Multiple model predictive control of grid connected solid oxide fuel cell for extending cell life time

Solid oxide fuel cells (SOFC) can be used for both distributed electricity generation and cogeneration purposes. They have higher efficiency and certain other advantages over proton exchange membrane fuel cells. However an important weak point of SOFC cells is their lifetime and durability. In particular, high temperature and fuel utilization variations resulting from load changes contribute to stack damage and significantly decrease the cell lifetime. In this paper, a model predictive control scheme for extending the cell lifetime is proposed. It makes use of the ability of predictive control to respect range and rate constraints. SOFC stack damage is prevented by satisfying temperature, fuel utilization and air utilization operational constraints. The cell behavior is significantly nonlinear. However as nonlinear MPC still has many issues, the nonlinearity was accounted for by using MPC scheme based on multiple linear models. The control scheme considers grid connected fuel cell and the main control objective is to deliver the desired power while respecting all constraints related to cell lifetime. Simulation results show that proposed life extending controller is able to control SOFC in a wide operational range and it gives good tradeoff between the cell life time and control system performance.