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EP-4317681-B1 - METHODS FOR FAST POWER RAMP UP, CONTROLLERS AND WIND TURBINES

EP4317681B1EP 4317681 B1EP4317681 B1EP 4317681B1EP-4317681-B1

Inventors

  • SCHULTEN, CHRISTOPH
  • ANAND, Nithya
  • MONROS GARRIGOSA, Miriam
  • LOPEZ GONZALEZ, Marta

Dates

Publication Date
20260506
Application Date
20220801

Claims (14)

  1. A method (100) for operating a wind turbine (10), the method comprising: increasing (110) electric power output from an initial power value (61) at a first power ramp rate (63); when reaching an intermediate power value (69), increasing (120) the electric power output to a target power value (59) at a second power ramp rate (67) which is different from the first power ramp rate (63); and wherein the intermediate power value (69) is the sum of the initial power value (61) and a predetermined power difference (71), wherein the predetermined power difference (71) is a predefined percentage (73) of the target power value (59).
  2. The method of claim 1, wherein the predefined percentage (73) is between 30 and 70%, specifically between 40 and 60%, and more specifically about 50%.
  3. The method of claim 1 or claim 2, wherein at least one of the first power ramp rate (63) and the second power ramp rate (67) is a predefined power ramp rate.
  4. The method of any of the preceding claims, wherein the second power ramp rate (67) is lower than the first power ramp rate (63).
  5. The method of any of the preceding claims, wherein while increasing electric power output from the initial power value (61) to the target power value (59) a power output limit is determined as the product of a prevailing wind turbine rotor speed value and a maximum torque value.
  6. The method of any of the preceding claims, wherein while increasing electric power output from the initial power value (61) to the target power value (59) one or more controller gains for power and/or one or more controller gains for generator torque is different from the corresponding controller gains during normal operation.
  7. The method of claim 6, wherein a first set of controller gains for power and generator torque is provided for the power ramp up at the first power ramp rate (63) and a second different set of controller gains is provided for the power ramp up at the second power ramp rate (67).
  8. The method of any of the preceding claims, further comprising refraining from performing oscillation damping actions while increasing electric power output from the initial power value (61) to the target power value (59).
  9. The method of any of the preceding claims, wherein a rotor speed setpoint (81) is kept at or above a minimum rotor speed threshold before increasing the electric power output from the initial power value (61).
  10. The method of any of the preceding claims, wherein an external power request of the target power value (59) is received by a controller (36) configured to control the wind turbine (10).
  11. The method of any of the preceding claims, further comprising detecting an end of an electrical grid event.
  12. A controller (36) comprising a communications module (43), a processor (40) and a memory (41), wherein the memory (41) comprises instructions that, when executed by the processor (40), cause the processor to execute the method of any of claims 1 - 11.
  13. The controller of claim 12, wherein the controller is configured to change a control mode during power ramp up when a pitch setpoint value equals a minimum optimum pitch value and when the wind turbine rotor speed is decreasing.
  14. A wind turbine (10) comprising: a wind turbine rotor (18) including a plurality of wind turbine blades (22); a generator (42); and the controller (36) of claim 12 or 13.

Description

The present disclosure relates to methods for operating a de-rated wind turbine, and in particular to methods for ramping up the power output of a wind turbine. The present disclosure further relates to controllers configured to control a wind turbine during power ramp up. The present disclosure further relates to wind turbines configured for such methods of operating. BACKGROUND Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly ("directly driven" or "gearless") or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid. The wind turbine hub may be rotatably coupled to a front of the nacelle. The wind turbine hub may be connected to a rotor shaft, and the rotor shaft may then be rotatably mounted in the nacelle using one or more rotor shaft bearings arranged in a frame inside the nacelle. The nacelle is a housing arranged on top of a wind turbine tower that may contain and protect the gearbox (if present) and the generator (if not placed outside the nacelle) and, depending on the wind turbine, further components such as a power converter, and auxiliary systems. In order to maintain the stability of the electrical grid, the production of electric power by the wind turbines and the consumption of electric power of loads connected to the electrical grid must remain balanced. If there is an imbalance, the frequency of the grid may deviate from its prescribed nominal value. For example, if power demand is higher than power production, the frequency of the electrical grid may decrease. And if power production is higher than the demand of power, the frequency of the electrical grid may increase. Typical values of nominal grid frequency are 60 Hertz (Hz) in the US and 50 Hz in Europe. Grid frequency is generally allowed to deviate very little from the nominal frequency within predefined frequency bands. The wind turbines may initiate regulation procedures to restore the stability of the grid if an imbalance, e.g. a frequency imbalance, is detected. In particular, wind farms or individual wind turbines may be requested to reduce power output below their capacity based on the prevailing wind speed. This process is called derating. Currently, wind farms are operated based on power ramp rates of the particular wind turbines. Each individual turbine may have a power ramp up rate and a power ramp down rate. For example, if power demand decreases, the power output may be ramped down from one level to a lower level. That is to say, the power generated by one or more wind turbines is reduced, e.g. based on a ramp down request, such that the stability of the electrical grid is maintained. Likewise, if power demand increases, the power output may be ramped up from one level to a higher level. The power generated by one or more wind turbines is increased, e.g. based on a ramp up signal, for maintaining the stability of the electrical grid. Grid codes increasingly require that wind turbines be able to ramp up power quickly. For example, grid codes may require a fast power ramping up from a de-rated power level, which may be as low as e.g. 10% of rated power. This may pose several challenges in the design and operation of wind turbines. In particular, controlling the wind turbine operation in such a manner that in different envisaged grid and wind scenarios, ramp-up can occur quickly enough is challenging. EP 2 738 904 A2 discloses a method for controlling operation of a wind turbine included within a power generation and delivery system. The method includes receiving, by a controller, a power command signal, wherein the power command signal indicates recovery from the grid contingency event; and increasing, in a non-uniform manner, power injected into a grid by a power conversion assembly in response to the power command signal wherein the controller controls the power conversion assembly. US 2018/171974 A1 relates to a control system for a wind turbine. The wind turbine comprises a power generator configured to generate power dependent on a power request. The control system comprises a ramp rate limiter configured to restrict a rate of change of the power request according to a rate of change limit and configured to determine the rate of change limit dependent on a power difference between the power request and an estimated available wind power. The present disclosure aims to provide improvements in ramping up power production of wind turbines. SUMMARY In an aspect of the present disclosure, a method for operating a wind turbine in accordance with claim 1 is provided. The method comprises in