Modeling and Design Optimization of a Bidirectional Ultrahigh Gain DC/DC Converter for Cell-Integrated Power Electronics

This article presents the modeling and optimization of a bidirectional CLL-based resonant converter, designed for high voltage gain and enhanced soft-switching capability. The converter efficiently bridges low-voltage (LV) battery cells with a high-voltage (HV) dc bus, facilitating grid integration. The study introduces a new modeling approach, termed enhanced generalized harmonic approximation (E-GHA), which incorporates detailed harmonic analysis and circuit parasitic elements for accurate loss modeling. To achieve the required gain with minimal power loss, a multiobjective, multivariable, and multiconstraint optimization framework is developed to optimize the resonant tank parameters and operating control variables. To validate the proposed model, a proof-of-concept 500-kHz CLL resonant converter was developed, demonstrating bidirectional conversion between 2.5 and 4 V and 360 V at loads ranging from 25 to 100 W. The prototype achieves peak discharging and charging efficiencies of 95.7% and 95.3%, respectively.