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Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes The German Case – Lessons and Experiences
Dipl.-Wirt.-Ing. Julian Langstädtler / FGH – Certification Office Dipl.-Wirt.-Ing. Frederik Kalverkamp / FGH – Certification Office
TECHWINDGRID 2011 Madrid, Spain, 14 DECEMBER 2011
FGH comprises: FGH Certification: Certification of power generation units (e.g. WTG) and
power generation clusters (e.g. wind farms) Calculation of power generation clusters‘ electrical behaviour Validation of simulation models
FGH Power Equipment Technology: Studies in IEC 61850 Smart Grids‘ primary and secondary Infrastructure
FGH System Studies: Research Projects focused on system stability Exp.: Effects of the shut-down of nuclear
power plants for the German Government
FGH Test Systems: LVRT-Test laboratories (test container)
Scientific Studies in cooperation with German universities and leading manufacturers; participation in national and international working groups (IEC, IEEE, EWEA, FGW, FNN…); global collaboration
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FGH Research Association for Power Systems and Power Economics – At a glance
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
2
Motivation of Modern Grid Codes
Structural Changes in Electric Power Systems
Past Concepts: Power Supply by large & central Plants Mainly directed Power Flow from high to low
voltage levels
Today & in Future: Increasing dispersed Power Generation
Substitution of Conventional Power Plants
Bi-directional Power Flow
Increasing trans-European Tradings
Adaption of Infrastructure (primary and secondary Technologies)
Admission of DER in System Control – Provision of Ancillary Services
Definition of Requirements wrt. the Electrical Characteristics of DER
110 kV
380/220 kV
20/10 kV
0,4 kV
Netzebene
CHP
H2O
V2G
Druck
€, kWh
Revision of Grid Codes mandatory
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
Need for System Operators to involve RES
Status of the energy supply where renewables have been highly promoted
3
Problems of the system operator
Frequency stability Voltage regulation Dynamic operation
• Lacking involvement of RES in balancing power oscillations
• Substitution of conventional power stations with reactive power supply
• Danger of deficit in power supply after fault clearance in case of disconnection
Increasing penetration of RES
Postulation of system services is mandatory
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
0,00
0,50
1,00
1,50
2 4 6 8 10 12 14 16 18 20 22 24
Cu
rren
t [A
]
Order
Harmonics
0
2
4
6
8
10
12
14
16
18
20
-6 -4 -2 0 2 4 6
Wir
kle
istu
ng
P [
MW
]
Blindleistung Q [MVAr]
Anlagenkennlinie am NAP Anforderung nach BDEW MS-RL 2008a
übererregter Betriebuntererregter Betrieb
Contemporary Grid Code Requirements for Wind Power
4
Grid Code requirements:
Active Power
Reactive Power
System perturbation
Protection Concepts
Fault Ride Through (FRT)
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
Requirements: Active Power Reactive Power Supply System Voltage Disturbances Protection Concept Behavior during Grid Faults
Renewable Energy Law (EEG)
(§ 6 Nr. 2; § 29, IV, 2; § 66, I, Nr.6)
Ordinance for System Services (SDLWindV)
(§ 2, 3, 6, 8)
Transmission Code (HV)
Medium Voltage Directive (MV)
Grid Codes of DSOs/TSOs
5
Technical guidelines (FGW) (Measuring (TR3), Validation (TR4),
Certification(TR8))
Grid codes required by law
Objective of Certification: Calculation of wind farms electrical caracteristics at the PCC and test of conformity according to Grid Codes (unit & cluster certification)
FGW: German Wind Energy association
Law, Grid Codes & Technical Guidelines in Germany
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
Classification of Wind Turbines according to SDLWindV
Deadlines for fulfillment depending on dates of commissioning
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Type A Commissioned until 31.12.01
Type B Commissioned between 01.01.02 and 31.12.08
Type C Commissioned between 01.01.09 and 30.06.10*
Type D Commissioned between 01.07.10 and 30.06.11
Type E Commissioned between 01.07.11 and 31.12.13
Type F Commissioned after 01.01.14
SDL Requirements
No Optional – without TC Specificatiion
Optional – without TC Specificatiion
Mandatory – without TC Specificatiion
Mandatory – with TC Specificatiion
Mandatory – with TC Specificatiion
SDL-Bonus if requirement fulfilled and testified
No Yes, testified per Expertise
Yes, testified per Expertise / Certificate
Yes, testified per Expertise / Certificate
Yes, testified per Expertise / Certificate
Yes, testified per Expertise / Certificate
Bonus No Bonus 0,7 ¢ / kWh 0,5 ¢ / kWh 0,7 ¢ / kWh 0,7 ¢ / kWh
Deadlines - 31.12.2010 31.12.2010** Instantly Instantly Instantly
Frequency Control LVRT-Capability
Frequency Control LVRT-Capability Dynamic Behavior Voltage Regulation
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
* delayed: 31.03.2011
**delayed: 30.09.2011
Implementation of Grid Code Requirements
Retrofit activities to improve the system reliability
Fulfillment of system services by upgrading existing turbines depending on their commissioning
Definition of most important requirements for basic performance
FGH has certified more than 2 GW so far
7
45%
55% 99%
1%
15 GW – intermediate turbines (2002-2008)
5 GW – transition turbines (2009-2011)
potential
retrofitted
Retrofitting has economically been beneficial for most projects
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
Impact of Retrofitting on Wind Power Industry
Effort to meet specific grid code requirements
8
0
0,5
1
1,5
2
2,5
3
Durchfahren von Netzfehlern ohne
Netztrennung
Verbleiben am Netz bei Netzfrequenzen
zwischen 47,5 Hz und 51,5 Hz
Wirkleistungsreduktion bei Netzfrequenzen
über 50,2 Hz
Blockierung der Wiederzuschaltung auf Anforderung
Sonstiges
Vollumrichter 1 DFIG1 DFIG2 Vollumrichter 2
Power
reduction at
overfrequency
Blocking of
Reconnection
on demand
Miscellaneous
LVRT
Remain
connected at
wide frequency
range
FC1 FC2 DFIG1 DFIG2
Value Effort Comment
1 small Software Update or new
parameter setting without any replacement of hardware
1,5 small/
medium
Replacement of small hardware components
(e.g. relay)
2 medium
Existing hardware is modified with additional devices (e.g. chopper design)
2,5 medium/
high
Many hardware components are changed and substituted
3 high
Replacement of old devices with new components that
changes the design considerably
(e.g. generator, converter)
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
9
General Approach of Wind Farm Certification
Validation (FGW-TR4) = Analysis of Deviations between Unit Model and Field
Test Results (P, Q, Ib)
Representing failure behaviour via dynamic Simulation
Validated Model
+
Wind farm
Grid Data
Dynamical Calculation of Wind Farms‘ Performance
at Voltage dips
Unit Model Unit‘s measurement (field test) FGW-TR3
Representing failure behaviour in Field Test
Active Power Control Reactive Power Control System Pertubations Protection Settings etc.
Unit
Calculation of Wind-Farms Characteristics based on Unit‘s Data
Comprehensive Compliance Test acc. to Grid Code
Requirements (FGW-TR8)
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
Calculation methods Dynamic Stability Analysis
FRT Field Tests for units…
… are performed on Wind Farm-level using validated models:
10
Medium
Voltage Grid
Current
Limiting
ReactorVariable
Reactor
controlling the dip‘s depth
Controlled
Circuit Breaker
X1
X2
X3
S
WECWEC
Transformer
Medium
Voltage Grid
Current
Limiting
ReactorVariable
Reactor
controlling the dip‘s depth
Controlled
Circuit Breaker
X1
X2
X3
S
WECWEC
Transformer
~ (Source: Zertifizierungsstelle der FGH e.V., Z 310)
(Field Tests with the FRT-container of FGH Test Systems GmbH)
Setup developed at FGH
Incorporated in
IEC 61400-21 measurement directive
Base for unit certification and calculations of the electrical caracteristics of the whole wind farm
Wind Farm Cluster: 1…n Units
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
11
Mixed wind farm constellations:
Many different constellations possible:
In these cases results of dynamic stability analysis are only approximately resilient!
Calculation methods Dynamic Stability Analysis
Unitnew
P.C.C.
Unitold Unitold Unitold Unitnew Unitnew
Prototypes (no models)
Units with sym. models
Units with sym./asym.
models
Old units with LVRT-capability
(no models)
Old (tripping) units (no models)
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
12 12
Required reactive
current deviation ∆IB
[p.u.]
dead band
Ud = +/- [0%..10%] Un
1.0
Limitation of the voltage by voltage
control (underexcited operation)
Voltage drop or
increase ∆U [p.u.] 0.5 0.3 - 0.3 - 0.5
- 1.0
Representation in reference variables:
Reference voltage is Vn
Reference current is In
Back-up of the voltage control
(overexcited operation)
Injection of Additional Reactive Current according to SDLWindV
0 ≤ K ≤ 10
K determined by DSO/TSO !
Requirements on Dynamics:
Response-Time: 30 ms Settling-Time: 60 ms
Exemplarily Crucial Grid Code Requirements Dynamic Voltage Support
= K ∙
∆IB
In
∆Ur
Un
High values of K can lead to critical voltage oscillations
K<1 can lead to instabilities
Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
ENTSO-E Pilot Network Code
Lessons from the German Case
Transition periods have been tight and deadlines had to be postponed several times
Lack of clearly defined requirements
Guidelines for testing and proving of grid code compliance have been developed during the transition periods Modifications and clarifications deferred the certification process
Heterogeneous principles in the assessment of wind farm bahavior (inconsistent evaluation by different certification bodies)
Retrofitting was an enormous effort of whole industry System Operators often do not make usage of all system services provided by
wind power plants (especially in medium voltage level)
Lacking information about turbine‘s behavior (=> confidentiality)
Focus may be more on ancillary services instead of compulsory technical requirements (provide what/where/when it is needed)
13 Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes Langstädtler | FGH – Certification
Conclusions and International Context
Grid Code compliance (certification) needed to ensure System Stability with increasing number of WTG in the future
Differentiation between unit and cluster certification
Validated models are essential for dynamic stability analysis and detailed represenation of wind farm is needed for correct verification of protections
Recommendations for verification of grid code compliance in future Sufficient time for transition periods needed
(for both technical implementation and certification procedures)
Clear definitions in Grid Codes (reference values and measurement points)
Well-defined methods and guidelines for verification and wind farm simulation
Periodical grid gode reviewing necessary to achieve the objectives efficiently
ENTSO-E‘s Pilot Network Code must take these aspects carefully into account
14 Wind Power Grid Integration - Grid Code Requirements & Compliance Schemes
Langstädtler | FGH – Certification