Modeling and Analysis of Frequency Modulated LLC Resonant Converter for Deeply Depleted Battery Charging Applications

This paper presents the variable frequency LLC resonant converter for charging the On-Board Electric Vehicle (OBEV) battery in a normal and deeply depleted state. Based on the battery's State of Charge (SoC), the presented charging circuit has three modes of operation Half Bridge Normal Mode (HBNM), Full Bridge Normal Mode (FBNM), and Full Bridge Voltage Doubler mode (FBVD). Both HBNM and FBNM modes are operated in deeply depleted states with end voltage ranges of 13.5 V and 24 V respectively. The FBVD mode is operated in the normal charging mode of a deeply depleted battery with an end voltage range of 42 V. A control logical circuit has been implemented to change the operation modes based on the battery's voltage range. The proposed converter is simulated in PSIM software with 36 V 12.5 Ah battery specifications, and the mathematical model is also implemented in MATLAB Simulink software.