This study presents innovative control algorithms for a hybrid energy system by a photovoltaic (PV) array and a polymer electrolyte membrane fuel cell (PEMFC). A single storage device, i.e., a Li- Ion battery module, is in the proposed structure. Linear proportional-integral (PI) and nonlinear flatness-based controllers for dc bus stabilization for power plants are compared. To verify the control algorithms, a hardware system is realized with analog circuits for the PV, FC and battery current control loops (inner controller loops), and with numerical calculation (dSP ACE) for the external energy control loops. Experimental results with small-scale devices, namely, a photovoltaic array (800 W, 31 A) manufactured by the Ekarat Solar Company, a PEMFC (1200 W, 46 A) manufactured by the Ballard Power System Company, and a Li-Ion battery module (11.6 Ah, 24 V) manufactured by the SAFT Company, illustrate the excellent energy-management scheme during load cycles, and the nonlinear differential flatness-based control provides improved dc bus regulation relative to a classical linear PI control method.
