Electrical Distribution Systems For Data Centers Of The Future : A Study On System Efficiency And Power Quality

Sammanfattning

Data centers accounted for 1.5% of the global final electricity consumption in 2024. This electricity consumption is forecasted to double by 2030, largely due to expected developments of AI trainingdata centers. Training of AI models is performed by server racks whose power capacities are predicted to reach 1 MW by 2030. During AI training, the racks synchronize their workloads, causing subsynchronous oscillations in the distribution network. These load oscillations may be transmitted from the data center to the connected grid; causing power outages or damage to power generating steam turbines. High availability is paramount for data centers as digital infrastructure such as healthcare, transactions, telecommunication and internet rely on data centers. To ensure high availability and reliability, data centers and their electrical distribution networks are designed with redundancy and with sufficient energy storage to keep the data center running in the case of a grid outage. Moreover, energy storage can also be used to mitigate load oscillations. Therefore, to design an electrical distribution system that distributes power efficiently while taking power quality, availability and electrical safety into consideration, the entire system must be evaluated.This thesis evaluates different voltage levels, different solutions for power quality, power conversion,availability and energy storage. The goal of this thesis is to examine design principles of different modular distribution systems that are applicable both for large data center installations as well as edge nodes. Evaluation was performed by conducting a literature study of current development in electricaldistribution and contacting leading electrical distribution companies. The literature study coveredsolid-state transformers, power converters, uninterruptible power supplies, supercapacitors and circuit breakers, with the purpose of examining how they function and their applicability at the examined voltage and power levels. The purpose of the market survey was to determine commercial availability for the solutions examined in the literature study while also learning leading companies in the industrypredicts the future development of electrical distribution for data centers. This resulted in a model of a complete electrical distribution system for a 1 MW server rack. Simulations were performed in Simscape Electrical with the purpose of achieving high total efficiency and high power quality while representing commercially available products. The simulations were performed using three models: an ideal model that conditions power usingpassive energy storage, one model that conditions power while representing passively connectedcommercial products and one model examining controlled power conditioning. A total distribution efficiency of ηtot ≈ 95% was achieved. For comparison, a 400 V AC system reached a distribution efficiency of ηtot400V = 97.1%, albeit without a UPS [1]. Assuming the same UPS efficiency of ηUPS = 97% used in this work, the corresponding 400 V AC system would have a distribution efficiency of 94.1%. To achieve high power quality, a passive capacitance of C50V = 106 F or C800Vbusbar = 781 F was required. With controlled power conditioning, good peak shaving was achieved by a capacitance of C_controlled,50V = 325 F. It was concluded that there are many ways to build an electrical distribution system and while thereare commercial solutions currently available, they are not directed toward data centers. It was also concluded that a power conditioning system should be controlled to achieve a good result while usinga feasible amount of capacitance