Abstract
In order to reduce greenhouse gas emissions in the transportation sector traditional combustion vehicles have to be replaced with low-emission alternatives, such as electric vehicles (EV)s and fuel cell (FC) vehicles. As (EV)s have a short driving range and a long recharging time and FC vehicles are limited by their slow power dynamics, the fuel cell hybrid vehicle (FCHV) is examined as it retains the advantages of the FC vehicle and the EV.
However, FCHV are held back by their shorter lifespan compared to traditional combustion vehicles. The shortened lifespan of a FCHV is caused by degradation of the FC. Thus, this thesis will focus on degradation-conscious control of the FCHV in an effort to pave the way for broad commercial use of FCHVs.
One of the biggest causes of degradation occurs due to flooding and drying of the FC (improper water management). Flooding lowers the FC effective power output while causing chemical degradation at the electrodes while drying lowers the membrane conductivity while causing cracking of the membrane. Furthermore, membrane degradation can also occur due to reactant starvation. Safe and efficient air path control can prevent the occurrence of reactant starvation.
Therefore, a degradation-conscious control strategy must take into account the proper water management and air path control. In order to achieve proper water management, the humidifier and the water dynamics are modelled. Additionally, to address the real-life application of FCSs a state estimator is used to estimate the system states.
The controller is implemented as a hierarchical control strategy to account for the different time constants found in the FCHV. Lastly the developed control strategy is tested according to standardised testing protocols. Furthermore, extreme scenarios are analysed to ensure degradationconscious control within the full scope of operation.