Future grid infrastructure

Field tests of LVDC distribution

LUT LVDC Research Group:

Andrey Lana, Pasi Nuutinen, Antti Pinomaa, Tero Kaipia, Pasi

Peltoniemi, Aleksi Mattsson, Jarmo Partanen

Introduction to utility grid LVDC

• Background

– Even though the Smart Grids is mainly development of intelligent applications and

related ICT, the largest investments will be made to the primary electric infrastructure

• LVDC solution

– Renaissance of “Edison's” direct current electric system based on modern power

electronics

• Basic property

– Improved technical performance compared to existing low voltage grid solutions – more

power transfer with higher control in the same power lines

• Special feature

– High penetration rate of intelligent hardware; thanks to power electronic converter

technology – ready to use hardware for implementing smart applications

• Main philosophy

– Replacing existing AC low voltage networks and parts of medium voltage grid with LVDC

reduces the total costs of electricity distribution

Hypothesis of LVDC Research

Power electronics and DC networks can reduce costs of power

distribution, improve power quality and provide opportunity to

integrate novel smart grid functionalities to power system and

to support improvement of energy efficiency.

r

≈=

≈=

≈=

r

rectifiers

MainsProtection

+750 VDC

-750 VDC

N

20 kV

r

DSOTSOAggregatorsRetailersetc.

Load

Load

Load

Load

Load

Load

=≃

=≃

==

=≈

Pow

er

line s

ignals

20 k

V

==

external control signals

Local communicationsinternal control signals

BMS

230/400 VAC

r

≈=

≈=

≈=

r

rectifiers

MainsProtection

+750 VDC

-750 VDC

N

20 kV

r

DSOTSOAggregatorsRetailersetc.

LoadLoad

LoadLoad

LoadLoad

LoadLoad

LoadLoad

LoadLoad

=≃

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==

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Pow

er

line s

ignals

20 k

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==

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external control signals

Local communicationsinternal control signals

BMS

230/400 VAC

PE

circuit

breakers

Insulation

monitor

Coupling

device

AC

DC

AC

DC

Substation earth

coupling

+750

N

-750

20

kV

MV

sup

ply

I >

3 I>

3 I>>

surge

arresters

Rectifier

Outg

oin

g

DC

cab

le

Co

nce

ntr

ic

PE

co

nd

uct

or

Cap

acit

ors

Auxiliary power

supply 230 VAC

Double-tier

transformer

20.5/0.53/0.53 kV

Control and

communications

electronics

Pad-mounted rectifier

substation

Cap

acit

ors

UDC+

UDC-

IDC

Concept of LVDC Electricity Distribution − Rated voltage range

− 75 – 1500 VDC (LVD 2006/95/EC)

− 120 – 1500 VDC (IEC)

− An LVDC distribution system comprises power electronic converters and DC connection between

the converters

− The entire low-voltage network is realised with DC system

− End-customers have either a direct DC connection, or an AC connection through a DC/AC

inverter, or a DC connection through a step-down DC/DC converter

− System comprises an integrated control and communications system

• LVDC system provides

– Safe and reliable electric energy transmission from the MV network to the LV customers

– Constantly good-quality voltage supply for customers

– An easy-to-control connection point for small-scale generation units and storages

– A ready-to-use platform for smart metering, demand management and network control

110/20 kV Substation

Unipolar customer connection

AC/DCDC/AC

DC/AC DC/AC

DC/AC

AC/DC

Bipolar LVDC system

Unipolar customer connection

AC/DCDC/AC

DC/AC DC/AC

DC/AC

AC/DC

Unipolar customer connection

AC/DCDC/AC

DC/AC DC/AC

DC/AC

AC/DC

Bipolar LVDC system

20 kV main line

NOP

LVDC s

uppl

y ar

ea

LVDC

20/PJ

DC/AC

AC

LVDC

20/1/0.4 kV

DC/AC

0.4 kV 0.4 kV

20/0.4 kV 20/0.4 kV20 kV

0.4 kV 0.4 kV

L

DC

AC

AC

AC

AC

AC

DCDCDC DC

AC

ACAC

AC

P

Backup connection

Suburban district

Indoor DC

AC 20 kV

Urban district

Public lighting

LVDC

20/PJ

DC/AC

AC

LVDC

20/1/0.4 kV

DC/AC

0.4 kV 0.4 kV

20/0.4 kV 20/0.4 kV20 kV

0.4 kV 0.4 kV

L

DC

AC

AC

AC

AC

AC

DCDCDC DC

AC

ACAC

AC

P

Backup connection

Suburban district

Indoor DC

AC 20 kV

Urban district

Public lighting

LVDC in Rural and Urban Environments

Highlights – Research Platforms

• Laboratory prototype

– Test environment for technical solutions, functionalities and design methods of LVDC technology

– Study implementation of developed solutions in practical environment

– Provide feedback for equipment development

• Impact of environmental conditions

• Requirements of installation and maintenance on equipment structures

• Compatibility with interconnected systems and devices

– Verification and development of system design, control algorithms and management systems

• Real-life network environment

– Durability and reliability of electronic components in demanding distribution network environment

– Inspections of installations and authorised approvals of structures

• Verification of electrical safety

• Equipment ratings

• Documentation

– Experiences from electricity end-users and from installations and operations personnel

– Practical experiences to support LVDC system standardisation

Field tests of LVDC distribution

by LUT and SSS Oy – 1.7 km bipolar LVDC network with three three-phase customer-end inverters supplying

four residential houses installed in Suomenniemi

– Objective to test converter technology and collect experiences from LVDC distribution

– Continuous 24/7 operation during June 2012 – May 2013

200

m

CEI #1

CEI #2

CEI #3

Connected to

–DC

Connected to

+DC

Connected to

+DC

±750

VDC

200

m

200

m

CEI #1

CEI #2

CEI #3

Connected to

–DC

Connected to

+DC

Connected to

+DC

±750

VDC

Field Installations by LUT and SSS Oy

1. Half-controlled thyristor rectifier

2. -750 V side moulded-case circuit breaker

3. +750 V side moulded-case circuit breaker

4. DC network surge protectors

5. DC network capacitors

6. Thyristor control, insulation monitoring, and

measurements

7. Rectifier control, embedded PC, and

communications

2.

3.4.

5.

1.

8.

10.

7.

6.

9.

1. DC supply bus

2. Common-mode choke

3. DC network surge protector

4. Electronics power supply

5. DC circuit breaker

6. Capacitor

7. Power electronics (IGBT)

8. Output filter

9. Output isolation transformer

10. Output bus

Rectifying substation

Inverter substation

1.

2.

4.5.

6.

7.3.

Fully customisable hardware and software platform for research purposes. Comply with national and IEC electrical safety requirements.

System Management

Web portal for monitoring and control

Examples of measurements and warnings (fault codes) during July 2012 thunderstorm.

M99131

ADSL modem

Backhaul

NW

VPN

Ethernet switch

Artila

Fiber/Ethernet

converter

Artila

Control board

Fiber/Ethernet

Switch

VS 1 2 3

Inverter 1

Server Client1

Artila

Inverter 2

Client2

Single mode Fiber

Artila

Inverter 3

Client3

Rectifier

Backhaul

NW

VPN

access with 3G

modem

Backup remote

Web-browser

controllableWeb-browser

controllable

Control board

Control board

Control board

Fiber/Ethernet

converterFiber/Ethernet

converter

Local ICT-system

• Control functions

– Rectifier control, i.e. DC network start-up and shutdown

– Remote emergency shutdown of the system

– Customer-end inverter (CEI) control (start-up, shutdown, reset)

• Real-time monitoring, rectifier

– DC network voltages and currents

– Rectifier power electronics temperature

– DC network isolation resistance

• Real-time monitoring, customer-end inverter

– DC voltage and current

– Customer-end phase voltages and currents

– Control electronics supply voltage and system temperatures (cabinet and power electronics)

– Customer-end frequency

• Fault situations

– Fault code display and reset

– Alarm reporting

– Recording of high-resolution waveforms before and after fault (“black box” operation)

• Logging

– 1 minute resolution data (maximum, minimum and mean values for powerflow, voltages and currents)

– Customer power quality data (currently with 16 seconds interval)

– Customer voltage and current harmonic content (1 minute interval snapshots)

– Network insulation measurements

– Faults and system events

System Management

System Management

Embedded ICT system

• Remote supervision and

management system providing

web-based portal with high-

resolution measurements,

logging, fault identification and

event recorder

• Power quality analyser functions

(IEEE Std 1459-2010)

Conclusions on field tests of LVDC distribution

First implementation of modern LVDC distribution and

CEI based supply in continuous use by a DSO

Very reliable, though it is a research setup

Special situations have been managed as planned

Quality of supply has been high, but there is still room for

improving the control algorithms

Platform for further development of smart grid

functionalities

Field Installations - Next steps

370 - 440 VDC

DC/AC

DC/DC

Medium

voltage

network

DC/DC

440 VDC

DC/DC

440 VDC

F F

F

F

F

F

F F

F

F

F

F

• Continuous collection of user experiences

• Updates to converter hardware and system controls

• Connection of energy storages and local generation

• Integration of microgrid controls

• Island mode control

• Market oriented control

• Standardization issues

16

Rectifying Substation

17

Double-Tier Transformer and Rectifier

18

CEI #3 and CEI Control Electronics

19

Rectifier Testing

20

First System Start-Up and CEI Tests

21

First System Start-Up and CEI Tests

22

RF EMI Measurements

23

PLC Communications Measurements

24

Winter 2012-2013

25

Researcher Exercising in February 2013

Thank you!