Ewec2007 Full Paper

8/3/2019 Ewec2007 Full Paper

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Power Performance Testing and Uncertainty Analysis

for a 1.5MW Wind turbine

Keon-Hoon Kim and Young-Chul Ju

[email protected] [email protected]

Korea Institute of Energy Research

305-343, 71-2 Jang-Dong, Yusong-Gu, Daejon, Rep. of KOREA

(T):+82 42 860 3434, (F):+82 42 860 3543

Abstract

The installed capacity of wind turbines in KOREA are growing and enlarging by the central government's

support program. Thus, the importance of power performance verification and its uncertainty analysis arerecognizing rapidly. This paper described the power testing results of a 1.5MW wind turbine and analysed

an uncertainty level of measurements. The measured power curves are very closely coincide with the

calculated one and the annual power production under the given Rayleigh wind speed distribution are

estimated with the 4.722.0% of uncertainty but, in the dominant wind speed region as 78m/s, the

uncertainty are stably decreased to 78%.

1. Introduction

Nowadays, by the increased respect and enlarged governmental subside, many wind turbines(WTs) are

installing and under operation. Thus, interesting on the power performance testing and its uncertainty

analysis for an operating WTs is also emphasized. But, the field results on the testing and analysis are

partially presented, it is fact that the more experiences and accumulations of technology are still needed. In

addition, the power testing is assured as important thing and the uncertainty analysis of the testing is also

considered as very important one as same as in the many testing fields. But, in Korea, the uncertainty

analysis for power performance testing for a WT is considered as a starting stage.

In this study, the power performance testing and its uncertainty analysis for a 1.5MW WT in Jeju-Do

island are treated, as a results the calculated power curve is compared with the tested one and through the

comparison with two curves the uncertainty of tested power curve is analyzed. That is, an operating

1.5MW WT(NM72C/1500, WTG ID:17799) on the coastal area of Jeju-Do island is a target WT for testing

and the testing period is from June 7th 2004 0:00 to June 30th 2005 23:50 nearly around one year. As

the previous description, the cases on the uncertainty analysis for WT field is seldom in Korea, thus the

meaning of this study is very important. And because we have a national certification system as KOLAS in

Korea, the uncertainty analysis must be considered as one of determined procedures in the testing

procedures for WTs.

2. Specifications of WT

The applied standard and regulations in the field are same as belows..

- IEC 61400-12 Wind Turbine Performance Testing, 1998

- MEASNET Power Performance Measurement Procedure, Version 3 Nov. 2000


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The above standard and procedures are applied and the measurements for the power curve which is the

most important factor for the assesment of the characteristics for WT are accomplished. And with the

pre-determined Rayleigh wind speed distribution, the annual energy production(AEP) of this target WT is

calculated. Finally, the uncertainty through the measurements are strictly estimated and the uncertainty of

AEP is also determined.

2-1 The overall view of the tested WT

In fig. 1, the overall view of the target WT(#3) and 60m height met mast are presented.

Fig. 1. Overall view of tested WT and a met mast

2-2 Technical specifications of the tested WT

The below table 1 shows a technical basic specifications of the tested WT. The tested WT is a

typical Danish type and the manufacturer of it is VESTAS(NEG-MICON) which has a rated capacity of

1.5MW and the power regulation technic as active stall. Thus in the normalization process of captured

data, the measured wind speed data not the measured power data are normalized with the IEC

standard.

3. Status of testing site

3-1 Position of testing site and facilities

The testing site is far away about 60km from Jeju-city, and located on the west-east-west direction fromthe Halla mountain. The next fig. 2 shows the location of testing site(Hankyung) in Jeju-Do island. In

overall view, testing site are faced with the sea from south-west to north-west direction. And the testing

site has a relatively flat terrain so it is not needed to have a site calibration. The below fig. 3 shows the

location of the tested WT, a met mast and the adjacent WTs on the topographical map. The TM

coordination(WGS84) for each WTs and a met mast are presented in tab. 2.

3-2 Topographcal features of the testing site

The topographical features of the testing site are satisfied with IEC61400-12 Annex A(Table A.1 - test

site requirements : topographical variations), thus the supplementary site calibration is not needed. The

distance L between tested WT and met mast is 180.0m and the rotor diameter of tested WT is 72.0m and

the the met mast is located on 330 direction from the tested WT.


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Tab. 1. Technical specifications of tested WT

Wind turbine

manufacturer VESTAS

type NM72C/1500kW

cut-in 4m/s

cut-out 25m/s

Rotor

power control Active Stall

rotor dia. 72m

hub height 62m

RPM 17.3

Blade

type AL35

air brake Full Blade

twist angle 10

Gear Boxtype planet/helical

gear ratio 1:70.2

Generator

rated power 1500kW

no. of poles 6

voiltage 3X600V/60Hz

rated current 1607A

Yawing type Ball bearing

Controller type Com./Thyristers

Tower type Steel Plate

Fig. 2. The location of testing site in Jeju-Do island Fig. 3. Location of tested WT and a met mast

Tab. 2. Local coordination of WTs and a met mast[Datum:TM(WGS84)]

No X(E) Y(N) altitude model

1 122610.9 33370.3 3.6 NM72C-1500

2 122295.0 33139.8 3.6 NM72C-1500

3(WT) 122337.4 32468.0 2.4 NM72C-1500

4 121910.2 32290.6 3.6 NM72C-1500

met mast 122247.4 32623.9 5.0 -

3-3 Undisturbed wind direction

By an IEC61400-12 annex A, the disturbed wind direction related on the tested WT must be considered.

The disturbed wind direction are determined by the relative positions(distance and angle) of no. 3 WT and

a met mast. The disturbed angle which is influenced by the adjacent obstacles and the other WT are same

as eq. 1.

disturbed sector = 2Arctan(2Dn/Ln + 0.25) -------------------------------------------------------- (eq. 1)


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No. X(E) Y(N) Dn angle Ln Ln/Dn

1 122610.9 33370.3 72.0 17 942.8 13.1 44

2 122295.0 33139.8 72.0 356 673.1 9.3 50

3(*) 122337.4 32468.0 72.0 - 0 0 -

4 121910.2 32290.6 72.0 247 462.6 6.4 59

No. X(E) Y(N) Dn angle Ln Ln/Dn

1 122610.9 33370.3 72.0 26 830.2 11.5 46

2 122295.0 33139.8 72.0 5 518.1 7.2 56

3 122337.4 32468.0 72.0 150 180.0 2.5 93

4 121910.2 32290.6 72.0 45 474.1 6.6 58

met mast 122247.4 32623.9 72.0 - 0 0 -

And the following tab. 3 are present the procedure for the calculation of undisturbed wind direction for

the measurement. That is, undisturbed angle at the measurement is determined as 55100 and 280

330.

Tab. 3. Determination of the disturbed and undisturbed angle[Datum:TM(WGS84)],()

4. Testing facilities

4-1 Testing parameters and sensors

In this measurement, all measured parametrs and used sensors is presented in tab. 4 and also thecalibration results and the location of the installed sensors beside the met mast are shown on fig. 4.

4-2 Calibration

The next tab. 5 presents a calibration results on the used sensors.

Tab. 4. Measurement parameters and the type of sensors

Fig. 4. Location of the sensors installed on and beside the met mast


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Tab. 5. Calibration results of sensors

Parameters Gain Unit Offset Unit

Hub height wind speed 0.62293 Hz/(m/s) 0.261 m/s

Reference wind speed 0.62364 Hz/(m/s) 0.255 m/s

Wind direction 1 180 deg

Temperature 0.101 mV/ -40.6

Barometric press. 0.092 mV/ 600 hPa

Precipitation 0.1 count 0 Dig

Power 0.6 mV/ 0 kW

Status signal 1 Dig. 0 Dig

Controller wind speed 0.56665 Hz/(m/s) 0.9274 m/s

5. Analysis of the measured data

5-1 Selection of the measured data

All procedures and methods in measurement are complied with an IEC61400-12 and MEASNETguidelines. All 10min averaged, standard deviation, maximum and minimum data are gathered and the data

are analyzed and selected as effective one with a below limitation.

- testing period : 2004. June 7th 0:00-2005. June 30th 23:50

- wind directition data must be included in the undisturbed sector

- averaging time have to be 600sec(10min averaged)

- STATUS signal must be 1

- WT must be under normal operatin.

- When wind speed is over 5.25m/sec, but power is lower than 30kW, then removed as abnormal data

5-2 Normalization of data[1],[2]All measuring procedures and methods are complied with the IEC61400-12 and MEASNET, the data

normalization for standard air condition[air density 1.225kg/m3, 15(dry air)and 1,013hPa] is accomplished

through belowed description.

All measured data are normalized as standard air density

- air density : determined by the measured atmospheric temperature and barometric pressure

------------------------------------------------------------------------------------------- (eq. 2)

- wind speed normalization by the active stall pitch control type

-------------------------------------------------------------------------------------- (eq. 3)

power curve is determined by the bin of 0.5m/s and the normalized wind speed and averaged power

data are used

- wind speed :

---------------------------------------------------------------------------------- (eq. 4)

- power data :

----------------------------------------------------------------------------------- (eq. 5)

AEP is calculated with the measured power curve and Rayleigh wind speed distribution

- reference wind speed for AEP : annual average wind speed 4, 5, 6, 7, 8, 9, 10, 11m/s


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--------------------------------------------------------- (eq. 6)

- Rayleigh accumulated probability distribution function

------------------------------------------------------------------------------ (eq. 7)

power coefficients are calculated by the measured power curve

- power coefficient :

--------------------------------------------------------------------------- (eq. 8)

5-3 Measured data and results

The measured dataset are sorted with bin-method, all of them satisfies the minimum requirements of the

IEC61400-12. The next fig. 5 shows the all scattered measured data. The measured turbulence intensity are

shown in fig. 6. and in fig. 7, the wind speed data are shown in the undisturbed wind direction sectors.

Fig. 8 also presents a turbulence intensity in the undisturbed sectors.

Fig. 5. Scatter diagram of measured data Fig. 6. Turbulence intensity data with wind speed

6. Measurements and analysis results

6-1 Measured power curve

Fig. 7. Wind speed in the undisturbed sectors Fig. 8. Turbulence intensity in the undisturbed sectors

The power curve which is plotted with the normalized wind speed is same as fig. 9 and the comparision

between the measured data and the calculated one is shown in fig. 10, and they are coincide well without

a big differences.


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-200

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 5 10 15 20 25 30

Wind speed(m/sec)

Power(kW)

Calculated Power Curve Measured Power Curve

6-2 Measured power coefficient curve

The comparison between the power coeffcient curve which are calculated with the normalized wind speed

data at standard air condition and the calculated one is shown fig. 11, then the coincidence is nearly same

with the casr of the power curve and, in the high wind speed region, the agreement of them is raised.

Fig. 9. Power curve with normalized wind speed Fig. 10. The binned power curve with

the normalized wind speed

0.0

0.1

0.2

0.3

0.4

0.5

0 5 10 15 20 25 30

Wind speed(m/sec)

PowerCoefficientCp

Calculated Cp Measured Cp

Fig. 11. The comparison between the measured and the calculated power coefficient

6-3 Uncertainty analysis of the measured power curve

In tab. 6, the A-type, B-type and the combined uncertainty of the measured power data are shown, the

ratio between the measured power curve and the calculated one on bin 7(4.48m/s) is 41.1% at minimum

level but the almost of tested power curve is coincide with the calculated one within 99%101% range. In

addition, the standard uncertainty are combined with A-type and B-type uncertainty and the standard

combined uncertainty has a low value in the low wind speed region, but the more wind speed and the

power can be got, the more uncertainty we can get, and the maximum value reached at the near rated

power as 9.97m/s(1,056.23kW) and 100.1kW. Because the wind turbine reaches to the power control

schemes at just before the rated wind speed, the high uncertainty is related with the big fluctuation of

power on this area[3].[4]. But, after the rated wind speed and the power, the wind turbine can produce the

power stably and the standard combined uncertainty are reduced dramatically by after 12.98m/s which

produce power of around 1,500kW. The A-type, B-type and the combined uncertainty through the wind

speed and the power are shown in the next fig. 12. and fig. 13.

6-4 AEP

Tab. 7 shows the estimated AEP with the measured power curve in this testing, the assumed Rayleigh

wind speed distribution and 100% availability and eq. 6 are used as calculation procedure.


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0

10

20

30

40

50

60

70

80

90

100

110

0 5 10 15 20 25

Wind speed(m/s)

Standarduncertain

ty(kW)

A-type uncertainty B-type uncertainty Combined uncertainty

0

10

20

30

40

50

60

70

80

90

100

110

0 200 400 600 800 1000 1200 1400 1600

Power(kW)

Standarduncertaint

y(kW)

A-type uncertainty B-type uncertainty Combined uncertainty

Fig. 12. The uncertainty analysis through Fig. 13. The uncertainty analysis through

the wind speed the power

Tab. 6. Uncertainty analysis of the measured power curve(standard air condition)

Bin no. Windspeed(m/s) Power(kW) No. of data Cp A-type SU(kW) B-type SU(kW) Combined SU(kW)

3 2.50 -2.85 499 -0.073 0.206 5.850 5.853

4 2.99 -2.54 502 -0.038 0.329 5.775 5.785

5 3.49 -4.60 386 -0.043 0.563 5.849 5.876

6 3.99 -6.65 335 -0.042 0.811 5.858 5.914

7 4.48 16.23 318 0.072 1.253 12.743 12.804

8 4.99 62.01 228 0.200 2.165 23.839 23.937

9 5.48 121.50 197 0.295 2.480 32.656 32.750

10 6.02 192.98 177 0.355 3.374 37.485 37.637

11 6.50 276.44 194 0.404 3.395 50.813 50.926

12 6.99 366.00 133 0.430 4.516 55.417 55.601

13 7.50 470.32 119 0.448 5.186 64.615 64.823

14 8.00 556.73 147 0.436 5.336 56.442 56.694

15 8.47 680.97 131 0.450 6.387 89.737 89.964

16 9.00 794.88 90 0.438 7.223 76.221 76.563

17 9.50 930.46 80 0.436 7.024 99.368 99.616

18 9.97 1056.23 102 0.427 6.406 99.979 100.184

19 10.52 1189.43 74 0.410 7.275 96.781 97.054

20 11.01 1298.11 86 0.390 5.579 90.323 90.496

21 11.50 1369.46 84 0.361 5.609 63.576 63.823

22 12.01 1436.77 65 0.333 5.153 59.915 60.137

23 12.50 1472.83 52 0.303 5.114 37.163 37.513

24 12.98 1500.30 54 0.275 3.144 31.352 31.509

25 13.48 1506.89 54 0.247 2.914 18.594 18.821

26 13.97 1510.05 51 0.222 2.715 17.787 17.993

27 14.49 1511.24 46 0.199 2.957 17.563 17.810

28 15.02 1512.86 40 0.179 2.676 17.610 17.812

29 15.53 1514.72 30 0.162 2.350 17.670 17.826

30 16.02 1509.16 22 0.147 3.069 18.599 18.820

31 16.54 1514.04 15 0.134 3.589 18.323 18.67132 17.02 1514.05 22 0.123 1.135 17.553 17.589

33 17.50 1503.83 24 0.113 3.147 21.528 21.757

34 18.06 1511.12 17 0.103 3.356 19.260 19.550

35 18.50 1514.17 21 0.096 4.154 18.068 18.540

36 19.04 1505.65 12 0.088 2.854 20.244 20.444

37 19.57 1514.63 8 0.081 3.997 20.748 21.130

38 20.04 1516.50 12 0.076 4.087 17.785 18.248

39 20.44 1513.26 11 0.071 4.142 18.373 18.834

40 20.91 1511.63 8 0.066 2.818 17.700 17.923

41 21.54 1516.35 8 0.061 2.237 18.292 18.428

42 22.03 1512.68 8 0.057 2.196 18.325 18.456

43 22.54 1505.20 3 0.053 1.608 20.388 20.452

44 23.05 1508.80 3 0.049 1.819 18.328 18.418

note) SU - standard uncertainty


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Tab. 7. Estimated AEP(standard air condition)

Wind speed(m/s)

Meas. AEP(MWh)

AEP uncertainty(MWh)

AEP uncertainty(%)

Extrap.AEP(MWh)

Suggest. AEP(MWh)

Extrap. AEP/Sug. AEP(%)

4 849 187 22.0 849 904 93.9

5 1859 276 14.8 1859 1910 97.3

6 3071 342 11.1 3071 3106 98.9

7 4306 379 8.8 4307 4321 99.7

8 5440 393 7.2 5447 5446 100.0

9 6401 391 6.1 6425 6424 100.0

10 7151 379 5.3 7205 7224 99.7

11 7679 363 4.7 7775 7835 99.2

7. Conclusion

With a 1.5MW wind turbine in the field, the power performance testing is accomplished and its AEP is

estimated with the given wind conditions. In addition, the uncertainty in the measurement of power curveand the calculation of AEP is analyzed.

In the low wind speed region, the power curve has the high uncertainty relatively, the maximum

uncertainty is reached just before the rated wind speed but, after this region, the power output is stabilized

and the uncertainty is maintained as low level. The uncertainty of power curve has a huge influence on the

AEP and thus the AEP in the low wind speed region also has a high level of uncertainty. That is, in low

wind speed region, the uncertainty of AEP reaches at over 1020% which is so high level. As the result

of this measurements, the uncertainty of AEP will be 22% through 4.7% with the wind speed of 4m/s

through 11m/s. By the consideration of the local annual wind speed of test site at Jeju-Do island, that is,

annual average wind speed of around 78m/s, it has around 78% of uncertainty in the estimation of

AEP.

References

1. IEC 61400-12 Wind Turbine Performance Testing, 1998

2. MEASNET Power Performance Measurement Procedure, Version 3 Nov. 2000

3. K.H.Kim, Power Performance Testin for a 1.5MW in Hankyung at Jeju-Do island, KIER, 2005.

4. Germanischer Lloyd, "testing of wind turbines", 1994.

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Ewec2007 Full Paper