I'd like to model 2 DC bus, is this possible?

You can do exactly that by modeling the PV array and its dedicated inverter as an AC PV array.  To do that, you need to:

1.       Set the output current to AC in the PV Inputs window.

2.       In the PV Cost Table and Sizes to Consider table, where you specify the rated capacity of the PV array, specify the capacity in kW AC.  For example, if the PV capacity is 1.364 kW and the efficiency of the dedicated inverter is 93%, the AC capacity would be 1.364 kW x 0.93 = 1.269 kW.

3.       In the PV cost table, where you specify the capital, replacement, and O&M costs, include the costs of both the PV array and the dedicated inverter.