Constraint Handling in a Fuel Cell System: A Fast Reference Governor Approach

A compressor-based air supply system in a fuel cell is susceptible to saturation during fast transients in load. Aggressive control of the air compressor may result in compressor surge or choke, disrupt the flow of air into the cathode of a fuel cell stack, and negatively impact the fuel cell power generation. Low partial oxygen pressure in the cathode caused by rapid increase in load may also damage the stack and reduce its life. A load governor can be added to the air supply control system to monitor the load and prevent violation of constraints (compressor surge, choke, and partial oxygen pressure) by modifying the load command to the fuel cell system. In this paper, we present the steps involved in the design of such a load governor for the fuel cell application. To reduce the online computations, we utilize the "fast" reference governor (FRG) approach which has been developed for linear systems. FRG utilize a "maximal constraint admissible set" calculated offline and, thus, require fewer online calculations. We propose a modification to the FRG design to make it applicable to the nonlinear fuel cell plant. The scheme is then implemented on a real-time simulation platform and it is shown that the computations of the load governor can be performed in real-time