Why does Vivado Sysgen not work when targeting UltraScale devices?
There is a known issue associated with all Vivado 2014.x releases for Sysgen when using an UltraScale only installation.
Sysgen will not work.
To work around this problem it is necessary to install the 7 Series devices into your Vivado installation.
This issue will be resolved in Vivado 2015.1.