One year operation of a 9 kW HVDC UPS 350 v at Gnesta municipality data center

The municipality of Gnesta, Sweden will in the future offer triple-play internet broadband services to its inhabitants. In the past the IT Service Department of Gnesta used small AC UPS of different ages to cope with the need for uninterruptible power backup at the data centre to match the reliability of telecommunications. Battery maintenance became a burden and they also found that this solution gave little or negligible back-up time. The IT-management of the Gnesta Municipality decided to try the HVDC UPS concept which seemed to promise superior transient protection, energy savings, reliability, power quality and economy. This paper describes one year of trial and full operation of a 350 V DC uninterruptible power system, which may very well be the world´s first in critical operation. The paper also describes the HVDC UPS system, designed by Netpower Labs AB and used at the Gnesta municipality. As the first commercial system it meets the ETSI standard EN 300 132-3. Since there currently are very few types of servers and data equipment specifically designed for direct operation from HVDC (350 V DC) Netpower has explored the possibility to use standard equipment and run them on HVDC as an intermediate step. Netpower has performed a study on various existing power supplies for data servers and other computer equipment to check their compatibility with the HVDC concept. The energy savings potential of 30 % made possible by HVDC UPS (compared to present AC UPS) is discussed in the paper. The conclusion is that a HVDC UPS 350 V gives superior transient protection, great energy savings and has potential for future enhanced data centre energy savings as well as it offers very high reliability and good economy.