The process that I've adopted for converting from a flat AutoCAD layout to PVSYST is to replace all of the PV racking rectangles with 3D faces within AutoCAD which represent the plane of the PV modules. Since we normally use AutoCAD blocks for each of the PV racks, you can just edit the block and draw a 3D face for the plane, the command in AutoCAD is just 3DFACE.
Once all of the 3D faces are there you can just save the file as a .DXF and use the AutoCAD FBX converter to convert to .DAE. The trick is that for some unknown reason, the FBX converter can't convert DXF directly to DAE, it must convert from DXF --> FBX, then you need to load in the newly created FBX to convert from FBX --> DAE.
The FBX converter is available here:
https://www.autodesk.com/developer-netw ... r-archives
A screenshot is attached to demonstrate what the 3D Face looks like in AutoCAD