Generalised transformer modelling for power flow calculation in multi-phase unbalanced networks

Low voltage systems are unbalanced networks where a significant share of the users is single-phase connected, so a multi-phase system needs to be considered in order to assess the mutual influence of the different phases. The presence of single-phase unevenly distributed users, leads to unbalances in the power flow on the three phases. This issue is emphasised considering the presence of local single-phase generators. This study presents a generalised method for transformers modelling in any multi-conductor grid representation in order to allow the analysis on unbalanced networks such as low-voltage distribution systems. The method, based on an incidence matrix approach, is proposed to represent any network object involving mutual connections among the phases, once the impedances for each single-phase equivalent circuit are known. Some application examples validate the approach and illustrate how to numerically realise the model.