Harmonies are eonsidered to be one of the power system disturbanees eausing voltage and eurrent waveform distortions due to the undesired high-frequeney eomponents. Not only power quality, but also power system operation ean be negatively affeeted by harmonies. Important sourees of harmonies are power eleetronies eontrolled deviees whieh have been inereasingly used for diversified purposes in eleetrieal power systems in the reeent years. In this work, harmonie problems due to Voltage Souree Converters (V:SCs) are studied in detail.In addition to the modelling of harmonie sourees, the modelling of power system elements is important for analysis of harmonie propagation into power systems. To serve this purpose, the frequeney domain modelling of transmission lines and transformers must be aeeurately done for the frequeney range up to some kHz. The frequeney-dependent parameters of the models have to be taken into aeeount due to the skin effeet. Under the assumption of symmetrieal harmonies in balaneed systems, harmonie analyses are generally earried out with the single-phase based symmetrieal eomponents. However, systems in operation are often unbalaneed. In those eases, it is neeessary to investigate harmonies in the original three-phase system. For different ealeulation purposes, the power system elements need to be modelled in the singlephase based symmetrieal eomponents and in the original three-phase system.