As data center energy consumption continues to increase, various options are being considered that could improve the efficiency of existing and future data centers. One way is to operate the facility on a DC distribution system. This can eliminate intermediate DC/AC and AC/DC power stages, thereby improving the efficiency of the entire data center power delivery system. While the benefits of a DC data center have been clearly proven through demonstrations and analysis, it is of paramount importance to analyze issues that will impact its practical implementation. Power quality is one such issue whose importance cannot be dismissed due to its direct connection to datacenter reliability and uptime. This paper discusses the various power quality disturbances that can occur in DC data centers, their impact on system performance, and design considerations that must be taken into account for mitigating such disturbances.Index Terms-DC data centers, 380 VDC, power quality, energy storage, battery.

This paper discusses the techniques, challenges, and results of measuring computer power supply (CPS) efficiency, power factor (PF), and input harmonic currents for the 80 PLUS® program since its beginning in 2002. To date, over 750 power supplies have been tested with many certified for the 80 PLUS® program. In spite of the large number of power supplies tested and years of testing, there is uncertainty within the computer power supply industry about the correct method for measuring efficiency, power factor, and harmonics. Moreover, in order to improve efficiency at light loading, manufacturers are adopting a duty-cycle control approach to power factor correction that raises even more questions on the proper measurement techniques. This paper presents detailed results of years of computer power supply testing, provides a detailed technical analysis on measurement accuracy with background on why specific measurement techniques were adopted, and looks to the future on upcoming technical difficulties and offers solutions for overcoming these difficulties.

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