Reduced-Parts Uninterruptible Power Supplies

The advances in power electronics in a great variety of new topologies and control strategies for uninterruptible power supply (UPS) systems. This chapter explains a new single-phase to three-phase hybrid line-interactive/on-line UPS system with reduced number of switches. Reducing the number of switches and passive elements in UPS topologies not only reduces the cost of the whole system but also provides some other advantages such as greater compactness, smaller weight, and higher reliability. One of the most important features of UPS systems is their reliability and availability. The component that influences the characteristics most considerably is the battery. Extensive computer simulations have been carried out, using PSIM simulation software, to help design the control for the new UPS system. The proposed UPS system has three operating modes: normal mode, stored-energy mode, and bypass mode. The performance of a UPS system is evaluated in terms of several factors.