System comprising a controller apparatus with maximum power point tracking, or MPPT, and an electric power generation system based on photovoltaic sources, the controller apparatus controlling the electric power generation system, the electric power generation system comprising two identical sections (1, 2) of a photovoltaic field, connected to two respective identical power converters (3, 4) with direct current input, each converter (3, 4) comprising switching means capable to periodically connect the input to the output of the same converter (3, 4), the two converters (3, 4) being controlled by two respective periodic signals for controlling the switching means which are generated by the controller apparatus, the output of each converter being capable to provide a respective pair of output electrical quantities consisting of an output voltage (vA2; vB2) and an output current (iA2; iB2), the outputs of the two converters (3, 4) being connected in such a configuration to have an identical first output electrical quantity (vA2, vB2; iA2, iB2) selected from said respective pair of output electrical quantities, characterised in that the controller apparatus comprises: - a first sensor for detecting a second output electrical quantity (iA2; vA2) selected from the pair of output electrical quantities of a first one of said two converters, for giving a first detection signal, - a second sensor for detecting a second output electrical quantity (iB2; vB2) selected from the pair of output electrical quantities of a second one of said two converters, for giving a second detection signal, - subtractor means capable to receive said first and second detection signals and to generate a difference signal (iA2- iB2; vA2-vB2) between the second output electrical quantity (iA2; vA2) of the first converter and the second output electrical quantity (iB2; vB2) of the second converter, - amplifier means capable to receive said difference signal (iA2-iB2; vA2- vB2) and to amplify the same by a constant gain k, outputting an amplified difference signal, - low-pass filter means capable to receive and to filter said amplified difference signal, for outputting a filtered amplified difference signal, - controller means capable to receive said filtered amplified difference signal and to carry out a proportional action and an integral action on the same, for outputting a processed signal vc(t), - first generator means (11, 12) capable to receive said processed signal vc(t) and to generate a first one of said two controlling periodic signals having an instant duty cycle dB(t) proportional to said processed signal vc(t) by a constant equal to 1/ VM, whereby dB t = vc t VM for outputting said first controlling periodic signal capable to control the second converter, - adder means capable to receive said processed signal and to add to it a constant displacement ( Displacement) having modulus VM * Δd, with Δd ranging from 0 to 1: 0 < Δ ⁢ d < 1, for outputting a displaced processed signal, and - second generator means (13, 14) capable to receive said displaced processed signal and to generate a second one of said two controlling periodic signals having an instant duty cycle dA(t) proportional to said displaced processed signal, for outputting said second controlling periodic signal capable to control the first converter, said constant gain k and said constant displacement ( Displacement) having the same sign. - a first sensor for detecting a second output electrical quantity (iA2; vA2) selected from the pair of output electrical quantities of a first one of said two converters, for giving a first detection signal, - a second sensor for detecting a second output electrical quantity (iB2; vB2) selected from the pair of output electrical quantities of a second one of said two converters, for giving a second detection signal, - subtractor means capable to receive said first and second detection signals and to generate a difference signal (iA2- iB2; vA2-vB2) between the second output electrical quantity (iA2; vA2) of the first converter and the second output electrical quantity (iB2; vB2) of the second converter, - amplifier means capable to receive said difference signal (iA2-iB2; vA2- vB2) and to amplify the same by a constant gain k, outputting an amplified difference signal, - low-pass filter means capable to receive and to filter said amplified difference signal, for outputting a filtered amplified difference signal, - controller means capable to receive said filtered amplified difference signal and to carry out a proportional action and an integral action on the same, for outputting a processed signal vc(t), - first generator means (11, 12) capable to receive said processed signal vc(t) and to generate a first one of said two controlling periodic signals having an instant duty cycle dB(t) proportional to said processed signal vc(t) by a constant equal to 1/ VM, whereby dB t = vc t VM for outputting said first controlling periodic signal capable to control the second converter, - adder means capable to receive said processed signal and to add to it a constant displacement ( Displacement) having modulus VM * Δd, with Δd ranging from 0 to 1: 0 < Δ ⁢ d < 1, for outputting a displaced processed signal, and - second generator means (13, 14) capable to receive said displaced processed signal and to generate a second one of said two controlling periodic signals having an instant duty cycle dA(t) proportional to said displaced processed signal, for outputting said second controlling periodic signal capable to control the first converter,