Abstract
The Smart Transformer (ST) is being envisioned as the possible backbone of future distribution grids given the enhanced controllability it provides. Moreover, the ST offers DC-link connectivity, making it an attractive solution for the deployment of hybrid AC/DC distribution grids which offer important advantages for the deployment of Renewable Energy Sources, Energy Storage Systems (ESSs) and Electric Vehicles. However, compared to traditional low-frequency magnetic transformers, the ST is inherently more vulnerable to fault disturbances which may force the ST to disconnect in order to protect its power electronic converters, posing important challenges to the hybrid AC/DC grid connected to it. This paper proposes a Fault-Ride-Through (FRT) strategy suited for grid-tied ST with no locally available ESS, which exploits a dump-load and the sensitivity of the hybrid AC/DC distribution grid’s power to voltage and frequency to provide enhanced control to the ST in order to handle AC-side voltage sags. The proposed FRT strategy can exploit all the hybrid AC/DC distribution grid (including the MV DC sub-network) and existing controllable DER resources, providing FRT against balanced and unbalanced faults in the upstream AC grid. The proposed strategy is demonstrated in this paper through computational simulation.
Highlights
The expected increase of Distributed Energy Resources (DER) in distribution grids, such as Renewable Energy Sources (RES), Electric Vehicles (EV) and distributed EnergyStorage Systems (ESS), is highlighting new challenges regarding operation and control of electric power systems [1,2,3,4,5]
The work presented in this paper addresses the presentation and discussion of a novel
Four important improvements comparatively to previously proposed FRT control strategies are exposed in this paper: The participation of the MV DC sub-network of the hybrid AC/DC grid, the use of frequency modulation to control the active power output in DER located in the LV
Summary
The expected increase of Distributed Energy Resources (DER) in distribution grids, such as Renewable Energy Sources (RES), Electric Vehicles (EV) and distributed Energy. It cannot exploit power-frequency sensitive DER located in the LV AC sub-network constituting the hybrid AC/DC distribution grid [27] This feature would enable the regulation of the net active power in the LV AC sub-network with minimal impact on non-controllable resources. It is not capable of exploiting complementary solutions In order to support net generation balance downstream from the ST following an AC MV grid fault, the proposed FRT control strategy relies on a dump-load incorporated in the ST for this purpose. AC grid while mitigating adverse impacts affecting the ST’s hybrid distribution grid, is demonstrated in this paper through computational simulation
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