© 2015 IEEE. This paper presents a novel control strategy based on fuzzy logic to adjust fittingly the total output-active power injected into a local grid from a large-scale photovoltaic (PV) farm to support grid-frequency regulation. The strategy consists of a central coordinating controller and local controllers at PV power agents. Wherein, the central controller uses a frequency regulation module based on a unique fuzzy logic controller (FLC) to determine the reference value of total active power needed; and then appropriately coordinates the individual reference value for the local controller at each PV agent. As well, each local controller drives all the power-electronic converters and battery charger installed at PV agent to deliver power to the grid exactly according to the reference value obtained from the central controller. Besides, in each local controller, a simulation module based on the mathematical model of PV panel is used to predict beforehand the maximum power from PV arrays, and a control algorithm to regulate state-of-charge (SOC) of the battery bank is also implemented. Simulation results show that the proposed strategy has good performance in delivering the active power to grid with regulating the grid frequency in tolerable ranges even if the AC-system load and solar irradiation unexpectedly vary. Moreover, efficacy in regulating grid frequency of the suggested strategy is also compared with the conventional strategy which uses the full maximum power point tracking (MPPT) mode.