FRT-Testing and Direct TSO-Control of Reactive Power Output of Large Wind Farms

1. FRT-Testing and Direct TSO-Control of Reactive Power Output of Large Wind Farms Peter Van Roy, H. Lemmens, T. Springuel, A. Dabin (Elia)Eckard Quitman (Enercon), Jaap-Jan Ferweda (WindVision)

2. Background • European pilot project “7MW-WEC-by-11” • 11 onshore windturbines, 7MW-class • Estinnes, Belgium • Connected to Elia-grid at 70 kV, during 2009-2010 • Partners: WindVision, Enercon, Sarens, Elia, Eneco, 3E, KUL, TSO-Cyprus, EAC-Cyprus, WIP (coordination) • More details at: www.7MW-WEC-by-11.eu • TSO-involvement • Elia: Belgian TSO, in charge of grids 30 – 380 kV • Compliance testing: FRT, Q-range of full wind farm, Power Quality • Direct control of wind farm by TSO, without 24/7 dispatch @ farm • Support to other partners

3. Requirements from TSO on wind farms • Fault-Ride-Through • Avoid loss of large amounts of power during grid fault • Voltage control • Operated with reactive power setpoints • Frequency control • By modifying active power from wind farm • Necessary for high penetration of wind power • Share of wind power in overall generation increases • Fewer “traditional” power plants to provide ancillary services • May offer extra stream of revenues • Depending on national tariff system

4. Compliance testing (1) – Fault-Ride-Through • Grid code requires FRT with 200 msec @ 0 V • Normally only type-testing on individual turbine • Test in Aurich, Germany, witnessed by Elia • Grid structure at Estinnes allows test on full wind farm • No fault current contribution required, so short interruption is similar to short-circuit regarding wind turbine operation • Isolate wind farm on 150/70 kV transformer • Open/close transformer within 5 seconds • Other nearby customers not impacted by test • Successful test done with 5 turbines operational, end 2009 • Graph showing applied voltage, and P and V on 1 wind turbine

5. Grid structure for test

6. FRT: Grid voltage

7. FRT: Turbine active power and voltage

8. Compliance testing (2) – Reactive power range • Grid code requires absorption and injection • Absorption reactive power: 10% of nominal active power • Injection reactive power : 45% of nominal active power • EU-process of harmonisation, consultation process in Belgium • Full test not always possible in operational grid • Same isolated grid operation allows full test • Initial voltage set by changing tap on 150/70 kV transformer • Limited by safe voltages and tap range of transformer • Lowest achievable reference voltage: 66.6 kV, due to tap limit • Highest safe reference voltage: 76.4kV • Q-injection and absorption tested at various V-levels • Very large Q-range available at all voltages

9. Reactive power range – Fixed transformer tap

10. Reactive power range – High and low voltage

11. Direct TSO control on wind farm • Potential disadvantage of requirements on active and reacive power: need for 24/7 dispatching centre • Not justified for smaller operators • Solution: direct control from TSO/DSO dispatching • Development of direct communication & control system • First application of this type for Elia • Between TSO/DSO dispatching centre and wind farm SCADA • Elia dispatcher enters reactive power setpoint • Wind farm SCADA receives setpoint and automatically distributes over individual turbines • Active power setpoint: only for emergency purposes

12. Conclusion • Innovative component of pilot project co-financed by EC • Development of Grid Code requirements &turbine capabilities • Development of compliance testing procedures • Fault-Ride-Through test on full wind farm • Reactive power range test at wide range of grid voltages • Development of direct communication & control • TSO control avoids need for 24/7 dispatch by farm operators • Essential developments for high penetration of wind power and other renewable energy sources • Further in pilot project: application in island system (Cyprus)