
18-1
18.1 Introduction
Uninterruptible power supply (UPS) systems become more and more important due to the growing
critical loads, such as telecommunication systems, computer sets, and hospital equipments. In the last
few years, an increasing number of publications about UPS systems research have appeared, and, at the
same time, dierent kinds of industrial UPS units have been introduced in the market. Furthermore,
the development of novel energy storage systems, power electronic topologies, fast electrical devices,
high-performance digital processors, and other technological advances yield new opportunities for UPS
systems [King03, Bekiarov ...