Modular multi-stage converter

1. A multi-stage converter comprising:

a branch connected between a positive busbar and a negative busbar; and

a control device;

wherein the branch has at least two arms connected in series;

the arms each comprise a series circuit including a plurality of two-pole transformers with a respective energy store and a communication connection to the control device;

the communication connection transmitting information about a state of charge of the energy store and a switching instruction for a switch of the respective transformers; and

for at least a subset of the tranformers, the communication connection comprises a common communication connection with a plurality of insulation paths having an insulation capability in each case of at most 5 kV.

2. The multi-stage converter as claimed in claim 1 , wherein the insulation paths each have an insulation capability case of at most 600 V.

3. The multi-stage converter as claimed in claim 1 , wherein the communication connections of each transformer of an arm or of a branch comprise a common communication connection.

4. The multi-stage converter as claimed in claim 1 , further comprising one communication connection corresponding to each of the arms.

5. The multi-stage converter as claimed in claim 1 , further comprising a common communication connection for all of the branches.

6. The multi-stage converter as claimed in claim 1 , wherein:

the communication connections form a bus connection; and

signals of each transformer are received directly by the control device and vice versa.

7. The multi-stage converter as claimed in claim 1 , wherein the common communication connection comprises a plurality of connections from a respective transformer to a next transformer.

8. The multi-stage converter as claimed in claim 1 , wherein the common communication connection between the connection points of two neighboring transfomers in the series circuit of the arm comprises one of the insulation paths.

9. The multi-stage converter as claimed in claim 1 , comprising a number of insulation paths at least half of a number of transformers.

10. The multi-stage converter as claimed in claim 1 , wherein an order of linkage of the transformers to the common communication connection corresponds to an order of the arrangement in the respective arm of the multi-stage converter.

11. The multi-stage converter as claimed in claim 1 , wherein the common communication connection comprises a ring with two strands connected in parallel to one another, the two strands connected to one another at the connection point of a first transformer and at the connection point of a second transformer.

12. The multi-stage converter as claimed in claim 11 , wherein both strands include the same number of insulation paths.

13. The multi-stage converter as claimed in claim 11 , wherein tranformers of a first arm of a first branch are connected to a first of the strands and transformers of a first arm of a second branch are connected to a second of the strands.