A new reduced parts on-line single-phase UPS system

This paper presents design considerations and performance analysis of a new reduced parts on-line single-phase uninterruptible power supply (UPS) system. The proposed new UPS system is based on the half-bridge topology. It employs only five IGBTs and one diode reducing the cost of the system compared to the conventional on-line UPS topology, while achieving excellent performance. The common neutral eliminates the need for an isolation transformer and makes the system cheaper and more compact. The proposed UPS system uses a step down battery charger avoiding the problems associated with the high battery voltage, such as: space, cost, reliability, and safety issues. It has sinusoidal input current with unity power factor and high quality output voltage even with nonlinear loads. Detailed circuit operation and analysis as well as simulation and experimental results are presented.