Highly reliable uninterruptible power supply using a bi-directional converter

A bi-directional converter and two switches have been added to the conventional circuitry in an uninterruptible power supply (UPS) to improve its reliability. If either the rectifier or inverter fails, the bi-directional converter automatically takes over their operation, so that power continues to be supplied to the load. Because a complicated control system is not needed, the increase in the size and cost of this highly reliable UPS is minimized. The reliability of the inverter supply is an order of magnitude higher than that of a conventional UPS. Moreover, the UPS is about 30% cheaper than a redundant-parallel-running UPS and requires about 30% less installation area.