Manipulation of Static and Dynamic Data Center Power Responses to Support Grid Operations

Abstract

This research investigates three frameworks for data centers to deliver fast frequency response services from their UPS storage systems, HVAC cooling units, and the ability of off-gridding the entire data center during transient frequency events. The aim of this is to provide dynamic injection during transients in real time for grid operators and for power sellers in hour ahead markets. A static and a dynamic model was developed in DIgSILENT PowerFactory. In the static model, the data centers are off-gridded in response to emergency frequency signals from system operator in a centralized manner, whereas in the dynamic model the UPS systems and shiftable cooling units power consumption was altered continuously in the data centers in response to local frequency measurements considering different real-time scenarios. The performance of the proposed operational frameworks is validated, and calibrated to actual frequency events that occurred in the Irish power system. The sensitivity analysis demonstrates that both static and dynamic load controls can significantly improve system frequency metrics, i.e., frequency nadir and rate of change of frequency during transients. The key findings show that demand response can only make a substantial frequency improvement if a large amount of energy delivered within the timeframe of inertial response. INDEX TERMS Battery and UPS, data centers, demand-side management, fast frequency response, inertia response, load modeling, power system dynamics, wind power generation. NOMENCLATURE PLo,j Pre-fault active power of a load at j th bus. QLo,j Pre-fault reactive power of a load. PL,j Active and reactive power of a load. QL,j Reactive power of a load at j th bus. vo,j Pre-fault voltage of j th bus. vj Post-fault voltage of j th bus. ui, uj Committed status. E Operational inertia floor constraint. Hi Inertia floor constraint of i th generators. Hsys Post-event system inertia constant. Si Stated nominal power limit. fo Nominal system frequency. fi Regional nominal frequency. fCOI Frequency at center of inertia.

Overview of frequency control techniques in power systems with high inverter‐based resources: Challenges and mitigation measures

“…As seen in Figure 4, increasing the penetration of GFLbased IBR in the system results in extreme frequency deviation and RoCoF for the same disturbance [14,15]. This is an example of a power system in which governor-equipped synchronous generators are replaced with GFL-based IBR operating at maximum power point tracking (MPPT) while the system still has a large amount of slow secondary reserve.…”

“…Flywheels are well-suited for applications that require near-constant cycling to maintain a balanced power system, addressing short-term energy balancing and power quality issues. Flywheels can provide advantages over BESS and super-capacitors in terms of complete depth of discharge cycles (approximately 200,000 vs. 5000 for BESS) and energy density, respectively [14,15]. Flywheels also offer fast-ramping capabilities, high roundtrip efficiency, and a lifespan of 20 years or more.…”

“…The frequency magnitude [133] or RoCoF [134] are commonly used to trigger FFR services based on a static step response as in Figure 13e. However, abrupt changes in active power can cause system oscillatory behaviour, so the power is progressively restored in multiple steps [14,15], as shown in Figure 13f. In emergencies, a centralised activation signal can cause a portion of demand to trip in a single step, but the active power must be restored gradually to avoid a second frequency disturbance.…”

“…It has the potential to reduce spinning reserve requirements under low inertia dispatches by quickly balancing power through the step response of some sources [136]. However, this control can only assist with extreme frequency deviations and cannot continuously control the frequency to the desired level, unlike droop‐based control [14, 15]. Coordination among all participating resources may be essential to achieve the best performance [137].…”

“…Variable renewable IBR replacing synchronous generators lead to a loss of both synchronous inertia response (SIR) and primary operating reserve (POR) capabilities, making it challenging for TSOs to maintain stability during severe contingencies. Low system inertia and spinning reserve increase the rate of change of frequency (RoCoF) and frequency deviation (nadir), which can trigger anti-islanding DG protection relays, leading to load shedding and eventually complete system blackout [14,15]. To address these issues, a fast frequency response (FFR) ancillary services market has been established in some island countries to help TSOs maintain a stable operating frequency and facilitate the integration of high IBR [16].…”