Abstract
The effects of rotor scale and control system lag were examined for a variable-speed wind turbine. The scale study was performed on a teetered rotor with radii ranging between 22.5m and 33.75m. A 50% increase in radius more than doubled the rated power and annual energy capture. Using blade pitch to actively control fluctuating flatwise moments allowed for significant reductions in blade mass for a fixed fatigue life. A blade operated in closed-loop mode with a 33.75m radius weighed less than an open-loop blade with a 22.5m radius while maintaining the same fatigue life of 5×109 rotations.Actuator lag reduced the effectiveness of the control system. However, 50% reductions in blade mass were possible even when implementing a relatively slow actuator with a 1 sec. time constant. Other practical limits on blade mass may include fatigue from start/stop cycles, non-uniform turbulence, tower wake effects, and wind shear. The more aggressive control systems were found to have high control accelerations near 60 deg/s2, which may be excessive for realistic actuators. Two time lags were introduced into the control system when mean wind speed was estimated in a rapidly changing wind environment. Thefirst lag was the length oftime needed to determine mean wind speed, and therefore the mean control settings. The second was the frequency at which these mean control settings were changed. Preliminary results indicate that quickly changing the mean settings (every 10 seconds) and using a moderate length mean averaging time (60 seconds) resulted in the longest fatigue life. It wasdiscovered that large power fluctuations occurred during openloop operation which could cause sizeable damage to a realistic turbine generator. These fluctuations are reduced by one half or more when aerodynamic loads are actively controlled.
Original language | American English |
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Pages | 306-314 |
Number of pages | 9 |
DOIs | |
State | Published - 1 Nov 2001 |
Externally published | Yes |
Event | 20th 2001 ASME Wind Energy Symposium - Reno, NV, United States Duration: 11 Jan 2001 → 14 Jan 2001 |
Conference
Conference | 20th 2001 ASME Wind Energy Symposium |
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Country/Territory | United States |
City | Reno, NV |
Period | 11/01/01 → 14/01/01 |
Bibliographical note
Work performed by RANN Incorporated, Palo Alto, CaliforniaNREL Publication Number
- NREL/CP-500-32340