On controllability and system constraints of the linear models of proton exchange membrane and solid oxide fuel cells

► The standard model of PEMFC is uncontrollable and should not be used for control. ► The standard model of SOFC is uncontrollable and should not be used for control. ► Constraints that the PEMFC and SOFC models must satisfy at steady state are imposed. ► Constraints that the PEMFC and SOFC models must satisfy at all times are imposed.