An electric transformer circuit for connecting electrical equipment, such as a renewable energy-based generator or an energy storage system, to an electric grid, said circuit including: - a first voltage converter suitable for connecting the electrical equipment to part of the electric circuit operating with an AC voltage with frequency f0, - a transformer connected to the first voltage converter and configured to perform an amplitude adaptation between the voltage of the electrical equipment and that of the electric grid, said transformer including a first coil connected to the first converter and a second coil magnetically coupled to the first coil, said first and second coils (L1, L2) being arranged secured in movement, the transformer forming the part of the electric circuit working with an AC voltage with frequency f0, - a second converter configured to connect said second coil to the electric grid, said circuit being characterized in that the transformer is a weakly coupled transformer, the magnetic coupling between the first coil and the second coil being less than 0.7, and in that the transformer includes a first and second capacitor (C1, C2) respectively associated with the first and second coils (L1, L2) so as the first capacitor forms with the first coil a first circuit resonating at frequency f0 and the second capacitor forms with the second coil a second circuit resonating at frequency f0, wherein the second converter includes a first, a second, a third and a fourth switch (S5, S6, S7, S8) connected in series and tow capacitor (Cpos, Cneg) connected in series, the two capacitor being arranged in parallel to the first to the fourth switches (S5, S6, S7, S8), the second coil being connected to the electrical grid through the first and the third switches (S5, S7) with a parallel placement with the two capacitor (Cpos, Cneg), the second and fourth switches (S6, S7) connecting the two terminals of the second coil so as to short circuit the second coil, wherein the first to the fourth switches are controlled independently regarding the state of the voltage of the electrical grid and the state of the current in the second coil, i.e. the second converter is working in open loop. - a first voltage converter suitable for connecting the electrical equipment to part of the electric circuit operating with an AC voltage with frequency f0, - a transformer connected to the first voltage converter and configured to perform an amplitude adaptation between the voltage of the electrical equipment and that of the electric grid, said transformer including a first coil connected to the first converter and a second coil magnetically coupled to the first coil, said first and second coils (L1, L2) being arranged secured in movement, the transformer forming the part of the electric circuit working with an AC voltage with frequency f0, - a second converter configured to connect said second coil to the electric grid, said circuit being characterized in that the transformer is a weakly coupled transformer, the magnetic coupling between the first coil and the second coil being less than 0.7, and in that the transformer includes a first and second capacitor (C1, C2) respectively associated with the first and second coils (L1, L2) so as the first capacitor forms with the first coil a first circuit resonating at frequency f0 and the second capacitor forms with the second coil a second circuit resonating at frequency f0, wherein the second converter includes a first, a second, a third and a fourth switch (S5, S6, S7, S8) connected in series and tow capacitor (Cpos, Cneg) connected in series, the two capacitor being arranged in parallel to the first to the fourth switches (S5, S6, S7, S8), the second coil being connected to the electrical grid through the first and the third switches (S5, S7) with a parallel placement with the two capacitor (Cpos, Cneg), the second and fourth switches (S6, S7) connecting the two terminals of the second coil so as to short circuit the second coil, wherein the first to the fourth switches are controlled independently regarding the state of the voltage of the electrical grid and the state of the current in the second coil, i.e. the second converter is working in open loop. said circuit being characterized in that the transformer is a weakly coupled transformer, the magnetic coupling between the first coil and the second coil being less than 0.7, and in that the transformer includes a first and second capacitor (C1, C2) respectively associated with the first and second coils (L1, L2) so as the first capacitor forms with the first coil a first circuit resonating at frequency f0 and the second capacitor forms with the second coil a second circuit resonating at frequency f0, wherein the second converter includes a first, a second, a third and a fourth switch (S5, S6, S7, S8) connected in series and tow capacitor (Cpos, Cneg) connected in series, the two capacitor being arranged in parallel to the first to the fourth switches (S5, S6, S7, S8), the second coil being connected to the electrical grid through the first and the third switches (S5, S7) with a parallel placement with the two capacitor (Cpos, Cneg), the second and fourth switches (S6, S7) connecting the two terminals of the second coil so as to short circuit the second coil, wherein the first to the fourth switches are controlled independently regarding the state of the voltage of the electrical grid and the state of the current in the second coil, i.e. the second converter is working in open loop.