This paper presents a method to operate a grid

connected hybrid system. The hybrid system composed of a Photovoltaic

(PV) array and a Proton exchange membrane fuel cell

(PEMFC) is considered. The PV array normally uses a maximum

power point tracking (MPPT) technique to continuously deliver

the highest power to the load when variations in irradiation and

temperature occur, which make it become an uncontrollable

source. In coordination with PEMFC, the hybrid system output

power becomes controllable. Two operation modes, the unit-power

control (UPC) mode and the feeder-flow control (FFC) mode, can

be applied to the hybrid system. The coordination of two control

modes, the coordination of the PV array and the PEMFC in the

hybrid system, and the determination of reference parameters

are presented