Research On Wireless Power Transfer For The In-motion Electric Vehicle Charging

The wireless power transfer for the in-motion electric vehicle charging is a new technology, which can provide energy for the in-motion electric vehicle in real time. The electric vehicle can be equipped with a small number of battery packs or without to solve the mileage problem, while improving power supply safety and convenience. And it’s helpful to reduce the initial cost of electric vehicle because of the high cost of large capacity battery, and to promote the market of electric vehicle. In recent years, the technology of wireless power transfer for the in-motion electric vehicle charging has become one of the research hotspots in the domestic and foreign, and it is getting more and more attention. In this paper, some problems related are studied.In this paper, based on the mutual inductance coupling theory, the energy transfer process between two primary windings with the secondary is clearly recognized, and the main factors which affect the output power and output efficiency are obtained. In order to compare the coupling characteristic of electromagnetic coupling mechanisms, whose coil structures is square-square, circular-circular and square-circular.we can derive the mutual inductance of two coil by using Neumann formula. And it is determined that the most stable and effective coil structure is the square-square.and the influence of the current phase on the magnetic field distribution of the primary contiguous windings is analyzed by MAXWELL simulation. By changing the size of the secondary winding, the magnetic field distribution of the 3 coils dynamic mode power supply system is analyzed, then it is determined that the system coupling performance is the best when the size of secondary winding is same with the primary winding.Two modes of multi primary windings in parallel system are analyzed, And the hybrid inverter is proposed to make the current phase in the primary contiguous windings opposite, then the operating mode and soft switching conditions are analyzed. Finally, in order to avoid the loss of energy, and the electric vehicle stably at the junction of the transition, the method of continuous switching power supply is put forward.Finally, according to the results of the simulation analysis, the experimental platform of the in-motion electric vehicle charging system is designed, while the output power is 150W, the transmission distance is 10cm, and the load is 10Ω, the efficiency of the device is about 80%. In the end, the aim that the car is charged while it’s moving is achieved. The segmental rail of the system is composed of 5 primary windings in parallel, We analyzed frequency characteristics, transmission distance characteristics and load characteristics. and in the same energy level, the system output power and efficiency of the single energy conversion- single winding mode and the hybrid inverter mode are compared.