Providing auxiliary power when a high-voltage link is non-functional

1. A method, comprising:

upon determining that a high-voltage link coupling a first wind turbine of a wind park to a grid is not functioning, operating the first wind turbine using an auxiliary control system that operates the first wind turbine to provide auxiliary power to a second wind turbine in the wind park while the second wind turbine is shutdown;

while the high-voltage link is not functioning:

generating a voltage magnitude using a reactive power control leg of the auxiliary control system, wherein the voltage magnitude is a sum of a nominal voltage value, a voltage adjustment value, and an output from a controller with an integral action, wherein the controller generates the output based on a difference between a desired active power value and an actual active power value; and

generating a voltage factor angle using an active power control leg of the auxiliary control system; and

upon determining that the high-voltage link is functioning, operating the first wind turbine and the second wind turbine using a primary control system to transmit power on the high-voltage link, wherein the primary control system has a different configuration than the auxiliary control system.

2. The method of claim 1 , wherein, when the high-voltage link is not functioning, the first wind turbine uses the auxiliary control system to deliver power to a local AC grid, wherein all the wind turbines in the wind park are coupled to the local AC grid.

3. The method of claim 1 , wherein the wind park is an off-shore wind park, and wherein the method comprises:

when the high-voltage link is not functioning, operating a first plurality of wind turbines in the off-shore wind park using the auxiliary control system to provide auxiliary power to a second plurality of wind turbines in the off-shore wind park, wherein the second plurality of wind turbines is shutdown.

4. The method of claim 3 , wherein the first plurality of wind turbines also provides auxiliary power for operating an AC-DC converter in an off-shore grid substation in the off-shore wind park when the high-voltage link is not functioning, wherein, when the high-voltage link is functioning, the AC-DC converter converts AC power on a local AC grid coupled to the first and second wind turbines to DC power transmitted on the high-voltage link.

5. The method of claim 1 , wherein the high-voltage link is a high-voltage direct current (HVDC) link, wherein the first and second wind turbines are coupled to the HVDC link via an AC-DC converter.

6. The method of claim 1 , wherein the high-voltage link is a high-voltage alternating current (HVAC) link, wherein the first and second wind turbines are coupled to the HVAC link via an AC-AC converter.

7. The method of claim 1 , wherein when operating the first and second wind turbines using the primary control system a power outputted by the first and second wind turbines is set using a controlled coupling circuit, wherein the controlled coupling circuit connects outputs of the first and second wind turbines to the high-voltage link.

8. The method of claim 1 , further comprising, after determining the high-voltage link is not functioning, performing one of:

starting the first wind turbine from a shutdown state using an internal auxiliary power supply; and

maintaining the first wind turbine in an operational state to provide auxiliary power to an auxiliary system in the first wind turbine when the high-voltage link is not functioning.

9. The method of claim 1 , further comprising:

reconfiguring the auxiliary control system to form the primary control system.

10. The method of claim 9 ,

wherein the controller comprises one of a proportional-integral (PI) controller and a proportional-integral-derivative (PID) controller, and

wherein reconfiguring the auxiliary control system comprises:

activating the controller that provides the output to the reactive power control leg; and

activating a reactive power adjuster that provides an output to the active power control leg.

11. The method of claim 10 ,

wherein the reactive power control leg comprises a first adder configured to receive the output from the controller, and

wherein the active power control leg comprises a second adder configured to receive the output from the reactive power adjuster.

12. The method of claim 11 ,

wherein the first adder is further configured to add the nominal voltage value, the voltage adjustment value, and the output from the controller to generate the voltage magnitude, and

wherein the second adder is further configured to add a desired angle value, an angle adjustment value, and the output from the reactive power adjuster to generate the voltage factor angle.

13. A first wind turbine comprising:

an auxiliary control system configured to operate the first wind turbine to output auxiliary power on a local alternating current (AC) grid to power an auxiliary system of a second wind turbine when (i) a high-voltage link coupling the first wind turbine and the second wind turbine to a grid is not functioning and (ii) while the second wind turbine is shutdown, wherein the auxiliary control system comprises:

a reactive power control leg configured to generate a voltage magnitude as a sum of a nominal voltage value, a voltage adjustment value, and an output from a controller with an integral action, wherein the controller generates the output based on a difference between a desired active power value and an actual active power value; and

an active power control leg configured to generate a voltage factor angle; and

a primary control system having a different configuration than the auxiliary control system, wherein the primary control system is configured to, when the high-voltage link is functioning, operate the first wind turbine to transmit power on the high-voltage link.

14. The wind turbine of claim 13 , wherein the first and second wind turbines are off-shore wind turbines and wherein the grid is an on-shore grid.

15. The wind turbine of claim 13 , wherein the high-voltage link is a high-voltage direct current (HVDC) link, wherein the first and second wind turbines are coupled to the HVDC link via a AC-DC converter.

16. The wind turbine of claim 13 , wherein when operating the first wind turbine using the primary control system a power outputted by the first wind turbine is set using a controlled coupling circuit, wherein the controlled coupling circuit connects an output of the first wind turbine to the high-voltage link.

17. The wind turbine of claim 13 , wherein when the second wind turbine is shutdown, the second wind turbine does not output power onto the local AC grid.

18. A wind turbine controller comprising:

a processor; and

a memory configured to store a program, which when executed by the processor performs an operation comprising:

upon determining that a high-voltage link coupling a first wind turbine of a wind park to a grid is not functioning, operating the first wind turbine using an auxiliary control system that operates the first wind turbine to provide auxiliary power to a second wind turbine in the wind park while the second wind turbine is shutdown;

while the high-voltage link is not functioning:

generating a voltage magnitude using a reactive power control leg of the auxiliary control system, wherein the voltage magnitude is a sum of a nominal voltage value, a voltage adjustment value, and an output from a controller with an integral action, wherein the controller generates the output based on a difference between a desired active power value and an actual active power value; and

generating a voltage factor angle using an active power control leg of the auxiliary control system; and

upon determining that the high-voltage link is functioning, operating the first wind turbine using a primary control system to transmit power on the high-voltage link, wherein the primary control system has a different configuration than the auxiliary control system.

19. A method, comprising:

upon determining that a high-voltage link coupling a wind turbine in a wind park to a grid is not functioning, operating the wind turbine using an auxiliary control system that operates the wind turbine to provide auxiliary power to a renewable power generator different than the wind turbine while the renewable power generator is shutdown;

while the high-voltage link is not functioning:

generating a voltage magnitude using a reactive power control leg of the auxiliary control system, wherein the voltage magnitude is a sum of a nominal voltage value, a voltage adjustment value, and an output from a controller with an integral action, wherein the controller generates the output based on a difference between a desired active power value and an actual active power value; and

generating a voltage factor angle using an active power control leg of the auxiliary control system; and

upon determining that the high-voltage link is functioning, operating the wind turbine using a primary control system to transmit power on the high-voltage link, wherein the primary control system has a different configuration than the auxiliary control system.