Energy transition toward smart grids with deep impact of renewables, energy storage systems, and electric vehicle charging stations will increasingly promote the establishment of energy communities that own portions of the electricity grid. The energy communities will consist of clusters of multiunit buildings and or single residential units aggregated sharing a common or multiple medium and low voltage (MV/LV) electrical substations. The size and impact of the location of these MV/LV substations can constitute a barrier especially for highly urbanized contexts where it is very complicated to provide technical spaces inside buildings for large technical systems like transformers, MV switchgear, etc. The idea of this work consists of developing a compact outdoor MV/LV substation to reduce the overall dimensions and to make the execution modularized to facilitate management and maintenance. Also an investigation of energy exchange between multiunit buildings, which are considered as the real energy community case study. The main objective for this case study is to minimize the operation cost of the system by maximizing the self-consumption.