Performance analysis of parallel-processing UPS systems

Parallel-processing inverter-based uninterruptible power supply (UPS) systems have advantages over the conventional rectifier-inverter systems. Control is more complex and design tools are not readily available. The modeling, control and performance of a typical system are analyzed, and important parameters are identified. This UPS consists of an inverter-battery subsystem in shunt between the AC mains and the load. Two control loops are employed to fully exploit the advantages of the proposed UPS system: (1) a fast load voltage regulation loop; and (2) a slower battery charging loop. Mathematical models are developed to design the required regulators and compensation networks for both loops. The predicted performance characteristics are verified by simulation. Experimental results on a 5 kVA unit confirm the theoretical analyses.<
>