Equation-based modeling of three-winding and regulating transformers using Modelica

The simulation of power transformer models is important when analyzing the dynamic behavior of power systems, in particular, when considering voltage magnitude or phase regulation controls. This paper reports results of extending the library of transformers in the iTesla Modelica Power Systems Library. Three transformer models have been implemented: a three-winding transformer, an under-load tap changing transformer (ULTC) and a phase shifting transformer (PST). An IEEE 14-Bus, power system test model was also implemented, both in Modelica and PSAT, to assess the performance of the models. Software-to-software validation is carried out against PSAT, a quantitative and qualitative assessment of the validation results between PSAT and Modelica is given.