Electromagnetic Simulation of HVDC Converter Transformers

Alstom Grid supplies a range of HVDC converter transformers for DC grid projects around the world. As part of the development and design process, we have carried out a variety of numerical simulations of the electromagnetic behaviour of such transformers. One aspect of simulations is to assess the effect of DC bias currents on stray losses. This work stresses the importance of modelling magnetic non-linearity not just in core steel but in structural components such as tanks and clamps. Also described are simulations of core behaviour on open-circuit, with and without DC bias currents, which have the benefit of experimental measurements for validation. This experimental work is reported in some detail. Finally we report on the development of time-domain surface impedance functionality to…