Shielded cabling, proper star-wired earthing and pull-ups on all inputs whether used or not, is all thats needed... a VFD is nothing more than a big switch-mode PSU. Problems that people have come from running unshielded power and signal side by side for long runs (> a few inches), creating ground loops by not wiring everything back to a common point (or grounding both ends of a shield), not grounding things at all, or in worst cases, powering different parts of the system off different ring mains on different phases (can induce huge ground offsets). Ok the latter is very rare but I discovered it in a commercial premises wired by cowboys (and it did have a P-certificate)