1 Marios Zarifakis, Electricity Supply Board, Dublin, IrelandTCD Transient stability of conventional generating stations during times of high wind penetration on the Island of Ireland Marios Zarifakis, Electricity Supply Board, Dublin, Ireland © 2016 ESB, TCD 1
2 Contents Introduction of the Irish Grid and ESBGovernment targets and policies Rate of Change of Frequency (RoCoF) and the Grid Code Definition Mathematical models Impact to generating plant and grid RoCoF impact studies with manufacturers Frequency oscillations
3 Contents Introduction of the Irish Grid and ESBGovernment targets and policies Rate of Change of Frequency (RoCoF) and the Grid Code Definition Mathematical models Impact to generating plant and grid RoCoF impact studies with manufacturers Frequency oscillations
4 ESB – Electricity Supply BoardVertically 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 European Transmission SystemROCOF Project Board Meeting
6 Contents Introduction of the Irish Grid and ESBGovernment targets and policies Rate of Change of Frequency (RoCoF) and the Grid Code Definition Mathematical models Impact to generating plant and grid RoCoF impact studies with manufacturers Frequency oscillations
7 Increase of sustainable energy sourcesEU 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
8 Perspectives and DependenciesEirGrid & SONI Focus ESB Generation Focus Security of supply Turbine Integrity Increase of Wind Voltage Stability Mechanical Issues Loading of Lines Generator Integrity
9 Contents Introduction of the Irish Grid and ESBGovernment targets and policies Rate of Change of Frequency (RoCoF) and the Grid Code Definition Mathematical models Impact to generating plant and grid RoCoF impact studies with manufacturers Frequency oscillations
10 Frequency Scale 50Hz 49Hz 51Hz Generation Consumers
11 Frequency and the Rate of Change of FrequencyRoCoF= 𝑑𝑓 𝑑𝑡 Frequency RoCoF
12 RoCoF mathematical definition (simplistic view)𝒅𝒇 𝒅𝒕 = 𝒇 𝒏 𝑷 𝟐 𝑯 𝒔𝒚𝒔𝒕𝒆𝒎 𝑺 𝒃 With: 𝑓 𝑛 = System Frequency 𝐻 𝑠𝑦𝑠𝑡𝑒𝑚 = System Inertia 𝑃 = Lost load or generation 𝑆 𝑏 = MVA rating of the system Generation 50Hz Consumers
13 Proposed Definition of RoCoFThe 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 𝑹𝒐𝑪𝒐𝑭𝑨𝑽𝑬𝑹𝑨𝑮𝑬= ∆𝒇 ∆𝒕 𝑹𝒐𝑪𝒐𝑭𝑰𝒏𝒔𝒕𝒂𝒏𝒕𝒂𝒏𝒆𝒐𝒖𝒔= 𝒅𝒇 𝒅𝒕
14 RoCoF Trace
15 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…
16 RoCoFAverage with Δt = 100ms and Δt = 500ms
17 Contents Introduction of the Irish Grid and ESBGovernment targets and policies Rate of Change of Frequency (RoCoF) and the Grid Code Definition Mathematical models Impact to generating plant and grid RoCoF impact studies with manufacturers Frequency oscillations
18 Conventional Swing Equation𝜏 𝑎 = 𝜏 𝑚 − 𝜏 𝑒𝑙 =0 𝐽 𝑔𝑒𝑛 𝜔 𝑚 𝑡 = 𝜏 𝑚 − 𝜏 𝑒𝑙 with 𝜔 𝑚 (𝑡)= 𝛿 (𝑡) 𝐽 𝑔𝑒𝑛 𝛿 𝑡 = 𝜏 𝑚 – 𝜏 𝑒𝑙 Introducing 𝐻= 1 2 𝐽 𝜔 2 𝑆 𝑁 2𝐻 𝜔 0 𝛿 𝑡 + 𝐾 𝐷 𝜔 0 𝛿 𝑡 = 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 = 𝜏 𝑚 2𝐻 𝜔 0 𝛿 𝑡 + 𝐾 𝐷 𝜔 0 𝛿 𝑡 +𝑘 𝐵 𝑅 𝐵 𝑆 𝛿 𝑡 = 𝜏 𝑚
19 Negative ROCOF, Steam Turbine0.25 Hz/s & 4 s 0.5 Hz/s & 2s 1 Hz/s & 1s 2 Hz/s & 0.5s
20 Positive ROCOF, Steam Turbine0.25 Hz/s & 4 s 0.5 Hz/s & 2s 1 Hz/s & 1s 2 Hz/s & 0.5s
21 Real Frequency Event, 27.04.2014, DBPPower Output Frequency Pnom=390MW Frequency and Power traces
22 Magnetic Field in a Synchronous GeneratorStable conditions: Tel=Tmech or 0=Tmech - Tel Dynamic conditions: J𝛼= Tmech-Tel J 𝜔 = Tmech-Tel - KD𝜔 J 𝜔 = Tmech - kBSBRsin𝛿 - KD𝜔
23 BR BS No gravity!!!
24 Damping depends on speed deviation! Asynchronous effect!Turbine Torque Grid Turbine Torque G1 Sum of all loads (Torque) G2 Electromagnetic Torque In the air gap of the generator To create the equation of motion using Lagrange
25 Swing Equation for light systems
26
27 Model verification Real event Model ROCOF Project Board Meeting
28 Frequency trace depends on system inertia
29 Contents Introduction of the Irish Grid and ESBGovernment targets and policies Rate of Change of Frequency (RoCoF) and the Grid Code Definition Mathematical models Impact to generating plant and grid RoCoF impact studies with manufacturers Frequency oscillations
30 Swings depend on electromagnetic torque
31 SN Curve
32 Calculations with parameters ± 1Hz/s & 1.2sOperational Point RoCoF, duration Remarks 1.) P=305 MW; Q=180Mvar -1Hz/s; 1.2s 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. +1Hz/s; 1.2s ΔP/Δt is substantial and can lead to trigger the “Remote Breaker Opening” logic which would close the control valves. 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.
33 Shaft line, exact modelling required for all stationsAnalysis for impact at turbine and generator components Torsional oscillations can create stresses to: Couplings Rotors and shafts Turbine blades and roots Generator rotor end bells
34 Risks related to mechanical integrityTorsional oscillations can create stresses to: Couplings Rotors and shafts Turbine blades Generator rotor end bells Generator stator end windings
35 Technical Risks Action Technical Risks Controller & Operational IssuesTurbine/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
36 Mechanical Integrity ConsequencesRoCoF Event Reduced Component Life Time Consequential Machine Damage Decreased overhaul intervals and Increased Inspection Requirements Forced Outage
37 Operational ConsequencesROCOF Event Further loss of Electrical Power Generations Cascade Tripping Event Load Shedding in the system System Brown/Black Out
38 Contents Introduction of the Irish Grid and ESBGovernment targets and policies Rate of Change of Frequency (RoCoF) and the Grid Code Definition Mathematical models Impact to generating plant and grid RoCoF impact studies with manufacturers Frequency oscillations
39 Frequency Traces
40 Frequency traces
41 Frequency traces
42 Study Scope
43 RoCoF 2Hz/s (Northern Ireland)Max and Min Load Leading Comparison. In both cases the allowed Stress is possibly exceeded
44 Impact on lifetime is unknownLife time and maintenance analysis to be undertaken
45 Project Timeline That’s it?? 2010 – 2012 Consultation PeriodRisk Paper OEM Engagement Understanding & Education Financial Appraisal Regulatory 2013 – 2014 CER ROCOF Paper Consultation Paper Decision Paper KEMA Challenge Study No Cost Recovery Position Procurement Strategy 2014 – 2016 Studies Tender Process Priorities 1 studies Digsilent Study Matlab/Simulink Model Torsional Probe Analysis Quality & Validation 2016 – 2018 Post Studies Level of Compliance Level of Investment Development of individual Business Cases Implementation That’s it??
46 Contents Introduction of the Irish Grid and ESBGovernment targets and policies Rate of Change of Frequency (RoCoF) and the Grid Code Definition Mathematical models Impact to generating plant and grid RoCoF impact studies with manufacturers Frequency oscillations
47 Real Event, DBP, 26.12.2014 C30 in Coolkeeragh Trip at 22:38DB1 MW; Hz 7 Min Oscillation Pk-Pk: ~0.3 – 0.4 Hz Period of Osc: 15 s (0.066 Hz)
48 Typical Turbine Generator control circuit
49 Questions? Fragen? ErwthseiV;
50 Thank You and Vielen DankFooter
51 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 (www.eirgrid.com and DNV GL Study on ESB Fleet Some animations were used from Dreiphasenwechselstrom Contributions by: Stephen Carrig, ESB GWM Manager C&I Prof. Dr. William T. Coffey, Trinity College Dublin,