The Thesis work is a study of the electro-magnetic field inside an HVDC converter station, focusing on some particular areas. Three are the main parts of the analysis: the area between the common coupling point and the transformers, the busbar between transformers and reactors and the reactors. In the first part of the Thesis, there is an overview of the HVDC technology, analysing the main parts of a station, a state of art of the VSC technology and the theorical approach for the study of the electro-magnetic field. There is also an introduction of the three software used for the simulations.