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BS EN IEC 61400-21-1:2019+A11:2020

BS EN IEC 61400-21-1:2019+A11:2020

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Wind energy generation systems – Measurement and assessment of electrical characteristics. Wind turbines

Published By Publication Date Number of Pages
BSI 2020 150
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This part of IEC 61400 includes:

  • definition and specification of the quantities to be determined for characterizing the electrical characteristics of a grid-connected wind turbine;

  • measurement procedures for quantifying the electrical characteristics;

  • procedures for assessing compliance with electrical connection requirements, including estimation of the power quality expected from the wind turbine type when deployed at a specific site.

The measurement procedures are valid for single wind turbines with a three-phase grid connection. The measurement procedures are valid for any size of wind turbine, though this part of IEC 61400 only requires wind turbine types intended for connection to an electricity supply network to be tested and characterized as specified in this part of IEC 61400.

The measured characteristics are valid for the specific configuration and operational mode of the assessed wind turbine product platform. If a measured property is based on control parameters and the behavior of the wind turbine can be changed for this property, it is stated in the test report. Example: Grid protection, where the disconnect level is based on a parameter and the test only verifies the proper functioning of the protection, not the specific level.

The measurement procedures are designed to be as non-site-specific as possible, so that electrical characteristics measured at for example a test site can be considered representative for other sites.

This document is for the testing of wind turbines; all procedures, measurements and tests related to wind power plants are covered by IEC 61400-21-2.

The procedures for assessing electrical characteristics are valid for wind turbines with the connection to the PCC in power systems with stable grid frequency.

NOTE

For the purposes of this document, the following terms for system voltage apply:

  • Low voltage (LV) refers to Un ≤ 1 kV;

  • Medium voltage (MV) refers to 1 kV < Un ≤ 35 kV;

  • High voltage (HV) refers to 35 kV < Un ≤ 220 kV;

  • Extra high voltage (EHV) refers to Un > 220 kV.

PDF Catalog

PDF Pages PDF Title
2 undefined
4 European foreword
5 1 Modification to the title page
2 Modification to the European foreword
7 English
CONTENTS
15 FOREWORD
17 INTRODUCTION
18 1 Scope
2 Normative references
19 3 Terms and definitions
27 Figures
Figure 1 – Example of step response
30 4 Symbols and units
31 5 Abbreviated terms
32 6 Wind turbine specification
7 Test conditions and test systems
7.1 General
7.2 Overview of required test levels
33 7.3 Test validity
Tables
Table 1 – Overview of required test levels
34 7.4 Test conditions
35 7.5 Test equipment
36 Figure 2 – Measurement system description including the most significant components
Table 2 – Specification of requirements for measurement equipment
37 8 Measurement and test of electrical characteristics
8.1 General
8.2 Power quality aspects
8.2.1 General
8.2.2 Flicker during continuous operation
38 Figure 3 – Fictitious grid for simulation of fictitious voltage
40 8.2.3 Flicker and voltage change during switching operations
43 8.2.4 Harmonics, interharmonics and higher frequency components
45 8.3 Steady-state operation
8.3.1 General
8.3.2 Observation of active power against wind speed
46 Figure 4 – Active power as a function of the wind speed (example)
Table 3 – Number of 10-min time-series per wind speed bin
Table 4 – Number of measurements per power bin (10 min average)
47 8.3.3 Maximum power
Figure 5 – Number of measurements in power bins (example)
Figure 6 – Number of measurements in wind speed bins (example)
48 Table 5 – Measured maximum active power values
49 8.3.4 Reactive power characteristic (Q = 0)
8.3.5 Reactive power capability
50 8.3.6 Voltage dependency of PQ diagram
Figure 7 – Example of PQ capability diagram for a given voltage at WT level
51 8.3.7 Unbalance factor
52 8.4 Control performance
8.4.1 General
8.4.2 Active power control
53 Figure 8 – Adjustment of active power reference value
Figure 9 – Example of active power response step
54 Table 6 – Accuracy of the active power control values
Table 7 – Results from the active power reference test
55 8.4.3 Active power ramp rate limitation
56 Figure 10 – Example of available active power and activepower in ramp rate limitation modefigue
Table 8 – Active power ramp rate calculation
57 8.4.4 Frequency control
Figure 11 – Example of an active power control function P=f(f), with the different measurement points and related steps of frequency
58 Table 9 – Example of Settings for the frequency dependent active power function
59 8.4.5 Synthetic inertia
60 8.4.6 Reactive power control
Figure 12 – Synthetic inertia – definitions
61 Figure 13 – Test for static error
62 Figure 14 – Test of dynamic response (example)
63 8.5 Dynamic performance
8.5.1 General
8.5.2 Fault ride-through capability
Table 10 – Test for static error
Table 11 – Test for dynamic response
64 Figure 15 – Example UVRT test equipment
65 Figure 16 – Tolerances of the positive sequence voltage for the undervoltage eventwith disconnected WT under test
66 Figure 17 – Tolerance of positive sequence overvoltage event
67 Figure 18 – Example OVRT capacitor test unit
68 Figure 19 – Example of an undervoltage test chart
Table 12 – Example of undervoltage events
69 Figure 20 – Example of an overvoltage capability curve
70 Table 13 – Example of overvoltage tests
71 8.6 Disconnection from grid
8.6.1 General
8.6.2 Grid protection
72 Table 14 – Grid protection tests
73 Figure 21 – Example of step ramp for overvoltage or frequency testing
74 Figure 22 – Example of pulse ramp for over voltage or frequency testing
Figure 23 – Example of the test levels to determine the release time
75 8.6.3 Test of rate of change of frequency RoCoF (df/dt) protection device
76 8.6.4 Reconnection test
77 Annex A (informative)Reporting
A.1 Overview
A.2 General
Table A.1 – General report information
78 Table A.2 – General data
Table A.3 – Nominal data
Table A.4 – Test conditions
79 A.3 Power quality aspects
Figure A.1 – Voltage flicker Pst vs. active power
Figure A.2 – Flicker coefficient c(30°) vs. active power
Table A.5 – Flicker coefficient per power bin (95th percentile)
80 Figure A.3 – Flicker coefficient c(50°) vs. active power
Figure A.4 – Flicker coefficient c(70°) vs. active power
Figure A.5 – Flicker coefficient c(85°) vs. active power
Table A.6 – Start-up at cut in wind speed
81 Figure A.6 – Time series of 3-phase voltages as RMSof start-up at the wind speed of … m/s
Figure A.7 – Time series of 3-phase currents as RMSof start-up at the wind speed of … m/s
Figure A.8 – Time series of active and reactive powerof start-up at the wind speed of … m/s
Table A.7 – Start-up at nominal active power
82 Figure A.9 – Time series of 3-phase voltages as RMSof start-up at nominal active power
Figure A.10 – Time series of 3-phase currents as RMSof start-up at nominal active power
Figure A.11 – Time series of active and reactive powerof start-up at nominal active power
Table A.8 – Worst-case switching between generators
83 Figure A.12 – Time series of 3-phase voltages as RMSof change from generator stage 1 to stage 2
Figure A.13 – Time series of 3-phase currents as RMSof change from generator stage 1 to stage 2
Figure A.14 – Time series of active and reactive powerof change from generator stage 1 to stage 2
Figure A.15 – Time series of 3-phase voltages as RMSof change from generator stage 2 to stage 1
Figure A.16 – Time series of 3-phase currents as RMSof change from generator stage 2 to stage 1
84 Figure A.17 – Time series of active and reactive powerof change from generator stage 2 to stage 1
Table A.9 – General test information
Table A.10 – 95th percentile of 10-min harmonic magnitudes per power bin
86 Table A.11 – 95th percentile of 10-min harmonic magnitudes per power bin
87 Table A.12 – 95th percentile of 10-min harmonic magnitudes per power bin
88 A.4 Steady-state operation
Figure A.18 – Max. of the 95th percentiles of integerharmonic currents vs. harmonic order
Figure A.19 – Max. of the 95th percentiles ofinterharmonic currents vs. frequency
Figure A.20 – Max. of the 95th percentiles of higherfrequency current components vs. frequency
Table A.13 – Active power against wind speed (see 8.3.2)
89 Figure A.21 – Active power as a function of the wind speed
Table A.14 – Measurement data set
Table A.15 – Maximum active power
90 Figure A.22 – Reactive power vs. active power
Table A.16 – Reactive power characteristic
91 Figure A.23 – PQ-Diagram
Table A.17 – PQ-diagram
92 Figure A.24 – PQ-Diagram
Table A.18 – PQ-diagram at maximum voltage
93 Figure A.25 – PQ-Diagram
Table A.19 – PQ-diagram at minimum voltage
Table A.20 – P-IUFi diagram
94 Figure A.26 – Mean 1-min current unbalance factor over active power
Figure A.27 – Time-series of active power reference values, available power and measured active power output during active power control for the evaluation of the static error
Figure A.28 – Time-series of measured wind speed during active power control during the test of the static error
Table A.21 – General test information
Table A.22 – Static error
95 Figure A.29 – Time-series of active power reference values, available power and measured active power output during active power control for the evaluation of the settling time
Figure A.30 – Time-series of available and measured activepower output during ramp rate limitation
Table A.23 – Dynamic response
Table A.24 – General test information
Table A.25 – Active power ramp rate calculation at start-up
96 Figure A.31 – Time-series of measured wind speed during ramp rate limitation
Figure A.32 – Time-series of available and measured activepower output during ramp rate limitation
Figure A.33 – Time-series of measured wind speed during ramp rate limitation
Table A.26 – General test information
Table A.27 – Active power ramp rate limitation at start-up
97 Figure A.34 – Time-series of available and measured activepower output during ramp rate limitation
Figure A.35 – Time-series of measured wind speed during ramp rate limitation
Table A.28 – General test information
Table A.29 – Active power ramp rate limitation at normal stop
Table A.30 – General test information
98 Figure A.36 – Time-series of available and measured activepower output during ramp rate limitation
Figure A.37 – Time-series of measured wind speed during ramp rate limitation
Table A.31 – Active power ramp rate limitation in normal operation
Table A.32 – General test information
99 Figure A.38 – Time-series of available power, measured active powerand reference value of the grid frequency change
Figure A.39 – Time-series of measured wind speed
Figure A.40 – Measured active power over frequency change
Table A.33 – Test at 0,25 × Pn < P < 0,5 × Pn
100 Figure A.41 – Time-series of available power, measured activepower and reference value of the grid frequency change
Figure A.42 – Time-series of measured wind speed
Figure A.43 – Measured active power over frequency change
Table A.34 – Test at P > 0,8 x Pn
101 Figure A.44 – Test 1, time-series of available power, measured active power and reference value of the grid frequency for 0,25 × Pn < P < 0,5 × Pn
Figure A.45 – Test 1, time-series of wind speed for 0,25 × Pn < P < 0,5 × Pn
Table A.35 – Synthetic inertia results
102 Figure A.46 – Test 2, time-series of available power, measured active power and reference value of the grid frequency for 0,25 × Pn < P < 0,5 × Pn
Figure A.47 – Test 2, time-series of wind speed for 0,25 × Pn < P < 0,5 × Pn
Figure A.48 – Test 3, time-series of available power, measured active power and reference values of the grid frequency for P > 0,8 × Pn
Figure A.49 – Test 3, time-series of wind speed for P > 0,8 × Pn
Figure A.50 – Test 4, time-series of available power, measured active power and reference value of the grid frequency for P > 0,8 × Pn
103 Figure A.51 – Test 4, time-series of wind speed for P > 0,8 × Pn
Figure A.52 – Test 5, time-series of available power, measured active power and reference value of the grid frequency for v > vn
Figure A.53 – Test 5, time-series of wind speed for v > vn
Figure A.54 – Test 6, time-series of available power, measured active power and reference value of the grid frequency for v > vn
Figure A.55 – Test 6, time-series of wind speed for v > vn
104 Figure A.56 – Time-series of reactive power reference values and measured reactive power during the test of reactive power control
Figure A.57 – Time-series of active power during the test of reactive power control
Table A.36 – General test information
Table A.37 – Static error
105 Figure A.58 – Time-series of reactive power reference values and measured reactive power during the test of reactive power dynamic response
Figure A.59 – Time-series of active power during the testof reactive power dynamic response
Table A.38 – Dynamic response
106 A.5 Dynamic performance (see 8.5)
Figure A.60 – Wave shape of 3-phase voltages during entrance of voltage dip/swell when the WT under test is not connected
Table A.39 – Results for tests where the WT is not connected
107 Figure A.61 – Wave shape of 3-phase voltages during clearance of voltage dip/swell when the WT under test is not connected
Figure A.62 – 3-phase voltages as RMS (1 line period) duringthe test when the WT under test is not connected
Figure A.63 – Positive sequence voltage during the test whenthe WT under test is not connected
108 Table A.40 – Results for tests where the WT is connected
109 Figure A.64 – Wave shape of 3-phase voltages during entranceof the voltage dip/swell when the WT under test is connected
Figure A.65 – Wave shape of 3-phase voltages during clearanceof the voltage dip/swell when the WT under test is connected
Figure A.66 – 3-phase voltages as RMS (1 line period) duringthe test when the WT under test is connected
Figure A.67 – Positive and negative sequence fundamental voltage duringthe test when the WT under test is connected
Figure A.68 – 3-phase currents as RMS (1 line period) duringthe test when the WT under test is connected
110 Figure A.69 – Pos. and neg. sequence fundamental current duringthe test when the WT under test is connected
Figure A.70 – Pos. sequence fundamental active power duringthe test when the WT under test is connected.
Figure A.71 – Pos. sequence fundamental reactive power duringthe test when the WT under test is connected
Figure A.72 – Pos. sequence fundamental active current duringthe test when the WT under test is connected
Figure A.73 – Pos. sequence fundamental reactive current duringthe test when the WT under test is connected
111 A.6 Disconnection from grid (see 8.6)
Figure A.74 – Wind speed or available power during the test whenthe WT under test is connected
Table A.41 – Voltage protection
Table A.42 – Frequency protection
Table A.43 – Complete trip circuit test
112 Figure A.75 – Voltage during the reconnection test of 10 s
Figure A.76 – Active power during the reconnection test of 10 s, including the recovery
Table A.44 – RoCoF test results
Table A.45 – RoCoF test information
Table A.46 – Reconnection test results
113 Figure A.77 – Time-series of measured wind speed during the reconnection test of 10 s
Figure A.78 – Voltage during the reconnection test of 60 s
Figure A.79 – Active power during the reconnection test of 60 s, including the recovery
Figure A.80 – Time-series of measured wind speed during the reconnection test of 60 s
Figure A.81 – Voltage during the reconnection test of 600 s
114 Figure A.82 – Active power during the reconnection test of 600 s including the recovery
Figure A.83 – Time-series of measured wind speed during the reconnection test of 600 s
115 Annex B (informative)Voltage fluctuations and flicker
B.1 Continuous operation
B.2 Switching operations
Figure B.1 – Measurement procedure for flicker duringcontinuous operation of the wind turbine
116 B.3 Verification test of the measurement procedure for flicker
B.3.1 General
Figure B.2 – Measurement procedure for voltage changes and flickerduring switching operations of the wind turbine
Table B.1 – Nominal values of the wind turbine usedin the verification tests
117 B.3.2 Fictitious grid performance testing
Table B.2 – Input relative current fluctuation, ΔI/I, for flicker coefficientc((ψk) = 2,00 ( 5 % when Sk,fic = 20·Sn
Table B.3 – Input relative current fluctuation, ΔI/I, for flicker coefficientc((ψk) = 2,00 ( 5 % when Sk,fic = 50·Sn
118 B.3.3 Distorted um(t) voltage with multiple zero crossings
B.3.4 Distorted um(t) voltage with inter-harmonic modulation
Table B.4 – Test specification for distorted voltage with multiple zero crossings
119 B.3.5 Slow frequency changes
B.4 Deduction of definitions
B.4.1 Flicker coefficient
120 B.4.2 Flicker step factor
121 B.4.3 Voltage change factor
122 Annex C (normative)Measurement of active power, reactive power and voltage
C.1 General
C.2 Generator convention of the signs
Figure C.1 – Positive directions of active power, reactive power, instantaneous phase voltages and instantaneous phase currents with generator convention
123 C.3 Calculation of positive, negative and zero sequence quantities
C.3.1 Phasor calculations
Figure C.2 – Examples of the power phasor diagrams of the generator convention in each quadrant with respective instantaneous phase voltage and current
126 C.3.2 Calculation of the positive sequence quantities using phasor components
127 C.3.3 Calculation of the negative sequence quantities using phasor components
128 C.3.4 Calculation of the zero sequence quantities using phasor components
130 Annex D (informative)Harmonic evaluation
D.1 General
D.2 General analysis methods
D.2.1 General
D.2.2 Harmonic voltages
D.2.3 Harmonic phase angles and magnitudes
131 Figure D.1 – Definition of the phase angles of the spectral line in generator convention – (5th harmonic with αI5 = + 120° and αU5 = + 170°shown as an example, thus 5th harmonic phase angle is φ5 = + 170° − 120° = + 50°)
132 Figure D.2 – Comparison of harmonic amplitude aggregation (dotted) no aggregated amplitude directly from DFT with 10-cycle window, (dashed) 10-second aggregation
133 Figure D.3 – Comparison of the prevailing angle ratio (PAR)
134 D.2.4 Statistical analysis
D.2.5 Sample rate adjustment
D.2.6 Determination of background harmonic voltage distortion
D.2.7 Diurnal variations of the harmonic voltage and current
135 D.2.8 Shutting down neighbouring WT or loads
D.2.9 Harmonics of current and voltage over power
136 D.2.10 Filters switching
137 D.2.11 Measuring at a standard source
D.2.12 Harmonics power flow + voltage measurement, phase angle
138 D.2.13 Voltage harmonics with and without operation of the tested wind turbine
Table D.1 – Example of measurements results presentation
139 D.2.14 Measurements at different sites
D.2.15 Harmonic model
D.3 Determination of harmonic amplitude affected by space harmonics at DFAG systems
141 Annex E (informative)Assessment of power quality of wind turbines and wind power plants
E.1 General
E.2 Voltage fluctuations
E.2.1 General
142 E.2.2 Continuous operation
E.2.3 Switching operations
143 E.3 Current harmonics, interharmonics and higher frequency components
144 Table E.1– Specification of exponents in accordance with IEC TR 61000-3-6
145 Annex F (informative)Guidelines for the transferability of test results to different turbine variants in the same product platform
146 Figure F.1 – Block diagram for generic wind turbine (source IEC 61400-27-1)
147 Table F.1– Main components influencing the electrical characteristics of the WT
149 Bibliography

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