Sine Amplitude Converters for efficient datacenter power distribution

Telecommunication and data centers are moving to greener technology to minimize operating costs and lessen environmental impact. Ultimately, the networking and computing loads in these applications are DC rather than AC, and many renewable energy sources develop DC power as well. Energy storage systems are also DC, such as those required for Uninterruptable Power Supplies (UPS), as well as those needed to further leverage the cost savings possible with intermittent renewable energy sources. Despite these predominantly DC sources and loads, most existing installations distribute AC power from the mains, and perform AC-DC conversion only at the cabinet or sub-system level. Energy sources used for UPS purposes must charge batteries from an AC source and subsequently perform DC-AC inversion to later power downstream loads. Integrating renewable energy sources into installations which distribute AC power at high efficiency and low cost is similarly frustrated, as each must function as a carefully synchronized source to match the existing mains AC power. When the building system is considered as a whole, PFC front end functionality and AC inverters are duplicated, often with significant overcapacity. Installations distributing 380 VDC power avoid efficiency and cost penalties associated with repeated AC-DC (PFC front end) and DC-AC (inverter) conversion when considered at the system level. They can more easily integrate renewable energy sources and energy storage methods. However, they cannot leverage the traditional AC transformer. This paper examines the Sine Amplitude Converter (SAC) as a replacement for the AC transformer in green telecom and data center applications. SAC DC-DCs offer high efficiency and bidirectional power transfer. Their pure ratiometric operation permits native paralleling for ease of scaling to larger power capacities. Several topologies using SAC technology are discussed, including real-time scaling of a converter to avoid losses typically assoc- ated with oversized supplies, and those achieving tight regulation of an otherwise unregulated secondary bus, without additional full conversion stages for regulation.