Operating circuit for coupling a synchronous machine with a voltage network and method for operating it

An operating circuit for coupling a synchronous machine with a voltage network,

• with a converter circuit that can be controlled by a control unit having a converter input connected to the synchronous machine and a converter output connected to the voltage network, whereby the converter circuit has a plurality of converter switches that can be controlled by the control unit and a switching arrangement that can be controlled by the control unit,
• whereby the converter circuit is switched by means of the switching arrangement between a direct converter configuration and a start converter configuration, whereby the control unit is adapted to control the converter circuit in the direct converter configuration depending on a voltage profile at the converter input in order to set an alternating voltage with a preset frequency at the converter output
• wherein the converter circuit comprises at least two converter branches, each having a first output terminal and a second output terminal of the respective converter branch and respectively a first input terminal, a second input terminal and a third input terminal of the respective converter branch, and wherein two output terminals of different converter branches are connected to one another directly.