Intuitive explanation of the Dual Active Bridge (DAB)

Most relevant paper

Evzelman, M., Zeltser, I., and Ben-Yaakov, S., DSP control of gyrator-behaved switch mode converter. European DSP Education & Research Symposium, EDERS-2008, 249-256, Tel-Aviv, Israel, 2008. 
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http://www.ee.bgu.ac.il/~pel/pdf-file...

Also relevant
An overall study of a Dual Active Bridge for bidirectional DC/DC conversion
Alberto Rodríguez Alonso, Javier Sebastian Student,
Diego G. Lamar, Marta M. Hernando, Aitor Vazquez;
2010

General Analysis of Switching Modes in a Dual Active Bridge with Triple Phase Shift Modulation
Carlos Calderon , Andres Barrado , Alba Rodriguez , Pedro Alou , Antonio Lazar , Cristina Fernandez, and Pablo Zumel
2018