Wind power plant with reduced losses

1. A method for controlling a wind power plant, the wind power plant comprising a plurality of wind turbine generators, each wind turbine generator comprising at least one power converter for providing active power and/or reactive power to an electrical grid, the method comprising:

in response to a control command to the wind power plant to deliver reduced active power to the electrical grid, curtailing the production of active power from a selected plurality of wind turbine generators;

determining a required amount of reactive power that still must be provided by the selected plurality of wind turbine generators that have curtailed active power production;

grouping the selected plurality of wind turbine generators into a first set of wind turbine generators and a second set of wind turbine generators for providing the required amount of reactive power;

supplying reactive power to the electrical grid from the first set of wind turbine generators; and

disconnecting the second set of wind turbine generators from the electrical grid for not supplying reactive power to the grid, in order to minimize active power losses.

2. The method for controlling a wind power plant according to claim 1 , the method further comprises;

monitoring at least one control variable of the electrical output of the wind power plant to the electrical grid and outputs of the individual wind turbine generators; and

grouping the plurality of wind turbine generators into a first set of wind turbine generators and a second set of wind turbine generators in response to the control variable for providing the required amount of reactive power.

3. The method for controlling a wind power plant according to claim 1 , the method further comprises;

deciding which wind turbine generators to group in the first set and which to group in the second set by using a prioritized list of the plurality of wind turbine generators.

4. The method for controlling a wind power plant according to claim 1 , the method further comprises;

comparing a number of operational hours of each of the wind turbine generator; and

selecting the wind turbine generator with lowest number of operational hours to be placed in the first group for supplying reactive power.

5. The method for controlling a wind power plant according to claim 1 , wherein the number of wind turbine generators of the first set of wind turbine generators is determined as the sum of a requested reactive-power capability and a user-defined margin divided by the reactive power capability of each wind turbine generator.

6. The method for controlling a wind power plant according to claim 1 , the method further comprises:

determining which wind turbine generators are capable of supplying the highest amount of reactive power at a point of common coupling;

grouping wind turbine generators in the first set to include those wind turbine generators that are capable of supplying the highest amount of reactive power.

7. The method for controlling a wind power plant according to claim 1 , wherein the number of wind turbine generators of the first set of wind turbine generators is determined to be calculated from a ramp-rate perspective.

8. The method for controlling a wind power plant according to claim 1 , wherein at least the step of grouping the plurality of selected wind turbine generators into a first set of wind turbine generators and a second set of wind turbine generators is executed using at least predefined events.

9. A wind power plant system, the system comprising:

a plurality of wind turbine generators, each wind turbine generator comprising at least one power converter arranged to provide active power and/or reactive power to an electrical grid;

a control system for controlling the amount of power to be delivered from the power plant to the electrical grid, the control system being configured, in response to a control command for delivery of reduced active power, for curtailing the production of active power from a selected plurality of wind turbine generators, the control system further configured for determining a required amount of reactive power that still must be provided by the selected plurality of wind turbine generators that have curtailed active power production, wherein the control system is configured to group selected plurality of wind turbine generators into a first set of wind turbine generators and a second set of wind turbine generators for providing the requested amount of reactive power;

the control system further configured for controlling the first set of wind turbine generators to supply reactive power to the electrical grid and for disconnecting the second set of wind turbine generators from the electrical grid for not supplying reactive power to the grid, in order to minimize active power losses.

10. The wind power plant system according to claim 9 , wherein the wind power plant further comprises:

a collector system including a network of conductors and/or transformers, wherein the wind turbine generators are connected to the at network of conductors;

and wherein the control system is optimized to minimize the active losses of both the plurality of wind turbine generator and the collector system.

11. The wind turbine generator according to claim 9 , wherein the power converter is arranged to disable a gate signal to at least one power switch of the power converter when receiving the control command.

12. At least one computer program product directly loadable into the internal memory of at least one digital computer, comprising software code portions for performing the steps of the method according to claim 1 when said at least one product is/are run on said at least one computer.