American nissan is more likely a brand name, not a name of a product. As Rocky said, it's a voltage regulator. I use an AVTEK regulator for the computer. They also makes speciallized ones for other items such as refrigerators, etc.
There are also "things" called "Constant Voltage Transformers", no electronics involved, just a big heavy special type of transformer. It does the same thing all these special "Voltage Regulators" being market here in the DR does.
Judging by the weight of my small AVTEK regulator I would guess it is just a fancy "Constant Voltage Transformer" with a power switch and an indicator light and a few other electronic control gadgets inside.
Another trick that works somewhat is to use a 220 volt to 110 volt transformer. Personally, I don't prefer that method, but a friend of mine does that and gets better results he saids for his inverter.
Third option would to be to purchase and have EdeNorte install a personal size transformer from the main transmission line to your house. I would go the extra expense of putting a pole just inside the yard to keep the neighbors from tapping into it. Another friend of mine has that situation, just him on the transformer, excellent voltage all the time (That is, when there is luz).
Don ♥ SantiagoDR