I think I would contact the company about the product in the links immediately above here to find out exactly what it is they do. They do appear to be some sort of regulator and not just a converter.
What the other products mentioned previously here as voltage regulators do is stabilize inconsistent 120VAC - in other words they can take low or high voltage from around 95VAC to 140VAC and keep it at a consistent voltage around 120VAC. These latest products mentioned above look like it is possible they can do this but they do not clarify in there info.
One thing I did notice in the pictures is the wire and plug they use which may not be adequate for 30amp service. We want at least 10 gauge wire and we want it wired to fit the plugs we generally use for RV use - which would include the ground wire which these do not show. You probably need more details from the company.