Design And Performance Optimization Of The Wireless Charging System In Electric Vehicles

The power of electric vehicle is from the battery. There are two ways for batterycharging, contact and non-contact charging. Compared with the contact charging,non-contact charging is easy to operate, safe, simple, no direct electrical connection andother advantages. This paper achieves the design of the non-contact charging system inelectric vehicles. The magnetic resonance technique is adopted for achievingnon-contact closed loop charging in electric vehicles. Increase the transmission distance,the introduction of closed-loop control. Optimized design including increasedtransmission distance and join the closed-loop control. Moreover, it studies themagnetic shielding system for radiation field.First, to study the theory of magnetic resonance wireless energy transfertechnology, the circuit coupled is employed. Based on a comparative analysis oftransmission mechanism between the SS compensation structure and SP compensationstructure, the SS compensation structure is application. The system modeling andsimulation are identified, which is to analyze the trend of system transmission effectedby inductance parameters and load parameters and to provide guidance for the design ofthe system platform.The coupling coefficient of loosely coupled transformer and the robustness of thesystem are improved through joining the core of planar structure to the system. Basedon the STM32processor as the master of primary and secondary side, the systemrealizes the primary and secondary closed loop communication by the wirelesscommunication. A PI control algorithm is proposed to adjust the operating frequency ofthe system for executing the closed-loop. A detailed analysis on the hardware designand software algorithm design is conducted.The System parameters characteristic experiment is employed against differentvertical spacing, different horizontal lateral displacement and different directional anglerespectively, for analyzing the transmission power and the overall efficiency of thesystem, then studying the transmission characteristic. A model for the radiation fielddistribution has been done, and then the magnetic shielding performance curves ofmagnetic shielding material and its impact on the transmission characteristics of thesystem have conducted. A PI control program is carried out to adjust the operatingfrequency of the system in real-time for reaching the fixed closed loop charge with along time and the closed loop charge with adjusting the vertical spacing or horizontallateral displacement dynamically.In this system, the wireless charging in electric vehicles are applied at20cm spacing transmission, achieving a3.3kW contactless energy transfer and the overallefficiency can reach89%. The closed-loop control by changing the frequency isemployed, for making the system operate normally at the vertical spacing ranging from20cm to25cm or the horizontal lateral displacement be in the range of-10cm-+10cm.The transmission power is changed in the range of3.1kW-3.3kW. And the overallsystem efficiency is changed in the range of85%-89%.