Coordinated control design for a PEMFC power system using adaptive VRFT method

For a proton exchange membrane fuel cell (PEMFC) power system containing a methanol reformer and a DC-DC converter, it is necessary to coordinate the subsystem controllers to achieve effective power tracking control and prevent constraint violations. This study focuses on the controller design of coordinating control scheme for a PEMFC power system to maintain stable fuel utilization ratio and meet the load demand simultaneously. Because the system exhibits considerable nonlinear behavior, a process model is difficult to identify and is prone to modeling errors. Therefore, this study employs the virtual reference feedback tuning (VRFT) method to design the controllers directly using the process input-output data. To address the process nonlinearity, an improved adaptive VRFT method is developed and applied to the adaptive PID controllers design for a cascade control system. Furthermore, the design parameter of the fuel cell current controller is adaptively tuned according to the deviation of fuel utilization ratio, so that the coordinating control is realized by keeping the dynamics of the current loop consistent with that of the fuel flow loop. Simulation results show that this coordinated control design enables the PEMFC power system to track the load power demand effectively while maintaining the fuel utilization ratio constant.