Patent ID: 8476854

Claim:
A power supply device for a variable rotation speed drive arranged on the seabed, comprising: a free-running converter connected on an AC side to a power grid located on land, an inverter having a DC side connected to a DC side of the converter and a load side connected to the variable rotation speed drive, the inverter comprising a plurality of phase modules, with each phase module having an upper and a lower valve branch and each valve branch having at least two series-connected, two-pole subsystems with distributed energy storage devices, the inverter being located on the seabed in immediate vicinity of the variable rotation speed drive, a direct-current cable electrically conductively connecting the DC side of the converter with the DC side of the inverter, and signal electronics of the inverter located on land, wherein a two-pole subsystem comprises an energy storage capacitor and two turn-off semiconductor switches electrically connected in series at a junction point forming a first connecting terminal of the two-pole subsystem, with the series-connected semiconductor switches being connected electrically in parallel with the energy storage capacitor and a pole of the energy storage capacitor forming a second connecting terminal of the two-pole subsystem.