Power delivery systems and methods for offshore applications

1. A system for delivering power to an offshore load, the system comprising:

an on-land source of three-phase power;

an on-land AC-to-DC power conversion module configured to convert the three-phase power to DC power;

a DC transmission line having a source end and a load end, wherein the source end is configured to receive DC power from the on-land AC-to-DC power conversion module; and

an offshore DC-to-AC power inverter configured to receive DC power from the DC transmission line, convert the DC power to three-phase AC power, and deliver the three-phase AC power to an offshore load,

the offshore DC-to-AC power inverter further comprising a plurality of converter sections, and each converter section comprising:

a DC-to-AC converter unit; and

a DC-to-DC converter unit, comprising:

an H-bridge AC-to-DC converter block that provides a DC output;

an H-bridge DC-to-AC converter block that receives a DC input; and

a transformer electrically connected between the DC-to-AC converter block and the AC-to-DC converter block.

2. The system of claim 1 , wherein the on-land AC-to-DC power conversion modules comprises a plurality of AC-to-DC power converter cells.

3. The system of claim 1 , the DC-to-AC converter block comprising a set of solid state switch pairs, wherein the DC-to-AC converter block receives the DC output and converts the DC output to a single phase AC output.

4. The system of claim 3 , the DC-to-AC converter block further comprising a capacitor connected in parallel with the set of solid state switch pairs.

5. The system of claim 3 , the DC-to-AC converter block further comprising a capacitor connected in parallel with a plurality of sets of diode devices.

6. The system of claim 1 , further comprising a plurality of ranks connected between the transformer and the AC-to-DC converter block, wherein each of the plurality of ranks includes one or more modules that receive the DC input in series, and wherein the plurality of ranks are connected.

7. The system of claim 1 , further comprising a plurality of ranks connected between the transformer and the AC-to-DC converter block, wherein each of the plurality of ranks includes one or more modules that receive the DC input in series, and wherein the plurality of ranks provides the DC output as a mesh.

8. The system of claim 1 , the offshore DC-to-AC power inverter further comprising:

a three-phase system comprising three legs electrically connected in parallel to the DC transmission line;

wherein each leg comprises a series circuit of submodules, each submodule comprising a series-connected pair of power semiconductors electrically connected in parallel with a power storage device; and

wherein each phase of the three-phase system provides a single phase AC output that comprises one of the three phases of AC power delivered to the offshore load.

9. The system of claim 1 , the offshore DC-to-AC power inverter further comprising:

a three-phase system comprising three legs electrically connected in parallel to the DC transmission line;

wherein each leg comprises a series circuit of submodules, each submodule comprising a series-connected pair of power semiconductors electrically connected in parallel with a power storage device; and

wherein each phase of the three-phase system provides a single phase AC output that is electrically connected to a second offshore load.

10. A method for delivering power to an offshore load, the method comprising:

connecting an on-land source of three-phase power to an on-land AC-to-DC power conversion module configured to convert the three-phase power to DC power;

connecting a source end of a DC transmission line to a DC power output from the on-land AC-to-DC power conversion module; and

configuring an offshore DC-to-AC power inverter to receive DC power from the DC transmission line, convert the DC power to three-phase AC power, and deliver three-phase AC power to an offshore load,

wherein the DC-to-AC power inverter further comprises a plurality of converter sections, wherein each converter section comprises a DC-to-AC converter unit and a DC-to-DC converter unit, further comprising:

configuring an H-bridge AC-to-DC converter block to provide a DC output;

configuring an H-bridge DC-to-AC converter block to receives a DC input; and

electrically connecting a transformer between the DC-to-AC converter block and the AC-to-DC converter block.

11. The method of claim 10 , wherein the on-land AC-to-DC power conversion modules comprises a plurality of AC-to-DC power converter cells.

12. The method of claim 10 , wherein the DC-to-AC converter block comprises a set of solid state switch pairs, and wherein the DC-to-AC converter block receives the DC output and converts the DC output to a single phase AC output.

13. The method of claim 12 , wherein the DC-to-AC converter block further comprises a capacitor connected in parallel with the set of solid state switch pairs.

14. The method of claim 12 , wherein the DC-to-AC converter block further comprises a capacitor connected in parallel with a plurality of sets of diode devices.

15. The method of claim 10 , wherein the inverter further comprises a plurality of ranks connected between the transformer and the AC-to-DC converter block, wherein each of the plurality of ranks includes one or more modules that receive the DC input in series, and wherein the plurality of ranks are connected.

16. The method of claim 10 , wherein the inverter further comprises a plurality of ranks connected between the transformer and the AC-to-DC converter block, wherein each of the plurality of ranks includes one or more modules that receive the DC input in series, and wherein the plurality of ranks provides the DC output as a mesh.

17. The method of claim 10 , further comprising:

providing a three-phase system by, at least, electrically connecting three legs in parallel to the DC transmission line;

wherein each leg comprises a series circuit of submodules, each submodule comprising a series-connected pair of power semiconductors electrically connected in parallel with a power storage device; and

wherein each phase of the three-phase system provides a single phase AC output that comprises one of the three phases of AC power delivered to the offshore load.

18. The method of claim 10 , further comprising:

providing a three-phase system by, at least, electrically connecting three legs in parallel to the DC transmission line;

wherein each leg comprises a series circuit of submodules, each submodule comprising a series-connected pair of power semiconductors electrically connected in parallel with a power storage device; and

wherein each phase of the three-phase system provides a single phase AC output that is electrically connected to a second offshore load.