H-infinity robust controller for wind turbine power boosting
Authors
Bordeasu, Dorin ; Debes, Ali
Term
4. semester
Education
Publication year
2017
Submitted on
2017-06-08
Pages
88
Abstract
En power-boosting-styring øger generatorens moment for midlertidigt at hæve en vindmølles nominelle effekt med op til 5 %, hvilket kan øge den årlige energiproduktion (AEP) med op til 2 %. Dette speciale opbygger en ikke-lineær model af NRELs 5 MW referencevindmølle og lineariserer den for at designe to H-infinity (H∞) robuste regulatorer: en standard og en power-boosting-variant. H∞-styring er en metode, der bevarer ydeevnen, selv når model og driftsforhold er usikre. Parametriske usikkerheder tilføjes en lineær tidsinvariant tilstandsrum-model, og en skiftelogik aktiverer boost-tilstanden ved bestemte vindhastigheder. Stabilitet, ydeevne og robusthed vurderes med frekvensdomæneværktøjer (Bode-diagrammer og pol-nul-kort). De to H∞-regulatorer sammenlignes med en gain-scheduled PI-basislinje. Basislinjen viser større variation i pitchvinklen (bladenes indstillingsvinkel), men mindre svingninger i generatorhastighed og -moment. Mellem de to H∞-regulatorer er pitchvinkel og generatorhastighed omtrent ens, mens generatorens moment adskiller sig tydeligere, sandsynligvis fordi momentets arbejdspunkter afviger fra lineariseringspunkterne. Ved højere vindhastigheder viser H∞-regulatorerne faldende generatorhastighed og kraftigt stigende generatormoment. Under de definerede betingelser (vindhastigheder 15–22 m/s) øger H∞-power-boosting-regulatoren den elektriske effekt fra 5,0 til 5,25 MW uden problemer. Træthedsvurdering baseret på skadesækvivalente laster beregnet ud fra standardafvigelsen af bøjende momenter viser små påvirkninger: tårnets træthedslaster øges ca. 1,2 %, og bladenes ca. 1,07 %. Samlet set giver H∞-power-boosting-strategien en beskeden ekstra effekt med kun små træthedspåvirkninger i denne undersøgelse.
A power-boosting controller increases generator torque to temporarily raise a wind turbine’s nominal power by up to 5%, which can increase annual energy production (AEP) by up to 2%. This thesis builds a nonlinear model of the NREL 5 MW reference turbine and linearizes it to design two H-infinity (H∞) robust controllers: a standard controller and a power-boosting version. H∞ control is a method that maintains performance even when the model and operating conditions are uncertain. Parameter uncertainties are added to a linear time-invariant, state-space model, and a switching logic engages the boosting mode at specific wind speeds. Stability, performance, and robustness are evaluated with frequency-domain tools (Bode plots and pole-zero maps). The two H∞ controllers are compared with a gain-scheduled PI baseline. The baseline shows larger variation in pitch angle (the blade angle) but smaller oscillations in generator speed and torque. Between the two H∞ controllers, pitch angle and generator speed are similar, while generator torque differs more clearly, likely because the torque operating points differ from the linearization points. At higher wind speeds, the H∞ controllers show decreasing generator speed and sharply increasing generator torque. Under the defined conditions (wind speeds 15–22 m/s), the H∞ power-boosting controller increases electrical output from 5.0 to 5.25 MW without issues. Fatigue assessment based on damage-equivalent loads computed from the standard deviation of bending moments indicates small impacts: tower fatigue loads rise by about 1.2% and blade fatigue loads by about 1.07%. Overall, the H∞ power-boosting strategy adds modest power with only minor fatigue penalties in this study.
[This abstract was generated with the help of AI]
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