is designed.The detection of different foreign objects by the detection coil is completed,and the influence law of different foreign object on the inductive voltage of the detection coil is obtained.（4）Based on the simulation,the experimental platform of MCR-WPT system in seawater medium and the foreign object detection device for foreign object detection are built.The variation of the induced voltage of the detection coil for foreign matter under different conditions is analyzed and compared,and the detection of small-size foreign matter is completed,which verifies the feasibility of the foreign matter detection scheme designed in this paper.