A Novel Oil-immersed Medium Frequency Transformer for Offshore HVDC Wind Farms
Journal article, 2021

Offshore wind farms pose the challenge of transmission of produced energy in an economic and effective way over long distances, justifying investments in High Voltage Direct Current (HVDC) systems. A solution to surmount the need for an expensive and large power transformer station is to connect each wind turbine to a DC/DC converter in which a Medium Frequency Transformer (MFT) is utilized to reduce the size of the station. Further, the DC outputs of the converters of the wind turbines can be connected in series to create a high DC voltage. In this solution, the MFTs are required to be insulated
against a high DC voltage to ground in a limited compartment. This contribution presents a prototype of a 50 kW oil-paper insulated MFT operating at biased 422/4500 V/V AC 5 kHz and 125 kV DC test voltage, which has been manufactured and subjected to verification HV tests. The dielectric design of the prototype MFT based on finite element solution of non-linear Maxwell-Wagner equations is introduced and the acceptance criteria and practical design considerations are discussed.

DC-DC power converters

finite element analysis

prototype design methodology

HVDC insulation design

Wind energy

medium frequency transformer


Mohammad Kharezy

Chalmers, Electrical Engineering, Electric Power Engineering

RISE Research Institutes of Sweden

Hassan Reza Mirzaei

University of Zanjan

Yuriy Serdyuk

Chalmers, Electrical Engineering, Electric Power Engineering

Torbjörn Thiringer

Chalmers, Electrical Engineering, Electric Power Engineering

Morteza Eslamian

University of Zanjan

IEEE Transactions on Power Delivery

0885-8977 (ISSN)

Vol. 36 5 3185-3195

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Basic sciences

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Electrical Engineering, Electronic Engineering, Information Engineering

Energy Systems



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