A critical analysis of the harmonic distortion procedure applied to wind farm connection

By considering the current growth of wind power all over the world, the development of power quality studies towards the evaluation of power quality impacts of wind farm upon the electric grid has become a matter of major importance. Within this context emerges the subject of harmonic interaction between the wind farm plant and the AC commercial system to be supplied by the focused generation. In this particular field one must considerer that the harmonic distortion studies often take into account just the harmonic current injection due to the wind farm and the connection busbar presenting no previous distortions. In case of necessity, the mitigation techniques are based on passive filters design and insertion at the PCC. Due to the adopted operational condition defined by the regulation agencies only the harmonic contribution related to the wind plant are considered and this may find real site difficulties due to the possibility of other source of harmonics originated by the AC grid. Under these circumstances, the filter units may be higher loaded than expected and thermal effects may result in their components failure. With this purpose, this paper is focused on this theme. A case study is described aimed at highlighting that harmonic studies can not neglect previous harmonic distortion already existing on the system.