A IPT System With Nature Constant Voltage And Constant Current Output Features For EV Charging

Wireless power transfer(WPT)is a novel power supply technology,featuring contactless,convenience,safety and flexibility.With the rapid development of electric vehicle industry,more and more electric vehicles begin to use inductive coupling wireless charging instead of traditional plug-in charging.This application also puts forward higher requirements for offset adaptability of wireless charging.As a charging object with wide load range,lithium batteries also require that the charging system has corresponding system output characteristics and can adapt to the battery charging characteristic curve.The coupling and offset characteristics of different transformer structures are compared and analyzed.The influence of winding structure on magnetic field distribution is analyzed by finite element simulation.A new kind of transformer structure with large offset adaptability is designed.By designing the corresponding resonant compensation topology,the system can achieve stable power output in a large offset range.Based on this transformer and the characteristics of battery load,a resonant compensation topology with natural constant voltage and constant current output characteristics is proposed by analyzing the transmission characteristics of various basic compensation topologies.The system can simultaneously obtain the natural constant current output ability and constant voltage output ability,and the system can automatically switch between different output modes according to the load resistance,without any complex controlling.The output characteristic curve of the system topology coincides with the two-stage charging curve of the battery.According to the proposed transformer structure and system topology,an experimental platform with offset adaptability and another experimental platform with natural constant voltage and constant current output characteristics are built for verification.The experimental results show that the proposed transformer structure has a high coupling coefficient between the primary side and the secondary side in a large offset range,and can meet the charging requirements of electric vehicles.The proposed system topology has good adaptability to wide load range,and can achieve different constant output characteristics at different load stages under open-loop conditions.