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Transmission and dynamics

Transmission and dynamics IEA Wind Task 25 recommendations Ana Estanqueiro ( LNEG ), Damian Flynn, Antje Orths, Frans van Hulle. Transmission and dynamics. Transmission – Static studies. Principles of Transmission Planning. Transmission planning may be:

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Transmission and dynamics

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  1. Transmission and dynamicsIEAWindTask 25 recommendationsAna Estanqueiro (LNEG), Damian Flynn, Antje Orths, Frans van Hulle

  2. Transmission and dynamics

  3. Transmission – Static studies

  4. Principles of Transmission Planning Transmission planning may be: • Long term, covering a time horizon n+10 < T <n+25 years • Short-term, performed for T < 5 years. Grid congestions can be (and are) mitigated using; • Dynamic line ratings, FACTs, Phase-shifting transformers, high temperature lines… • Operational methods can delay some grid reinforcements, When large amounts of wind are added, and in cases of weak grids, new transmission is unavoidable • But new transmission has often also other benefits than just for wind

  5. Steps for Long Term Transmission Planning • Scenario development covering spatial location/ generation/ load/policy (national vs. int.; Green vs. BAU, etc.); • Market modeling, determining energy flows caused by the energy market on an annual basis; • Transmission expansion planning aiming at a system based on socio-economic welfare; • System reliability and risk analysis; • Detailed grid studies, considering both static and dynamic system modeling.

  6. Transmission planning contd. • Includes creating a number of credible load flow and stability base case snapshots - challenging cases (e.g. high wind/low load and and low wind/high load) and use it to analyse physical flows, contingencies, loading of assets, voltage profile, line congestions, etc…

  7. Reactive Power Requirement (conventional vs. wind)

  8. Source:

  9. RecommendationsTransmission planning Scenarios (and ID of snapshots) should be carefully identified using long-term wind/load data series; An holistic approach accounting for other RES or load synergies is mandatory; Reliability tools should be used; Cost effective expansion alternatives should be studied: • the target is to minimize the difference between ideal power flows from market model and physical power flows.

  10. Transmission and dynamics

  11. Short Circuit Faults • Low voltages due to short-circuits may lead to the disconnection of large shares of (old technology) wind power production 0.8 p.u. 0.5 p.u. • Voltage Profile • Red < 15 % • Yellow 15 – 50 % • Green 50 – 80 % slide 11 of 27

  12. Fault Ride Through Characteristics ...to ensure the robustness and stability of the system, most countries require a reactive current injection during a fault to support system voltages, reflecting the capabilities of modern convertor based designs

  13. Frequency Stability Frequency response, Irish example: ENTSO-e draft network code proposes: “The Generating Unit shall not disconnect from the network due to rates of change of frequency up to 2 Hz/s other than triggered by loss of mains protection”

  14. Recommendations for Dynamic Analysis Dynamics • After steady-state analyses, critical snapshots can be studied –failures to stable state and recovery from disturbances • Can also be used for mitigation options/grid code requirements • Specificconcerns for highwindpenetration : • Small ratio of synchronous machines on-line • Largeexchange of surpluswindpoweracrosswideareas • Gather trustful input data and use validated simulation models of the components in the grid; • Careful select the snapshot situations. ID the wind/load correlations (value of using challenging rare situations?) • Cases to study: Voltage stability, frequency stability and governor response, small-signal stability,… • [Iteration loop to definition of transmission scenarios].

  15. TSO view of Transmission Planning - examples for input - Scenarios Market Modelling Tool Conceptual Grid Designs Loadflow Tool with Grid Model ReliabilityAsessment dynamicAnalyses • additional Input • components’ reliability indices (MTTF, MTTR) • statistical data • logistic model of connections between components Input - Consumption - Production capacities by fuel type - Exchange capacities - Units’ production characteristics - units’ thermal and electric efficiency, - Must-run constraints, - minimum power, - Start-up time etc - Fuel prices - CO2 prices - Wind time series - Data outside area of interest • additional Input • location of production • substations • environmental constraints • technology details • additional Input • detailed dynamic model

  16. Scenarios Market Modelling Tool Conceptual Grid Designs Loadflow Tool with Grid Model ReliabilityAsessment DynamicAnalyses TSO view of Transmission Planning - examples of outputs - • Results: • Adequacy Check • Merit Order of PPs • Production, Operation, Exchange Data; • Costs, Emissions, Fuel consumption • hourly marked flows • need for grid expansion? • Statistical statements about congestions, effect of mitigation measures etc. • Benefits • Results: • Comparison of investment costs of several variants • Results for selected hours/scenarios: • Physical flows in the Grid: • Voltages and currents for lines and nodes • Utilization of lines • Physical congestions • => physical need for grid expansion?

  17. Transmission planning key-points • The trade-off of transmission planning requires multiple studies • Integration studies traditionally focus on unit commitment/ economic/market related issues • At higher wind penetration levels dynamic concerns begin to take precedence • Accurate assessment of future system performance requires validated wind turbine models + proposal of control strategies • Verification of conventional generation capabilities + dynamic load representation • Relative importance of voltage / transient / small-signal / frequency stability issues will be system dependent • Network topology, underlying plant portfolio including other renewables, e.g. solar, wind turbine types + location, grid code requirements

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