A Low-cost Technique for Minimizing the SEIG Electromechanical Transient from Islanded to Grid-connected Configuration in Hydropower Plants

This paper deals with hydraulic plants with turbines coupled to induction generators (IG) and faces the problem related to their electromechanical transients from the islanded to the grid-connected operation, occurring after a failure of the power grid. Such transients imply long out-of-order time intervals and could be very severe and potentially dangerous for both the IG and the turbine. Starting from this consideration, a space-vector dynamic model of the self-excited IG (SEIG) has been developed. Such a model is valid in the case of both grid-connected and islanded SEIG operations. Then, a low-cost technique for the smooth transition between the above-cited working conditions has been proposed. Such a technique has been tested in numerical simulation adopting the devised SEIG model.