Error handling approach of a PEM fuel cell system by nonlinear model predictive control

For an efficient chemical reaction and a safe operation for both stationary and dynamic loads all values of anode and cathode gas pressures and stack temperature must fall within specific ranges. System error can result in values outside of these ranges, in turn causing serious damage to the fuel cell (FC). In addition the energy supply by the FC is at risk, because an emergency shutdown is possible. Therefore it is necessary to implement strategies for handling error cases in order to ensure safe operation. A common method for controlling the operation of PEM FC is a model predictive control, which allows for fault tolerance. In literature, error handling strategies are only considered for special parts of FC, but not for the whole system. This paper deals with real-time nonlinear model predictive control (NMPC) of electrical power with applied error handling strategies for a PEM FC system. Different types of errors are discussed in connection with various solution approaches. This fault tolerant NMPC handles all kinds of dynamic load changes and allows a safe operation of the FC in the event of errors, while maximizing power efficiency. Any emergency shutdown is not necessary and energy supply is still guaranteed. All experiments were verified on a test bench with a 4.4kW PEM FC.