Coordinated frequency and Voltage Overload Control of Smart Transformers

A Smart Transformer (ST) is a power electronics-based transformer that aims not only to substitute the traditional transformer but to upgrade also the LV and MV grid. In order to limit the costs, the ST must be carefully designed, constraining the current carried by the ST. In this paper a Combined Frequency and Voltage Controller is proposed, in order to manage a possible overload without derating the ST. Aiming to reduce the current, this control enhances the ST security against the overload situation interacting with the local Distributed Generation (DG) and the local loads.