Increase of the Rate of Change of Frequency (RoCoF) and its impact to the Conventional Power Generation in the Island of Ireland

Transcription

1 TCD Increase of the Rate of Change of Frequency (RoCoF) and its impact to the Conventional Power Generation in the Island of Ireland or Transient stability of conventional generating stations during times of high wind penetration on the Island of Ireland September 2015, International Energy Studies Workshop, Rome, Italy Marios Zarifakis, Electricity Supply Board, Dublin, Ireland 2015 ESB, TCD

2 Real Frequency Event, , DBP Power Output Frequency Pnom=390MW Frequency and Power traces 2 tcd.ie esb.ie

3 Contents 1. Introduction of the Irish Grid and ESB 2. Government targets and policies 3. Rate of Change of Frequency (RoCoF) and the Grid Code Definition 4. Mathematical models 5. Impact to generating plant and grid 6. RoCoF impact studies with manufacturers 7. Frequency oscillations 3 tcd.ie esb.ie

4 Contents 1. Introduction of the Irish Grid and ESB 2. Government targets and policies 3. Rate of Change of Frequency (RoCoF) and the Grid Code Definition 4. Mathematical models 5. Impact to generating plant and grid 6. RoCoF impact studies with manufacturers 7. Frequency oscillations 4 tcd.ie esb.ie

5 ESB Electricity Supply Board Vertically Integrated Utility Involved in most types of generation The first ESB generation plant (in 1927) was a hydro station at Ardnacrusha The ESB group is one of the largest wind generators in Ireland, and ESB has been involved in development, construction and management of Irelands wind resources since the 1980s. Large international business. ESB owns a number of international power stations and has O&M contracts for several other generation stations. 5 tcd.ie esb.ie

6 Transmission System Ireland 6 tcd.ie esb.ie

7 European Transmission System 7 tcd.ie esb.ie ROCOF Project Board Meeting

8 Contents 1. Introduction of the Irish Grid and ESB 2. Government targets and policies 3. Rate of Change of Frequency (RoCoF) and the Grid Code Definition 4. Mathematical models 5. Impact to generating plant and grid 6. RoCoF impact studies with manufacturers 7. Frequency oscillations 8 tcd.ie esb.ie

9 Increase of sustainable energy sources EU 2020 Policy 20% of the EU s energy demand to be from renewable sources by 2020 Irish Government Targets 40% of Ireland s total electricity consumption to be met by renewables TSO s DS3 Programme Safe and secure power system with high levels of renewable generation 9 tcd.ie esb.ie

10 Operating Zones 10 tcd.ie esb.ie

11 System and Wind Generation Areas where Wind Generation had to be curtailed 11 tcd.ie esb.ie ROCOF Project Team Meeting

12 Timeline 12 tcd.ie esb.ie

13 Perspectives and Dependencies Security of supply Turbine Integrity EirGrid & SONI Focus Voltage Stability Loading of Lines ESB Generation Focus Mechanical Issues Generator Integrity 13 tcd.ie esb.ie

14 Contents 1. Introduction of the Irish Grid and ESB 2. Government targets and policies 3. Rate of Change of Frequency (RoCoF) and the Grid Code Definition 4. Mathematical models 5. Impact to generating plant and grid 6. RoCoF impact studies with manufacturers 7. Frequency oscillations 14 tcd.ie esb.ie

15 Frequency Scale 50Hz 51Hz 49Hz Generation Consumers 15 tcd.ie esb.ie

16 Frequency (Hz) Generation-Load Balance Sample Low Frequency RoCoF Generation Load Frequency (Hz) Time (s) 16 tcd.ie esb.ie

17 Frequency and the Rate of Change of Frequency RoCoF= df dt Frequency RoCoF 17 tcd.ie esb.ie

18 RoCoF mathematical definition (simplistic view) df dt = f n P 2H system S b With: f n = System Frequency H system = System Inertia Generation 50Hz Consumers P = Lost load or generation S b = MVA rating of the system 18 tcd.ie esb.ie

19 Proposed Definition of RoCoF The new definition by both TSOs, EirGrid and SONI, for the Grid Code is: remain synchronised to the Transmission System for a Rate of Change of Frequency up to and including 1 Hz per second as measured over a rolling 500 millisecond period Mathematical Definition of RoCoF RoCoF AVERAGE = f t RoCoF Instantaneous = df dt 19 tcd.ie esb.ie

20 RoCoF Trace 20 tcd.ie esb.ie

21 Definition of RoCoF (500ms window) RoCoF values at various substations (trip of EWIC) (Eirgrid Study 2012) Maximum RoCoF measurements for different time windows Ardnacrusha (AA), Aghada (AD), Cathaleen s Fall (CF), Louth (LOU), Carrickmines (CKM), Great Island (GI), Ballylumford (BALLY) and Poolbeg (PB) (*1) Problem: Generator sees actual values 21 tcd.ie esb.ie

22 RoCoF Average with Δt = 100ms and Δt = 500ms 22 tcd.ie esb.ie

23 Contents 1. Introduction of the Irish Grid and ESB 2. Government targets and policies 3. Rate of Change of Frequency (RoCoF) and the Grid Code Definition 4. Mathematical models 5. Impact to generating plant and grid 6. RoCoF impact studies with manufacturers 7. Frequency oscillations 23 tcd.ie esb.ie

24 Conventional Swing Equation τ a = τ m τ el = 0 J gen ω m t = τ m τ el with ω m (t) = δ(t) 2H ω 0 δ t 2H ω 0 δ t J gen δ t = τ m τ el Introducing H = + K D ω 0 δ t = 1 2 Jω2 S N τ m τ el And with τ el = k ω 0 B R B S sin δ t 2H ω 0 δ t + K D ω 0 δ t + k ω 0 B R B S sin δ t = + K D ω 0 δ t + kb R B S δ t = τ m τ m 24 tcd.ie esb.ie

25 Negative ROCOF, Steam Turbine 0.25 Hz/s & 4 s 0.5 Hz/s & 2s 1 Hz/s & 1s 2 Hz/s & 0.5s 25 tcd.ie esb.ie

26 Positive ROCOF, Steam Turbine 0.25 Hz/s & 4 s 0.5 Hz/s & 2s 1 Hz/s & 1s 2 Hz/s & 0.5s 26 tcd.ie esb.ie

27 Real Frequency Event, , DBP Power Output Frequency Pnom=390MW Frequency and Power traces 27 tcd.ie esb.ie

28 Magnetic Field in a Synchronous Generator Stable conditions: Tel=Tmech or 0=Tmech - Tel Dynamic conditions: Jα = Tmech-Tel J ω = Tmech-Tel - KDω J ω = Tmech - kbsbrsinδ - KDω 28 tcd.ie esb.ie

29 B R B S No gravity!!! 29 tcd.ie esb.ie

30 Damping depends on speed deviation! Asynchronous effect! Turbine Torque Grid G 1 G 2 Turbine Torque To create the equation of motion using Lagrange 30 tcd.ie esb.ie

31 Swing Equation for light systems K e (q 11) K e q 11 P (q 11) V q 11 Q 11 u d K e (q 12) K e q 12 P (q 12) V q 12 Q 12 u 1q K e (q 13) K e q 13 P (q 13) V q 13 Q 13 τ mgen K e (q 14) K e q 14 P (q 14) V q 14 Q 14 0 d dt + + = = K e (q n1) K e q n1 P (q n1) V q n1 Q n1 u d K e (q n2) K e q n2 P (q n2) V q n2 Q n2 u nq K e (q n3) K e q n3 P (q n3) V q n3 Q n3 τ nmgen K e (q n4) K e q n4 P (q n4) V q n4 Q n tcd.ie esb.ie

32 Model verification Real event Model 32 tcd.ie esb.ie ROCOF Project Board Meeting

33 Frequency trace depends on system inertia 33 tcd.ie esb.ie

34 Contents 1. Introduction of the Irish Grid and ESB 2. Government targets and policies 3. Rate of Change of Frequency (RoCoF) and the Grid Code Definition 4. Mathematical models 5. Impact to generating plant and grid 6. RoCoF impact studies with manufacturers 7. Frequency oscillations 34 tcd.ie esb.ie

35 Swings depend on electromagnetic torque 35 tcd.ie esb.ie

36 Restrictions Updated?! 36 tcd.ie esb.ie

37 Reactive power influences swings (MP1) 305MW 100MW with higher reactive power the damping is stronger 37 tcd.ie esb.ie ROCOF Project Board Meeting

38 Calculations with parameters ± 1Hz/s & 1.2s Operational Point RoCoF, duration 1.) P=305 MW; Q=180Mvar -1Hz/s; 1.2s Remarks The generated active power increases to 540MW. Generator experiences 150% of rated stator current. The stator current limiter in the AVR is triggered. 2.) P=305MW; Q=0Mvar The generated active power increases to 503MW. Generator experiences 140% rated stator current. The stator current limiter in the AVR is triggered. 3.) P=305MW; Q=-120Mvar The generated active power increases to 530MW. The stator current limiter in the AVR is triggered. The reactive power triggers the under-excitation limiter and under-excitation protection. I> protection picks up. 4.) P=100MW; Q=-160Mvar The reactive power triggers the under-excitation limiter and the under-excitation Protection. 1.) P=305 MW; Q=180Mvar +1Hz/s; 1.2s ΔP/Δt is substantial and can lead to trigger the Remote Breaker Opening logic which would close the control valves. 2.) P=305MW; Q=0Mvar ΔP/Δt is substantial and can lead to trigger the Remote Breaker Opening logic which would close the control valves. 3.) P=305MW; Q=-120Mvar ΔP/Δt is substantial and can lead to trigger the Remote Breaker Opening logic which would close the control valves. 4.) P=100MW; Q=-160Mvar ΔP/Δt is substantial and can lead to trigger the Remote Breaker Opening logic which would close the control valves. Reverse Power Pick up (-125MW). Torsional Oscillations become more evident on low loads. 38 tcd.ie esb.ie

39 Shaft line, exact modelling required for all stations Analysis for impact at turbine and generator components Higher RoCoF values might trigger Eigen-Frequencies 39 tcd.ie esb.ie

40 Risks related to mechanical integrity Torsional oscillations can create stresses to: Couplings Rotors and shafts Turbine blades Generator rotor end bells Generator stator end windings 40 tcd.ie esb.ie

41 Impact on lifetime is unknown Life time and maintenance analysis to be undertaken 41 tcd.ie esb.ie

42 Technical Risks Technical Risks Controller & Operational Issues Turbine/Governor Controller AVR/PSS Controllers Protection Systems Turbine Protection Generator & Transformer Protection Mechanical Integrity Turbine Components Generator Components Lifetime Assessments Electrical Integrity Impact of Auxiliary Systems Motors, Fans, Pumps Action Studies to be completed to assess impact Modelling Scenarios Rotor Dynamic Analysis Operational Analysis Internal Modelling work Torsional Probes Matlab/Simulink Model Build Digsilent Study 42 tcd.ie esb.ie

43 Mechanical Integrity Consequences RoCoF Event Reduced Component Life Time Consequential Machine Damage Decreased overhaul intervals and Increased Inspection Requirements Forced Outage 43 tcd.ie esb.ie

44 Operational Consequences ROCOF Event Further loss of Electrical Power Generations Cascade Tripping Event Load Shedding in the system System Brown/Black Out 44 tcd.ie esb.ie

45 Real Event, Poolbeg CT 65 MW 45 tcd.ie esb.ie

46 Contents 1. Introduction of the Irish Grid and ESB 2. Government targets and policies 3. Rate of Change of Frequency (RoCoF) and the Grid Code Definition 4. Mathematical models 5. Impact to generating plant and grid 6. RoCoF impact studies with manufacturers 7. Frequency oscillations 46 tcd.ie esb.ie

47 Study Scope Type MW (Exp) Unit # Studies Required Study Priority CCGT * 1 Peat Coal Gas OCGT Pump Storage Hydro studies to be completed Timeframe for Priority 1 Units 18 months 47 tcd.ie esb.ie

48 Timeline going forward Studies required to demonstrate compliance High priority 18 months - high run hours, frequently constrained on, frequently run during high wind Mid priority 24 months - units not in other categories Low priority 36 months - low run hours, infrequently constrained on, infrequently run during high wind Exempt units units soon to retire, very low runs hours or units which in EirGrid s operational experience have ridden through high RoCoF events in the past ESB will need to be compliant (or derogated/exempted) by these dates to ensure it incurs zero penalties. 48 tcd.ie esb.ie

49 Project Timeline Consultation Period Risk Paper OEM Engagement Understanding & Education Financial Appraisal Regulatory CER ROCOF Paper Consultation Paper Decision Paper KEMA Challenge Study No Cost Recovery Position Procurement Strategy Studies Tender Process Priorities 1 studies Digsilent Study Matlab/Simulink Model Torsional Probe Analysis Quality & Validation Post Studies Level of Compliance Level of Investment Development of individual Business Cases Implementation That s it?? 49 tcd.ie esb.ie

50 Contents 1. Introduction of the Irish Grid and ESB 2. Government targets and policies 3. Rate of Change of Frequency (RoCoF) and the Grid Code Definition 4. Mathematical models 5. Impact to generating plant and grid 6. RoCoF impact studies with manufacturers 7. Frequency oscillations 50 tcd.ie esb.ie

51 Real Event, DBP, C30 in Coolkeeragh Trip at 22:38 DB1 MW; Hz 7 Min Oscillation Pk-Pk: ~ Hz Period of Osc: 15 s (0.066 Hz) 51 tcd.ie esb.ie

52 Typical Turbine Generator control circuit 52 tcd.ie esb.ie

53 Response to a sinusoidal disturbance Output of controllers swing almost in phase with disturbance which amplifies the disturbance Currently installed turbine controllers need major attention. 53 tcd.ie esb.ie

54 Real event in Germany (Rhein-Ruhr Region) 54 tcd.ie esb.ie

55 Questions? Fragen? ErwthseiV; 55 tcd.ie esb.ie

56 Footer Thank You and Grazie

57 Acknowledgements Models used: Matlab from Mathworks with Simulink and SimPowerSystem Literature: Power System Stability and Control, Prabha Kundur Handbook of Electrical Power System Dynamics, M. Eremia, M. Shahidehpour Elektrische Schaltvorgaenge, Reinhold Ruedenberg Various publications by Eirgrid and CER ( and DNV GL Study on ESB Fleet Some animations were used from Dreiphasenwechselstrom Contributions by: Prof. Dr. William T. Coffey, Trinity College Dublin, Ireland 57 tcd.ie esb.ie