When supply fan VFD starts up it causes communication problems for my energy management controller
Start with the VFD manual. Check to see that all of the wiring conforms to the manufacturer's recommendations. There are usually recommendations to have input power wiring, motor wiring and VFD start\stop, speed command etc. wiring in different conduits. Any signal wiring needs to be separate from relay wiring. The VFD enclosure and motor should be grounded to earth. It is best to run the protective earth ground conductors to the service entrance ground. Check to make sure that the "unit controller" wiring is well separated from the VFD wiring. If the installation is as it should be, contact the VFD supplier for recommendations. You may need a noise filter at the VFD power input.