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 Research Association for Power Systems and Power Economics At a glance 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 1
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, kwh H 2O Netzebene 380/220 kv 110 kv Substitution of Conventional Power Plants Druck Bi-directional Power Flow Increasing trans-european Tradings 20/10 kv CHP 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 V2G Revision of Grid Codes mandatory 0,4 kv 2
Need for System Operators to involve RES Status of the energy supply where renewables have been highly promoted Increasing penetration of RES 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 Postulation of system services is mandatory 3
Current [A] Wirkleistung P [MW] Contemporary Grid Code Requirements for Wind Power Active Power 20 18 16 14 12 10 8 6 4 2 Fault Ride Through (FRT) Grid Code requirements: 1,50 1,00 0,50 0-6 -4-2 0 2 4 6 untererregter Betrieb Blindleistung Q [MVAr] übererregter Betrieb Reactive Anlagenkennlinie am NAP Anforderung nach BDEW MS-RL 2008a Power Harmonics Protection Concepts System perturbation 0,00 2 4 6 8 10 12 14 16 18 20 22 24 Order 4
Law, Grid Codes & Technical Guidelines in Germany Grid codes required by law Renewable Energy Law (EEG) ( 6 Nr. 2; 29, IV, 2; 66, I, Nr.6) Ordinance for System Services (SDLWindV) ( 2, 3, 6, 8) Technical guidelines (FGW) (Measuring (TR3), Validation (TR4), Certification(TR8)) FGW: German Wind Energy association Medium Voltage Directive (MV) Transmission Code (HV) Requirements: Active Power Reactive Power Supply System Voltage Disturbances Protection Concept Behavior during Grid Faults Grid Codes of DSOs/TSOs Objective of Certification: Calculation of wind farms electrical caracteristics at the PCC and test of conformity according to Grid Codes (unit & cluster certification) 5
Classification of Wind Turbines according to SDLWindV Deadlines for fulfillment depending on dates of commissioning 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 Bonus No Bonus 0,7 / kwh 0,5 / kwh 0,7 / kwh 0,7 / kwh Yes, testified per Expertise / Certificate Deadlines - 31.12.2010 31.12.2010** Instantly Instantly Instantly Frequency Control LVRT-Capability Frequency Control LVRT-Capability Dynamic Behavior Voltage Regulation * delayed: 31.03.2011 **delayed: 30.09.2011 6
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 15 GW intermediate turbines (2002-2008) 5 GW transition turbines (2009-2011) 55% 45% 99% 1% potential retrofitted Retrofitting has economically been beneficial for most projects 7
Impact of Retrofitting on Wind Power Industry Effort to meet specific grid code requirements Value Effort Comment Miscellaneous Sonstiges Blockierung der Wiederzuschaltung auf Anforderung Blocking of Reconnection on demand FC1 Durchfahren von Netzfehlern ohne Netztrennung 3 2,5 2 1,5 1 0,5 0 LVRT Remain connected at wide frequency range Verbleiben am Netz bei Netzfrequenzen zwischen 47,5 Hz und 51,5 Hz Power reduction at overfrequency Wirkleistungsreduktio n bei Netzfrequenzen über 50,2 Hz FC2 Vollumrichter 1 DFIG1 DFIG2 Vollumrichter 2 1 small 1,5 small/ medium 2 medium 2,5 medium/ high 3 high Software Update or new parameter setting without any replacement of hardware Replacement of small hardware components (e.g. relay) Existing hardware is modified with additional devices (e.g. chopper design) Many hardware components are changed and substituted Replacement of old devices with new components that changes the design considerably (e.g. generator, converter) 8
General Approach of Wind Farm Certification Unit Unit Model Representing failure behaviour via dynamic Simulation Unit s measurement (field test) FGW-TR3 Representing failure behaviour in Field Test Active Power Control Reactive Power Control System Pertubations Protection Settings etc. Validation (FGW-TR4) = Analysis of Deviations between Unit Model and Field Test Results (P, Q, I b ) Calculation of Wind- Farms Characteristics based on Unit s Data Validated Model Wind farm Grid Data + Dynamical Calculation of Wind Farms Performance at Voltage dips Comprehensive Compliance Test acc. to Grid Code Requirements (FGW-TR8) 9
Calculation methods Dynamic Stability Analysis FRT Field Tests for units Setup developed at FGH Incorporated in Medium Voltage Grid IEC 61400-21 measurement directive Base for unit certification and calculations of the electrical caracteristics of the whole wind farm Current Limiting Reactor WEC X WEC 2 Transformer Variable Reactor controlling the dip s depth S Controlled Circuit Breaker are performed on Wind Farm-level using validated models: X 1 X 3 (Field Tests with the FRT-container of FGH Test Systems GmbH) Wind Farm Cluster: 1 n Units ~ (Source: Zertifizierungsstelle der FGH e.v., Z 310) 10
Calculation methods Dynamic Stability Analysis Mixed wind farm constellations: P.C.C. Prototypes (no models) Units with sym./asym. models Unit new Unit new Unit new Units with sym. models Unit old Unit old Unit old Old units with LVRT-capability (no models) Old (tripping) units (no models) Many different constellations possible: In these cases results of dynamic stability analysis are only approximately resilient! 11
Exemplarily Crucial Grid Code Requirements Dynamic Voltage Support Injection of Additional Reactive Current according to SDLWindV IB In = K Ur Un 0 K 10 K determined by DSO/TSO! Requirements on Dynamics: Response-Time: 30 ms Settling-Time: 60 ms dead band Ud = +/- [0%..10%] Un - 0.5 Back-up of the voltage control (overexcited operation) - 0.3 Required reactive current deviation I B [p.u.] 1.0-1.0 0.3 Limitation of the voltage by voltage control (underexcited operation) 0.5 Voltage drop or increase U [p.u.] Representation in reference variables: Reference voltage is V n Reference current is I n High values of K can lead to critical voltage oscillations K<1 can lead to instabilities ENTSO-E Pilot Network Code 12
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
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
Thank you for your attention! 15