400Vdc power distribution: Overcoming the challenges

The issues discussed in this paper revolve around the challenges faced and some of the progress to-date in development and deployment of 400Vdc power distribution networks targeted at telecom and data networks as an alternative to AC distribution and AC UPS power deployment. There has been an increasing interest in the development and deployment of higher voltage DC in power distribution networks as a replacement for both traditional 48 V DC distribution and AC UPS supported distribution systems. The advantages sited in this interest include increased efficiency, reduced copper requirements, reduced floor space, and increased availability. On the other hand, there remains a series of challenges in moving this effort forward, including standards, components, safety, and general acceptance. While there has been, to date, no widespread deployment of this solution, there have been many studies proposed, sample systems developed and tested, preliminary testing, and a great deal of specification debate in the areas of voltage levels, and safety requirements. This paper reviews the current activities and positions of various groups and organizations such as the Green Grid, NTT, ETSI, EPRI, and the Power Sources Manufacturing Association (PSMA). Potential deployment barriers to implementation are identified and evaluated. Also reviewed is the status of efforts to overcome the bottlenecks by various industry organizations. Areas of interest include component requirements for this distribution approach including protection devices, power supplies, rectification, and distribution panels. Various system structures targeted at optimal HVdc DC distribution (380Vdc) are evaluated, including an overview of bulk versus modular approaches. Various system architecture proposals are reviewed for cost, efficiency, and availability metrics. Systems approaches will include power room based centralized distribution and "co-located" power system deployment in the rack area. Bus voltage selections discussed as well. A review of available battery string sizes and how they relate to an optimal selection of bus voltage are examined. The relative concerns of battery systems including rectifiers, and distribution approaches versus the power supply systems that are fed by distribution are looked at, taking into account the potential design needs for the power supplies in various battery voltage level approaches. Safety concerns and issue are also reviewed with respect to the voltage in the distribution system. Areas such as split bus grounding and isolation and their impact on systems realization as well as human interface are examined. Finally there is a review of the various Tier levels and the impact of DC distribution on availability in different Tier approaches to Datacenter power options.