Research on positioning technique of wireless power transfer system for electric vehicles

The relative position of the energy transmitting coil and the energy receiving coil has a great influence on the transfer efficiency of the wireless power transfer systems. The transfer efficiency has a marked fall when the two coils are misaligned. Thus it is important to know the exactly position of the two coils to achieve high system efficiency. This paper focuses on the positioning solution for guiding the electric vehicles to the charging area and ensuring the alignment of the two coils. This solution is based on the RFID(radio frequency identification) technique and combined with the magnetic field coupling method to achieve high accuracy and large scale in positioning. The RFID is considered as one of the most preferable ways for the position estimation in indoor and local environment. The positioning system calculates the real-time position of the vehicle in the parking area. Then the position signal is sent to the screem to show the driver where the car actually is. When the two coils are well aligned, the wireless power transfer system can start charging the vehicle.