the challenges facing hvdc in the early 21st century

The Challenges facing HVDC inthe Early 21st Century

Dr Norman MacLeodTechnical Director, HVDC

Visiting Professor, Leeds University

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Contents

• HVDC – a very brief history• Development of ±800kV equipment• Development of VSC-HVDC solutions• New challenges

• 1100kV transmission• High altitude stations/lines• Building the DC Super Grid• Building the Smart Grid

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3

HVDC Scheme/Technology Progression

0

5

10

15

20

25

30

Y/E 55 Y/E 60 Y/E 65 Y/E 70 Y/E 75 Y/E 80 Y/E 85 Y/E 90 Y/E 95 Y/E 00 Y/E 05 Y/E 10 Y/E 15

IGBT

Thy

Merc

Number of schemes per 5 year interval

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Power/Voltage Progression

0

1000

2000

3000

4000

5000

6000

7000

8000

0 100 200 300 400 500 600 700 800 900

Pow

er(M

W)

DC Voltage (kV)

Contents

• HVDC – a very brief history• Development of ±800kV equipment• Development of VSC-HVDC solutions• New challenges

• 1100kV transmission• High altitude stations/lines• Building the DC Super Grid• Building the Smart Grid

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500kV Thyristor ValvesSource : Alstom

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660kV Thyristor ValveSource : Alstom

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600kV Converter TransformerSource : Alstom

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Air Breakdown TestingSource : Alstom

Switching impulsevoltage tests on thyristorvalve test object – VITLaboratory in Ukraine

• Test voltages up to2200kV• Clearance to wall/floorup to 9m

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Switching Impulse TestsSource : Alstom

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Switching Impulse TestSource : Alstom

Voltage = 2200kV

Clearance = 9m to wall

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Long Arc PhysicsSource : Alstom

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Long Arc PhysicsSource : Alstom

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Long Arc PhysicsSource : Alstom

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Long Arc PhysicsSource : Alstom

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UHV Switching Impulse TestingSource : ABB

Rod – plane air gap Sphere – plane air gap

“Intriguing observation on the breakdown trajectory of large air gaps under switchingimpulse voltages”, L Ming, D Wu. U Astrom and G Asplund, 16th International Symposium onHigh Voltage Engineering, Cape Town, South Africa, 2009

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800kV DisonnectorSource : Siemens

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800kV DC Current TransducerSource : Alstom

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±800kV Transmission lineSource : SGCC

Contents

• HVDC – a very brief history• Development of ±800kV equipment• Development of VSC-HVDC solutions• New challenges

• 1100kV transmission• High altitude stations/lines• Building the DC Super Grid• Building the Smart Grid

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VSC HVDC - Principle

Steady DCVoltage

Input

+

Alternating Voltage Output

VSC

By controlling the phase angle and magnitude of the output voltage,the VSC converter can control real power and reactive power flowinto the AC system. It looks like a “generator” or “load”

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VSC – HVDC StationSource : ABB

Contents

• HVDC – a very brief history• Development of ±800kV equipment• Development of VSC-HVDC solutions• New challenges

• 1100kV transmission• High altitude stations/lines• Building the DC Super Grid• Building the Smart Grid

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1100kV DC Wall BushingSource : Alstom

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Altitude Effects

Atmospheric pressure correctionimpacts on insulation clearances.

From IEC 60071 – 2, section 4.2Correction factor Ka = em(H/8150),where

H = altitude (m)m =1.0 for lightning impulsem < 1.0 for switching impulse 0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 1000 2000 3000 4000Ka

Altitude (m)

m = 1.0

m = 0.5

High Altitude

• HVDC schemes at elevated altitude• China - >4000m (Tibetan plateau)• USA - >12,000ft (Rocky Mountains)

• China has a high altitude testing station in Tibet

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Off-shore Wind Farm

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Multiple Off-shore Wind Farms

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Off-shore DC Grid

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DC Super GridSource : FOSG

The Super Grid - Questions

• How do we achieve “standardisation” of solutions?• Can we develop a DC/DC “transformer”?• How do we ensure “interoperability” between multiple

vendors equipment?• How do we control the power flows between nodes?• What and how do we communicate from dispatch to the

nodes?• How do we protect the Super grid?• Can we develop a DC circuit breaker – at reasonable cost?

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The Existing AC grid

ACAC

132 kV 132 kV

400 V 400 V

11 kV

400 kV

400 V

11 kV

11 kV

AC

AC

AC

AC

AC

AC

AC

AC

AC

ACAC

AC

AC

AC

AC

AC

The AC/DC Grid of Tomorrow?

ACAC

DCDC

132 kV 132 kV

400 V 400 V

11 kV

400 kV

400 V

11 kV

11 kV

Offshorewind farm

150 kV 150 kV 150 kV150 kV

Bulk power import using UHVDC

600 kV

ACDC

DC

DC

AC

DC

AC

DC

50 kV 50 kV

DC

DC

DC

DC

AC

AC

AC

AC

AC

AC

AC

ACAC

AC

AC

AC

AC

AC

AC

DC

DC

DC

DC

DC

DC

DC

DC

DC500 V

Electric VehicleCharging Stationstation

AC

DC

AC

AC

10 kV 10 kV

AC

DC

AC

AC

500 V

BatteryEnergyStorageSystem

PhotoVoltaic

DC

DC

PowerCells

The Smart Grid - Questions

• Can we develop MVDC technology at reasonable cost?• Can we integrate different power electronic technologies?

• AC – DC converters• DC – DC converters• STATCOM• Wind turbines• Inverters from PV, EV, BESS, etc

• Can we integrate Automation solutions (EMS, WAM, PMU)with Power Electronic solutions?

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Conclusions

• Even after 60 years of HVDC technology advancement thereare still many challenges ahead.

• The challenges can be solved, but we need Engineers.

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Thank you for your attentionAny Questions?

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