Design and implementation of a DC line-interactive uninterruptible power supply (UPS) with load leveling

In this paper a novel DC line-interactive uninterruptable power supply (UPS) with load leveling feature is proposed. The new UPS replaces the common AC three phase UPS and can be used for systems with pulse loads, and has superiority in performance and efficiency. The DC UPS utilizes Li-ion battery module in the DC link to perform the load leveling feature and UPS functionality. A Li-ion LFP based battery module is developed and tested along with associated management system. The proposed system operates in four operating modes. Performance of the system in one of the modes is discussed. A dual-loop control scheme is used to manage the performance of the system in various modes. Simulation results are provided to verify the performance of the proposed system.