Legislations worldwide are focusing on the achievement of significant abatements of pollutants and GHG emissions from the transportation sector. Hybrid electric vehicles are considered a promising solution to achieve a sustainable transportation system in the near future. However, their potential can be fully exploited by only means of an ad hoc energy management system, capable of achieving an optimal partition between the different power sources available on board of the vehicle. Consequently, the aim of this thesis is the definition of a procedure to design an optimal powertrain control strategy for a P2 Plug-in Hybrid Electric Vehicle (PHEV).