I believe ps audio has come up with these, there may be other companies as well.Not sure how long PS Audio has been in the Regeneration business. One thing I would look for if you are interested in a regenerator, make sure the equipment has safe guards to shut its self down To protect your audio equipment.
Will it shut itself down for,
* output over voltage (what %)
* output under voltage (what%)
* frequency shift, changes either way + or - from 60 hertz (max/min)
* true sine wave, not squared off caused from excessive connected load/s.
PS audio P1000 problem
A "True" high quality UPS will do this. A "True UPS" will cost you more to buy, but what is your audio equipment worth to you.....