A modular multilevel power conversion device with AC output and AC or DC input comprising: a modular multilevel DC/AC converter having several arms (1.1, 1.2, 1.3) mounted in parallel whose ends define DC input terminals (27, 28), each arm comprising two chains of switching modules (4.11, 4.12, 4.13, 4.14, 4.15, 4.16) in series, linked to a common terminal (3.1, 3.2, 3.3), this common terminal defining an AC output terminal of the modular multilevel power conversion device, each switching module (4.11, 4.12, 4.13, 4.14, 4.15, 4.16) comprising at least one pair of electronic power switches (T111, T211) arranged in series, mounted on the terminals of an energy storage device (4.3), the electronic power switches (T111, T112, T113) of one and the same chain, which are linked to a terminal of like polarity of the energy storage device (4.3) being termed homologues, the modular multilevel DC/AC converter being designed to adjust the output frequency of the modular multilevel conversion device and furthermore comprising control means for the electronic power switches so as to place them in an on or off state, characterized in that the control means are adapted to apply full-wave control to the electronic power switches during at least one part of a time interval of operation of the power conversion device, the switching modules (4.11, 4.12, 4.13) of one and the same chain then having homologous electronic power switches (T111, T112, T113) in one and the same state simultaneously, the control means are adapted to apply, during at least one other remaining part of the time interval, a PWM control to the electronic power switches (T111, T211, T112, T212, T113, T213), the PWM control being applied when an output current of the modular multilevel power conversion device is less than a threshold and the full-wave control being applied when the output current is greater than or equal to the threshold, and in that it furthermore comprises a converter with DC output and DC or AC input comprising two output terminals (A, 22) linked to the DC input terminals (27,28) of the modular multilevel converter, said converter with DC output being designed to adjust the output amplitude of the power conversion device. a modular multilevel DC/AC converter having several arms (1.1, 1.2, 1.3) mounted in parallel whose ends define DC input terminals (27, 28), each arm comprising two chains of switching modules (4.11, 4.12, 4.13, 4.14, 4.15, 4.16) in series, linked to a common terminal (3.1, 3.2, 3.3), this common terminal defining an AC output terminal of the modular multilevel power conversion device, each switching module (4.11, 4.12, 4.13, 4.14, 4.15, 4.16) comprising at least one pair of electronic power switches (T111, T211) arranged in series, mounted on the terminals of an energy storage device (4.3), the electronic power switches (T111, T112, T113) of one and the same chain, which are linked to a terminal of like polarity of the energy storage device (4.3) being termed homologues, the modular multilevel DC/AC converter being designed to adjust the output frequency of the modular multilevel conversion device and furthermore comprising control means for the electronic power switches so as to place them in an on or off state, characterized in that the control means are adapted to apply full-wave control to the electronic power switches during at least one part of a time interval of operation of the power conversion device, the switching modules (4.11, 4.12, 4.13) of one and the same chain then having homologous electronic power switches (T111, T112, T113) in one and the same state simultaneously, the control means are adapted to apply, during at least one other remaining part of the time interval, a PWM control to the electronic power switches (T111, T211, T112, T212, T113, T213), the PWM control being applied when an output current of the modular multilevel power conversion device is less than a threshold and the full-wave control being applied when the output current is greater than or equal to the threshold, and in that it furthermore comprises a converter with DC output and DC or AC input comprising two output terminals (A, 22) linked to the DC input terminals (27,28) of the modular multilevel converter, said converter with DC output being designed to adjust the output amplitude of the power conversion device.