Converter arm and associated converter device

1. A converter arm of a phase leg for power conversion comprising:

a plurality of converter cells, wherein each converter cell comprises a plurality of semiconductor switches, an energy storage element and at least three control signal connections arranged to control the conducting state of the plurality of semiconductor switches;

wherein each converter cell is connected to receive a control signal from at least three entities via said control signal connections, wherein at least two of the three entities are neighbouring converter cells, and each converter cell is arranged to forward a control signal to all connected neighbouring converter cells via said control signal connections,

wherein at least two of the converter cells of the converter arm of the phase leg are directly connected to a main controller.

2. The converter arm according to claim 1 , further comprising a shortcut connection between two non-neighbouring converter cells wherein the non neighbouring converter cells each comprises at least four control signal connections.

3. The converter arm according to claim 2 , wherein each converter cell is arranged to detect a blocking message supplied to the control signal connections separately from other messages supplied to the control signal connections, wherein the blocking message instructs the converter cell to turn off all semiconductor switches of the converter cell.

4. The converter arm according to claim 2 , wherein four of the converter cells are directly connected to a main controller, arranged to generate control signals arranged to control the conducting state of the plurality of semiconductor switches of the converter cells.

5. The converter arm according to claim 2 , wherein each converter cell comprises a cell controller and the at least three control signal connections of each converter cells are connected to the cell controller, wherein the cell controller is arranged to control the semiconductor switches of the converter cell via respective gate units arranged to condition control signals for the semiconductor switches to a suitable format.

6. The converter arm according to claim 1 , wherein each converter cell is arranged to detect a blocking message supplied to the control signal connections separately from other messages supplied to the control signal connections, wherein the blocking message instructs the converter cell to turn off all semiconductor switches of the converter cell.

7. The converter arm according to claim 6 , wherein four of the converter cells are directly connected to a main controller, arranged to generate control signals arranged to control the conducting state of the plurality of semiconductor switches of the converter cells.

8. The converter arm according to claim 6 , wherein each converter cell comprises a cell controller and the at least three control signal connections of each converter cells are connected to the cell controller, wherein the cell controller is arranged to control the semiconductor switches of the converter cell via respective gate units arranged to condition control signals for the semiconductor switches to a suitable format.

9. The converter arm according to claim 1 , wherein each converter cell comprises a cell controller and the at least three control signal connections of each converter cells are connected to the cell controller, wherein the cell controller is arranged to control the semiconductor switches of the converter cell via respective gate units arranged to condition control signals for the semiconductor switches to a suitable format.

10. The converter arm according to claim 1 , wherein each converter cell comprises an auxiliary power input, wherein each auxiliary power input is arranged to power control functions of the respective converter cell without charging the energy storage element of the respective converter cell.

11. The converter atm according to claim 10 , further comprising at least one battery connected to the auxiliary power inputs of the converter cells.

12. The converter arm according to claim 11 , wherein each converter cell comprises a battery connected to its auxiliary power input.

13. The converter arm according to claim 1 , wherein each one of the control signal connections is a bidirectional connection.

14. The converter arm according to claim 1 , wherein each one of the control signal connections is arranged to communicate via optical connections.

15. A converter device for converting power in at least one direction between an alternating current, AC, and a direct current, DC, comprising at least one converter arm according to claim 1 .

16. The converter device according to claim 15 , wherein the converter device comprises a plurality of phase legs connected in parallel between terminals of a DC connection, and each phase leg comprises at least one of said converter arms.

17. A converter arm for Dower conversion comprising:

a plurality of converter cells, wherein each converter cell comprises a plurality of semiconductor switches, an energy storage element and at least three control signal connections arranged to control the conducting state of the plurality of semiconductor switches,

wherein each converter cell is connected to receive a control signal from at least three entities via said control signal connections, wherein at least two of the three entities are neighbouring converter cells, and each converter cell is arranged to forward a control signal to all connected neighbouring converter cells via said control signal connections,

wherein each converter cell is arranged to detect a blocking message supplied to the control signal connections separately from other messages supplied to the control signal connections, wherein the blocking message instructs the converter cell to turn off all semiconductor switches of the converter cell, and

wherein each converter cell is arranged to detect and forward the blocking message without fully decoding a control signal comprising the blocking message.

18. The converter arm according to claim 17 , wherein four of the converter cells are directly connected to a main controller, arranged to generate control signals arranged to control the conducting state of the plurality of semiconductor switches of the converter cells.

19. A converter arm for power conversion comprising:

a plurality of converter cells, wherein each converter cell comprises a plurality of semiconductor switches, an energy storage element and at least three control signal connections arranged to control the conducting state of the plurality of semiconductor switches;

wherein each converter cell is connected to receive a control signal from at least three entities via said control signal connections, wherein at least two of the three entities are neighbouring converter cells, and each converter cell is arranged to forward a control signal to all connected neighbouring converter cells via said control signal connections,

wherein four of the converter cells are directly connected to a main controller, arranged to generate control signals arranged to control the conducting state of the plurality of semiconductor switches of the converter cells.

20. The converter arm according to claim 19 , wherein the converter cells directly connected to the main controller are connected to only two neighbouring converter cells, and any converter cells not directly connected to the main controller are connected to three neighbouring converter cells.