Foreign Objects Detection Technology And Its Implementation Based On Impedance Characteristics For EV Wireless Charging Systems

In recent years,the electric vehicle technology developed rapidly at home and abroad,charging approach with cables is the main charging style at present.But this way of charging has many malpractices such as unreliable contact,contact resistance damage caused by increased temperature,cumber some charging equipments,inconvenient operation and so on,in order to solve these problems,wireless charging is adopted.Now because of the EV wireless charging system is generally used in the level of point-to-point coupling,metal objects and living organism may fall into the charging area occasionally when EVs are being wireless charged,which will result in eddy current in the metal objects and cause fires,and metal objects will change the parameters of the coupling mechanism,which will make the system deviate from the normal operating point,in serious cases will make the system completely unable to work properly.And living things may be hazarded by the high density electromagnetic field.So we need to detect metals foreign objects and organisms foreign objects,so that the safety of charging process and reliability of the system can be ensured.Based on this requirement,a foreign object detection system is presented in the paper,it can detect foreign objects effectively and guarantee the safety of the wireless charging systemWith EV wireless charging systems as the basic research objects,this paper analysis the importance of foreign object detection after analyzes the application requirements during system operation.And then,the development status of data transfer at home and abroad is generalized.Finally,the significance of the research of this issue is obtained after analyzing the limitations of the currently available method and technology.Based on the EV wireless charging systems,this paper presents a method to realize the foreign object detection based on impedance characteristics.The principle of the program is that the metal and the organism enter into the magnetic field will cause the parameters change of magnetic field,and then cause impedance changes of the measurement coil.So we can detect organisms and metals by this feature.The verification test data of the scheme is given based on overall design scheme of the system,the scheme mechanism has been verified.The key problems in the system design process are analyzed and the solutions are given.Designed the software flow and analysis the feature extraction algorithm.At the same time built the hardware experiment platform.With this platform,the detection function of the foreign objects in the system under different conditions was verified.,and the results show that the expected performance of the scheme has achived.The system can detected metal foreign object and biological foreign object under the premise of have no influence on the main circuit transmission power and efficiency,so the feasibility of the method in practical can be verified.