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From DC building to a DC distribution and transmission:

‘How direct will the future electricity be?’

prof.dr.ir. P.Bauer

DC Systems, Energy Conversion & Storage

Disruptive technologies

RE at optimal locations

Local generation and local consumption

Increased role of power

electronics and digitalization

Status now? AC gridControl, stability, production follows demand

Impetus?

Renewables &

& Electric Vehicles

Aging infrastructure

Uncertainty

• Grid Innovation

• Regulation and Policy

• Climate change

• Geo-political issues

• Public support

• license to operate

• customer preference

How?

• Redesign the system for (partially) DC

• Integrate storage

• System of Systems approach (social, ecological & technological)

• Interface, interaction, integration

Where we want to be?

• Sustainable, reliable high efficient, low cost distribution grid

• Grid (DC) with Renewable energy, Electric Vehicles

• Demand follows production

• Towards flexibility and modularity

• De-centralized control

• New distribution of costs & market structures

• System integration (gas&elec.)

Smart grid – chance for revival of DC

6

De Doncker, IPEC Hiroshima 2014

http://www.supergrid-institute.com/en/news/dc-dc-100-

kw-power-converter

Material usage AC and DC grid

Is DC disruptive technology ?

Rick de Doncker 2014

DC Nanogrids• Radial DC feeders(lighting,trolley)• Devices, protection, stability

DC Nanogrids V2.0

• Bidirectional power flow • PV and storage• DC house nanogrid• PV charging systems of EVs• DC ready devices and USB power delivery• Enable demandresponse

DC microgrids / DC links

• Towards local generation local use (storage, EVs)

• Cellular concept

• Sizing (optimization)

• Protection, grounding

• Stability of DC grids

• Optimal power flow

• Demand side management

• Data over power line

• Power management

• Markets

• Enabling Blokchain

Radial DC grids

• Connecting DC microgrids

• Refurbishing the system for (partially) DC infra

• Modular converters with integrated protection

• Integrated control market approach

• Integrating cells/microgrids

• Interface, interact, integrate

Meshed DC distribution grids

• Sustainable, reliable, high efficient, low cost DC distributiongrid with renewable energy, andelectric vehicles

• Fexibility and modularity

• Decentralized control

• New distribution of costs, market and usage structures

• Integration of multiple energy carriers (gas&elec.)

Roadmap for DC Systems

DC Nanogrids• Radial DC feeders(llighting,trolley)• Devices, protection, stability

DC Nanogrids V2.0



Trolley bus charging

PV Array

Charging

Converter

Bi-

directional

Converter

Energy

Storage

Electric Vehicle

DC Bus

EV

Charger

DC Nanogrids• Radial DC feeders(lighting,trolley)• Devices, protection, stability

DC Nanogrids V2.0



Electric Vehicles

PhD Gautam Ram

PV Charging of Electric Vehicles

PhD Gautam Ram

• Higher power density

• Higher efficiency

• Bidirectional EV charging

EV

PVEV-PV

50cm x 50cm !!!

• SiC MOSFET

• SiC diode

• Powdered alloy inductors

10kW EV-PV power converter

• Higher power density

• Higher efficiency

• Bidirectional EV charging

EV

PVV-PV

50cm x 50cm !!!

• SiC MOSFET

• SiC diode

• Powdered alloy inductors

10kW EV-PV power converter

DC Nanogrids• Radial DC feeders(lighting)• Devices, protection, stability

DC Nanogrids V2.0



PV for smart cities applications

Solar Powered Electrical Bike and Scooter Charging Station

System topology

Energy fed ˅

Energy taken4 x (12 V, 220 Ah)

series-connected batteries for 1 day

of autonomy

Solar Powered Electrical Bike and

Scooter Charging Station

PV for smart cities applications


DC Nanogrids V2.0



“To Develop Efficient and Intelligent Residential

Nanogrids Suitable for Future Smart Grid Integration”

PhD Soumya Bandyopathay

Disruptive technology ?

‘Research Goal

PhD Nishant Narayan

• Number of layers?

• Voltage Levels selection?

• Hybrid ac-dc architecture?

• Protection and grounding?

• USB-C architecture?

• Demand response and

Bi-directional power flow?

• Wired or Wireless?

• Demand Response

Potential?

• Storage size

optimization?

• Economic

analysis

• Power

Management

• Clustering

strategy of

houses?

#1

#2

#3

#4

#5

‘Research Challenges

“To Develop Efficient and Intelligent Residential

Nanogrids Suitable for Future Smart Grid Integration”

PULSE BUILDING TU DELFT

MULTI-PORT CONVERTERS (MPC) FOR

SOURCE-LOAD INTEGRATION

QAB CONVERTER

LED Lighting

EV Loads

N13:1

N1

2:1

FBM

FBM FBM

FBM

N11:1

N14:1

Quad-Active Bridge (QAB)

Energy Storage

AC Loads

DC Loads SELV Grid350 V

48 V

Li

viCi

Full Bridge Module (FBM)

i = {1,2,3,4}

QAB BASED DC MICROGRID

+ 350 Vdc -350 Vdc

MPC #1

PV system

EV

DC House #1

MPC #2

PV system

EV

DC House #2

MPC #n

PV system

EV

DC House # n

• High reserve battery capacity

• Isolated from non-linear in-house loads

• Isolated from nanogrid fault propagation

• Economic optimization energy management

possible

Advantages:

POWER FLOW BY PHASE SHIFT MODULATION

N13:1

N1

2:1

FBM

FBM FBM

FBM

N11:1

N14:1

Quad-Active Bridge (QAB)

ø4

ø3

ø2

ø1

V1'

V2'

V3'

V4'

DC Nanogrids• Radial DC feeders(lighting, Trolley)• Devices, protection, stability

DC Nanogrids V2.0



DC READY DEVICES

PhD Laurens Mackay


DC Nanogrids V2.0












• Markets



Sopra and CSGriP

36

Bipolar Single-Bus

37

Bipolar Single-Bus

PhD Li Ma

38

Hybrid AC-DC

39

Hybrid AC-DC


DC Nanogrids V2.0












• Markets




DC Nanogrids V2.0












• Markets


Radial DC grids








PhD Aditya Shekhar

Refurbished AC to DC Links

Outer

Substation AInner City

Substation B5-20 km

MV/LV

Radial In-city

Distribution

dc

ac

ac

dc

• existing ac link conductors can be refurbished to operate under

dc by bringing two converters at each end

Parallel AC-DC Reconfigurable Links

Outer

Substation AInner City

Substation B5-20 km

MV/LV

Radial In-city

Distribution

dc

ac

ac

dc

• In most cases, the bulk power transfer link depicted in figure

consists of multiple conductors for double, triple or more

three phase links.

• parallel ac-dc operation can offer the same power capacity

using reconfiguration techniques. The active power can be

steered using the dc link converters to run the system at

maximal efficiency for any load demand.

In-City Compact Power Redirection

Outer

Substation A

Inner City

Substation B

MV/LV

Radial In-city

Distribution

dcac

acdc

• power can be redirected compactly within the same

geographical area from local areas of excess generation to

those with higher demand.

Zonal InterconnectionOuter

Substation A1Inner City

Substation B15-20 km

dc

ac

dc

ac

Outer

Substation A2Inner City

Substation B2

• Zonal interconnection for efficient power transfer between

different geographical locations can be advantageous in

achieving lower distribution losses

49

Capacity Enhancement

0% 25% 50% 75%

Link length = 10 km, Load power factor = 0,9, XLPE Medium Voltage

Cable

Current EnhancementDielectric

LossesThermal

ProximitySkin

Effect

Correction factor

relevant for special

cases

A. Shekhar, E. Kontos, L. Ramírez-Elizondo , A. R. Mor and P. Bauer, "Grid Capacity and Efficiency Enhancement by Operating Medium Voltage

AC Cables as DC Links with Modular Multilevel Converters," Journal submitted for review.

50

IMPLEMENTING THE CONCEPT

• Even though physically more than 50 % capacity enhancement is

possible with dc, the actual gains depend on the topology of the

system during normal and contingent operation.

CASE-STUDY: ALLIANDER’S MV DISTRIBUTION SYSTEM

Breaker

Breaker

Breaker

Breaker

Breaker

Breaker

A

B

C

10 kV 3 phase

ac bus (SS1)10 kV 3 phase

ac bus (SS2)

20 MVA

regulators

11 km

L1

L2

L3

ryb

Each transfer link x1, x2 and x3 consists of a 3 phase, crosslinked

polyethylene (XLPE) 3x1x630A aluminium cored cable A, B and C

respectively

It can be observed that the maximum MVA demand limit of

1 p.u. during (n-1) contingency is breached several times

between day 270 and 365

ALLIANDER’S SYSTEM

Breaker

Breaker

Breaker

Breaker

Breaker

Breaker

A

B

C

10 kV 3 phase

ac bus (SS1)10 kV 3 phase

ac bus (SS2)

20 MVA

regulators

11 km

L1

L2

L3

ryb

20

MVA

PROPOSED TOPOLOGY 1

C

Breaker Breaker

A

SS1

MMC

Breaker

MMC

Breaker

MMC

MMC

Breaker

MMC

Breaker

MMC

SS2

B

Breaker Breaker

pn

L1

L2

L3

L4

• During normal operation proposed topology has a capacity

of 40 MVA as against 30 MVA for the original system

• refurbished 6 conductors of 3-core cables A and B to

operate as dc links .


DC Nanogrids V2.0












• Markets


Radial DC grids








Modularity

PhD Pavel Purgat

MVDC/LVDC

Connection

LVDC/LVDC

Connection

LVDC Electric Vehicle

Charging

Low Voltage DC System Designer’ View

i1 i2

+

_

+

_

control signals

Power

flow

V2V1

v2

i2 i2 i2

i2 i2

Class A Class B Class C

Class D Class E

v2 v2

v2 v2

V2V1

Lk

S3S1

S2 S4

S7S5

S6 S8

iLk

vT1vT2

1:n

DAB module

I1 I2

DC- DC Converter – Electronic transformer

Edison’s missing link

VBUS

V2

VGEN

V2

V2

VBUS VGEN

Series -parallel

THE PFCC FOR BIPOLAR LVDC DISTRIBUTION

+

control board

TRIPLE ACTIVE BRIDGE

62 of 15


DC Nanogrids V2.0












• Markets


Radial DC grids







Meshed DC distribution grids

• Sustainable, reliable, high efficient, low cost DC distributiongrid with renewable energy, andelectric vehicles

• Fexibility and modularity

• Decentralized control

• New distribution of costs, market and usage structures

• Integration of multiple energy carriers (gas&elec.)


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