Research On Compensation Circuit Topology And Magnetic Coupling Structure Of Electric Vehicles Wireless Charging System

Compared with wired charging methods,wireless charging for electric vehicles has the advantages of safe operation and low maintenance cost.It is the future development trend to realize full automation of driving with driverless technology.In practical applications,there are factors such as size and position misalignment,which lead to a decrease in system transmission capability.To improve the output power,transmission efficiency and misalignment resistance of the system under the space constraint while considering the safety of electromagnetic radiation.This paper focuses on two modules of compensation circuit topology and magnetic coupling structure in the wireless charging system for electric vehicles.The main research contents are as follows:(1)Based on the analysis of the current research situation,the theoretical analysis is focused on the two modules of compensation circuit topology and magnetic coupling structure.First,the working principle and components of the magnetically coupled resonant wireless charging system for electric vehicles are analyzed as the theoretical support for building the platform.Then,the theoretical models of four basic compensation circuit topologies are established as the basis for the subsequent comparative study of compensation circuit topologies.Subsequently,the analysis methods of three magnetic coupling structures,coupled model theory,two-port network theory and mutual inductance model theory,are compared to lay the foundation for the study of wireless charging system for electric vehicles.(2)The transmission characteristics of different compensation circuit topologies are studied,and finally the double LCC type compensation circuit topology is selected as a component of the system for parameter design and research.First,the transmission characteristics are simulated and analyzed for SS type,SP type,PS type,and PP type compensation circuit topologies under the same parameters.Then,in order to meet the requirements of high power and high efficiency transmission in EV wireless charging scenarios.The double LCC type compensation circuit topologies are investigated considering the effects of coupling coefficient and load variation on power and transmission efficiency.Finally,simulation experiments are conducted around different compensation circuit topologies to verify the high transmission efficiency and stability of the double LCC type compensation circuit topology at high power.(3)Optimize the parameters of the coil and shield in the magnetically coupled structure to improve the coupling coefficient and misalignment resistance of the magnetically coupled structure while ensuring the safety of electromagnetic radiation.First,there is a contradictory relationship between space constraint and coupling coefficient.The shape and number of turns of single coil are designed for the difficult problem of low transmission efficiency and weak misalignment resistance under space constraint.And the structural parameters such as wire diameter and turn spacing are optimized after combining into D4 coils.Then the actual application of electric vehicles may have different position misalignment and chassis height.So two types of transceiver asymmetric magnetic coupling structures are designed on the basis of D4 coil to improve the coupling coefficient and anti-misalignment capability.Then,the thickness,area and position of the two shielding layers are optimized and designed respectively to ensure system safety.Finally,simulation tests are performed in different directions of misalignment,rotation and multiple misalignments simultaneously.The transceiver asymmetric D4 Q double-layer coil has wireless transmission capability within the occurrence of transverse misalignment 230 mm,longitudinal misalignment 310 mm,transmission distance 230 mm,diagonal misalignment 523 mm and rotational misalignment 45°.(4)Based on the research on the compensation circuit topology and magnetic coupling structure.An experimental platform for wireless charging of electric vehicles is built to verify the misalignment resistance and efficient transmission characteristics and electromagnetic safety of the system.First,the experimental platform is built based on the existing conditions in the laboratory,combining the double LCC type compensation circuit topology and the transceiver asymmetric D4 Q double-layer coil.Tests were conducted at a transmission distance of 150 mm,with a lateral misalignment of 200 mm and a vertical misalignment of 300 mm,and a load resistance of 5 Ω to 15 Ω.The test results show that the transmission efficiency of the system remains above 85% and have 89.53% transmission efficiency at an output power of5.35 kW.Finally,the test results of measuring the magnetic field above the system are close to the simulation results.The maximum value meets the national standard requirements.The experiment proves the feasibility and safety of the proposed scheme.