Grid Code Frequency Response Working Group Requirements for

Grid Code Frequency Response Working Group Requirements for System Inertia Antony Johnson, System Technical Performance

Overview ® Summary of Issues / Resume’ ® Additional System Studies ® High Level Proposals ® Further Work

1320 MW Loss – Effect of Inertia and FR Full H – Three Machines selected for FR to achieve 49. 19 Hz (approx 49. 2 Hz) H/2 – Six Machines selected for FR to achieve 49. 19 Hz (approx 49. 2 Hz) F = 49. 19 Hz H/2 – Three Machines selected for FR as in Red Curve

1320 MW Loss – Effect of Inertia and FR H/2 – Six Machines selected for FR to achieve 49. 19 Hz (approx 49. 2 Hz) – Blue H/2 – Three Machines selected for FR as in Red Curve - Green Full H – Three Machines selected for FR to achieve 49. 19 Hz (approx 49. 2 Hz) - Red Frequency Insensitive Plant Frequency Sensitive Plant

Summary of Issues to Date ® To date studies have been based on an energy balance spread sheet and multi-machine study in Power Factory ® In both cases, clear evidence demonstrated that inertia has a significant effect on the rate of change of system frequency and the minimum frequency achieved. ® There is also clear evidence to suggest that higher volumes of fast acting frequency response would be required without any contribution to system inertia. In this last example shown, an additional 3 machines would need to be selected to provide frequency response (Typical figures - £ 15/MWhr Frequency Response + £ 50/MWhr Deload)! ® A clear requirement exists for all Generators to contribute to System Inertia. ® For those Generators which inherently do not contribute towards System Inertia an additional Control System will be required to ensure such a capability can be delivered. ® Based on current wind farm and equivalent power electronic based technology, the Generator Active Power is not affected by changes in the frequency or deviations from nominal frequency ® Based on information published to date and system studies this would need to be achieved by injecting active power into the network for a short time period based upon a df/dt control

Spread Sheet Results – Effect of Inertia – 1800 MW Loss 1 ® The spread sheet used in the early part of the investigations have been re-run to also demonstrate the effect of inertia: ® Key Points ® 25 GW load ® 23. 2 GW of Coal ® 3. 6 GW of Pumped Storage (Response) ® 50% Delivery of Pumped Storage – ie 1. 8 GW ® Generation Loss = 1. 8 GW ® Demand Reduction – 2%/Hz ® Zero Secondary Response Provided – Beyond Study Timescales

Spread Sheet Results – Effect of Inertia – 1800 MW loss 2 H Equivalent (MWs/MVA) ROCOF (Hz/s) Loss (MW) Min Frequency (Hz) Time to Min Frequency (s) 0 0. 67 1800 47. 99 5. 75 1 0. 466 1800 48. 37 6. 6 2 0. 3575 1800 48. 62 7. 1 3 0. 2898 1800 48. 8 7. 6 4 0. 2437 1800 48. 94 7. 85 5 0. 2102 1800 49. 05 8. 1 6 0. 1848 1800 49. 14 8. 3 7 0. 16492 1800 49. 22 8. 5 8 0. 148875 1800 49. 28 8. 7 9 0. 13567 1800 49. 33 8. 7 10 0. 124625 1800 49. 37 8. 8 11 0. 11524 1800 49. 42 8. 9 12 0. 107168 1800 49. 45 8. 9

A summary of the Requirement / Issue 1) Initial Rate of change of frequency limited by stored energy of the rotating mass ( ie the size of the inertia) Frequency (Hz) 2) Primary Response acts within 10 seconds and sustained for a further 20 to contain and start correcting frequency deviation 49. 2 Hz -4 s 0 s ~8 s Time (s) Power (MW) PTemp (5 -10% PNom) Additional power delivered by synchronous machines – area under the curve is the kinetic energy released by the rotating mass Power output of decoupled Wind Generation – Ideally such plant should behave like that of a synchronous plant through a controlled action PNom Primary response delivered by de-loaded machines PDeload -4 s 0 s 2 s 12 s Time (s)

Manufacturer Capability / Requirements ® Based on published information to date, most wind turbine manufacturers have advised that they are capable of providing a controlled short term active power contribution of up to approximately 10% of rated power for a short term period of up to 10 seconds. ® Based on Transmission System need, Non Synchronous decoupled plants (ie those which do not inherently contribute to system inertia) would be required to supply short term Active Power. ® The initial controlled increase in active power output would be dependant upon the initial rate of change of system frequency. This is to prevent excessive injections of active power for only small rates of change of system frequency ® The short term power injection provided will need to be injected on a pro-rata basis depending upon the rate of change of system frequency ® The Control System should be designed to prevent interference with other User’s plant ® Noise issues – Adequate filtering ® Adjustable Deadband – Initial Setting 0. 003 Hz/s ® Operation required only in limited frequency sensitive mode of operation

Deadband

High Level Requirements (1) Power (MW) PIncrease (Max 10% PNom) Time of Machine loss triggered by df/dt (Power injection determined by df/dt) PNom 0 s 10 s Time (s) PIncrease (MW) PIncrease Max ~10 PNom 0. 003 0. 1 df/dt (Hz/s)

High Level Requirements (2) Power (MW) PIncrease (~10% PNom) Time of Machine loss triggered by df/dt (Power injection determined by df/dt) PIncrease (MW) PNom PIncrease Max 10 PNom 0 s 10 s Time (s) Power (MW) PIncrease (~5% PNom) 0. 003 0. 05 0. 1 df/dt (Hz/s) Time of Machine loss triggered by df/dt (Power injection determined by df/dt) PNom 0 s 10 s Time (s)

Study Results (1) – Spread Sheet

Study Results (2) – Spread Sheet – Controlled Inertial Capability of Wind when H = 0

Further Work Required ® Finalise modelling to determine settings based on the minimum needs of the Transmission System ® Maximum value of PIncrease 10% ® Time Duration – 10 seconds ® Exponential decay requirements ® Deadband settings ® Active Power injection during lower rates of change of system frequency ® Additional discussions required with manufacturers ® Legal drafting

References / Further Information ® Contribution of Wind Energy Converters with Inertia Emulation to frequency control and frequency stability in Power Systems – Stephan Wachtel and Alfred Beekmann – Enercon – Presented at the 8 th International Workshop on Large Scale Integration of Wind Power into Power Systems as well as on Offshore Wind Farms, Bremen Germany, 14 – 15 October 2009. ® Variable Speed Wind Turbines Capability for Temporary Over-Production – German Claudio Tarnowski, Philip Carne Kjaer, Poul E Sorensen and Jacob Ostergaard ® Study on Variable Speed Wind Turbine Capability for Frequency Response - German Claudio Tarnowski, Philip Carne Kjaer, Poul E Sorensen and Jacob Ostergaard ® GE Energy – Wind. INERTIATM Control fact sheet – Available on GE Website at : - http: //www. geenergy. com/businesses/ge_wind_energy/en/downloads/GEA 17210. pdf ® Transmission Provider Technical Requirements for the Connection of Power Plants to the Hydro-Quebec Transmission System – February 2006 ® Amendment Report SQSS Review Request GSR 007 Review of Infeed Loss limits – Prepared by the SQSS Review Group for Submission to the Authority – 10 th September 2009 available at: - http: //www. nationalgrid. com/NR/rdonlyres/EF 5 C 0829 -1 C 5 E-4258 -8 F 73 -70 DC 62 C 43 F 49/36936/SQSS 1320 Reportv 10_final. pdf