Networked control of Distributed Energy Resources: Application to solid oxide fuel cells

This paper presents a model-based networked control approach for managing distributed energy resources (DERs) over communication networks. As a model system, we consider a solid oxide fuel cell (SOFC) plant that communicates with the central controller over a bandwidth-constrained communication network that is shared by several other DERs. The objective is to regulate the power output of the fuel cell while keeping the communication requirements with the controller to a minimum in order to reduce network utilization and minimize the susceptibility of the SOFC plant to possible communication disruptions in the network. Initially, an observer-based output feedback controller is designed to regulate the power output of the SOFC plant at a desired set-point by manipulating the inlet fuel flow rate. Network utilization is then reduced by minimizing the rate of transfer of information between the fuel cell and the supervisor without sacrificing stability or performance. To this end, a dynamic model of the fuel cell is embedded in the supervisor to approximate the dynamics of the fuel cell when measurements are not transmitted by the sensors, and the state of the model is updated using the observer-generated state estimate that is provided by the SOFC plant sensors at discrete time instances. An explicit characterization of the maximum allowable transfer time between the sensor suite of the fuel cell and the controller (i.e., the minimum allowable communication rate) is obtained in terms of model uncertainty and the choice of the control law. The characterization accounts for both stability and performance considerations. Finally, numerical simulations that demonstrate the implementation of the control architecture and its disturbance handling capabilities are presented.