Energy management strategies for a P1 mild hybrid light commercial vehicle: evaluation of fuel consumption and CO2 emission reduction

The progressive tightening of European CO2 emission regulations for light-duty vehicles is driving the automotive industry towards the electrification of conventional powertrains. In this context, mild hybrid systems represent a cost-effective and technically viable solution to improve vehicle efficiency without requiring major changes in overall architecture or the use of large and expensive battery packs. Among the available layouts, the P1 configuration, where the electric machine is mechanically coupled to the internal combustion engine through a clutch or directly to the crankshaft, offers a good balance between complexity, performance, and potential fuel savings, especially for light commercial vehicles (LCVs). This thesis presents the development of a P1 mild hybrid system model, along with its implementation into an existing Simulink model of a light diesel commercial vehicle. The work focuses on the design of the electric subsystem, comprising battery, inverter, and electric motor models, and on the setting up of different energy management strategies aimed at optimizing the overall efficiency of the powertrain. Three control approaches have been investigated with increasing level of implementation complexity: a rule-based strategy dependent on the battery state of charge (SOC), a classical Equivalent Consumption Minimization Strategy (ECMS), and an Adaptive ECMS (A-ECMS) featuring a variable equivalence factor dynamically tuned according to the SOC error. The control algorithms have been integrated into the vehicle model and tested over a WLTC driving cycle for the 3a and 3b vehicle classes. Each strategy was assessed in terms of total fuel consumption, CO2 emissions, and variation in SOC. Additional functionalities were implemented to improve model realism, such as dynamic interpolation of engine maps based on simulation time and torque limit checks for the electric machine. Specific control techniques have been introduced in the A-ECMS formulation to prevent abrupt torque transitions. The simulation results show that both the ECMS and A-ECMS strategies lead to improvements in fuel economy and CO2 emissions compared to the conventional ICE configuration, with reductions of approximately 1.5 to 2% under the tested conditions considered. The A-ECMS, in particular, was able to maintain the SOC within the imposed limits for a wide range of initial and target SOC values. These findings confirm the potential of advanced energy management strategies (i.e. ECMS and A-ECMS) to enhance the efficiency of mild hybrid architectures, especially when applied to light commercial vehicles operating in urban and peri-urban environments.