Small Signal Modeling and Close-Loop Controller Design of a Current-Fed Three-Level Dual Active Bridge DC–DC Converter With an Auxiliary Inductor for Energy Storage System

Abstract

Three-level dual-active-bridge (DAB) DC–DC converters offer superior voltage-blocking capability, larger step-up ratios, and increased degrees of freedom (DoF) compared to traditional two-level DAB converters. These, combined with bidirectional power transmission capability, make them particularly suitable for connecting energy storage modules to DC buses. This article proposes a novel current-fed three-level DAB converter topology with an auxiliary inductor that realizes the benefits of multilevel DAB converters. However, the control complexity increases with the number of DoFs. To address this challenge, small-signal modeling has been conducted on the proposed converter, leading to the design of an effective control structure that strictly regulates the DC bus voltage across all possible load variations. The developed controller significantly improves transient response by minimizing overshoot and reducing settling time during sudden load changes. The proposed converter and control structure have been validated on a laboratory prototype operating at 1.2-kW power output and 100-kHz switching frequency, achieving voltage conversion from 90 to 650 V. Experimental results demonstrate a peak efficiency of 96.7%, which is at least 4% higher than the voltage-fed DAB converter reported in recent literature. Additionally, ∼77% faster dynamic performance compared to the work by Zhang et al. (2024) is achieved, ensuring rapid and stable voltage regulation under transient conditions.