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Abstract A new structure for the anti-windup (AW) compensation for rate limited actuation is proposed which is less conservative than structures currently used. For peak bounded disturbances or reference inputs, we develop AW augmentation loops for both magnitude and rate actuator saturation. To reduce conservatism further, the proposed technique is combined with a multi-stage AW loops to obtain different gains for different levels of saturation. [ABSTRACT FROM AUTHOR]

A dynamic solid oxide fuel cell (SOFC) model is used to investigate the effects of different flow arrangements, as well as those of non-uniform air flow across channels, on temperature profile and thermal gradients under transient and steady state response. A high performance multi-input multi-output feedback controller has been developed to minimize SOFC spatial temperature variations during changes in power demands for different flow patterns. Numerical results show that the controller would result in negligible temperature variations for the modified cross-flow arrangement proposed here, even for large changes in the power drawn. The combination of a high performance controller and design modification results in a more uniform temperature profile at steady state nominal conditions, and modest variations in temperature profile, from the nominal, for ±15% change in power. Similarly, non-uniform air flow rate decreases the temperature gradient as well as maximum temperature across the cell, though its effect is less pronounced in the closed loop response. [ABSTRACT FROM AUTHOR]

Abstract: A high performance feedback controller has been developed to minimize SOFC spatial temperature variation following significant load perturbations. For thermal management, spatial temperature variation along SOFC cannot be avoided. However, results indicate that feedback control can be used to manipulate the fuel cell air flow and inlet fuel cell air temperature to maintain a nearly constant SOFC electrode electrolyte assembly temperature profile. For example temperature variations of less than 5K are obtained for load perturbations of ±25% from nominal. These results are obtained using a centralized control strategy to regulate a distributed temperature profile and manage actuator interactions. The controller is based on H-infinity synthesis using a physical based dynamic model of a single co-flow SOFC repeat cell. The model of the fuel cell spatial temperature response needed for control synthesis was linearized and reduced from nonlinear model of the fuel cell assembly. A single 11 state feedback linear system tested in the full nonlinear model was found to be effective and stable over a wide fuel cell operating envelope (0.82–0.6V). Overall, simulation of the advanced controller resulted in small and smooth monotonic temperature response to rapid and large load perturbations. This indicates that future SOFC systems can be designed and controlled to have superb load following characteristic with less than previously expected thermal stresses. [Copyright &y& Elsevier]