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육상풍력발전단지에서의 풍력터빈 후류모델 예측정확성 검토

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Author(s)
전상현
Issued Date
2015
URI
http://dcoll.jejunu.ac.kr/jsp/common/DcLoOrgPer.jsp?sItemId=000000007435
Abstract
A wind turbine is a device that converts kinetic energy from wind into electrical
power. The speed of the wind that penetrates a rotor disk decreases with the
amount of kinetic energy derived from the wind, which is absorbed by the blades. In
addition, the wind kinetic energy at the downwind side of the rotor disk is recovered
by the mixing process with ambient flow. Hence, turbulence intensity increases
during this process. Wake effects, which induce velocity deficit and increased
turbulence intensity, can affect the power performance and dynamic mechanical
loading of the downstream wind turbines.
For this reason, wind turbines installed in a wind farm can be affected by wake
from neighboring wind turbines, which reduces power production and shortens
turbine life due to mechanical fatigue. Therefore, careful consideration of the wake
effects is necessary before establishing an optimum layout design for wind farms.
Until now, various numerical models have been developed and applied to
evaluate the wake effects, but comparison among (and verification of) the
measurement results conducted at numerous wind farms have been few and
insufficient. To verify the prediction accuracy of engineering wake models, namely,
eddy viscosity, Larsen, Jensen, Lange and Frandsen(for predicting the velocity
deficit and wake turbulence) models, which are widely used in wind energy business,
the current study presents the results of the comparative analysis of the values
measured at a commercially operated onshore wind farm.
The prediction accuracies of the four velocity deficit models and two wake
turbulence models widely used in wind-turbine wake assessment was verified under
a single-wake condition, and the following results were obtained:
The Jensen model demonstrated the highest prediction accuracy of the velocity
deficit estimated at the wake center when the free-stream wind speed was 8.5 m/s.
However, when the wind speed exceeded 8.5 m/s, the Larsen and eddy viscosity
models displayed higher prediction accuracy than the Jensen model, but the
difference in the prediction accuracy occurred because of the changes in the
downstream distance. On the other hand, in terms of the form and width of the wake
profile, the eddy viscosity and Larsen models made the most accurate predictions,
and the Jensen model could not replicate the form of the actual wake profile
because of the simplicity of its formulation.
Because the Frandsen model is designed for large offshore wind farms with wind
turbines arranged in a grid pattern, it displayed the largest prediction errors.
Therefore, we conclude that the Frandsen model is not appropriate for predicting the
wake velocity deficit of onshore wind farms, which are not affected much by multiple
wakes. Further, when the yaw angle of the downstream wind turbines was ± ,
these turbines are barely affected by the velocity deficit from the upstream wind
turbines, and barely any loss in the power output was incurred even if half of the
rotors of the rear wind turbines were exposed to the wake effects.
In the results of the prediction accuracies of two wake turbulence models, the
Frandsen turbulence model using an effective turbulence showed tendency to
overestimate the wake turbulence, while the Lange model displayed good prediction
accuracy on turbulence with its profile as well in the downstream wind turbine.
The engineering wake models examined in this study show the differences in the
estimation accuracy according to the downstream distance (corresponding to near
wake, intermediate wake and far wake) and free stream wind speed variation in
onshore wind farm under single wake conditions; hence, a wake model that is
suitable for all conditions could not be presented. Therefore, to obtain reliable wake effect prediction results, careful selection of a wake model adequate for specific
calculation conditions is necessary.
Alternative Title
Comparison and verification of wind turbine wake models in an onshore wind farms
Department
대학원 풍력특성화협동과정
Advisor
허종철
Awarded Date
2016. 2
Table Of Contents
1. 서론 . 1
1.1 연구배경. 1
1.1.1. 풍력터빈의 후류영향 2
1.1.2. 풍력발전단지에서의 후류영향 5
1.2. 연구동향 및 연구목적 . 7
1.2.1. 후류모델 검증을 위한 선행연구 7
1.2.2. 연구목적 . 13
2. 후류모델 15
2.1. 풍속저감예측을 위한 후류모델 15
2.1.1. Jensen 모델 . 15
2.1.2. Eddy viscosity 모델 16
2.1.3. Larsen 모델 18
2.1.4. Frandsen(SAM) 모델 19
2.2. 난류강도예측을 의한 후류모델 21
2.2.1. Quarton(Ainslie) 모델 . 21
2.2.2. Lange 모델 . 22
2.2.3. Frandsen 모델 23
3. 후류모델 검증. 27
3.1. 후류 풍속저감 측정 및 모델 예측값과의 비교 . 27
3.1.1. 성산풍력발전단지 . 27
3.1.2. 풍력터빈 출력데이터 분석 . 30
3.1.3. 풍속저감 예측을 위한 후류모델 정확도 검증 . 34
3.2. 후류 난류강도 측정 및 모델 예측 값과의 비교 . 47
3.2.1. 풍력발전단지에서의 난류강도 측정 . 48
3.2.2. 대표난류강도와 유효난류강도 52
3.2.3. 난류강도 예측을 위한 Frandsen 후류모델 정확도 . 53
3.3. 단일 풍력단지에서의 모델 예측 값과 측정값 비교 . 56
3.3.1. 후류에서의 풍속저감 61
3.3.2. 후류에서의 난류강도 64
3.4. 이웃터빈 후류영영에 위치한 풍력터빈 하중해석 . 69
4. 결론 . 77
참고문헌 . 81
부 록 . 85
Degree
Doctor
Publisher
제주대학교 대학원
Citation
전상현. (2015). 육상풍력발전단지에서의 풍력터빈 후류모델 예측정확성 검토
Type
Dissertation
Appears in Collections:
General Graduate School > Multidisciplinary Graduate School Program for Wind Energy
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