model of a Wye-Wye with Delta Tertiary Winding Autotransformer

Hi Everyone,

I would like to ask on how to construct a Wye-Wye with Delta Tertiary Winding Autotransformer Using single-phase transformers.. If you can provide a single-line diagram for it will be very helpful.. I am currently using MatLab software and however there is no autotransformer block to comply with the requirements.

Thanks a lot..