A method of controlling the energy level of the arms (2, 3) of a multi-phase power converter having 3 or more phases, wherein the arms (2, 3) comprise a plurality of switching modules, the switching modules comprise one or more capacitors and one or more switches, wherein the switching modules are controlled based on non-clamped reference phase voltages and further controlled in successive energy control periods by a control signal from a converter controller, wherein the energy levels of the individual arms (2, 3) are controlled in the successive energy control periods according to the following steps: - by switches of a first subset of the switching modules, in a first part of an energy control period, clamping the highest positive phase output voltage of said 3 or more phases to a determined value having a first voltage potential, the first voltage potential being a first DC rail voltage potential, or a controllable distance from the first DC rail voltage potential, the controllable distance being below a module voltage, - by switches of a second subset of the switching modules, in a second part of the energy control period, clamping the lowest negative phase output voltage of said 3 or more phases to a determined value having a second voltage potential, the second voltage potential being a second DC rail potential, or a controllable distance from the second DC rail voltage potential, the controllable distance being below a module voltage, wherein the first and second voltage potentials are different, - wherein said clamping to said first voltage potential in said first part of said energy control period and said clamping to said second voltage potential in said second part of said energy control period adds an additional common mode voltage to the phase voltages of all of said 3 or more phases, wherein said additional common mode voltage is the difference between the non- clamped reference phase voltages and the clamped phase output voltages, - in each of the first and second parts of the energy control period, calculating circulating current command values required to establish a desired energy level in the capacitors at the end of the energy control period, and - controlling circulating currents in the arms (2, 3), based on the calculated current command values and synchronized to the clamped phase output voltages in order to establish a voltage level of the capacitors required to establish the desired energy level in order to obtain an energy reset within the energy control period. - by switches of a first subset of the switching modules, in a first part of an energy control period, clamping the highest positive phase output voltage of said 3 or more phases to a determined value having a first voltage potential, the first voltage potential being a first DC rail voltage potential, or a controllable distance from the first DC rail voltage potential, the controllable distance being below a module voltage, - by switches of a second subset of the switching modules, in a second part of the energy control period, clamping the lowest negative phase output voltage of said 3 or more phases to a determined value having a second voltage potential, the second voltage potential being a second DC rail potential, or a controllable distance from the second DC rail voltage potential, the controllable distance being below a module voltage, wherein the first and second voltage potentials are different, - wherein said clamping to said first voltage potential in said first part of said energy control period and said clamping to said second voltage potential in said second part of said energy control period adds an additional common mode voltage to the phase voltages of all of said 3 or more phases, wherein said additional common mode voltage is the difference between the non- clamped reference phase voltages and the clamped phase output voltages, - in each of the first and second parts of the energy control period, calculating circulating current command values required to establish a desired energy level in the capacitors at the end of the energy control period, and - controlling circulating currents in the arms (2, 3), based on the calculated current command values and synchronized to the clamped phase output voltages in order to establish a voltage level of the capacitors required to establish the desired energy level in order to obtain an energy reset within the energy control period.