Transformer Capacity Expansion Planning in Low-Voltage Distribution Power Systems with Renewables and Electric Vehicles

Electricity distribution utilities face emerging challenges related to the growing impact of photovoltaic generation and electric vehicles. Charging of electric vehicles can systematically overload distribution transformers and current conductors during peak hours, while reverse power flows from dispersed generation during low-load periods can impose operational stresses. These issues increase the likelihood of accelerated aging of the transformers, potentially necessitating their premature replacement, which is costly and disruptive to the network. Possible directions for addressing these challenges include the adoption of smart charging strategies, informed capacity expansion planning, and optimization of the operation of distribution transformers. This study demonstrates that under high penetrations of photovoltaic systems and electric vehicles, smart charging alone would only partially amend the named challenges. Installing an additional transformer at distribution substations and enabling alternate or parallel operation of two transformers can effectively minimize power losses and mitigate equipment aging below dangerous rates.