Uninterruptible power supplies: classification, operation, dynamics, and control

This paper presents a comprehensive review of uninterruptible power supply (UPS) systems in terms of topologies, operation, dynamics and control. UPS systems are classified with emphasis on static systems. This paper also addresses fundamental problems faced in these systems in different distributed and centralized applications. In addition, a brief description of the conventional UPS systems, their disadvantages, scope for improvement, advanced architectures, role of power electronics and current trends in UPS research are explained. Negative impedance dynamics in UPS systems with constant power loads are also introduced. Finally, this paper concludes with a brief outline of the advancement to be made in the future