The present invention concerns a method, and the related controller device, for controlling an electric power generation system, based on at least one energy source, in particular a renewable energy source, preferably a photovoltaic or fuel cell source, said system operating according to operating performance representable by at least one performance indicative function (P; ΔP) having at least one optimal value (P
target ), operation of said system being dependent on at least two controllable parameters (V
c , K; ω
cmd , β), the method perturbing the values of said at least two controllable parameters (V
c , K; ω
cmd , β), so as to perturb a first controllable parameter (X; Y) with a same perturbation sign (SX) as long as it is detected that, after each single perturbation, a distance of a value of said at least one performance indicative function (P; ΔP) from said at least one optimal value (P
target ) decreases, whereas when it is detected that said distance increases, the method passes to perturb a different controllable parameter (Y) with a perturbation sign (SY) opposite to the sign of the immediately preceding perturbation of such different controllable parameter (Y).