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Synchronous Condensers for reliable HVDC operation and bulk power transfer Hans Abildgaard, Nan Qin .dk 15PESGM3046

Denmark is located between a thermal-

and a hydro-dominated power systems

• High interconnection

capacity

• First HVDC interconnector established in 1965 • DK west – 6 LCC poles (2300 MW) – 1 VSC pole (700 MW) • DK East – 2 LCCs (1200 MW)

Danish Power system 2015

1632 MW Two synchronous areas

West:

Consumption 1400 - 3500 MW Primary power stations 2250 MW 680/740 MW

AC Local CHP plants 2000 MW Wind turbines 3700 MW DC Photo voltaic 450 MW

1300/1700 MW East: Consumption 900 - 2500 MW 600 MW Primary power stations 2900 MW Local CHP plants 650 MW Wind turbines 1000 MW Photo voltaic 200 MW 1500/1780 MW 600 MW excl. Bornholm, mothballed and blackstart units import / export [MW]

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Energinet.dk

Wind power is still increasing

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Must-run is costly

50

40

30

DK2 € DK1 M 20

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0 2006 2007 2008 2009 2010 2011 2012 2013 2014

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Why must-run?

• Short circuit power – voltage step changes after shunt

switching

– hvdc load rejection • Dynamic voltage control – commutation of HVDC LCC – reactive power consumption from old wind turbines • Continuous voltage control – hvdc ramping – high voltages during low load (steady state) (Active power reserves are bought in separate markets and do not give rise to must-run)

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Dynamic voltage control

Type 4 (FCG) 20%

Type 3 (DFIG) 13% Type 1 (SCIG) 59%

Type 2 Simulated fault recovery without (VRIG) and with wind power in case of 8% insufficient dynamic voltage Onshore capacity per technology support.

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Minimise risk of commutation failures

propagation

• On August 23, 2009 a

successful reclosing on a

132 kV in the Southern part of Sweden caused a commutation failure on and Konti-Skan 1+2 (inverter). • The current drawn by the rectifier end of the two Konti-Skan poles lead to commutation failure on Skagerrak 3 in

Synchronous condensers in

Denmark

Station Area PCC Sn Year kV MVA

Vr. Hassing DK1 150 100 1965/2013 Tjele DK1 150 160 1976/2012 Bjæverskov DK2 400 270 2013 Herslev DK2 400 200 2014 Fraugde DK1 400 200 2014

Kyndbyværket DK2 132 330 1976/199x Enstedværket DK1 150 880 1979/2013

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Location of new SynCons

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Main data of the new SynCons

BJS (2013) FGD/HKS (2014)

Generator data 270MVA, 15.75kV±5% 200MVA, 15.75±10%

Cooling DAC TEWAC Circuit Breakers HV HV+LV Start-up time 15..20 min 10-15 min

GSU data 2W, u SC~14%, 420/15.75kV 3W, u SC~10%, 400/15.75kV GSU energization Together with generator From 400kV side GSU tap changer On-load ±10 steps of 1.25% None

SSC’’_HV, guaranteed >800 MVA >1000 MVA

QHV, guaranteed -150/215 Mvar -120/180 Mvar Auxillary power Redundant from local 10kV From GSU tertiary winding Breaking/stopping Regenerative+HV-brake Regenerative AVR controlling node 400 kV 16 kV

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New SynCons - Purpose and

requirements

• To significantly reduce the number and duration of ”must-

run” requests for conventional thermal power stations, i.e. significant savings. – Short circuit level contribution – Dynamic and continuous voltage regulation – Fault-ride-through capability • High level of availability and reliability – Well proven equipment – Redundant auxiliary systems – Detailed design reviews – Test and verification

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Inertia - currently not an issue

• In interconnected operation, the system inertia is

currently sufficient – Redefinition of primary control response could be necessary. • The inertia provided by the new SynCons is one third of a typical steam unit. – If required additional rotating mass can be fitted to an external flange.

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Summary and outlook

• The market share for the conventional generation in the energy market continues to fall leading to

mothballing and decommissioning • The necessary system support is built into the grid – A level playing field in the energy market – Lower socio economic costs – Maintain high security of supply • Need for must-run will gradually decline over the next ten years – Decommissioning of Type 1 wind turbines – Commissioning of new VSC connections (COBRAcable, Kriegers Flak DK-GE, )

UK NL GE Thank you for your attention!

Hans Abildgaard Nan Qin Chief Engineer PhD-student [email protected] [email protected]

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