A Comprehensive Analysis on Complex Power Flow Mechanism in an AC-AC Dual Active Bridge

An ac-ac Dual Active Bridge (DAB) as a Solid State Transformer (SST) is investigated for active and reactive power flows in this article. Analytical expressions for the required phase shifts in open-loop operation are derived. The leakage inductance of the DAB and switching frequency are shown to be critical parameters in the design of DAB as an SST, and a design rule is formulated based on the derived results. A simulation model of the converter is run using the closed-form solutions for the phase obtained, and the ac-ac DAB is shown to meet the real and reactive power demands accurately.