experience on technical solutions -...

Experience on Technical Solutions for Grid Integration of Offshore Windfarms

18 June 2007, DTI Conference Centre, London

Liangzhong Yao

Programme ManagerAREVA T&D Technology Centre

Experience on Offshore Windfarms3 3

Agenda

The 90MW Barrow Offshore Wind Farm

The 400MW Sandbank 24 Offshore Wind Farm


1. The 90MW Barrow Offshore Wind FarmIn the UK



Offshore Platform

132kV Cable

Wind farm



Connect 30, VESTAS V-90 3MW Wind Turbines (DFIGs) to the Grid System via an offshore sub-stationVoltages: 1kV/33kV/132kVCables

Offshore (3-core)

33kV 120mm2, 300mm2, 22.3kM

132kV 300mm2, 27km, offshore

Onshore (1-core)

132kV 400mm2, 2.6km, onshore

Ensure the connection meets the requirements of the connection agreement


The Key Connection Requirements

The steady state reactive power flow at the Heyshamsubstation connection point shall be unity power factor+/- 5MVAr for active power flow in the range of 0 and 90MW into the NGT system.

Voltage Operation Range33kV 95% - 105%

132kV 80% - 110%

The system shall remain stable and connected to the system without tripping for a solid three phase fault or any unbalanced short circuit for a total fault clearance time of up to 140ms

Wind turbine may trip

GridQ =0<±5MVAr


Design Solution

Reactive Power Capability Designed by Vestas V-90

Voltage Control120MVA Transformer with a tap changer range: -18% / +12%

Reactive Power Compensation Installation of a 132kV 24MVAr permanently connected reactor at Heysham Grid connection point

Installation of 2x5MVAr switchable shunt capacitors on the 33kV offshore substations

Pg

-Qg

Cosph=-0.96

Cosph=0.98+Qg

Reactive Power Capability Considered for Vestas V-90

1p.u.

+Qg

-Qg

Pg1p.u.


Design Solution

Other Issues Considered/StudiedCable Rating

Load Flow

Losses

Three Phase and Single Phase Fault Levels

Transient Stability and Fault Ride Through Capability

Insulation Co-ordination

Ferro Resonance

Transients Due to Capacitor Switching

Circuit Energisation/De-Energisation

Harmonic

Cable Thermal Study, etc


Some of Case Studies

Pgneration=100%

Less than +/- 5MVAr

A Example of Reactive Power Compensation


Some of Case Studies

(a) Voltage Dip

(c) WTG Speed(b) P and Q at the Connection Point

P

Q

Wind Farm “ Ride through” the Fault

Dynamic Responses for a 3-Phase Fault at the Connection Point

Fault Ride Through


Connection at Heysham


Offshore SubstationModularised equipment

33kV Board - including protection B

33/132kV 120MVA Transformer with OLTC

132kV GIS

Relay and control panel suite room A

LVAC and DC plant room (incs UPS for navigation lights) C

225kVA standby diesel generator

Refuge, mess and workshop module D

5MVAr Shunt Capacitor bank modules E

HVAC systems

INERGEN/Water mist fire suppression system. A

OverviewLength – 23m

Width – 15m

Height – 10m

Weight – 440 tonnes


2. The 400MW Sandbank 24 Offshore Wind Farm

in North Sea, Germany


Introduction

Sandbank 24 Offshore Wind Farm80 Turbine Generators (5MW per turbine,DFIG, Repower)

400MW Wind Generation

Estimated Circuit Length

approximately 80kM offshore cable for wind farm, and

190kM Offshore + 50kM Onshore cables for connection

Water Depth: 25m to 30m

Connection Point: E.ON Brunsbüttel

7 phase projects in the region, and maximum WTGs to be installed=

900


Introduction

Wind Farm Location

Sandbank 24

Sandbank 24


Introduction

Wind Farm LayoutGrid ConnectionPoint

Offshore substation


Introduction

Scope of Grid Connection Option Studies

Technical feasibility and availability in terms of

manufacturing feasibility & availability and

meeting the E.ON connection requirements

Costing optimisation of each connection, including a

summarised cost breakdown for each solution


Grid Code Requirements for Connection

Some Key Technical RequirementsReactive Power /Voltage Control Range

For example, 0.925 pf lagging to 0.95 leading depending on voltage level

Fault Ride Through CapabilitySolid grid fault up to 150ms

Power / Frequency CharacteristicFrequency Control Power Quality – Harmonics, FlickerOthers

Ref: E.ON Netz GmbH, "Grid Code: High and Extra High Voltage", August 2003

Wind turbine may trip


Connection Options

AC Connection + Switchable/Permanently Connected Capacitors/Reactors

Fixed shunt inductors to compensate for Cable CapacitanceTransformer tap changer to control Q and V

AC Connection + Dynamic Reactive Compensation

(FACTS)SVCSTATCOM

Voltage Source HVDC (VS HVDC)Line Commutated HVDC (LC HVDC)

Needs Synchronous Compensator or STATCOM


Connection Options

DFIG Wind Farm Connection

Connection type Doubly Fed Induction Generator orDirect Drive Synchronous Generator

AC

Risk of Harmonic resonanceHigh charge current for long cables

☺ V & Q control depending on WTG converter rating

AC +SVC or

STATCOM

Risk of Harmonic resonanceHigh AC charge current for long cables

☺ V & Q control depending on WTG converter & SVCor STATCOM rating

VS HVDC

Switching Losses ☺ P, V & Q control☺ No AC charge current

LC HVDC

P Control but needs STATCOM or Synchronous Compensator for V&Q control☺ No AC charge current☺ Lowest losses


Option Proposals and Case Studies

Proposed Connection Options

150kV AC

220kV AC

450kV Mono-Polar HVDC

±240kV Bi-Polar HVDC

±150kV VSC HVDC

AC Connection

Conventional HVDC Connection



An Example of 150kV HVAC Connection OptionOne of Problems with HVAC Connection

0.920.930.940.950.960.970.980.99

11.011.021.031.041.051.061.071.081.091.1

1.111.121.131.141.15

B18

B19

B20

B21

B22

B23

B24

B25

B26

B27

B28

B29

B30

B31

B32

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B50

B51

B52

B53

B54

B55

B56

B57

B58

B59

B60

B61

B62

B63

B64

B65

Bus Name (Location)

Volta

ge M

agni

tude

in p

.u.

(150

kV H

VAC

Con

nect

ion )

0% Wind Generation50% Wind Generation100% Wind Generation

190kM Offshore Cable 50kM OnshoreCable


0.920.930.940.950.960.970.980.99

11.011.021.031.041.051.061.071.081.091.1

1.111.121.131.141.15

B18

B19

B20

B21

B22

B23

B24

B25

B26

B27

B28

B29

B30

B31

B32

B33

B34

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B37

B38

B39

B40

B41

B42

B43

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B48

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B50

B51

B52

B53

B54

B55

B56

B57

B58

B59

B60

B61

B62

B63

B64

B65

Bus Name (Location)

Volta

ge M

agni

tude

in p

.u.

(150

kV H

VAC

Con

nect

ion )

0% Wind Generation50% Wind Generation100% Wind Generation



BrunsbuttelGrid

10kM

10kM

ConnectionPoint

Group 1: 50MW

Group 2: 50MW

Group 3: 50MW

Group 4: 50MW

Group 5: 50MW

Group 6: 50MW

Group 7: 50MW

Group 850MW

33kV

150kV

150kV

150kV 380kV

150kV

190kM Offshore cable 50kM Onshore cable

Offshore Substation Onshore/Grid Substation

6kV

6kV

SVC/STATCOM

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

42 43 44

61

605958 62 63 64 65

18 19 20

37

363534 38 39 40 4166

21

45

67

250MVA18%

250MVA18%

250MVA18%

250MVA18%

L18

L42

L37

L61

170kV3x1x1200mm2 KQ

170kV3x1x1200mm2 KQ

BrunsbuttelGrid

10kM

10kM

ConnectionPoint

Group 1: 50MW

Group 2: 50MW

Group 3: 50MW

Group 4: 50MW

Group 5: 50MW

Group 6: 50MW

Group 7: 50MW

Group 850MW

33kV

150kV

150kV

150kV 380kV

150kV

190kM Offshore cable 50kM Onshore cable

Offshore Substation Onshore/Grid Substation

6kV

6kV

SVC/STATCOM

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

42 43 44

61

605958 62 63 64 65

18 19 20

37

363534 38 39 40 4166

21

45

67

250MVA18%

250MVA18%

250MVA18%

250MVA18%

L18

L42

L37

L61

170kV3x1x1200mm2 KQ

170kV3x1x1200mm2 KQ

Voltage Rise along with Cable Circuit

It is the same as 220KV HVAC connection



An Example of HVDC Connection Option- 450kV Mono-Polar HVDC

Group7

Group87475767778 737980

5556575859 546061 53 52 51

3435363738 333940 32 31 30

1415161718 1319 12 11 10 56789 4 3 2 1

2324252627 222829 21 20

4445464748 434950 42 41

6566676869 647071 63 6272

190kM Offshore Cable

50kM Onshore Cable

33kV

500MVA18%

1kM

450kV 1x800 mmsq Cu Cable24kV 1x800mmsq Return Cable400MW, 915A

Connection Point

Group1

Group2

Group3

Group4

Group5

Group6

5MW

6/33kV

500MVA18%

AC Filter

AC Filter

Brunsbuttel380kV Grid

Reactive Power Compensator

Reactive Power Compensator

450kV 1x800/1390 mmsq Offshore Cable with Integrated Return

Monopolar HVDC Link

Group7

Group874747575767677777878 737379798080

5556575859 546061 53 52 5155555656575758585959 545460606161 5353 5252 5151

3435363738 333940 32 31 3034343535363637373838 333339394040 3232 3131 3030

1415161718 1319 12 11 1014141515161617171818 13131919 1212 1111 1010 56789 4 3 2 15566778899 44 33 22 11

2324252627 222829 21 2023232424252526262727 222228282929 2121 2020

4445464748 434950 42 4144444545464647474848 434349495050 4242 4141

6566676869 647071 63 6265656666676768686969 646470707171 6363 62627272

190kM Offshore Cable

50kM Onshore Cable

33kV

500MVA18%

1kM

450kV 1x800 mmsq Cu Cable24kV 1x800mmsq Return Cable400MW, 915A

Connection Point

Group1

Group2

Group3

Group4

Group5

Group6

5MW

6/33kV

5MW

6/33kV

500MVA18%

AC FilterAC Filter

AC FilterAC Filter

Brunsbuttel380kV Grid

Reactive Power CompensatorReactive Power CompensatorReactive Power Compensator

Reactive Power CompensatorReactive Power CompensatorReactive Power Compensator

450kV 1x800/1390 mmsq Offshore Cable with Integrated Return

Monopolar HVDC Link


Technical Performance Comparison

Losses Comparison of Various Options

Assume:Transformer copper loss: 0.5% @400MWTransformer iron (no-load) loss: 0.1% @400MWLCC HVDC Converter loss: 0.75% @400MW per converter (CIGRE)VSC HVDC Converter loss: 2% @400MW per converter (CIGRE)

1% @0MW per converter (CIGRE)

0%

10%

20%

30%

40%

50%

60%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Wind Generation Level (%)

Pow

er L

osse

s (%

) of V

ario

us O

ptio

ns

VSC HVDCBi-Polar HVDCMono-Polar HVDC150kV HVAC220kV HVAC

P Loss (%)

Pg

AC and VSC HVDC

HVDC


Conclusions

Technical solutions for large wind farm connection can be

AC Connection

AC + FACTS

LCC HVDC Connection

VSC HVDC connection

For 400MW Sandbank 24 offshore wind farm, both LCC HVDC and VSC HVDC technical solutions are very attractive options

LCC HVDC - low power losses, increased availability, and large power transfer capability

VSC HVDC – Capability of P &Q control to meet the gridcode requirement

To reach an engineering design solution for a wind farm connection with a grid, a number of further studies need to be done to identify the best technical and cost-effective solution

Thank you for your attention!

[email protected]

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