Research On Full-bridge LLCC Inductively Coupled Power Transfer Device

As a novel power transfer method, inductively coupled power transfer (ICPT) technique which utilizes the electromagnetic coupling theory to achieve contactless power transfer has been a global popular research project in recent years. ICPT device using loosely coupled transformer realizes both electrical and physical isolation. As no wires are needed in ICPT device, dangers from contact such as spark and mechanical wear could be avoided. Besides safe and convenient charging for general electronic devices and electrical vehicles, ICPT can be widely used in special conditions, such as mining wells, underwater, and some other inflammable and explosive environment.In this paper, the principle, research status and development trends of ICPT are briefly introduced. The magnetic circuit of loosely coupled transformer is analyzed particularly. The division method is used to accurately calculate the gap magnetic resistance with air gap and magnetic core size. Under the condition of ignore the secondary factors, the equivalent magnetic circuit of large air gap U magnetic core is given in this paper. And achieve the relationship among coupling coefficient, magnetic flux and magnetic resistance. Because of traditional transformer model does not apply to loosely coupled transformer, the mutual inductance model is introduced. Based on the analysis above, the parameters of loosely coupled transformer are designed in details.Then introduced the structure of ICPT device, and discussed some designing points based on its characteristics. Furthermore, the ICPT circuit is analyzed by the base wave mode approximate analysis method.The large air gap of loosely coupled transformer lead to the coupling coefficient is low. To improve the performance of ICPT device, the primary and secondary compensation circuit is focused on. The function of the primary compensation capacitor and secondary compensation capacitor are analyzed from reducing capacity requirements of the power supply and promoting the power transfer capability. According to the analysis, the full-bridge resonant converter with series compensation capacitor on primary and parallel compensation capacitor on secondary is proposed and its working models are analyzed in detail. The circuit is simulated by Matlab/Simulink. At last, a1.5kW ICPT experimental prototype was build. The efficiency of ICPT device vs. air gap for different capacitor compensation circuits and working frequency are compared and analyzed by experiment. The Experiment results verified the theoretical analysis and simulation before. According to the practical application, the experiment of transformer magnetic core tolerance is conducted. It provides the experimental data for ICPT technology applications.