DS2 – Grid Integration Dynamic Modelling of Wind Generation in Ireland

1. DS2 – Grid IntegrationDynamic Modelling of Wind Generation in Ireland Margaret Riordan ESB National Grid, Ireland (email: Margaret.Riordan@EirGrid.com tel: +353-1-7026941 fax: +353-1-6615375) Co Authors – Jane McArdle & Yvonne Coughlan ESB National Grid, Ireland

2. Presentation Overview • Background • Irish Transmission System • Wind Penetration • Dynamic Analysis • ESBNG Work to Date • Dynamic Modelling • Model Features • Model Testing • System Studies • Connection Studies • Next Steps • Summary

3. Presentation Overview • Background • Irish Transmission System • Wind Penetration • Dynamic Analysis • ESBNG Work to Date • Dynamic Modelling • Model Features • Model Testing • System Studies • Connection Studies • Next Steps • Summary

4. Overview of the Irish Transmission System Small Island system • Approximately 200 110kV lines • Approximately 50 220kV lines • 2 400kV lines Present system demand records are: • Peak (Winter) 4,823 MW • Min(Summer) 1,735 MW

5. SCOTLAND 450 MWHVDC IRELAND ENGLAND WALES DC Overview of the Irish System - Interconnection Lightly interconnected to Northern Ireland • Typical North South Interconnector flows ~100MW • Total AC System winter peak ~ 6500MW Northern Ireland has a DC interconnection with UK

6. Wind Generation - Penetration in Ireland 320MW Connecting in 2006 European Union Renewable Directive Target for Ireland is 13.2% of electricity from renewable sources by 2010. This requires about 9% from wind ≈ 1,000 MW installed.

7. Importance of dynamic modelling in power systems • ESBNG is committed to facilitating the continuing growth of wind power while safeguarding system security for all electricity customers • To safeguard system security, dynamic analysis to predict the performance of the system under a wide range of conditions is required • The transient stability and voltage stability of the system are of particular concern

8. Transient Stability – What is it? • During a fault close to a generator, the generator can’t export its power. Therefore it speeds up. • When the fault clears, it should slow down to synchronous speed. • A generator may not re-synchronise with the others if there is a transient stability problem

9. Transient Stability 220 kV fault lasting 100 ms close to a large generator

10. Transient Stability 220 kV fault lasting 150 ms close to a large generator

11. Voltage Stability – What is it? • Ability of the system voltage to recover following a disturbance. • Large induction machines (motors and generators) tend to inhibit voltage recovery. • During the fault, generators accelerate • Once the fault is cleared, they will try to slow down • In slowing down, they take reactive power from the network; this tends to pull the voltage down.

12. Voltage Stability – Voltage Recovers

13. Voltage Stability – Voltage Fails to Recover

14. Presentation Overview • Background • Irish Transmission System • Wind Penetration • Dynamic Analysis • ESBNG Work to Date • Dynamic Modelling • Model Features • Model Testing • System Studies • Connection Studies • Next Steps • Summary

15. Work to Date - Dynamic modelling • Due to the high level of wind generation in Ireland dynamic analysis now must include windfarms, requiring the development of wind turbine models Prior to December 2003 • PSS/E (software package widely used to carry out system analysis worldwide) did not contain any suitable models for wind, either in its libraries or as user written code • After testing the models that had been developed at this time, it was found that they didn’t perform satisfactorily.

16. Work to Date - Dynamic modelling • Requested WTG manufacturers to provide dynamic modelling information • Published a document outlining the need for dynamic models and a brief description of what is required in the models It also included a brief overview of what studies were to be carried out once the models were received • Updated the Grid Code to include a section on Wind Dynamic Modelling Requirements • Obtained and tested numerous models • Ongoing work on Model Validation, Testing, System Studies and Individual Connection Assessments

17. Work to Date – Model Features • Most dynamic models received represent some or most of the following features:

18. WTG Model Testing • 23 WTG models, 7 different manufacturers • Improvements have been made to the models, but work still remains to be done Siemens / Bonus Enercon GE / Enron Gamesa DE Wind Nordex Vestas / Neg Micon

19. Model Testing Process Set up load flow case • Associate dynamic models and parameters with case Compile and link models Initialise simulation Select output channels Check for steady state Apply a disturbance Analyse results Testing and Progress 121 times

20. WTG Model Testing, Typical Issues – Initialisation

21. WTG Model Testing, Typical Issues – Numerical Instability

22. WTG Model Testing - Status Model Status Document • Published on www.EirGrid.com updated regularly

23. System Study - Assumptions • 605 MW Wind Generation included in study • Windfarms included utilise 18 different turbines, due to certain models being unsuitable or unavailable, studies were carried out with 12 different models • Trial study highlighted issues such as: • Sustained Oscillation • Numerical Instability with some of the models, so they were removed and the studies re-run using 5 different models.

24. System Study Issues - Model Oscillations

25. System Study Issues - Numerical Instability

26. System Studies - Update Currently • Suspect models removed, case now contains 5 different models • Compiling Report from Phase I work completed • Preliminary results depict possible voltage Issue Future • Development of scope of work for Phase II

27. System Studies - 200ms close proximity severe 110kV fault 110 kV busbar 90%V Recovery to 90% V 0.1s following fault clearance No Wind Generation

28. 110 kV Busbar 90%V Recovery to 90% V 1.3s following fault clearance Wind Generation System Studies - 200ms close proximity severe 110kV fault

29. Connected Application Offer Accepted 120 days Individual Connection Assessments • Timeline • 320 MW connecting in 2006 Dynamic model suitable for Connection offer process Grid Code compliant model 120 days prior to connection

30. Individual Connection Assessments • All connected windfarms are included in the study • Only problems caused by the connection of the windfarm are associated with it. • Although models currently contain some limitations they are being used for carrying out some initial wind farm connection studies, through use of various workaround techniques • To date there have been no issues

31. Presentation Overview • Background • Irish Transmission System • Wind Penetration • Dynamic Analysis • ESBNG Work to Date • Dynamic Modelling • Model Features • Model Testing • System Studies • Connection Studies • Next Steps • Summary

32. Next Steps – Model Validation • It is important that the behaviour shown by the model under simulated conditions is representative of the behaviour of the real equipment under equivalent conditions • The confidence with which simulated results can be viewed is dependent upon the quality of the validation material provided by the manufacturers • ESBNG plan to engage in further dialogue and consultation with manufacturers, developers and any other relevant stakeholders with a view to adopting a more coordinated and focussed approach to wind turbine model validation.

33. Presentation Overview • Background • Irish Transmission System • Wind Penetration • Dynamic Analysis • ESBNG Work to Date • Dynamic Modelling • Model Features • Model Testing • System Studies • Connection Studies • Next Steps • Summary

34. Summary • ESBNG have Obtained and Tested 23 WTG models, 5 of which are now suitable for the full system studies ESBNG would like to pay tribute to the turbine manufacturers work to date while also highlighting that there is a large amount of work still to be done • ESBNG are running a system study with a number of working models to assess the dynamic impact of high levels of wind generation on the Irish power system Next Step Model Validation

35. Questions Thank you for your attention Further information www.eirgrid.com