Active Damping Method for LC-DAB System Based on a Power-Based Impedance Model

Abstract

A cascaded system, consisting of an LC filter and a dual active bridge (DAB), can exhibit certain instability due to terminal impedance mismatch. In this regard, the existing impedance models of DAB are not convenient for designing the active damping methods, owing to strong coupling between the phase-shift ratios. To solve this problem, this work proposes an active damping method based on the power-based impedance model (PBIM) for LC-DAB. First, the input impedance of DAB is derived using PBIM, which shows high simplicity and generality because it is decoupled from the modulation methods. Then, based on PBIM, the stability of LC-DAB is discussed. Next, to achieve stabilization of LC-DAB, an active damping method without any additional sensors, named the virtual-current series virtual impedance control (VC-SVIC) is proposed, which assists in maintaining the original fast-dynamic performance of DAB. Finally, the performance of VC-SVIC is validated by the relevant experiments. Essentially, this work puts forward an easy and effective way to guarantee the stability of cascaded LC-DAB system, while achieving a good dynamic performance.