3 wind and solar plant performance

Power Systems & Energy Course: Wind and Solar Plant Performance Jason MacDowell Advanced Higher functionality is required for: a) Bigger farms b) Weaker systems c) Grids with higher wind penetration Basic Performance Requirements Grid Requirements Evolution Protection Volt/VAR Control LVRT Primary Frequency Fast Frequency Response Response Application Characteristics Single WTGs Low Penetration Large Farms Multiple Farms High Penetration © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 2/ Load & Wind Measurements July 17, 2006 30,000 200 Load Wind 25,000 150 15,000 100 MW Wind MW Load 20,000 Feeder circuit trips 10,000 50 5,000 00:01:00 04:01:00 08:01:00 12:01:00 16:01:00 20:01:00 Time © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 3/ Interconnection Issues – Dynamic Performance • Voltage Regulation • Dynamic voltage response • Flicker • Fault Tolerance/Low-Voltage Ride-Through • Stability • Maintaining Synchronism • Damping • Voltage Stability • Active Power Control • Frequency Regulation • Intertie Flow Regulation • Unit commitment © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 4/ Grid Friendly Wind Power Plant © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 5/ Wind Turbines and Reactive Power Control Reactive Power…Voltage control Current leads voltage or “overexcited” Lightly Loaded Overhead Lines VIDEO System Load Voltage Cable Circuits Generators Capacitive Compensators Flow from Other Areas Generators Consumer Loads The Reactive Power Tank Transformers Inductive Compensation Heavily Loaded Overhead Lines The Sources and Sinks of Reactive Power The Reactive Power Balance must be struck on a local basis Courtesy of National Grid Co, UK Flow to Other Areas Current lags voltage or “underexcited” Reactive/Voltage Requirement Variations • Fixed power factor Q P • Power factor range (permissive) Q Permissive Range P • Dispatched reactive or pf, within pf range Q • Voltage regulation, within pf range – May regulate local or remote bus © 2016 General Electric International, Inc All rights reserved Not for distribution without permission Required Range P 8/ GE 1.5 MW Reactive Capability • • • • Full leading and lagging range over full power range Faster reactive response than synch generator Capability of reactive compensation with no wind No need for FACTS devices © 2016 General Electric International, Inc All rights reserved Not for distribution without permission WTG Reactive Power Capability Reactive Power for Voltage Support • • • • Steady-state PF range - 0.90 under-excited/0.90 over-excited Dynamic range meets or exceeds steady-state range WTG reactive capability often sufficient to satisfy PF requirements at POI VAR capability reduced at low power due to units cycling off-line Rating Point Terminal Bus P gen WTG Active Power Q gen © 2016 General Electric International, Inc All rights reserved Not for distribution without permission Simulations: 1800 1500 Power (kW) 1200 900 600 300 m/s Avg Meas 10 m/s Avg Meas 14 m/s Avg Meas m/s PSLF 10 m/s PSLF 14 m/s PSLF 0 10 20 30 40 50 60 70 80 90 Time (Seconds) WindINERTIA simulations capture key aspects of observed field performance © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 72 / Summary & Conclusions • Need and demand for inertial response from WTGs has been growing • GE now offers a new, grid friendly feature to meet this need • The feature has been field tested; a dynamic model has been created • Fundamental physical differences in WTGs mean that inertial behavior is not identical to synchronous machines • Future grid codes may require inertial response; they must recognize physical reality & constraints WindINERTIATM - another aid to the continued successful large scale integration of wind power © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 73 / Interconnection of Renewable Plants to Weak Grids Nomenclature considerations • In this context, the following terminology refers to the same subject: • Connection of plants to “Weak Grids” • Connection of plants to “Low system strength” conditions • Connection of plants to a “Low SCR” system © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 75 / Conventional and PE sources • Relevant electrical characteristics of Power-Electronic (PE) sources Performance aspect Conventional generation Power-Electronic Sources Short circuit contribution (system strength) Around pu Small/none Inherent to constructive characteristics Sharing depends on size and impedances of the machines Fast current controls force current sharing Current sharing/distribution • • All current-controlled PE sources require grid strength to operate reliably and stably Grid strength is high when electrically close to conventional generation © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 76 / Conventional and PE sources • Long transmission corridors (low system strength) typically have power transfer limited below thermal limits due to stability challenges Conventional generation Transient Stability Dynamic stability Power-Electronic Sources Fast control stability Voltage stability Voltage stability • Fast control stability refers to interactions between transmission system and PE sources (Wind Turbine Generators (WTG) , SVCs, STATCOMs, etc.) © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 77 / WTGs and system strength • Modern WTGs and solar PV are PE sources • Some applications may need mitigations to achieve desired system performance under very low system strength conditions : – Transmission upgrades – New lines – Meshed vs radial – Series compensation – Synchronous condensers (System strength, dyn VARs) – SVC, STATCOM (dyn VARs, control challenges) – Special protection schemes (such as transfer trips) • GE WTGs have control features to improve performance in low system strength conditions © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 78 / Weak grid applications • Extremely weak application with risk of fast control instability • Fault and clear into N-1 with different control features • Interactions of fast regulators • Converter controls cannot solve all system stability issues, but have important impact Active Power Reactive Power WTG settings for normal system strength Voltage Active Power Reactive Power WTG settings and features for low system strength © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 79 / Weak grid applications Field Recordings 345kV Voltages 1.4000 Voltage 1.2 1.1 1.2000 1.0000 1.0 V pu Control improvements (simulation) 0.9 0.8000 0.8 V Omega Receiving end345 0.7 V HHGT345 0.6000 Sending end 0.6 0.5 0.00 0.10 0.20 0.30 0.40 0.50 0.60 Voltage 0.4000 0.0000 1.0000 HHGT 345kV: 345kV Voltage HHGT Omega 345 kV: 345kV Omega seconds 345kV Power 825.00 1.0 600 700.00 pu 500 575.00 400 P Omega Power 300 pu MW towards Kendall 700 450.00 P HHGT 345 200 100 0.00 0.10 0.20 0.30 0.40 0.50 0.60 seconds 0.3 pu 200.00 0.0000 500.00 MVAr towards Kendall 200 • • • • • -100 -200 -300 -400 1.0000 lne_4200_3001_2: Reactive power Omega 345kV lne_4200_3001_2: Acti ve Power HHGT 345kV 345kV Reactive 100 Power 325.00 Extremely weak application with risk of voltage collapse Stable at fault clearing, collapse during power pickup before improvements Time frame of collapse is dictated by active power recovery Simulation data base validated based on recordings and used to define mitigations Converter controls cannot solve all system stability issues, but have important impact -500 0.00 250.00 Q Omega 0.00 Q HHGT 345 -250.00 0.10 0.20 0.30 seconds 0.40 0.50 0.60 -500.00 -750.00 0.0000 1.0000 lne_4200_3001_2: Reactive Power Omega 345kV lne_4200_3001_2: Reactive power HHGT 345kV 3pu/s © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 10% power increase Kbooster=0.05 80 / DIgSILENT Weak grid applications 1.025 N-1 1.019 Voltage 1.013 1.007 1.001 0.995 0.00 2.00 4.00 Reactive Pow er Control: WindControl V oltage N-0 Reactive Pow er Control: WindControl V oltage N-1 6.00 8.00 [s] 10.00 2.00 FC Converter Control: Qgen N-0 FC Converter Control: Qgen N-1 6.00 8.00 [s] 10.00 N-0 0.226 0.182 Reactive Power 0.138 0.093 0.049 0.005 0.00 GE • • • • • • 4.00 Same WC settings CSCR variation due to N-1 Contingency performance Date: 10/15/2014 Annex: /4 Close loop voltage regulators are affected by system strength Systems tuned for fast response in strong conditions may become oscillatory in weak conditions Typically not a power transfer limitation Plant level controllers are more sensitive Not related to fault conditions Less complex than previous application examples © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 81 / How “strong” are grid conditions? • The industry has used the Short Circuit Ratio (SCR) to assess the system strength for the connection of power electronic converters • SCR varies with system conditions • There are few different SCR calculations proposed in the industry SCR  short circuit MVA of AC System converter MW rating Wind Plant HVDC rectifier © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 82 / SCR applied to Wind Plants • • Characterization of system strength has to take into account all electrically close converters (Multi-infeed) Composite SCR (CSCR) considers the grid strength as seen by all electrically close converters and is used for wind plants Converter locations © 2016 General Electric International, Inc All rights reserved Not for distribution without permission WP1 WP WP 83 / Composite SCR • Composite short circuit level (in MVA): – 3Ph short circuit at 34.5 KV buses - all interconnected – Low load conditions (low/realistic commitment of conventional generation) – Contingency conditions also considered – No contribution from converters © 2016 General Electric International, Inc All rights reserved Not for distribution without permission WP1 WP WP 84 / Composite SCR: Recommended Practice Composite SC MVA CSCR   converter MW rating • Composite SCR is useful to characterize grid strength and screen for system stability risks • Understanding of the grid parameters, system operation and future wind projects is required to meaningfully estimate CSCR • Grid entities/consultants should estimate this parameter for normal and contingency operation and communicate to developers • For very low CSCR applications, dedicated detailed analysis is recommended © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 85 / Summary      Large concentration of wind plants connecting to same (or close) transmission node can result in moderate to low grid strength Understanding and potential remediation of very low grid strength wind plant operation requires collaboration between system operator, planners, developers and OEMs CSCR estimation is an initial step in such collaboration PV and QV analysis can provide useful analytics considering time frame of operation of controllers involved Time simulations typically required to test mitigations Modern technology includes control features and settings to facilitate reliable operation in low CSCR sites © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 86 / [...]... Interconnection Actual measurements from a 162MW wind plant Voltage at POI Wind Plant Voltage • Minimizes Grid Voltage Fluctuations Even Under Varying Wind Conditions • Regulates Total Wind Plant Active and Reactive Power through Control of Individual Turbines Wind Plant Power Output Average Wind Speed Voltage and Reactive Power Regulation Like A Conventional Power Plant © 2016 General Electric International,... without permission 27 / WindFREETM Reactive Power Control WindFREETM Reactive Power Control for Wind- Turbine Generators Kara Clark, Nicholas Miller GE Energy Nordic Wind Power Conference May 23, 2006 WindFREE Reactive Power • Benefits weak grids and systems with high wind penetration • Voltage support continues without active power generation…even following trips Turbine kVAR • Wind Turbine converter... Zone © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 15 / Wind Plant vs Wind Turbine Reactive Capabilities Wind Plant pf capability  wind turbine pf spec Reactive Gains Reactive Losses • I2X of unit transformer • I2X of collector lines and cables • I2X of substation transformer • V2BL of shunt reactors • QL of dynamic compensator • • • • V2BC of... without wind (kW) 0 0 Field Test Results (2.5 unit) Reactive Power 75 Time (seconds) 150 Active Power (zero) Reactive Power - even without wind: A valuable option – An unreasonable requirement © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 30 / WindFREE Reactive Power Control Concept Wind turbines generally operate unless: • Low wind speeds • High wind. .. operation: no active power produced active power 1 6080 reactive power 4 6060 2 6040 3 6020 6000 2 Turbine kVAR command ramped down to zero; voltage declines about 1% 3 Turbine kVAR command stepped up to 200 kVAR; slight voltage rise 4 Turbine kVAR command stepped up to 1100 kVAR; voltage jumps up about 1% 5980 0 19 37 56 75 94 112 131 time (s) © 2016 General Electricinfluenced International, Inc All rights... distribution without permission 33 / Economic Benefits Wind plants with WindFREE Reactive Power Control Reduce Grid Capital Costs • Avoid requirement for other dynamic reactive power equipment • Avoid transmission system reinforcements Reduce Grid Operating Costs • Avoid requirement to run un-economic generation to meet stability and voltage regulation requirements • Reduce losses and other costs associated... without permission 34 / Wind Turbine Fault Tolerance Ride-Thru Capabilities GE's Standard WindRIDE-THRU Offerings  Remains on-line and feeds reactive power through system disturbances Voltage at Point of Interconnection (Percent) 120  Meets present and emerging grid requirement with Low/Zero Voltage Ride Through (LVRT/ZVRT) Zero Voltage capability Event  Meets transmission reliability standards similar... 8/19/2014 Wind Farm V Q Diagram (EN): Total Pow er of All Wind Turbines at LV Level in Mvar / Voltage at PCC in p.u Annex: Reactive /5 Annex: /5 -45.000 -15.000 15.000 45.000 Wind Farm V Q Diagram (EN): Reactive pow er reference (at Pn) in Mvar / Voltage at PCC in p.u Wind Farm V Q Diagram (EN): Reactive pow er at PCC in Mvar / Voltage at PCC in p.u Wind Farm V Q Diagram (EN): Total Reactive Pow er of All Wind. .. power (kVAR) without wind (kW) © 2016 General Electric International, Inc All rights reserved Not for distribution without permission 31 / Field Tests from Operating Multi-MW Turbine Power (kW) / Reactive power (kVAR) 1600 130 0 Turbine kVAR 1 4 1000 1 Initially turbine supplies 1100 kVAR; voltage 101% 700 2 400 Turbine kW 3 100 -200 0 19 Voltage (medium voltage side) 37 56 75 94 112 131 time (s) 6120 6100... 8/19/2014 Wind Farm V Q Diagram (EN): Total Reactive Pow er of All Wind Turbines at LV Level in Mvar / Voltage at PCC in p.u Annex: /5 Annex: /5 -15.000 15.000 45.000 Wind Farm V Q Diagram (EN): Reactive pow er reference (at Pn) in Mvar / Voltage at PCC in p.u Wind Farm V Q Diagram (EN): Reactive pow er at PCC in Mvar / Voltage at PCC in p.u Wind Farm V Q Diagram (EN): Total Reactive Pow er of All Wind ... measurements from a 162MW wind plant Voltage at POI Wind Plant Voltage • Minimizes Grid Voltage Fluctuations Even Under Varying Wind Conditions • Regulates Total Wind Plant Active and Reactive Power... permission 15 / Wind Plant vs Wind Turbine Reactive Capabilities Wind Plant pf capability  wind turbine pf spec Reactive Gains Reactive Losses • I2X of unit transformer • I2X of collector lines and cables... permission 27 / WindFREETM Reactive Power Control WindFREETM Reactive Power Control for Wind- Turbine Generators Kara Clark, Nicholas Miller GE Energy Nordic Wind Power Conference May 23, 2006 WindFREE