Medium Frequency Power Distribution Architectures for Next Generation Photovoltaic Farms and Data Centers
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With the recent advancement of power electronics devices, the power electronics converters take more vital roles in the modern power systems given the increased renewable energy penetration such as wind turbines, solar photovoltaic(PV), ocean power …etc. In the same time, the conventional market for power converters that include motor drives and power supplies always increase their requirements bar towards high efficiency, low cost, high density, and high reliability. The key to a high density power supply is to decrease the magnetic elements within the power converters namely the inductors and transformers. The wide band gap based power electronics devices open the door to satisfy the aforementioned power converters’ requirements with its ability to fast switching at lower losses and smaller footprint. The focus of this dissertation is to propose and analyze two architectures for utility scale PV farms and data centers employing medium frequency (MF) transformers. The proposed utility scale PV structure is shown to increase power density and improves system modularity while maintaining high efficiency levels. The PV panels power standard three phase voltage source inverters to generate MF ac voltage. Various voltage source inverter outputs are combined in series via MF transformers to form the proposed MF ac collection grid. A three phase ac-ac cycloconverter interfaces the MF grid with the 60Hz mains. An 80MW PV power plant located in Eggebek/Germany is used for comparison as a design example. Detailed simulation and calculations of the proposed system demonstrates size/weight reduction and overall efficiency improvement of 2%. The second proposal is for a medium-voltage (MV) data center power distribution system (DC-PDS) architecture using medium-frequency (MF) link transformer isolation. The proposed approach significantly improves power density while maintaining high efficiency compared to conventional line-frequency based solutions. The approach also contributes to a reduction in PVC and copper used in conventional DC-PDS. First the MV transformed from the utility, is interfaced with a MV switch gear system and a diesel power generator (DPG) system. Then this MV is converted to the low voltages (LVs) required by the loads via MF transformer. The MF transformer primary side windings are connected to stacked AC-AC converters. The LV secondary windings are interfaced with several load systems and battery energy storage system (BESS) using different topologies like boost power factor corrector (PFC), PWM inverter, etc. The presence of MV switch gear and MF transformer in the architecture results in higher efficiency and power density. Extensive finite element (FEA) results are carried out to optimize the transformer design for this proposal. Afterwards, simulation results along with experimental results are presented to validate the proposed concept. Finally, highlights of all the contributions alongside with the recommended future research opportunities are summarized at the end.
SubjectMedium frequency transformers
PV collection grid
Data center power supply
Finite element analysis
Hafez, Bahaa Eldeen (2015). Medium Frequency Power Distribution Architectures for Next Generation Photovoltaic Farms and Data Centers. Doctoral dissertation, Texas A & M University. Available electronically from