Three-mode grid-forming control for data center UPS

The paper proposes a three-mode grid-forming control framework for centralized medium-voltage UPS systems in large AI data centers to improve grid interaction and fault performance.

• Technical contribution: A centralized MV UPS-BESS architecture with three modes: (1) DC bus regulation and grid-draw shaping in normal operation, (2) current-limited fault-mode P–Q priority with battery buffering and rate-limited post-fault “soft return”, and (3) optional droop-based fast frequency response via grid-draw modulation; simulations on a 50 MW block, SCR = 1.5, 0.5 p.u. dip for 150 ms show zero unserved IT energy, reduced peak inverter current (0.57 p.u. vs 1.02 p.u. baseline), nonzero fault-window grid draw (0.20 p.u. vs 0), and improved PCC voltage minimum (0.79 p.u. vs 0.66 p.u.).
• Context and evaluation: Motivated by AI workload-induced pulsing and weak-grid stress at data center interconnection points, the study includes a 1 Hz ±0.25 p.u. pulsed-load case where normal-operation shaping filters the oscillation seen by the grid and the UPS-BESS buffers the pulsing component; the work is a peer-reviewed-style control/systems analysis hosted on arXiv with DOI registration pending via DataCite.