07/11/2014

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Direct Current Distribution Network an opportunity for a distribution system operator?

Hans Schneider, Liander Frans Provoost , Liandon

European Utility Week 2014, Amsterdam, November 5th 2014

Outline

Context

1. DSO Liander – company profile

2. Local sustainable energy supply with a Direct Current Grid?

3. Direct Current, WHY?

Case

4. Feasibility study

5. Some design issues

6. Preliminary conclusions

7. The road ahead

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DSO

electricity

& natural

gas

DSO

electricity

& natural

gas

Engineering,

projects,

consultancy

Liander: Distribution System Operator.

Member of the Alliander Group

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6

Sustainable energy for a new business park near Lelystad Airport…

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Will a DC-grid add value

to local green energy solutions?

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Main actors:

• Lelystad Airport – the fast-growing daughter of Schiphol

Airport

• OMALA – the ambitious area developer

• Liander – the cautious grid company

The common objective:

• Investigate whether a (public) DC-grid connecting solar &

wind supply with local DC demand is a feasible

undertaking.

Some artist impressions

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Leisure dome

Fast-charging

filling station

Solar-parking

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A DC-grid?

Why for heaven’s sake?!

Direct current applications are everywhere

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Should Liander consider a DC-grid?

NO! Too many challenges for DC:

• No standards

• No certified metering

• No maintenance & safety protocols

• Legal fuzziness

• No economy of scale – components far too expensive

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Should Liander consider a DC-grid?

YES! Interesting claims for DC:

• Lower standby and conversion losses

• No reactive power

• Lower distribution losses

• Longer technical lifetime of components

• Active & passive safety

• Reliability:

- More redundancy in converters & feed-in locations

- Possibility to keep outage areas very small in case of

cable damage or sabotage.

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DSO (AC)

~ = ~ = ~ = ~ =

Customers

DC AC DC AC DC AC DC AC

Regular AC-grid

AC-DC conversion on client’s site

DSO (AC + DC)

Customers

DC AC DC AC DC AC DC AC

~ =

Mixed AC & DC-grid

AC-DC conversion by DSO

Partial balancing within DC-grid possible

Fewer converters needed

Can DC create smarter grid designs?

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How? The feasibility study

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A long list of demands, risks & issues

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• Safety

• Reliability

• Redundancy & back up

• Failure detection

• Maintenance & repair

• Metering

• Voltages

• Design issues

• Cables

• Converters

• Power Quality

• Power management

• Pricing

• Freedom of choice for all

clients in the area?

• Free energy supplier

access?

• And so on…

Feasibility study

Co-creation process with three main stakeholders:

• Area developer OMALA

• Lelystad Airport

• DSO Liander

Feasibility study with 3 main themes:

• Business case

• Technical issues

• Legal & regulatory issues

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How? Some grid design issues

Potential clients at the business park Projected power demand & supply

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2.930 kW

(200 DC

-3.130 DC)

1.130 kW

(500 AC

630 DC)

2.350 kW

(-2.350 DC)

225 kW

(225 DC)

Eventueel V2G

500 kW

(-500 DC)

1.130 kW

(500 AC

630 DC)

Solar

Parking

Hotel

LED-lichting

Leisure dome Long stay

EV Parking

DC-power for

aircrafts

LED lighting

platform

Te

rmin

al

Large solar

plant

LED lighting

landing strip

Small wind

farm Multi fuel

filling station

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Three grid design scenarios

1. Reference scenario

Regular AC grid for all clients

Regular DC-AC conversion at the client’s site

2. Full DC-grid

with DC-AC conversion for AC clients

3. Mixed AC-DC grid

Regular AC-grid for AC-clients

DC-grid for DC-clients

(with conversion to AC-grid by DSO)

Scenario 1: Reference AC-grid

MS-rail substation MS-rail substation

PV solar field Wind farm Solar Parking

Feeder A

Feeder B

Offices Leisure

dome

Airport

Parking Airport Hotel

Multi-fuel

station

LED

lighting

Regular AC-grid with two connections to substation for high power PV-installations

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Separate

connection to

substation

Low Voltage Alternating Current (LV - AC)

Medium Voltage Alternating Current (MV-AC)

Separate

connection to

substation

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Scenario 2: Full DC-grid

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Feeder A Feeder B

Low Voltage Alternating Current (LV-AC)

Medium Voltage Alternating Current (MV-AC)

Low Voltage Direct Current (LC-DC)

Medium Voltage Direct Current (MV-DC)

PV solar field Wind farm Solar Parking

Offices

Leisure

dome

Airport

Parking Airport

Hotel Multi-fuel

station

LED

lighting

Scenario 3: Mixed AC-DC grid (1/2)

DC-grid

connecting wind

Feeder B Feeder A

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OMALA AC/DC station

Synergy due to short distances

AC

DC

DC DC+

AC AC

PV solar field Airport

Low Voltage Alternating Current (LV-AC)

Medium Voltage Alternating Current (MV-AC)

Low Voltage Direct Current (LC-DC)

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(Clustering load and generation around Solar Parking)

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Offices Leisure

dome

Hotel

DC zon

-880 kW

AC

DC

AC

320 kW

465 A AC

80 kW

120 A

AC

100 kW

140 A

DC

315 kW

450 A

DC

170 kW

240 A

DC

100 kW

140 A

DC

2 kW

3 A

DC

50 kW

70 A

DC

225 kW

320 A

DC zon

-780 kW

DC zon

-780 kW

DC zon

-680 kW

600 kW 600 kW 600 kW 600 kW

LV DC

LV AC

MV AC Trafo

2.000 kVA

Converters

2.000 kW

280 A

DC load

200 kW

OMALA AC

Max load : 1.550 kW

Max Gen : 1.880 kW

Trafo

1.000 kVA

Trafo

1.000 kVA Trafo

1.000 kVA

OMALA DC

Max load : 1.050 kW

Max Gen : 2.280 kW

Scenario 3: Mixed AC –DC grid (2/2)

Solar Parking

Airport

Parking

Multi-fuel

station

LED

lighting

Solar Parking Solar Parking Solar Parking

Transformers and power converters

needed in each scenario

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Component Unit

Scenario 1

Regular

AC-grid

Scenario 2

Full

DC-Grid

Scenario 3

Mixed

AC/DC-

grid

Transformers

(MV/LV)

kVA 7.650 0 4.850

Total

converter

power

kW 7.450 12.020 5.100

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Preliminary conclusions

Technical issues

• No real show stoppers

• Interesting unforeseen design opportunities

- smart combinations of supply & demand within the DC-grid lead to smaller

client-grid-connections

- partially due to design restrictions in (regulated) AC-grid

- shorter overall (MV) cabling

• A lot of practical implementation issues:

- training of technical personnel,

- maintenance,

- quality assurance,

- safety

• Low availability of proven power electronic devices

• DC metering not yet available as a certified service

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Business case

• No positive business case in the short term

• Split incentive:

- advantages for clients;

- cost & risks for DSO

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Legal & regulatory issues

• DC-meters not yet certified and require law adjustments.

• A DC-grid is currently not identified as a public service of

the DSO under Dutch law.

• Are DC- and AC-grids not both ‘natural monopolies’ which

should be a public service of the DSO?

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The road ahead

The road ahead for DC-grids

in the Netherlands

1. The long and winding road of discussion on policies,

law adjustments and business rules...

2. Learning by doing and/or more R&D

3. An open eye for specific niches & game changers:

- DC-supply & DC-demand close together

- The possibilities of power electronics

- Gains in smarter grid design

- Specific ‘game changing’ clients like

data-centres, EV-chargers and wind & solar parks.

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Thank you for your attention!

Contact details:

Hans.Schneider@alliander.com

@SchneiderHans

nl.linkedin.com/in/hanscschneider/

www.alliander.com