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Adaptive Pitch Control for Variable Speed Wind Turbines

National Renewable Energy Laboratory

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Technology Marketing Summary

Wind energy is increasingly recognized as a viable option for complementing and even replacing other types of energy such as fossil fuels. In the early development of wind energy, the majority of wind turbines or wind turbine generators were constructed for operation at a constant speed, but more recently, the trend is toward using variable-speed wind turbines to better capture available wind power. In most cases, wind turbine pitch angles can be adjusted to control the operation of the variable speed wind turbine.

Wind turbine manufacturers use variable-speed turbines to capture available wind power over a wide range of wind speeds. To be effective, though, these variable speed wind turbines require active control systems to react to changing wind and other operating conditions. One concept that is fundamental to the control dynamics for a wind generator is that changing speed is a relatively slow process due to the large inertia values involved, and this makes it difficult to use a power converter in the turbine or in the turbine’s “plant” to control the rotor speed. As a result, manufacturers and operators of variable speed wind turbines also use pitch control on an ongoing basis to regulate power flow at the high speed limit. In other words, a control system is used to vary pitch rapidly in response to rotor speed, and significant efforts have been made to improve this ongoing pitch control system.

Description

Engineers at the National Renewable Energy Laboratory (NREL) have developed an adaptive method for adjusting blade pitch angle, and controllers implementing such a method, for achieving higher power coefficients. Average power coefficients are determined for first and second periods of operation for the wind turbine. When the average power coefficient for the second time period is larger than for the first, a pitch increment, which may be generated based on the power coefficient, is added (or the sign is retained) to the nominal pitch angle value for the wind turbine. When the average power coefficient for the second time period is less than for the first, the pitch increment is subtracted (or the sign is changed). A control signal is generated based on the adapted pitch angle value and sent to blade pitch actuators that act to change the pitch angle of the wind turbine to the new or modified pitch angle setting and this process is iteratively performed.

Benefits
  • Increased accuracy of nominal pitch angle
  • Increased efficiency in capturing available wind power
Applications and Industries
  • Wind turbines
  • Wind power
  • Wind energy
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 8,174,136
Patent
8,174,136
Adaptive pitch control for variable speed wind turbines
An adaptive method for adjusting blade pitch angle, and controllers implementing such a method, for achieving higher power coefficients. Average power coefficients are determined for first and second periods of operation for the wind turbine. When the average power coefficient for the second time period is larger than for the first, a pitch increment, which may be generated based on the power coefficients, is added (or the sign is retained) to the nominal pitch angle value for the wind turbine. When the average power coefficient for the second time period is less than for the first, the pitch increment is subtracted (or the sign is changed). A control signal is generated based on the adapted pitch angle value and sent to blade pitch actuators that act to change the pitch angle of the wind turbine to the new or modified pitch angle setting, and this process is iteratively performed.
National Renewable Energy Laboratory 05/08/2012
Issued
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 05-33DevelopmentAvailable03/15/201603/15/2016

Contact NREL About This Technology

To: Erin Beaumont<erin.beaumont@nrel.gov>