Multi-level voltage converter for converting a DC voltage into an AC voltage, comprising: - a DC interface comprising first and second poles (201, 202), and an AC interface (203, 204, 205); - at least one arm, comprising an upper half-arm connected between the first pole and an intermediate node, and a lower half-arm connected between the second pole and the intermediate node, each half-arm comprising several sub-modules connected in series (51, 52, 53), the sub-modules each comprising a capacitive energy storage element and a circuit for selectively bypassing the capacitive element or connecting it in series with the other sub-modules of the half-arm; the intermediate node being configured to be connected to an AC network via the AC interface (203;204;205); - characterised in that at least one sub-module is an improved sub-module including several electrical energy exchange devices, each comprising: - an electrical energy storage device; - a DC/DC converter having a first interface (711, 712) and a second interface (713, 714) connected to the terminals of the electrical energy storage device, the DC/DC converter further comprising a switching circuit (721, 722) for selectively controlling the discharging or recharging of the electrical energy storage device via the first interface, so that, for a voltage Uc(t) across the terminals of the capacitive element of this improved sub-module, Uc(t)= Um+Uh(t), Um being the DC component of this voltage Uc(t) and Uh(t) being the oscillating component of this voltage Uc(t), |Uh| being the maximum value of the voltage oscillation Uh(t), the voltage Us(t) across the terminals of the second interface of the DC/DC converter being defined by Us(t)=Usm+Ush(t), Usm being the continuous component of this voltage Us(t) and Ush(t) being the oscillating component of this voltage Us(t), Ush(t) satisfying the relationship Ush(t)<0.3*|Uh|/ns, where ns is the number of energy exchange devices of this improved sub-module, the switching circuit (721, 722) including switches having a switching frequency greater than 10 kHz; - the first interfaces (711, 712) of the DC/DC converters being connected in series between the terminals of the capacitive element of the sub-module. - a DC interface comprising first and second poles (201, 202), and an AC interface (203, 204, 205); - at least one arm, comprising an upper half-arm connected between the first pole and an intermediate node, and a lower half-arm connected between the second pole and the intermediate node, each half-arm comprising several sub-modules connected in series (51, 52, 53), the sub-modules each comprising a capacitive energy storage element and a circuit for selectively bypassing the capacitive element or connecting it in series with the other sub-modules of the half-arm; the intermediate node being configured to be connected to an AC network via the AC interface (203;204;205); - characterised in that at least one sub-module is an improved sub-module including several electrical energy exchange devices, each comprising: - an electrical energy storage device; - a DC/DC converter having a first interface (711, 712) and a second interface (713, 714) connected to the terminals of the electrical energy storage device, the DC/DC converter further comprising a switching circuit (721, 722) for selectively controlling the discharging or recharging of the electrical energy storage device via the first interface, so that, for a voltage Uc(t) across the terminals of the capacitive element of this improved sub-module, Uc(t)= Um+Uh(t), Um being the DC component of this voltage Uc(t) and Uh(t) being the oscillating component of this voltage Uc(t), |Uh| being the maximum value of the voltage oscillation Uh(t), the voltage Us(t) across the terminals of the second interface of the DC/DC converter being defined by Us(t)=Usm+Ush(t), Usm being the continuous component of this voltage Us(t) and Ush(t) being the oscillating component of this voltage Us(t), Ush(t) satisfying the relationship Ush(t)<0.3*|Uh|/ns, where ns is the number of energy exchange devices of this improved sub-module, the switching circuit (721, 722) including switches having a switching frequency greater than 10 kHz; - the first interfaces (711, 712) of the DC/DC converters being connected in series between the terminals of the capacitive element of the sub-module. - an electrical energy storage device; - a DC/DC converter having a first interface (711, 712) and a second interface (713, 714) connected to the terminals of the electrical energy storage device, the DC/DC converter further comprising a switching circuit (721, 722) for selectively controlling the discharging or recharging of the electrical energy storage device via the first interface, so that, for a voltage Uc(t) across the terminals of the capacitive element of this improved sub-module, Uc(t)= Um+Uh(t), Um being the DC component of this voltage Uc(t) and Uh(t) being the oscillating component of this voltage Uc(t), |Uh| being the maximum value of the voltage oscillation Uh(t), the voltage Us(t) across the terminals of the second interface of the DC/DC converter being defined by Us(t)=Usm+Ush(t), Usm being the continuous component of this voltage Us(t) and Ush(t) being the oscillating component of this voltage Us(t), Ush(t) satisfying the relationship Ush(t)<0.3*|Uh|/ns, where ns is the number of energy exchange devices of this improved sub-module, the switching circuit (721, 722) including switches having a switching frequency greater than 10 kHz; - the first interfaces (711, 712) of the DC/DC converters being connected in series between the terminals of the capacitive element of the sub-module.