Method and device of determining a reference output power for an energy storage system in a wind power generation system

1. A method of determining a reference output power for an energy storage system in a wind power generation system, comprising

filtering an actual wind power output to obtain a desired power output delivered to a grid;

determining a reference output power for the energy storage system from the actual wind power output and the desired power output delivered to the grid;

adjusting the reference output power for the energy storage system based on a change in predicted wind power output at a next time point; and

wherein the adjusting includes increasing the reference output power for the energy storage system by determining a difference between the actual wind power output and a minimum of the following two parameters: (1) a maximum allowable total power outputs under power output ramping rate limit and (2) a maximum allowable total power outputs under energy storage system output power amplitude limit.

2. The method of claim 1 , wherein the adjusting the reference output power for the energy storage system based on a change in predicted wind power output at the next time point comprises any one of

increasing the reference output power for the energy storage system if an increase in the predicted wind power output is larger than a predetermined increase threshold; and

decreasing the reference output power for the energy storage system if a decrease in the predicted wind power output is larger than a predetermined decrease threshold.

3. The method of claim 2 , wherein the decreasing the reference output power for the energy storage system further comprises

determining the reference output power for the energy storage system as a difference between a maximum of a minimum allowable total power outputs under power output ramping rate limit and under energy storage system output power amplitude limit and the actual wind power output.

4. The method of claim 1 , further comprising:

adjusting the reference output power for the energy storage system based on a ramping rate limit.

5. The method of claim 4 , wherein the adjusting the reference output power for the energy storage system based on a ramping rate limit further comprises

determining the reference output power for the energy storage system as a difference between a maximum of a minimum allowable total power outputs under one-minute power output ramping rate limit, ten-minute power output ramping rate limit and energy storage system output power amplitude limit and the actual wind power output if a negative ramping rate boundary crossing is detected.

6. The method of claim 4 , wherein the adjusting the reference output power for the energy storage system based on a ramping rate limit further comprises:

determining the reference output power for the energy storage system as a difference between a minimum of a maximum allowable total power outputs under one-minute power output ramping rate limit, ten-minute power output ramping rate limit and energy storage system output power amplitude limit and the actual wind power output if a positive ramping rate boundary crossing is detected.

7. The method of claim 1 , further comprising:

modifying, before adjusting the reference output power for the energy storage system, the reference output power for the energy storage system with a power value h(t) expressed by

h ( t )=1/ T [ E ( t )− E Bn m 1 −αTP set ( t )]

wherein T denotes a filter time constant for filtering the actual wind power output, E(t) denotes energy remaining in the energy storage system at time t, E Bn denotes a rated capacity of the energy storage system, m 1 denotes a minimum energy percentage limitation, α denotes a battery energy limit factor, and P set (t) denotes the desired power output delivered to the grid.

8. The method of claim 1 , further comprising:

limiting the reference output power for the energy storage system within output power amplitude limitation of the energy storage system.

9. A device for determining a reference output power for an energy storage system in a wind power generation system, comprising

a power output filtering unit configured to filter an actual wind power output to obtain a desired power output delivered to a grid;

a reference power determination unit configured to determine a reference output power for the energy storage system from the actual wind power output and the desired power output delivered to the grid; and

a power prediction adjustment unit configured to adjust the reference output power for the energy storage system based on a change in predicted wind power output at a next time point;

wherein the power prediction adjustment unit is configured to increase the reference output power for the energy storage system by determining a difference between the actual wind power output and a minimum of the following two parameters: (1) a maximum allowable total power outputs under power output ramping rate limit and (2) a maximum allowable total power outputs under energy storage system output power amplitude limit.

10. The device of claim 9 , wherein the power prediction adjustment unit is further configured to:

increase the reference output power for the energy storage system if an increase in the predicted wind power output is larger than a predetermined increase threshold; and/or

decrease the reference output power for the energy storage system if a decrease in the predicted wind power output is larger than a predetermined decrease threshold.

11. The device of claim 10 , wherein the power prediction adjustment unit is configured to decrease the reference output power for the energy storage system by

determining the reference output power for the energy storage system as a difference between a maximum of a minimum allowable total power outputs under power output ramping rate limit and under energy storage system output power amplitude limit and the actual wind power output.

12. The device of claim 9 , further comprising:

a ramping rate control unit configured to adjust the reference output power for the energy storage system based on a ramping rate limit.

13. The device of claim 12 , wherein the ramping rate control unit is configured to

determine the reference output power for the energy storage system as a difference between a maximum of a minimum allowable total power outputs under one-minute power output ramping rate limit, ten-minute power output ramping rate limit and energy storage system output power amplitude limit and the actual wind power output if a negative ramping rate boundary crossing is detected.

14. The device of claim 12 , wherein the ramping rate control unit is configured to:

determine the reference output power for the energy storage system as a difference between a minimum of a maximum allowable total power outputs under one-minute power output ramping rate limit, ten-minute power output ramping rate limit and energy storage system output power amplitude limit and the actual wind power output if a positive ramping rate boundary crossing is detected.

15. The device of claim 9 , further comprising:

a state of charge adjustment unit configured to modify, before adjusting the reference output power for the energy storage system, the reference output power for the energy storage system with a power value h(t) expressed by

h ( t )=1/ T [ E ( t )− E Bn m 1 −αTP set ( t )]

wherein T denotes a filter time constant for filtering the actual wind power output, E(t) denotes energy remaining in the energy storage system at time t, E BN denotes a rated capacity of the energy storage system, m1 denotes a minimum energy percentage limitation, a denotes a battery energy limit factor, and P set (t) denotes the desired power output delivered to the grid.

16. The device of claim 9 , further comprising:

a power amplitude limit unit configured to limit the reference output power for the energy storage system within output power amplitude limitations of the energy storage system.