Abstract: The invention relates to a pumped storage power plant, in particular to an electric unit 1 comprising a converter 3, a rotating electric synchronous machine 4 and a charging unit 5, wherein the charging unit 5 has at least one transformer 6 and one switch 7 and can be connected to a supply grid 2, on the one hand, and to the converter 3, on the other. The invention also relates to a method for using the electric unit 1 comprising at least opening a generator switch 15 in order to disconnect the synchronous machine 4 from the converter 3; charging cells of the converter 3 which have capacitors and/or accumulators by closing a switch 7 of the charging unit 5, wherein by closing the switch 7 the converter 3 is connected to the supply grid 2 via the transformer 6 of the charging unit 5; opening the switch 7 of the charging unit 5 after the complete charging of the converter 3; and closing the generator switch 15 in order to connect the synchronous machine 4 to the converter 3 and/or the secondary line 11.

Abstract: A converter system is provided for the switching of at least three voltage levels and for the switching of two voltage levels. A method is also provided for the operation of a converter system for the switching of at least three voltage levels and for the operation of a converter system for the switching of two voltage levels.