Modular Series-Stacked Bidirectional AC/DC Architecture for 3-Phase Grid-Tied Applications

As the demands of systems such as power-to-hydrogen (P2H) and extreme fast charging (XFC) increase, there is a need for highly customizable and scalable grid-tied power electronics. This paper presents a bidirectional converter architecture comprised of stackable three-phase ac/dc converter modules, scalable to high-power and high-current applications. Multiple converter modules containing a converter power stage and controls can be stacked to obtain a medium-voltage ac (MVAC) tied system without the need for a line frequency transformer. The modular system architecture is made possible by a quadruple active bridge (QAB) dc/dc converter that provides isolation between each of the three ac-side phases within each module and the dc load. The system also removes the need for bulk energy storage by taking advantage of constant balanced three-phase power flow. Decentralized module-level controllers are also implemented to allow for system modularity and scalability. The proposed architecture is validated by simulations of a P2H system consisting of 18 modules and a scaled proof-of-concept hardware prototype consisting of two modules.