Optimum Design And Research On Coupling Coil Of Wireless Power Transfer System For Heating Problem

Wireless Power Transfer?WPT?has been widely used in the fields of household appliances,electric vehicles,mobile phones,transportation and so on because of its safety,cleanliness,flexibility,reliability and applicability to various special power supply occasions.This technology has also become one of the research hotspots in recent years.Magnetic Coupled Wireless Power Transfer?MC-WPT?is one of the main research directions,and its application is mature and extensive.As one of the core parts of MC-WPT technology,coupling coils and electromagnetic mechanism are the key parts to ensure efficient transmission.The parameters of coils can directly affect the overall performance of the system.There are many articles about the optimization of coil's main performance,but very few articles pay attention to the heating problem of coils in practical work.The coil temperature rise caused by heating loss will directly decide whether the system can work safely and efficiently for a long time.Focusing on the heating problem of coupling coils,this paper takes the primary coil under the LCL-Series?LCL-S?resonant network structure as the main research object,analyses and studies the coupling system from the aspects of coil as heat source and heat transfer,finally represents a new optimization method and design process.Firstly,the influence of the main parameters of the coupling coils is analyzed,and the loss of each part of the system is calculated and explained from a energy standpoint.Secondly,from the aspect of coil heating,based on the structure of LCL-S resonant compensation network,an optimization method of primary coil parameters with the optimization objective of?is proposed.By deriving the functional relationship between the key parameters such as turn numbers N and AC resistance R_ac and self-inductance L_p,the optimization objective equation is established and solved by partial differential method.Finally,the optimal turn number solution under minimum heat loss power of primary coil is obtained.Combining with the secondary coil and the system performance,the reasonable value range of the optimal turn number is given,and the flow chart of the optimal design of the coil is presented.Considering that although coil design meets the minimum heating loss,still can not reduce the temperature to the desired range in some cases,thus,the coupling system is analyzed from the perspective of heat transfer.In this part,at first,the phenomenon of uneven temperature distribution on the surface of closely wound disc coil is described and explained by establishing a heat conduction differential equation.Then,the thermal network model of the coupled system is established to study each heat dissipation link.Combined with Comsol finite element simulation software,various factors affecting the coil temperature rise are systematically analyzed,and the corresponding improvement suggestions and heat dissipation design flow chart are given.Finally,the simulation is carried out with Comsol and Simulink software,and the rationality and feasibility of the theoretical analysis are verified by some experiments.