An In-depth Comparative Analysis and Efficiency Evaluation of Dual- and Quad-active Bridge for Solid State Transformer Applications

Researchers have recently focused on increasing the power density of the SST by replacing the Modular Dual Active Bridge (DAB) with a Quadruple-Active-Bridge (QAB) which utilizes less number of High Frequency (HF) transformers and switches. However, to replace the DAB with QAB, it is necessary to examine the impact of efficiency based on switching frequency and transformer turns ratio. The main objective of this paper is to analyze the behavior of both DAB converter and QAB converter-based systems on the above factors to illustrate the effect of replacing the DAB in the SST. This paper contains a comparative analysis of the efficiencies of modular DAB and QAB using results obtained by PLECS simulation models of the two systems. Finally, scaled down hardware prototypes of the two systems are implemented to validate the simulation outcomes resulting higher efficiency in QAB-based system compared to the DAB-based system for particular switching frequency and transformer ratio.