arXiv:2610.41249v1 Announce Type: new Abstract: Artificial intelligence data center (AIDC) campuses contain sustained power variations and subsecond power fluctuations, requiring both sufficient stored energy and fast response. A shared hybrid energy storage system (HESS) can mitigate aggregate AIDC power deviations, but interval-based schedules cannot capture the delay between commanded and delivered power at the campus point of common coupling (PCC). To this end, this paper proposes a multi-timescale scheduling model for mitigating AIDC power fluctuations with the shared HESS. First, it models electrical pooling at the campus bus and constrains the shared HESS to a single PCC injection. Second, a two-layer model passes five-minute scheduled power, energy state, and reserve capacity to a causal fast response model that distinguishes commanded power from delivered power. Case studies using the National Laboratory of the Rockies (NLR) GenAI Power Profiles Dataset show reductions in both PCC and fast integral absolute error (IAE), while retaining most of the improvement available under ideal response.