Wind power plant frequency control

1. A method of operating a wind power plant, with at least one wind turbine generator connected to an electrical grid, wherein the method comprises:

monitoring a frequency parameter and comparing it with a frequency set point, as to select a low or high frequency event;

determining a power reference to the at least one wind turbine generator, based on the frequency parameter, wherein:

in response to detection of a high frequency event, the power reference is determined as a minimum of a selection of at least a first and a second minimum power reference,

wherein the first minimum power reference is a pre-event electrical power output subtracted a power amount proportionally to the grid frequency deviation (ΔPFC) and

wherein the second minimum power reference is a pre-event curtailed electrical power reference subtracted a power amount proportionally to the grid frequency deviation (ΔPFC),

in response to detection of a low frequency event, the power reference is determined as a maximum of a selection of at least a first and a second maximum power reference,

wherein the first maximum power reference is a summation of a pre-event electrical power output and a power amount proportionally to the grid frequency deviation (ΔPFC), and

wherein the second maximum power reference is a summation of a curtailed electrical power output and a power amount proportionally to the grid frequency deviation (ΔPFC); and

dispatching the power reference to the at least one wind turbine generator; and

adjusting a power output of the at least one wind turbine generator using the power reference.

2. The method according to claim 1 , wherein the curtailed electrical power reference is a power reserve.

3. The method according to claim 2 , wherein the power reserve is combined with a limitation function, as to reduce power fluctuations from the wind power plant.

4. The method according to claim 1 , wherein the power amount proportionally to the grid frequency deviation, ΔP FC further comprises a threshold component.

5. The method according to claim 4 , wherein the threshold component consists of a low frequency threshold value and a high frequency threshold value.

6. The method according to claim 1 , wherein the adjustment reduces at least one adverse effect associated with a power fluctuation resulting from a change in stability of the electric grid.

7. A wind power plant, comprising at least one wind turbine generator connected to an electrical grid, and a power plant controller, wherein the power plant controller is arranged to monitor a frequency parameter and compare it with a frequency set point, as to select a low or high frequency event, and

said power plant controller is arranged to determine a power reference to the at least one wind turbine generator, based on the frequency parameter, wherein:

in response to detection of a high frequency event, the power reference is determined as a minimum of a selection of at least a first and a second minimum power reference,

wherein the first minimum power reference is a pre-event electrical power output subtracted a power amount proportionally to a grid frequency deviation (ΔPFC) and

wherein the second minimum power reference is a pre-event curtailed electrical power reference subtracted a power amount proportionally to the grid frequency deviation (ΔPFC),

in response to detection of a low frequency event, the power reference is determined as a maximum of a selection of at least a first and a second maximum power reference,

wherein the first maximum power reference is a summation of a pre-event electrical power output and a power amount proportionally to the grid frequency deviation (ΔPFC), and

wherein the second maximum power reference is a summation of a curtailed electrical power output and a power amount proportionally to the grid frequency deviation (ΔPFC); and

and said power plant controller is arranged to dispatch the power reference to the at least one wind turbine generator; and

adjust a new power output of the at least one wind turbine generator using the power reference.

8. A wind power plant, with at least one wind turbine generator connected to an electrical grid, and a wind power plant controller configured to carry out the following:

monitoring a frequency parameter and comparing it with a frequency set point, as to select a low or high frequency event;

determining a power reference to the at least one wind turbine generator, based on the frequency parameter, wherein:

in response to detection of a high frequency event, the power reference is determined as a minimum of a selection of at least a first and a second minimum power reference,

wherein the first minimum power reference is a pre-event electrical power output subtracted a power amount proportionally to a grid frequency deviation (ΔPFC) and

wherein the second minimum power reference is a pre-event curtailed electrical power reference subtracted a power amount proportionally to the grid frequency deviation (ΔPFC),

in response to detection of a low frequency event, the power reference is determined as a maximum of a selection of at least a first and a second maximum power reference,

wherein the first maximum power reference is a summation of a pre-event electrical power output and a power amount proportionally to the grid frequency deviation (ΔPFC), and

wherein the second maximum power reference is a summation of a curtailed electrical power output and a power amount proportionally to the grid frequency deviation (ΔPFC);

dispatching the power reference to the at least one wind turbine generator; and

adjusting a power output of the at least one wind turbine generator using the power reference.

9. The wind power plant according to claim 8 , wherein the adjustment reduces at least one adverse effect associated with a power fluctuation resulting from a change in stability of the electric grid.