Improvement of Energy Management Strategy of a Hybrid Electric Vehicle considering battery thermal behavior and State of Health

In the recent years there has been an increasing investment by car manufacturers in the production of electric and hybrid electric vehicles. The reason for this sudden change can be associated with the stringent environmental constraints imposed by government regulations. The consequence is that many researches are now focusing on the employment of new strategies to keep up with these restrictions. These studies develop technologies both at vehicle-level (control strategies) and subsystem-level (powertrain and energy storage components). An important component to manage the power supply of Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) is the Energy Storage System (ESS). Batteries are the most common ESS component thanks to their energy density, compact size and reliability. When the vehicle undergoes significant variation of power, the battery cell, as the only element of ESS, may not be able to supply the required power demand or absorb the power from regenerative braking. To solve this problem, hybrid energy storage systems (HESS) combine two or more types of storage components with complementary features. One of the most functional combinations studied for a HESS is composed by supercapacitor and battery. Research results have proven that the use of supercapacitors in parallel with batteries greatly improves energy storage capabilities. The vehicle considered in this thesis work is a 48V P1 hybrid light-duty commercial vehicle. This type of architecture leads to a high current rate due to the 48V. The solutions can be the limitation of the current, the employment of components with higher performance or adding a supercapacitor. In this work two different approaches are analyzed. The first one considers the feasibility of a HESS composed by a supercapacitor in parallel of the main battery, while the second one considers the improvement of the EMS considering battery thermal behavior and State-of-Health estimation. Starting from the forward vehicle model in Matlab Simulink, the model of the supercapacitor is introduced and its performance analyzed. Then, a new battery model is introduced considering the thermal dynamics and cooling, while State-of-Charge and State-of-Health estimation algorithms are implemented. The results of the analysis are twofold: on one hand, the introduction of the supercapacitor does not contribute to the improvement of the efficiency of ESS for the 48V P1 architecture. On the other hand, the thermal modeling and the algorithm to estimate the State-of-Health enhance battery usage if considered during the design of the EMS.