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windtest grevenbroich gmbh. Power performance measurement techniques 功率特性 测量技术. Wang,Qi. Table of contents. Introduction . Physics of the wind. Instrumentation. How it works. Measurements and measurement procedures. Evaluation of the power performance. Small wind turbines.

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Windtest grevenbroich gmbh

windtest grevenbroich gmbh

Power performance measurementtechniques 功率特性测量技术

Wang,Qi


Table of contents
Table of contents

  • Introduction.

  • Physics of the wind.

  • Instrumentation.

  • How it works.

  • Measurements and measurement procedures.

  • Evaluation of the power performance.

  • Small wind turbines.


Introduction
Introduction

  • The acoustic noise measurement technique is based on the IEC 61400-12-1.

  • The purpose is to ensure consistency, reproducibility and accuracy in measurement and analysis of power performance by wind turbine generator system.

  • The standard provides guidance in the measurement, analysis and reporting of power performance testing.

  • The key element of power performance testing is the measurement of wind speed.


Introduction1
Introduction

  • Procedural overview.


Power of the wind
Power of the wind

Volume

Density

Mass

Energy

Power

MassFlow


Extracted mechanical power p mech
Extracted mechanical power Pmech

Constant mass flow

Maximum:


Power coefficient c p
Power coefficient cp


Maximum power coefficient c p
Maximum power coefficient cp

Maximum

Betz factor


Summary
Summary

Power of the wind

Extracted mechanical Power

Betz Factor

Tip Speed Ratio




Instruments
Instruments

  • Electric power.

    • Power transducer: shallfulfill IEC 60688 Class 0.5 or better.

    • Not a power transducer: the accuracy should be equivalent to Class 0.5 power transducers.

    • The full-scale range of measurement device should be set to -50% to +200% of the rated power.

  • Anemometers.

    • Should use the class better than 1.7A.

    • Should use the class better than 2.5B or 1.7S if site calibration requiring.

    • The difference between the regression lines of calibration and recalibration shall be within ±0.1 m/s in the range 6 m/s to 12 m/s.

    • The cup anemometer shall be mounted at hub height of ±2.5%.


Instruments1
Instruments

  • Wind direction transducer.

    • The combined calibration, operation, and orientation uncertainty shall be less than 5°.

  • Air density.

    • Shall be derived from the measurement of air temperature and pressure.

    • At high temperature, it is recommended also that relative humidity be measured and corrected for.

    • Thermometer.

      • Shall be mounted within 10 meter of hub height.

    • Hygrometer.

    • Barometer.

      • Shall be corrected to the hub height according to ISO 2533.


Instruments2
Instruments

  • Rotational speed and pitch angle.

    • If specific need, i.e. measurements connection with acoustic noise tests.

  • Blade condition.

    • Particularly for stall regulated turbines.

    • Precipitation, icing and bug etc.

  • Data acquisition system (DAS).

    • Sampling rate per channel of at least 1Hz shall be used.


How it works

Frequency

Wind Speed

Shaft Rotation

Electrical transducer

Cup

How it works

  • Wind speed measurement.

    • The shaft of an anemometer is coupled to an electrical transducer which produces an electrical output signal, typically a DC voltage proportional to shaft rotation rate and therefore to wind speed.

  • The wind speed can be calculated from the frequency in online-famos using equation:

VW : Wind speed

a0 : The regression coefficient [m/s]a : The regression coefficient [m/s/Hz].f: Frequency


How it works1
How it works

  • Wind speed measurement.

Pulse signal transformation


How it works2

2K Ohm

Wind vane direction

Potentiometer

How it works

  • Wind direction measurement.

    • When the wind blows past the vane, the change of wind direction is measured by the sensor as the aerodynamics of the counter-weight and the tail try to keep aligned to the path of the wind. The motion of the wind vane is translated to the potentiometer shaft causing a change in the potentiometer's resistance, as a change in voltage.


How it works3
How it works

  • Temperature measurement.

    • PT100 is a temperature-dependent resistance. It has 100 ohms with 0°C , the temperature coefficient amounts to depending upon platinum material +0.385 ohm/ °C. The voltage drop at the platinum sensor rise with increasing temperature and concomitantly the difference at the instrument amplifier.

  • Humidity measurement.

    • The capacitive sensors sense water by applying an AC signal between two plates and measuring the change in capacitance caused by the amount of water present. The resistive sensors use a polymer membrane which changes conductivity according to absorbed water.


How it works4

Meteorological box

How it works

  • Temperature and humidity measurement.

  • Pressure measurement.

    • PTB100 barometers feature the silicon capacitive absolute pressure sensor. The sensor have 0-5 VDC output and 800-1060 mbar pressure range.

    • The barometric pressure can be calculated from the measured output voltage using a simple equation:


Measurements and measurement procedures
Measurements and measurement procedures

  • Location of the meteorological mast and measurement sector.

    • Shall be positioned at a distance from the wind turbine of between 2D and 4D of the wind turbine, 2.5D is recommended.

Distance of the meteorological mast and maximum allowed measurement sectors


Measurements and measurement procedures1
Measurements and measurement procedures

  • Assessment of terrain at the test site.

    • If the terrain complies with the requirements of Table B.1, then no site calibration is required.

    • If wind speed different between the anemometer position and the turbine’s hub less than 1% at 10 m/s for the measurement sectors, then no site calibration is required.

Table B.1 Test site requirements: topographical variations


Measurements and measurement procedures2
Measurements and measurement procedures

  • Measurement procedure.

    • General

      • The measurement procedure shall be documented, as detailed in Clause 9.

      • Accuracy of the measurements shall be expressed as described in Annex D.

      • During the measurement period, data should be periodically checked, and the test logs shall be maintained to document all important events.

    • Wind turbine operation.

      • Shall be in normal operation and the machine configuration may not be changed.

      • Any special maintenance actions during the test shall be noted.


Measurements and measurement procedures3
Measurements and measurement procedures

  • Measurement procedure.

    • Data collection.

      • Selected data sets shall be base on 10-min periods derived from contiguous measured data.

      • Data shall be collected continuously at a sampling rate of 1 Hz or higher.

      • Air temperature, pressure, wind turbine status and precipitation may be sampled at a slower rate, but at least once per minute.

      • The data shall store either sampled data or statistics of data sets as:

        • Mean value.

        • Standard deviation.

        • Maximum value.

        • Minimum value.


Measurements and measurement procedures4
Measurements and measurement procedures

  • Measurement procedure.

    • Data rejection.

      • To ensure that only data obtained during normal operation are used in analysis and data are not corrupted. Data sets shall be excluded following circumstances:

        • Wind speed are out of the operating range;

        • Turbine fault, manually shutdown, in test or maintenance operating mode;

        • Failure or degradation of test equipment;

        • Wind directions outside valid sectors.

      • To ensure that only data obtained during normal operation are used in analysis and data are not corrupted. Data sets shall be excluded following circumstances:

        • Wind speed are out of the operating range;

        • Turbine fault, manually shutdown, in test or maintenance operating mode;

        • Failure or degradation of test equipment;

        • Wind directions outside valid sectors.

      • Two data sets shall be presented because the effect of hysteresis. One shall include all data points (Database A), the other shall exclude the turbine has stopped generating power due to cut-out at high wind speed (Database B).


Measurements and measurement procedures5
Measurements and measurement procedures

  • Measurement procedure.

    • Data correction.

      • Wind speed shall be corrected for flow distortion from site calibration.

      • Air pressure shall be corrected if measured at 10 meter difference that closed to hub height.

    • Database.

      • Filtered database shall include a minimum of 180 h of sampled data.

      • Each bin shall include a minimum of 30 min of sampled data.

      • The selected data sets shall at least cover a wind speed range extending from 1 m/s below cut-in to 1,5 times the wind speed at 85% of the rated power of the wind turbine.

      • Alternatively, the wind speed range shall extend from 1m/s below cut-in to a wind speed at which "AEP-measured" is greater than or equal to 95% of "AEP-extrapolated"


Evaluation of the power performance
Evaluation of the power performance.

  • AEP (annual energy production).

    • AEP is estimated by applying the measured power curve to different reference wind speed frequency distributions.

    • AEP shall be made for hub height annual average wind speed of 4, 5, 6, 7, 8, 9, 10 and 11 m/s according to :

and

Nh: number of hours in one year ≈8760N: number of binsVi : normalized and averaged wind speed in bin i

Pi:normalized and averaged power output in bin i

Vave: annual average wind speed at hub height

V: wind speed

F(V): the Rayleigh cumulative probability distribution function for wind speed


Evaluation of the power performance1
Evaluation of the power performance.

  • AEP (annual energy production).

AEP calculation


Evaluation of the power performance2
Evaluation of the power performance.

  • Measured power curve.

    • Determined by “method of bins” for the normalized dataset.

    • Using 0.5 m/s bins and calculation of the mean values of wind speed and power output for each bin according to:

and

Vi : normalized and averaged wind speed in bin i

Vn,i,j : normalized wind speed of dataset j in bin i

Pi:normalized and averaged power output in bin i

Pn,i,j : normalized power output of dataset j in bin i

Ni: number of 10 min datasets in bin i


Evaluation of the power performance3
Evaluation of the power performance.

  • Power coefficient

    • Ratio of the net electric power output of a wind turbine to the available power in the free stream wind over the rotor swept area.

    • Shall be determined from the measured power curve according to:

and

0 : reference air density (1.225 kg/m³)

A : swept area of the wind turbine rotor

Pi:normalized and averaged power output in bin i

Vi : normalized and averaged wind speed in bin i

CP,i: Power coefficient in bin i


Evaluation of the power performance4
Evaluation of the power performance.

  • Power coefficient

Power coefficient CP


Evaluation of the power performance5
Evaluation of the power performance.

  • AEP and power curve.

AEP and power curve measured and extrapolated


Evaluation of the power performance6
Evaluation of the power performance.

  • Measured power curve and corrected to sea level.

Measured power curve and corrected to sea level 1.225 kg/m³


Evaluation of the power performance7
Evaluation of the power performance.

  • Measured power curve and corrected to sea level.

Measured power curve and corrected to sea level


Small wind turbines
Small wind turbines

  • Small wind turbines require special provisions.

    • When battery charging performance, the wind turbine generator system shall include the turbine, tower, controller (may incl. dump load), and wiring between the turbine and the load.

    • When system output to a grid, shall be noted above if the charge controller and dump load are used.

    • The wind turbine shall be connected to an electrical load that is representative of the load for which the turbine is designed.

    • If no specific mounting system, the generator should be mounted at a hub height of at least 10 meter.

    • The connection to the load shall be no closer than the base of the turbine tower and no farther than three times the tower height.


Small wind turbines1
Small wind turbines

  • Small wind turbines require special provisions.

    • If more practical to mount the anemometer to the tower, a separate meteorological mast is not required, but all such components shall be located at least 3 meter away from any part of the rotor.

    • The air temperature and pressure sensor shall be mounted at least 1.5 rotor diameter below hub height even if such mounting results less than 10 meter above ground level.

    • All subsequent references to 10-min datasets in the standard shall apply to 1-min datasets, and the datasets has met the following criteria:

      • Each wind speed bin between 1 m/s below cut-in and 14 m/s shall contain a minimum of 10 min of sampled data.

      • The total database contain at least 60 hours of data within the wind speed range.

      • In the case of furling turbines, the database should include completed wind speed bins characterizing performance when the turbine is furled.


Small wind turbines2
Small wind turbines

  • Small wind turbines require special provisions.

    • In cases the turbine does not shut down in high winds, AEP measured and AEP projected shall be calculated as though cut-out wind speed were the highest, filled wind speed bin or 25 m/s, whichever is greater.

    • It is recommended that additional performance data be obtained to quantify the effect that changes of battery bank voltage have on turbine performance. These additional power curves should be obtained by setting the battery bank voltage to the optional low and high settings, and at least 30 h of data using 1-min pre-averaging.

Battery bank voltage settings