Experimental Testing and Model Validation of a Decoupled-Phase On-Load Tap Changer Transformer in an Active Network

Antonio Zecchino, Junjie Hu, Massimiliano Coppo, Mattia Marinelli

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Due to the increasing penetration of single-phase small generation units and electric vehicles
connected to distribution grids, system operators are facing challenges related to local unbalanced voltage
rise or drop issues, which may lead to a violation of the allowed voltage band. To address this problem,
distribution transformers with on-load tapping capability are under development. This paper presents
model and experimental validation of a 35 kVA three-phase power distribution transformer with independent on-load tap changer control capability on each phase. With the purpose of investigating and
evaluating its effectiveness under different operative conditions, appropriate scenarios are defined and
tested considering both balanced and unbalanced situations, also in case of reverse power flow. The
experimental setup is built starting from an analysis of a Danish distribution network, in order to
reproduce the main feature of an unbalanced grid. The experimental activities are recreated in by carrying
out dynamics simulation studies, aiming at validating the implemented models of both the transformer as
well as the other grid components. Phase-neutral voltages’ deviations are limited, proving the effectiveness of the phase-independent tap operations. Furthermore, minor deviations of the results from simulations and experiments confirm that all the system components have been properly modelled.
Original languageEnglish
JournalIET Generation Transmission and Distribution
Issue number15
Pages (from-to)3834-3843
Publication statusPublished - 2016

Bibliographical note

"This paper is a postprint of a paper submitted to and accepted for publication in 'IET Generation, Transmission & Distribution' and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library"

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