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Wind turbine grid connection and interaction

This ENERGIE publication is one of a series highlighting the potential for innovative non-nuclear energytechnologies to become widely applied and contribute superior services to the citizen. European Commissi-on strategies aim at influencing the scientific and engineering communities, policy makers and key marketactors to create, encourage, acquire and apply cleaner, more efficient and more sustainable energy solutionsfor their own benefit and that of our wider under the European Union s Fifth Framework Programme for Research, technological Developmentand Demonstration (RTD), ENERGIE s range of supports cover research, development , demonstration,dissemination, replication and market uptake - the full process of converting new ideas into practical solutionsto real needs.

ment and Sustainable Development”, supplemented by coordination and cooperative activities of a sectoral ... medium voltage system of the grid future large offshore wind farms will be connected to the high ... breaker is located at the medium voltage system inside a substation, where also the electricity meter for the settlement purposes is ...

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Transcription of Wind turbine grid connection and interaction

1 This ENERGIE publication is one of a series highlighting the potential for innovative non-nuclear energytechnologies to become widely applied and contribute superior services to the citizen. European Commissi-on strategies aim at influencing the scientific and engineering communities, policy makers and key marketactors to create, encourage, acquire and apply cleaner, more efficient and more sustainable energy solutionsfor their own benefit and that of our wider under the European Union s Fifth Framework Programme for Research, technological Developmentand Demonstration (RTD), ENERGIE s range of supports cover research, development , demonstration,dissemination, replication and market uptake - the full process of converting new ideas into practical solutionsto real needs.

2 Its publications, in print and electronic form, disseminate the results of actions carried out underthis and previous Framework Programmes, including former JOULE-THERMIE actions. Jointly managed byDirectorate-General Energy and Transport & Directorate-General Research, ENERGIE has a total budget of1042 million Wover the period 1999 to is organised principally around two Key Actions, Cleaner Energy Systems, including RenewableEnergies, and Economic and Efficient Energy for a Competitive Europe, within the theme Energy, Environ-ment and Sustainable development , supplemented by coordination and cooperative activities of a sectoraland cross-sectoral nature. With targets guided by the Kyoto Protocol and associated policies, ENERGIE sintegrated activities are focussed on new solutions which yield direct economic and environmental benefits tothe energy user, and strengthen European competitive advantage by helping to achieve a position of leaders-hip in the energy technologies of tomorrow.

3 The resulting balanced improvements in energy, environmentaland economic performance will help to ensure a sustainable future for Europe s the support of the EUROPEAN COMMISSIOND irectorate-General for Energy and TransportLEGAL NOTICEN either the European Commission, nor any person acting on behalf of the Commission,is responsible for the use which might be made of the information contained in this publication. European Communities, 2001 Reproduction is authorised provided the source is in GermanyProduced byDeutsches Windenergie-Institut GmbHFritz Santjer, Gerhard J. Gerdes Ebertstra e 96 D-26382 WilhelmshavenTel.: +49 4421 48080 Fax: +49 4421 480843 Tech-wise A/SPeter Christiansen Kraftv rksvej 53 DK 7000 Fredericia DenmarkDM EnergyDavid Milborrow 23 The Gallops UK BN7 1LR Lewes East Sussex United KingdomWind turbine Grid connection and InteractionDeutsches Windenergie-Institut GmbH Germany Tech-wise A/S Denmark DM Energy United of wind Power Generation and Components of the system .

4 Supply Network .. offshore grid connection .. Losses ..93 Generator Systems forWind Fixed Speed wind turbines .. Variable Speed wind Turbines .. Inverter systems ..104 interaction with the Local Electricity Short circuit power level .. Voltage variations and flicker .. Harmonics .. Frequency .. Reactive power .. Protection .. Network stability .. Switching operations and soft starting .. Costs of Grid connection .. Safety, Standards and Regulations .. Calculation methods ..195 Integration into the National Emission Savings .. Energy Credit .. Capacity Credit ..236 Case Tun Knob wind farm, DK .. Rejsby Hede wind Farm, DK .. Delabole wind farm, UK .. Cold Northcott wind Farm, UK.

5 Wybelsumer Polder, D .. Belvedere, D .. turbine Grid connection & Interaction51 IntroductionWind energy is now firmly established as a maturetechnology for electricity generation and over13,900 MW of capacity is now installed, world-wide. It is one of the fastest growing electricity-generating technologies and features in energyplans across all five continents, both in theindustrialised and the developing differs, however, in several respects from the conventional thermal sources of electricitygeneration. Key differences are the small sizes ofindividual units, the variable nature of the wind andthe type of electrical generator. Each is consideredin this unit sizes: The small unit sizes mean that bothwind farms and individual wind turbines (WT) areusually connected into low voltage distributionnetworks rather than the high voltage transmissionsystems and this means that a number of issuesrelated to power flows and protection systems needto be addressed.

6 Electrical safety is an importantissue under this : The variable nature of wind is oftenperceived as a difficulty, but in fact poses fewproblems. The variations in output do not cause anydifficulty in operating electricity systems, as theyare not usually detectable above the normal variati-ons in supply and demand. With significant amountsof wind power roughly 30 % or more of demand -low cost solutions can be found and some island sys-tems operate with high proportions of wind energy. Variability also needs to be taken into account at thelocal level, to ensure consumers are not affected by flicker . Appropriate care in electrical design,however, can eliminate this properties: Early WT followed steamturbine practice with synchronous generators, butmany modern WT have induction generators.

7 Thesedraw reactive power from the electricity network,necessitating careful thought to electrical powerflows. Other machines, however, are capable ofconditioning the electrical output and providing acontrollable power factor. This is an asset, especi-ally in rural areas, where it may be undesirable todraw reactive power from the in wind - turbine technology and theresults of nearly two decades of research mean thatthe integration of WT and wind farms into elec-tricity networks generally poses few problems. Thecharacteristics of the network and of the turbines donevertheless need to be evaluated but there is now awealth of experience upon which to draw. The factthat Denmark is planning to supply 30 percent of itselectricity needs from wind energy is testimony tothe fact that its potential is Overview of wind Power Generation and TransmissionWT convert wind energy into electrical energy,which is fed into electricity supply systems.

8 Theconnection of WT to the supply systems is possibleto the low voltage, medium voltage, high voltage aswell as to the extra high voltage system . While mostof the turbines are nowadays connected to themedium voltage system of the grid future largeoffshore wind farms will be connected to the highand extra high voltage Components of the SystemThe three main components for energy conversion inWT are rotor, gear box and generator. The rotorconverts the fluctuating wind energy into mechani-cal energy and is thus the driving component in theconversion system . The generator and possibly an electronic inverterabsorb the mechanical power while converting itinto electrical energy, fed into a supply grid. Thegear box adapts rotor to generator speed.

9 The gearbox is not necessary for multipole, slow main components for the grid connection of theWT are the transformer and the substation with thecircuit breaker and the electricity meter inside of the high losses in low voltage lines, eachFigure :Yearly installed capacity of wind energy in Europe and wold-wideof the turbines has its own transformer from thevoltage level of the WT (400 or 690 V) to themedium voltage line. The transformer are locateddirectly beside the WT to avoid long low-voltagecables. Only for small WTGS it is possible toconnect them directly to the low voltage line of thegrid without a transformer or, in a wind farm ofsmall WT, to connect some of the small WT to onetransformer.

10 For large wind farms a separate sub-station for transformation from the medium voltagesystem to the high voltage system is necessary. At the point of common coupling (PCC) betweenthe single WT or the wind farm and the grid a circuitbreaker for the disconnection of the whole windfarm or of the WT must exist. In general this circuitbreaker is located at the medium voltage systeminside a substation, where also the electricity meterfor the settlement purposes is installed. This usuallyhas its own voltage and current transformers. The medium voltage connection to the grid can beperformed as a radial feeder or as a ring feeder,depending on the individual conditions of theexisting supply system . Fig. gives an overviewof the necessary components in case of connectionof the WTGS to the medium voltage system .


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