Design and Application of a Boost-LLC Converter for Vehicle-Integrated Photovoltaic Systems

To address the impedance mismatch between the DC output of vehicle-integrated photovoltaic systems and the high-voltage charging requirements of traction batteries, a boost-half-bridge LLC two-stage dc-dc converter is proposed specifically designed for vehicular environments. The front-stage boost circuit achieves a wide-range step-up from 48 V to 90 V, while the rear-stage LLC resonant circuit, through multiparameter collaborative optimization, delivers stable 400 V DC output to meet the efficient charging demands of traction batteries across wide state of charge (SOC: 30% - 90%) ranges. A global circuit parameter optimization was completed based on the combined fundamental harmonic approximation theory and state-space modeling approach. The steady performance and dynamic response characteristics of the converter were validated through MATLAB/Simulink simulations. Finally, real-vehicle tests were conducted to evaluate the voltage gain and boost efficiency under different SOC conditions of the traction battery. Experimental results indicate that the system achieves optimal voltage gain and boost efficiency when the traction battery operates at a medium SOC. This study provides new insights for optimizing the battery management system and energy routing strategies in vehicle-integrated photovoltaic systems.