Design of hybrid AC-DC-AC topology for Uninterruptible Power Supply

A hybrid AC-DC-AC topology for Uninterruptible Power Supply (UPS) is investigated, which is composed of a two level three-phase four-wire rectifier and a three level T-type inverter. It has distinct advantages for the applications of on line UPS. The grid side power quality can be easily satisfied with the front-end two level three-phase rectifier. Since output voltage´s THD is challenge to UPS with sever nonlinear load, the T-type inverter is used to enhance the load power quality with higher conversion efficiency. The rectifier is transformed into step-up converter for the battery during the grid faults. The efficiency optimization of the proposed UPS with the hybrid AC-DC-AC topology is studied. The control strategies for the UPS are investigated. At last, the UPS prototype with 200kVA is designed and tested to validate the performance of the proposed UPS.