AC-UPS reliability and availability performance: comparison of available solutions

Uninterruptible power supply (AC-UPS) systems are studied from the reliability and availability (R&A) performance point of view. The objective is to find out the basic reason for using a UPS system as well as its impact on the optimal solution; and how the basic mission can be carried out in an optimal way. The alternatives are series power processing (also called true UPS) and parallel power processing (also called stand-by UPS or line-interactive UPS). It is shown that the available UPS solutions are nearly equal from the R&A point of view and that if high reliability is of prime concern, optimal results can be obtained by means of line-interactive UPS