A method for operating an energy generation system containing a photovoltaic generator and an inverter, wherein electric power is transferred between the inverter and an AC voltage grid, and wherein the transferred electric power comprises an active power (P) and a reactive power (Q) is disclosed. The method includes operating the photovoltaic generator, in a first operating mode, at a maximum active power point (MPP) by way of the inverter, and setting the active power (P) of the photovoltaic generator via the inverter in a second operating mode depending on a grid frequency instantaneous value (f) and on a grid frequency rate of change (df/dt), and in the second operating mode, setting the reactive power (Q) depending on a grid voltage instantaneous value (U) and on a grid voltage rate of change (dU/dt).