Comparative Evaluation of MVAC-LVDC SST and Hybrid Transformer Concepts for Future Datacenters

Abstract

A transition from state-of-the-art 400 V AC to 690 V AC or 800 V DC (+/- 400 V DC) distribution improves the overall power conversion efficiency of datacenter power supply systems. The latter requires megawatt-level isolated medium-voltage (MV) AC to low-voltage (LV) DC conversion stages that operate with an efficiency of at least 98 AD. Whereas today's most advanced industrial MVAC-LVDC solid-state transformer (SST) prototypes do achieve this, they are highly complex and do not show any clear advantages in terms of efficiency and power density over alternative approaches that retain the low-frequency transformer (LFT) to provide isolation and decoupling from harsh MV grid realities. We thus comparatively evaluate MVAC-LVDC SSTs against such alternative concepts, i.e., LFTs with LV-side SiC PFC rectifiers, or 12-pulse rectifier systems hybridized with active filters that just provide sufficient power processing capability to achieve unity power factor operation.