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. Two operation modes, the unit-power control (UPC) mode and the feeder-flow control (FFC) mode, can be applied to the hybrid system. In the UPC mode, variations of load demand are compensated by the main grid because the hybrid source output is regulated to reference power. Renewable energy is currently widely used. On e of these resources is solar energy. The photovoltaic (PV) array normally uses a maximu m power point tracking (MPPT) technique to continuo usly deliver the highest power to the load when there are variations in irradiation and temperature. The disadvantage of PV energy is that the PV output po wer depends on weather conditions and cell temperature, making it an uncontrollable source. Furthermore, it is not available during the night
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