How should I translate old TIG statement from UCF to new Vivado XDC files?
set_false_path is not only for for internal paths.

You can use set_false_path for

The port from which all paths are to be set as false paths:

set_false_path -from [get_ports ]

set_false_path -to [get_pins {}]
set_false_path -through  [get_pins {}]
set_false_path -from  [get_pins {}]

set_false_path -from [get_cells &lt;&gt;] -to [get_cells &lt;&gt;]


If you want to set all paths between two clock domains:

set_false_path -from [get_clocks ] -to [get_clocks ]


Because you want to set false paths from i/o ports,use 

set_false_path -from [get_ports FanControl_PWM]
set_false_path -from [get_ports FanControl_Tacho]