Circuit for converting power between a three-phase grid and a single-phase grid
View Patent ↗Described is a circuit for converting electric power between a three-phase grid and a single-phase grid. The circuit includes, in at least one embodiment, a first transformer that is connected to the three-phase grid, a number of first converter stages assigned to the first transformer, the associated DC intermediate circuits and the associated second converter stages. The second converter stages are connected to each other at the alternating-current side outputs with the aid of a series connection.
1. A circuit for converting electric power between a three-phase grid and single-phase grid, comprising:
a plurality of first transformers, each of the plurality of first transformers having a primary side and a secondary side, the primary side and the secondary side each having a number of windings, and being connected to the three-phase grid;
a plurality of first converter stages connected to the plurality of first transformers wherein a number of plurality of first converter stages corresponds to the number of the windings on the secondary side;
a plurality of DC intermediate circuits connected to the plurality of first converter stages; and
a plurality of second converter stages connected to the plurality of first converter stages;
a plurality of series connections including a number of the plurality of second converter stages connected in series with one another at alternating-current outputs of the plurality of second converter stages; and
wherein each series connection of the plurality of series connections is respectively connected with a separate input of the plurality of DC intermediate circuits and the plurality of series connections together form a three-phase configuration to be connected to the single-phase grid.
2. The circuit according to claim 1 , wherein the plurality of DC intermediate circuits comprises:
a second transformer assigned to the plurality of second converter stages and connected to the single-phase grid, wherein the second converter stages are connected via the plurality of series connections to the second transformer.
3. The circuit according to claim 2 , wherein each series connection of the plurality of series connections is connected to a winding of the second transformer.
4. The circuit according to claim 2 , wherein each series connection of the plurality of series connections is connected to a separate winding of the second transformer.
5. The circuit according to claim 4 , wherein the plurality of first transformers includes three first transformers.
6. The circuit according to claim 5 , wherein, the second transformer comprises three windings and the plurality of series connections comprises three series connections, wherein each series connection of the three series connections is connected to a winding of the three windings, respectively.
7. The circuit according to claim 2 , wherein the plurality of first transformers includes three first transformers.
8. The circuit according to claim 7 , wherein, the second transformer comprises three windings and the plurality of series connections comprises three series connections, wherein each series connection of the three series connections is connected to a winding of the three windings, respectively.
9. The circuit according to claim 1 , wherein the plurality of DC intermediate circuits each comprise a linear choke, and each series connection of the plurality of series connections is connected via the linear choke to the single-phase grid.
10. The circuit according to claim 9 , wherein the plurality of series connections are connected to an overhead wire or line for a railroad grid.
11. The circuit according to claim 1 , wherein the plurality of first converter stages includes at least five first converter stages, wherein the plurality of DC intermediate circuits includes at least five DC intermediate circuits and the plurality of second converter stages includes at least five second converter stages.
12. The circuit according to claim 1 , wherein each of the plurality of first converter stages includes three phase modules.
13. The circuit according to claim 12 , wherein the three phase modules are embodied as 3-level-neutral point clamped (NPC) converters.
14. The circuit according to claim 1 , wherein each of the plurality of second converter stages includes two phase modules.
15. The circuit according to claim 14 , wherein the two phase modules are connected in parallel.
16. The circuit according to claim 14 , wherein the two phase modules are embodied as 3-level-neutral point clamped (NPC) converters.
17. The circuit according to claim 16 , wherein the two phase modules are connected in parallel.
18. The circuit according to claim 1 , further comprising:
an absorption circuit including a capacitor and a coil.
19. A circuit for converting electric power between a three-phase grid and single-phase grid, comprising:
a plurality of first transformers, each first transformer having a primary side and a secondary side, the primary side and the secondary side each having a number of windings, and being connected to the three-phase grid;
a plurality of first converter stages connected to the plurality of first transformers wherein a number of plurality of first converter stages corresponds to the number of the windings on the secondary side;
a plurality of DC intermediate circuits connected to the plurality of first converter stages; and
a plurality of second converter stages connected to the plurality of first converter stages; wherein a number of the plurality of second converter stages are connected in series with one another by forming a a plurality of series connections at alternating-current outputs of the plurality of second converter stages; and
at least one second transformer, wherein each of the plurality of series connections together form a three-phase configuration connected to the second transformer, and the second transformer is connected to the single-phase grid.