Example of Model Validation according to the Spanish ... - DIgSILENT

DIgSILENT GridCode:
Model validation according to the
Spanish Grid Code
DIgSILENT Ibérica
Madrid, 15 February 2012

Model Validation according to the Spanish Grid Code
New version Nr 10 of the Spanish Wind Energy Association document (PVVC_v10) is published in
response to the revision of the Spanish Grid Code (P.O.12.3 and P.O.12.2):
“PROCEDIMIENTOS DE VERIFICACIÓN, VALIDACIÓN Y CERTIFICACIÓN DE
LOS REQUISITOS DEL P.O.12.3 SOBRE LA RESPUESTA DE LAS
INSTALACIONES EÓLICAS Y FOTOVOLTAICAS ANTE HUECOS DE TENSIÓN”
The document can be found at the Spanish Wind Energy Association website:
http://www.aeeolica.org/
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Model Validation according to the Spanish Grid Code
Procedure for model validation PVVC_v10 (WIND TURBINES):
- STEP 1: LVRT Field testing of the wind turbines according to the Spanish Grid Code and measurement procedures
in the PVVC_v10. Measurements can be either performed at the MV or LV side of the wind turbine.
- STEP 2: The dynamic simulation model is built.
- STEP 3: Simulations are executed reproducing the same events (voltage dips) performed during field testing.
- STEP 4: Results obtained from every simulation case are compared against the corresponding field test
measurements.
- STEP 5: The validation method is based on the calculation of the absolute error:
- Where:
- Xmed: Field testing measurement data (in SI)
- Xsim: Dynamic simulation data (in SI)
- Xnom: Rated value of the compared variable (in SI)
- Δx: Absolute Error (in %)
- The model is validated when 85% of the calculated errors are below 10%.
- Two variables are compared: Three phase active power (P), Three phase reactive power (Q)
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Model Validation according to the Spanish Grid Code
Some comments to the method:
- Measurement data at LV side of the Wind Turbine are used for validation purposes. The voltage dip is performed
at MV side.
- The validation window is not specified. The PVVC_v10 document mentions the measurement window during field
testing as:
- 10 seconds prior to the voltage dip � too long for validation purposes, it could have a positive impact on
the validation results (more than 65% of data can be easily validated during steady state prior to the dip!).
One second prior to the voltage dip is adequate to validate the correct initialization of the model, as
proposed in the new draft of the IEC61400-27.
- 5 seconds after the voltage recovery � ok.
- Three phase dips and two phase dips are required in the Spanish Grid Code. Fundamental-frequency positive and
negative sequence of simulation and field data is used for error calculation. The positive and negative sequence is
calculated according to the IEC61400-21 Ed2.
- More variables need to be compared in addition to the active and reactive power of the wind turbine. The
variables proposed in the IEC61400-27 will be evaluated in this example:
- Wind turbine active current (Ip in p.u.)
- Wind turbine reactive current (Iq in p.u.)
- Wind turbine terminal voltage (V in p.u.)
- Wind turbine Reactive power (Q in p.u.)
- Wind turbine Active power (P in p.u.)
- Resampling is used when measured values and simulation values are sampled at different rates.
- A low pass filter with a cut off frequency of 15Hz is included in this analysis, as proposed in the IEC61400-27 (to
compare the same bandwidth simulation-measurements).
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Example of Model Validation according to the Spanish Grid Code
STEP 1: Building the example to test the Spanish Case: DFIG model against FC model
To avoid using field measurements to illustrate the Spanish method, the behavior of the dynamic model of a
Doubly Fed Induction Generator (DFIG) is validated against the dynamic model of a Full Converter (FC) wind
turbine. The following example is built in DIgSILENT PowerFactory 14.1.2 (x86). The project includes two wind
turbine models from the DIgSILENT PowerFactory global library templates:
-1xDFIG, rated 2MW
- DFIG WT transformer 400V/20kV, rated 2.22MVA
- 1xFC, rated 2MW
- FC WT transformer 400V/20kV, rated 2.3 MVA
- The PCC is rated 110kV
- The substation transformer is rated 80MVA, 110/20kV
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Example of Model Validation according to the Spanish Grid Code
STEP 2: Simulation of LVRT events according to the Spanish Grid Code:
RMS simulation - 1kHz time step
Tinit = 0s, Tend = 6.5s, Tdip init = 1s, Tdip end = 1.5s
Filtering RMS results (low pass filter, cut off 15Hz) + Conversion to 50Hz � export signals
Voltage dip location: at the Wind Farm MV terminal, 20kV side
Voltage dip measurements: at the LV side of the wind turbines
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Example of Model Validation according to the Spanish Grid Code
STEP 2: Simulation of LVRT events according to the Spanish Grid Code:
The field and simulation tests are included in the PVVC procedure:
-Voltage dip prefault loading level of the wind turbines:
-Partial load � 10-30%, cos φ � 0.9i- 0.95c
-Full load � >80%, cos φ � 0.9i- 0.95c
-Type of Voltage dip and loading level:
-Category I and II � three phase voltage dips at partial and full load respectively
-Category III and IV � two phase voltage dips at partial and full load respectively
-Voltage depth, duration, tolerances:
- Three phase dips � remaining voltage 20% + 3% Urated, during ≥450ms
- Two phase dips � remaining voltage 60% + 10% Urated, during ≥450ms
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HV
MV
LV_FC
Trf_ST Trf_ST
Trf_FC Trf_FC
AC Voltag..
V ~
FC 2MW
Example of Model Validation according to the Spanish Grid Code
STEP 3: Export required signals from VIs in DIgSILENT PowerFactory:
LV_DFIG
Trf_DFIG Trf_DFIG
G ~
DFIG_2MW
Three phase dip at MV side, 20% remaining voltage, 500ms
Ua(t), Ub(t), Uc(t) � Volts
Ia(t), Ib(t), Ic(t) � Amps
Textfile, white space/tab separated format
VOLTAGE AND CURRENT
MEASUREMENTS
7500.0
4500.0
1500.0
-1500.0
-4500.0
-7500.0
0.0000 1.2999
2.5998
3.8997
5.1996
[s]
Conversion DFIG: UA
Conversion DFIG: UB
Conversion DFIG: UC
Conversion DFIG: IA
Conversion DFIG: IB
Conversion DFIG: IC
Voltage dip 20% - DFIG
6.4995
DIgSILENT
DIgSILENT
7500.0
4500.0
1500.0
-1500.0
-4500.0
-7500.0
0.0000 1.0998
2.1997
3.2995
4.3993
[s]
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Conversion FC: UA
Conversion FC: UB
Conversion FC: UC
Conversion FC: IA
Conversion FC: IB
Conversion FC: IC
Voltage dip 20% - FC
5.4992
DIgSILENT

Example of Model Validation according to the Spanish Grid Code
STEP 4: Analysis with DIgSILENT GridCode � MODEL VALIDATION TOOL
Default window:
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Example of Model Validation according to the Spanish Grid Code
STEP 4: Analysis with DIgSILENT GridCode � MODEL VALIDATION TOOL
STEP 4.1: File Types & Channels Editor � Create File Type to read DIgSILENT PowerFactory
exported results.
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Example of Model Validation according to the Spanish Grid Code
STEP 4: Analysis with DIgSILENT GridCode � MODEL VALIDATION TOOL
STEP 4.1: File Types & Channels Editor
STEP 4.2: Open file 1 and 2 to compare, select file format and base values.
Select file 1
Select file format
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Example of Model Validation according to the Spanish Grid Code
STEP 4: Analysis with DIgSILENT GridCode � MODEL VALIDATION TOOL
STEP 4.1: File Types & Channels Editor
STEP 4.2: Open file 1 and 2 to compare, select file format and base values.
Select
base values
for FC and DFIG
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Example of Model Validation according to the Spanish Grid Code
STEP 4: Analysis with DIgSILENT GridCode � MODEL VALIDATION TOOL
STEP 4.1: File Types & Channels Editor
STEP 4.2: Open file 1 and 2 to compare, select file format and base values.
STEP 4.3: Select Spanish method and variables to compare. Click “Synchronize and Compare”.
Absolute errors
Select variables
to compare
GO!
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Select reference
variable for
synchronization
Example of Model Validation according to the Spanish Grid Code
STEP 4: Analysis with DIgSILENT GridCode � MODEL VALIDATION TOOL
STEP 4.1: File Types & Channels Editor
STEP 4.2: Open file 1 and 2 to compare, select file format and base values.
STEP 4.3: Select Spanish method and variables to compare. Click “Synchronize and Compare”.
STEP 4.4: Manual synchronization series 1 and 2.
Use scroll bars to
synchronize both
data series
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Example of Model Validation according to the Spanish Grid Code
STEP 5: Analysis of results� Summary of results is reported in table format
Variable
Percentile 85
(p.u.)
Error Max
(p.u.)
Error Avg
(p.u.)
volts:abs:pos [pu] 0.000 0.226 0.002
power:real:pos [pu] 0.046 0.407 0.026
power:real:ABC [pu] 0.046 0.247 0.025
power:reactive:pos [pu] 0.005 0.676 0.011
power:reactive:ABC [pu] 0.005 0.615 0.011
amps:real:pos [pu] 0.046 0.736 0.049
amps:reactive:pos [pu] 0.006 1.343 0.025
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Example of Model Validation according to the Spanish Grid Code
STEP 5: Analysis of results� Graphs are reported according to the PVVC_v10
STEP 5.1: Example, three phase active power (power:real:ABC)
BLUE � The reference variable is the FC active power ABC.
BLACK � A tolerance band is added to the reference variable (±10%).
RED � The DFIG active power ABC.
Graphically, the user can check if most of the samples in both data
series fit within the tolerance band.
The plot shows that 85% of compared samples are below the maximum
error level (10%) � validation criteria is fulfilled
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Example of Model Validation according to the Spanish Grid Code
STEP 5: Analysis of results� Graphs are reported according to the PVVC_v10
STEP 5.1: Example, three phase active power (power:real:ABC)
STEP 5.2: Example, three phase reactive power (power:reactive:ABC)
BLUE � The reference variable is the FC reactive power ABC.
BLACK � A tolerance band is added to the reference variable (±10%).
RED � The DFIG reactive power ABC.
Graphically, the user can check if most of the samples in both data
series fit within the tolerance band.
The plot shows that 85% of compared samples are below the maximum
error level (10%) � validation criteria is fulfilled
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Example of Model Validation according to the Spanish Grid Code
STEP 5: Analysis of results� Graphs are reported according to the PVVC_v10
STEP 5.1: Example, three phase active power (power:real:ABC)
STEP 5.2: Example, three phase reactive power (power:reactive:ABC)
STEP 5.3: More variables can be observed:
Fund. Freq. positive sequence active current (Ip+) � Ok Fund. Freq. positive sequence active power (P+) �Ok
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Example of Model Validation according to the Spanish Grid Code
STEP 5: Analysis of results� Graphs are reported according to the PVVC_v10
STEP 5.1: Example, three phase active power (power:real:ABC)
STEP 5.2: Example, three phase reactive power (power:reactive:ABC)
STEP 5.3: More variables can be observed:
Fund. Freq. positive sequence reactive current (Iq+) � Ok Fund. Freq. positive sequence reactive power (Q+) �Ok
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Example of Model Validation according to the Spanish Grid Code
REPORTING
Results are reported in Word format.
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Example of Model Validation according to the Spanish Grid Code
CONCLUSIONS
The Spanish Method as proposed in the PVVC_v10 is verified with DIgSILENT GridCode, comparing
two wind turbine models that separately can fulfill the requirements of the Spanish Grid Code
(P.O.12.3). The following conclusions can be drawn:
- The DIgSILENT GridCode tool is very flexible:
- Different file formats can be configured
- Different data series can be compared
- The user can define the variables of interest � the report automatically will include the
variables selected by the user
- Manual synchronization is a good approach to overlap both series.
- A report is automatically generated in Microsoft Word© format.
- More validation methods are rising worldwide and will be included in next versions:
- German validation method according to TR4
- IEC61400-27 validation method
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DIgSILENT GridCode Contact
Ana Morales/Xavier Robe
DIgSILENT Ibérica S.L.
Ribera del Loira, 46
28042 Madrid – Spain
Phone: +34 911273723/24
Email:
a.morales@digsilent.com
x.robe@digsilent.com
Website:
www.digsilent.com
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