Multi-level supervisory control of a standalone hybrid fuel cell power system

Fuel Cells supplemented with energy storage system are considered as the promising source of alternative energy for portable, transportation and distributed generation applications. High power density of the supercapacitor and high energy storage capability of the battery make them ideal choice as the energy storage system. The integration of these three power sources however, poses several difficulties for control system designers. In this paper, it is shown that a supervisory based control system can well handle the situation associated with the integration. The higher level supervisory controller monitors the load demand, power availability of the fuel cell and state of the charge of the battery/supercapacitor and decides the operating condition of the system. The operating parameters are sent to the lower level power electronics controllers. A unidirectional DC/DC converter and two bidirectional DC/DC converters are designed for the power electronics interface. All the simulations are carried out in the matlab/simulink environment. The supervisory controller is implemented using stateflow and fuzzy logic toolbox of matlab.