Method for modulating turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of a primary-side and secondary-side self-commutated converter (46, 48) of a series resonant DC/DC converter of a multi-level medium-frequency infeed of a traction converter, wherein the two self-commutated converters (46, 48) are linked to one another on the AC voltage side by means of a medium-frequency transformer, wherein a resonant capacitor ( C R) is connected in series with the leakage inductance ( L σ) of the medium-frequency transformer, and wherein an intermediate circuit capacitor (52, 54) is connected electrically in parallel on the DC voltage side to each of these two self-commutated converters (46, 48), with the following method steps: a) synchronous and in-phase modulation of the turn-off power semiconductor switches ( T 1,...,T 4; T' 1,..., T' 4) of the two self-commutated converters (46, 48) of the series resonant DC/DC converter such that a positive voltage ( U d,p, U d,s) is present on the terminals thereof in the AC intermediate circuit in each case, b) blocking the turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of the two self-commutated converters (46, 48) for a predetermined inverter cutoff time ( T v), c) synchronous and in-phase modulation of the turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of the two self-commutated converters (46, 48) of the series resonant DC/DC converter such that a negative voltage ( U d,p, U d,s) is present on the terminals thereof in the AC intermediate circuit in each case, d) blocking the turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of the two self-commutated converters (46, 48) for a predetermined inverter cutoff time ( T v), characterised in that according to the method steps a) and c), for a modulation pause of a variable length the turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of the primary-side or secondary-side self-commutated converter (46, 48) of the series resonant DC/DC converter are actuated such that the medium-frequency transformer of the series resonant DC/DC converter is short-circuited on the primary side or secondary side, wherein the turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of the secondary-side or primary-side self-commutated converter (46, 48) of the series resonant DC/DC converter are blocked. a) synchronous and in-phase modulation of the turn-off power semiconductor switches ( T 1,...,T 4; T' 1,..., T' 4) of the two self-commutated converters (46, 48) of the series resonant DC/DC converter such that a positive voltage ( U d,p, U d,s) is present on the terminals thereof in the AC intermediate circuit in each case, b) blocking the turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of the two self-commutated converters (46, 48) for a predetermined inverter cutoff time ( T v), c) synchronous and in-phase modulation of the turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of the two self-commutated converters (46, 48) of the series resonant DC/DC converter such that a negative voltage ( U d,p, U d,s) is present on the terminals thereof in the AC intermediate circuit in each case, d) blocking the turn-off power semiconductor switches ( T 1,..., T 4; T' 1,..., T' 4) of the two self-commutated converters (46, 48) for a predetermined inverter cutoff time ( T v),