Modeling and Design Optimization of a Bidirectional Ultra-High Gain DC/DC Converter for Cell-integrated Power Electronics

This paper presents the modeling and optimization of a bidirectional CLL-based resonant converter, designed for high voltage gain and enhanced softswitching capability. The converter efficiently bridges low-voltage battery cells with a high-voltage 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. In order to achieve the required gain with minimal power loss, a multi-objective, multivariable, and multi-constraint 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 2.5V-4V and 360V at loads ranging from 25W to 100W. The prototype achieves peak discharging and charging efficiencies of 95.7% and 95.3%, respectively.