The interest in electrification of vehicles is growing due to their environmental benefits regarding emissions and fuel consumption. Hybrid electric vehicles are the first generation of electrified vehicles which in addition to an internal combustion engine have an electric motor and an electric energy storage. HEVs can improve the fuel efficiency due to the possibility to downsize the engine, the ability to recover braking energy, the extra power control freedom gained by the two power sources, and the ability to stop the engine at idle.
Compared to hybrid electric vehicles, plug-in hybrid electric vehicles have the additional ability to store electricity from the grid, which reduces vehicle dependency on petroleum and potentially reduces CO2 emissions. However, the transition from conventional vehicles to PHEV is not trivial, as the trade-off between cost effectiveness and performance of the vehicle is highly sensitive to the components size (battery, electric motor and internal combustion engine), the varying prices of fuel and components, and the driving and charging pattern. Moreover, the design process of PHEVs is even more difficult when using simulations, since the problem of components sizing is intertwined with the energy management strategy, which means that the final assessment of various design decisions will be affected by both.
In this project convex optimization approach is used to find the optimal sizing of combustion engine, electrical motor and battery simultaneously with the optimal energy management strategy. This requires appropriate models that describe how the electric motor and internal combustion engine sizes affect the power flows and cost of these components. In addition, different levels of certain performance requirements are added to the problem as constraints. In this work, the effect of performance constrains, change in prices of components and energy, and different driving and charging patterns on the components size and total cost is studied.