After a long hiatus, Old School Tech has posted the first article in a new series, this time about creating a double-conversion uninterruptible power supply, which is useful for driving loads such as freezers or mission-critical items. Like a computer UPS, this power supply waits, fully-charged, until it is needed. Unlike a computer UPS, however, it produces clean, pure sine wave power. It also can be scaled up in capacity as desired, operating for hours, or days, as needed. For self-sufficiency enthusiasts, a system such as this removes the need to get a generator or other power supplies running immediately when power fails. This buys time for other activities, such as defending your family from the antifas who took out utility power in the first place. As noted in the linked article, a double-conversion UPS can also absorb a variety of glitchy power inputs, increasing the options for using less expensive generators, or allow swapping generators out for maintenance or refueling without compromising the load. The same system, fed with solar during the day, or generators at night, with long gaps of battery operation between, allows much more flexibility and peace of mind than a generator or solar setup alone. This first article shows how to create this system; future articles will report on real world long-term results and multiple topologies we’ve tested.