EPE '14 ECCE Europe Tutorial #2 - Challenges on the Road to Future High-Voltage Multi-Terminal DC Networks

Challenges on the Road to Future High-
Voltage Multi-Terminal DC Networks
Introduction
Dr. R. Teixeira Pinto, Delft University of Technology
R.TeixeiraPinto@tudelft.nl /rteixeirapinto @Hredric
Co-authors:
Prof.Dr. P. Bauer, TU Delft (P.Bauer@tudelft.nl)
Dr. J. Enslin, UNC Charlotte (jenslin@uncc.edu)

Introduction
Table of Contents
1 Introduction
Today's Agenda
The NSTG Project
Additional Material
2 Background
Motivation
Problem De

nition
MTdc Network Challenges
Objectives and Research Questions
Outline and Approach
Dr. R. Teixeira Pinto (TU Delft) MTdc Networks Tutorial: EPE'14-ECCE EU August 25, 2014 2 / 18

Introduction Today's Agenda
Agenda
9:30{9:50 { P. Bauer / R. T. Pinto: Introduction

Agenda
9:50{10:20 { P. Bauer: A review of MTdc networks with Classic HVdc

Agenda
10:20{10:50 { P. Bauer: The modern VSC-HVdc technology

Agenda
10:50{11:10 { Coee Brake

Agenda
10:50{11:10 { Coee Brake
11:10{11:40 { R. T. Pinto: Challenges on the road to future MTdc
networks

Agenda
10:50{11:10 { Coee Brake
networks
11:40{12:20 { R. T. Pinto: Optimal load-
ow control of MTdc
networks

Agenda
10:50{11:10 { Coee Brake
networks
ow control of MTdc
networks
12:20{13:00 { R. T. Pinto : MTdc network modelling and
experimental validation

Agenda
10:50{11:10 { Coee Brake
networks
ow control of MTdc
networks
12:20{13:00 { R. T. Pinto : MTdc network modelling and
experimental validation
13:00{14:00 { Lunch break

Introduction The NSTG Project
NSTG Project Timeline
Main project goal: identify and study
technical and economical aspects of
a transnational electricity network in
the North Sea for the connection of
oshore wind power and to promote
energy trade between countries.

WP1
energy trade between countries. 1 2 3 4
WP3
WP2
WP4
WP5
WP6
WP7

WP1
WP3
WP2
WP4
WP5
WP6
WP7
WP3 - NSTG operation and control
WP4 { Real-time multi-terminal network testing

WP1
WP3
WP2
WP4
WP5
WP6
WP7
WP1 { Inventory of available technology, modularity and
exibility
WP2 { Technical and economic evaluation of dierent solutions
WP3 - NSTG operation and control
WP4 { Real-time multi-terminal network testing
WP5 { Optimisation of NSTG solutions
WP6 - Grid integration: planning, congestion and stability
WP7 - Costs, bene

ts, regulations and market aspects of the NSTG

Introduction Additional Material
More information and materials can be found on:
NSTG website:
http://www.nstg-project.nl/
Ph.D. Thesis
Multi-Terminal DC Networks:
System Integration, Dynamics and
Control

Background
Table of Contents
1 Introduction
Today's Agenda
The NSTG Project
Additional Material
2 Background
Motivation
Problem De

nition
MTdc Network Challenges
Objectives and Research Questions
Outline and Approach

Background Motivation
General Background and Motivation
17
15
13
11
9
7
5
3
1
1970 1980 1990 2000 2010 2020 2030
Year
Energy [Billion toe], Population [Billion]
Primary Energy use
Electricity Consumption
Population
Worldwide Primary Energy Use.
5000
3000
1000
700
500
300
100
70
50
30
10
5 7
3
1
0.7
0.5
0.3
0.1
0.07
0.05
0.03
1970 1980 1990 2000 2010 2020 2030
Year
Electricity Generation [TWh]
Total
Renewables
Onshore Wind
Offshore Wind
Electricity generation in the
European Union.

nition
Why use HVdc Transmission
19th century - AC was preferred mainly because: easier to achieve higher
voltages (lower transmission losses) / Three-phase synchronous generators
was easier, cheaper and more ecient than dynamos.
Reasons for choosing HVdc over HVac today:
1 Greater power per conductor: an overhead HVdc line can take 1.5 to
2.1 times more power than a HVac overhead line, and an
underground HVdc line can take 2.9 to 3.8 times more power than an
underground HVac equivalent.
2 Higher voltages possible: Since 2010, HVdc voltages of up to 1600
kV ( 800 kV) were already possible (Xiangjiaba { Shanghai HVdc
line [1]) x 1200 kV for HVac (achieved in Russia 1988-1996).
3 Simpler line construction

nition
50 m
± 500 kV
100 m
2 x 500 kV
ROW Comparison between HVac and
HVdc lines [2].
Transmission of 2000 MW:
500 kV HVdc line, the ROW
is circa 50 m.
For a HVac line, due to stability
limits, the ROW is doubled
(additional three-phase circuit is
needed to transmit the same
2000 MW [2].
Therefore (in this case) an HVdc line
is usually 30% cheaper than for its
HVac equivalent [3].
Right-of-way for an AC Line designed to
carry 3,000 MW is more than 70% wider.

nition
4 Transmission distance is not limited by stability
Active power [MW] Voltage at receiving node [kV]
0 1000 2000 3000 4000
800
700
600
500
400
300
200
100
0
cos(φ)=0.95 cap
cos(φ)=1
cos(φ)=0.95 ind
Transmission Distance = 250 km
800
700
600
500
400
300
200
100
0 1000 2000 3000 4000
Active power [MW]
0
Voltage at receiving node [kV]
cos(φ)=0.95 cap
cos(φ)=1
cos(φ)=0.95 ind
Transmission Distance = 500 km

nition
4 Transmission distance is not limited by stability
4
pu]
[SIL 3.5
/ Power 3
2.5
Transmittable 2
1.5
Maximum 1
0.5
0
Transmission Distance [km] 69 kV line
115 kV line
230 kV line
345 kV line
500 kV line
765 kV line
50 100 150 200 250 300 350 400 450 500 550 600
Maximum transmittable power

nition
5 No skin, proximity eect or need for reactive power compensation.
6 Each conductor = independent circuit (if ground can be used).
7 Synchronous operation is not required.
8 Does not contribute to short-circuit current of the ac system.
9 Less problems with resonances.
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
2.5
2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
conductor radius [mm]
0
Current distribution [pu]
Drake
Hokkaido
Honshu
50 Hz
Hokkaido-Honshu HVdc link
(600 MW, ±250 kV)
60 Hz
Shin Shinano
CSC (600 MW)
Shikoku
ac transmission line (500 kV)
ac transmission line (187 ~ 275 kV)
substations
back-to-back converter
dc-ac converter
dc transmission line
Anan-Kihoku HVdc link
(2800 MW, ±250 kV)
Sakuma
CSC (300 MW)
Higashi-Shimizu
CSC (300 MW)
Minami-Fukumitsu
CSC (300 MW)
HVdc in Japan

nition
When use HVdc Transmission for OWFs
Depends on a technical-economic analysis.
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 20 40 60 80 100 120 140 160 180 200 220 240
Transmission Distance [km]
Transmittable Power [pu]
132 kV AC - 630 mm2
132 kV AC - 1000 mm2
220 kV AC - 630 mm2
220 kV AC - 1000 mm2
400 kV AC - 630 mm2
400 kV AC - 1000 mm2
80 kV DC - 300 mm2
80 kV DC - 1200 mm2
150 kV DC - 300 mm2
150 kV DC - 1200 mm2
320 kV DC - 300 mm2
320 kV DC - 1200 mm2
Maximum transferrable power x transmission distance for ac and dc submarine cables.

nition
HVdc x HVac Transmission - Costs
Not an exact science: break-even area not break-even point.
AC
Losses
AC
Line
AC
Term.
DC
Losses
DC
Line
DC
Term.
Transmission distance
Costs
Break-even
area
Cost Comparison between HVac and HVdc
transmission systems.
Average transmission line cost in the
USA (a 500 kV line):
HVDC - 1.5 { 2.0 M$/mile
HVAC - 3.0 { 3.5 M$/mile
Data used in exercise at TU Delft:
AC Cable Cost: 0.9 Me/km
AC Substation Cost: 3 Me each
Q (SVC) Compensation Cost:
0.04 Me/MVAr
DC Cable Cost: 0.7 Me/km
Converter Cost: 70 Me each

nition
The need for HVdc transmission systems
Future vision of the NSTG by
the OMA [4].
UK1
UK2
BE1
DE2
NL1
NL2
DE1
DK2
DK1
HUB1
HUB2
HUB3
NL
UK
BE
DK
DE
HUB4
HUB5
Future vision by the NSTG
project.

nition
The need for HVdc transmission systems
Future vision of the NSTG by
the OMA [4].
UK1
UK2
BE1
DE2
NL1
NL2
DE1
DK2
DK1
HUB1
HUB2
HUB3
NL
UK
BE
DK
DE
HUB4
HUB5
Future vision by the NSTG
project.
Best renewable resources sites: remotely
located.
Using HVdc transmission is more ecient
(than HVac).
Oshore wind potential: 28% of wind energy
share [5]
44 GW of OWF by 2020: 31.3% annual growth
(on average).
New OWFs: further away and higher capacity
[6]
30% of all generation goes ac/dc before
consumption. Prediction: staggering 80%.
dc networks (level): microgrids (house) and
smart grids (district), electronic power
distribution systems (cities/country) [7] and
supergrids (country/continent) [8, 9].

Background MTdc Network Challenges
There are 5 main technical challenges
Challenge 1
System Integration
Challenge 2
Power Flow Control
Challenge 3
Dynamic Behaviour
Challenge 4
Stability
Challenge 5
Fault Behaviour

Background Objectives Research Questions
Research Questions
Chapter 2: What is the best HVdc technology and con

guration for a
MTdc network in the North Sea?

guration for a
Chapter 3: How does the power
ow in MTdc networks?

guration for a
Chapter 4: How to model the combined dynamic behaviour of a
MTdc network?

guration for a
MTdc network?
Chapter 5: What are the shortcomings of the main methods for
controlling the direct voltage in MTdc networks?

guration for a
MTdc network?
Chapter 6: What is needed to control the power
ow in MTdc
networks?

guration for a
MTdc network?
ow in MTdc
networks?
Chapter 7: What is needed for a MTdc network to be able to
withstand and recover from faults in the connected ac systems, or in
the dc grid itself, without halting its operation?

guration for a
MTdc network?
ow in MTdc
networks?
Chapter 8: What are the main variables aecting the small-signal
stability of MTdc networks?

guration for a
MTdc network?
ow in MTdc
networks?
Chapter 8: What are the main variables aecting the small-signal
stability of MTdc networks?
Chapter 9: To what extent is it possible to reproduce the behaviour
of a high-voltage MTdc network through a low-voltage one?

Background Outline
Outline and Approach Part I.
Introduction
Literature Review
Part II.
Part V.
Steady-State
Analysis
Part III.
Dynamic Analysis
Part IV.
Experimental
Stability Analysis
Work
Conclusions
1. System Integration
2. Power Flow Control
3. Dynamic Behavior
4. Stability
4. Stability
5. Fault Behavior
3. Dynamic Behavior
4. Stability
3. Network
Operation and
Power Flow
2. HVdc
Transmission
Systems
4. Dynamic
Modelling
5. Control of MTdc
Networks
8. Small-Signal
Analysis
7. Fault Analysis
9. Laboratory Setup
of a LV-MTdc
System
6. The Distributed
Voltage Control
Strategy

References
[1] J. Dorn, H. Gambach, and D. Retzmann, HVDC transmission technology for
sustainable power supply, in 9th International Multi-Conference on Systems,
Signals and Devices (SSD), 2012, pp. 1{6.
[2] M. Rashid, Power Electronics Handbook: Devices, Circuits and Applications, ser.
Engineering. Elsevier Science, 2010, iSBN: 9780080467658.
[3] M. Bahrman, HVDC transmission overview, in IEEE/PES Transmission and
Distribution Conference and Exposition, 2008, pp. 1{7.
[4] The Oce for Metropolitan Architecture. ZEEKRACHT, NETHERLANDS, THE
NORTH SEA, 2008: A masterplan for a renewable energy infrastructure in the
North Sea. Last Accessed: 07 February, 2013. [Online]. Available:
http://oma.eu/projects/2008/zeekracht
[5] Energy Company of the Netherlands (ECN), Renewable Energy Projections as
Published in the National Renewable Energy Action Plans of the European Member
States Summary report, ECN, Petten, Technical Report November 2011, 2011.
[Online]. Available:
http://www.ecn.nl/docs/library/report/2010/e10069 summary.pdf
[6] European Wind Energy Association, Wind in power: 2011 european statistics,
EWEA, Brussels, Technical Report, 2012. [Online]. Available:

References
http://www.ewea.org/

les/library/publications/statistics/
Wind in power 2011 European statistics.pdf
[7] D. Boroyevich, I. Cvetkovic, D. Dong, R. Burgos, F. Wang, and F. Lee, Future
electronic power distribution systems a contemplative view, in 12th International
Conference on Optimization of Electrical and Electronic Equipment. IEEE, May
2010, pp. 1369{1380.
[8] S. Taggart, G. James, Z. Dong, and C. Russell, The Future of Renewables Linked
by a Transnational Asian Grid, Proceedings of the IEEE, vol. 100, no. 2, pp.
348{359, 2012.
[9] M. Aredes, A. F. Da Cunha De Aquino, C. Portela, and E. Watanabe, Going the
distance - Power-Electronics-Based Solutions for Long-Range Bulk Power
Transmission, IEEE Industrical Electronics Magazine, no. March, p. 13, Mar. 2011.

A Review of MTdc Networks with
Classic HVdc
Part I
Co-authors:

Early HVdc Systems
Table of Contents
1 Early HVdc Systems
The Thury System
The World's 1st MTdc Network
2 HVdc Classic Systems
Past
Present
Future
3 HVdc Transmission Systems Con

gurations
Monopolar Homopolar
Bipolar Con

guration
4 From Point-to-Point to MTdc Networks
SACOI
Hydro-Quebec { New England
5 MTdc Network Topologies
Technology
Series x Parallel
Classi

cation Dr. R. Teixeira Pinto (TU Delft) MTdc Networks Tutorial: Part I August 25, 2014 2 / 23

Early HVdc Systems The Thury System
12 kV
v
G
100 A
v
G
v
G
M M M M
100
kW
50
kW
M
v
M
v
M
v
G
300
kW
300
kW
Diagram of a 1.2 MW Thury system.
Despite HVac success, eorts for HVdc
development continued.
Dr. R. Teixeira Pinto (TU Delft) MTdc Networks Tutorial: Part I August 25, 2014 3 / 23

12 kV
v
G
100 A
v
G
v
G
M M M M
100
kW
50
kW
M
v
M
v
M
v
G
300
kW
300
kW
Rene Thury (Swiss): dc generators and
motors in series. Constant current and
variable voltage to meet power demand.

12 kV
v
G
100 A
v
G
v
G
M M M M
100
kW
50
kW
M
v
M
v
M
v
G
300
kW
300
kW
Generators/motors had series switch to
short-circuit when not used. For
generator operation: speed up until
nominal line current and then
short-circuit switch was opened.

150
100
58
22
14
6
Chambéry
Lyon - Moutiers -
La Bridoire - Bozel
Wilesden -
Irongridge
Lyon - Moutiers
- La Bridoire
Lyon -
Moutiers
St. Maurice - Lausanne
La Chaux - de-Fonds
Gorzente River - Genoa
1889 1897 1906 1912 1925
Year
Direct Voltage
[kV]
Direct voltages in the Thury systems
between 1889 and 1925.
By the 1910s: at least 15 Thury
systems in Europe (France, Hungary,
Italy, Russia, Spain and Switzerland)
[1].

150
100
58
22
14
6
Chambéry
Lyon - Moutiers -
La Bridoire - Bozel
Wilesden -
Irongridge
Lyon - Moutiers
- La Bridoire
Lyon -
Moutiers
St. Maurice - Lausanne
La Chaux - de-Fonds
Gorzente River - Genoa
1889 1897 1906 1912 1925
Year
Direct Voltage
[kV]
Direct voltages in the Thury systems
between 1889 and 1925.
By the 1910s: at least 15 Thury
systems in Europe (France, Hungary,
Italy, Russia, Spain and Switzerland)
[1].
Bipolar voltages of up to 150 kV where
successfully achieved.

Early HVdc Systems The World's 1st MTdc Network
Moutier-Lyon-Bridoire-Bozel Thury system
Start: 4.3 MW HVdc system between
Lyon and Moutier (hydroelectric plant)
v v v v
Bozel
9 MW
v v v v
v v v v
v
12 kV
v
150 A
La Bridoire
6 MW
Moutier
4.3 MW
Lyon
19.3 MW
29 kV
40 kV
129 kV
Layout of the 1st HV MTdc network
Lyon
19.3 MW
La Bridoire
6 MW
Moutier
4.3 MW
129 kV
89 kV
direct voltage
transmission distance
90 km 45 km 11 km
60 kV
Bozel
9 MW
Voltage and distances the terminals.

75 A and the voltage up to 57.6 kV (16
generators at Moutier).
v v v v
Bozel
9 MW
v v v v
v v v v
v
12 kV
v
150 A
La Bridoire
6 MW
Moutier
4.3 MW
Lyon
19.3 MW
29 kV
40 kV
129 kV
Lyon
19.3 MW
La Bridoire
6 MW
Moutier
4.3 MW
129 kV
89 kV
direct voltage
90 km 45 km 11 km
60 kV
Bozel
9 MW

1911: 1st upgrade. 2nd hydro plant at
La Bridoire (6 MW). The current was
doubled to 150 A.
v v v v
Bozel
9 MW
v v v v
v v v v
v
12 kV
v
150 A
La Bridoire
6 MW
Moutier
4.3 MW
Lyon
19.3 MW
29 kV
40 kV
129 kV
Lyon
19.3 MW
La Bridoire
6 MW
Moutier
4.3 MW
129 kV
89 kV
direct voltage
90 km 45 km 11 km
60 kV
Bozel
9 MW

doubled to 150 A.
Finally, a third hydroelectric plant,
rated at 9 MW, was added in Bozel.
v v v v
Bozel
9 MW
v v v v
v v v v
v
12 kV
v
150 A
La Bridoire
6 MW
Moutier
4.3 MW
Lyon
19.3 MW
29 kV
40 kV
129 kV
Lyon
19.3 MW
La Bridoire
6 MW
Moutier
4.3 MW
129 kV
89 kV
direct voltage
90 km 45 km 11 km
60 kV
Bozel
9 MW

doubled to 150 A.
Finally, a third hydroelectric plant,
rated at 9 MW, was added in Bozel.
Until 1937, when it was dismantled, the
Moutier-Lyon-Bridoire-Bozel Thury
system operated with four terminals
and can be assumed the world's 1st
multi-terminal HVdc network.
v v v v
Bozel
9 MW
v v v v
v v v v
v
12 kV
v
150 A
La Bridoire
6 MW
Moutier
4.3 MW
Lyon
19.3 MW
29 kV
40 kV
129 kV
Lyon
19.3 MW
La Bridoire
6 MW
Moutier
4.3 MW
129 kV
89 kV
direct voltage
90 km 45 km 11 km
60 kV
Bozel
9 MW

HVdc Classic Systems
Table of Contents
The Thury System
Past
Present
Future

HVdc Classic Systems Past
Mercury-arc Valve HVdc Systems
Photography from the
Gotland 1 mercury-arc valve
hall during the 1950s [2].
1st system: 1930 (USA). From hydroelectric
power plant in Mechanicville to Schenectady
(NY). 37 km / 12 kV / 5 MW. Interesting fact:
40 Hz at plant and 60 Hz in NY [1].

Mercury-arc Valve HVdc Systems
Photography from the
Gotland 1 mercury-arc valve
hall during the 1950s [2].
1st system: 1930 (USA). From hydroelectric
power plant in Mechanicville to Schenectady
(NY). 37 km / 12 kV / 5 MW. Interesting fact:
40 Hz at plant and 60 Hz in NY [1].
1939: Back

re issue solved by Uno Lamm
(Sweden).

(Sweden).
1939 - 1951: 7 experimental HVdc transmission
systems using mercury-arc valves were built in
Switzerland, Germany, Sweden and Russia.

(Sweden).
1939 - 1951: 7 experimental HVdc transmission
systems using mercury-arc valves were built in
Switzerland, Germany, Sweden and Russia.
1st commercial system: 1954, Gotland 1
(Sweden - ASEA) [2]. Connected the Swedish
mainland, at Vstervik, to Ygne in the island of
Gotland. 98 km / 20 MW / 100 kV [3].

HVdc Systems Comeback
After war of the currents: 60
years for HVdc transmission
systems to

ghtback.
600
500
400
300
200
100
0
Pacific DC Intertie
Volgograd-
Donbass
Konti-Skan 1
Moscow–Kashira
Legend
Elbe-Project
Charlottenburg-
Moabit
Zurich-
Wettingen
Gotland 1
Lehrte-Misburg
Kingsnorth
Nelson River
Bipole 1
Inter-Island 1
Vancouver Island 1
SACOI 1
Sakuma B2B
Cross-Channel
Trollhattan-Merud
Mechanicville–Schenectady
1930 1935 1940 1945 1950 1955 1960 1965 1970 1975
Commissioning Year
Direct Voltage [kV]
Biggest
1620 MW
Average
357 MW
Evolution of mercury-arc valves HVdc systems.

ghtback.
1970s: voltages 400 kV and
capacities 1000 MW.
600
500
400
300
200
100
0
Pacific DC Intertie
Volgograd-
Donbass
Konti-Skan 1
Moscow–Kashira
Legend
Elbe-Project
Charlottenburg-
Moabit
Zurich-
Wettingen
Gotland 1
Lehrte-Misburg
Kingsnorth
Nelson River
Bipole 1
Inter-Island 1
Vancouver Island 1
SACOI 1
Sakuma B2B
Cross-Channel
Trollhattan-Merud
1930 1935 1940 1945 1950 1955 1960 1965 1970 1975
Commissioning Year
Direct Voltage [kV]
Biggest
1620 MW
Average
357 MW

ghtback.
1970s: voltages 400 kV and
capacities 1000 MW.
Paci

c Intertie: 1440 MW,
500 kV
Nelson River: 1620 MW,
450 kV [1, 3, 4, 5, 6].
600
500
400
300
200
100
0
Pacific DC Intertie
Volgograd-
Donbass
Konti-Skan 1
Moscow–Kashira
Legend
Elbe-Project
Charlottenburg-
Moabit
Zurich-
Wettingen
Gotland 1
Lehrte-Misburg
Kingsnorth
Nelson River
Bipole 1
Inter-Island 1
Vancouver Island 1
SACOI 1
Sakuma B2B
Cross-Channel
Trollhattan-Merud
1930 1935 1940 1945 1950 1955 1960 1965 1970 1975
Commissioning Year
Direct Voltage [kV]
Biggest
1620 MW
Average
357 MW

HVdc Classic Systems Present
HVdc Classic: Thyristor Technology
Thyristor (or SCR): possible to
achieve higher voltages.
6-inch HVdc thyristor.

A modern 6-inch thyristor: up
to 4 kA / block up to 8.5 kV [7].
Blocking Voltage [kV]
8.5kV 27000
Si-area [mm²]
9
8
7
6
5
4
3
2
1
0
1.65
kV
1.5 “
1970 1975 1980 1985 1990 1995 2000 2005 2010
24000
21000
18000
15000
12000
9000
6000
3000
1000 MW converter
à 14.000 thyristors
1000 MW converter
à 400 thyristors
6 “
0
Evolution of thyristor technology.

Thyristor valves improvements:
larger powers through longer
distances.
0 500 1000 1500 2000 2500 3000
1800
1600
1400
1200
1000
800
600
400
200
0
Direct Voltage [kV]
Transmission distance [km]
Evolution of CSC-HVdc voltage.

distances.
1st commercial system: 1972
Eel River link in Canada (GE).
B2B / 320 MW / 160 kV [3, 4].
0 500 1000 1500 2000 2500 3000
1800
1600
1400
1200
1000
800
600
400
200
0
Direct Voltage [kV]

distances.
1st commercial system: 1972
Eel River link in Canada (GE).
B2B / 320 MW / 160 kV [3, 4].
Very mature technology
( 140 HVdc systems
worldwide) [4].
0 500 1000 1500 2000 2500 3000
1800
1600
1400
1200
1000
800
600
400
200
0
Direct Voltage [kV]

The HVdc Classic Station (24-pulse converter)
11 1) Converter bridges
10
Metallic
Return
Neutral
bus
6 6
3 3
1 1
AC System
AC
FILTERS
AC
FILTERS
DC
FILTERS
DC
FILTERS
DC LINE
DC LINE
Earth
electrode
1 1
2 2
5 4 7
4 5
8
9
2) Converter transformers
3) Smoothing reactors
4) AC

lters
5) Reactive power supply
6) DC

lters
7) Surge arresters
8) Neutral bus surge
capacitor
9) Fast dc switches
10) Earth electrode
11) DC line

HVdc Classic Systems Future
Undisputed for bulk transmission
Boxplot distribution of HVdc Classic projects worldwide.
7200
6000
5000
2500
1000
500
30
Installed Capacity [MW]
1600
1000
700
500
35
Transmission Voltage [kV]
2375
2090
1000
700
178
12
Transmission Distance [km]
Interquartiles (50%):
180 - 1000 km
( 250 kV) - ( 500 kV)
500 - 2500 MW

HVdc Classic Systems Future
Undisputed for bulk transmission
Worldwide installed capacity.
200
180
160
140
120
100
80
60
40
20
0
1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
Installed Capacity [GW]
UHVdc ratings up to 1600 kV ( 800 kV) and 7.2 GW.
(e.g. Jinping - Sunan link in China [8]).
Only in China more than 270 GW over 40 project are predicted
between 2010 and 2020 (for further info)

gurations
Table of Contents
The Thury System
Past
Present
Future

gurations Monopolar Homopolar
Homopolar Con

gurations
Idc
Vdc
2Idc
Vdc
Idc
Ground return

gurations
Idc
Vdc
2Idc
Vdc
Idc
Ground return
Idc
Vdc
2Idc
Vdc
Idc
Metallic return

gurations
Idc
Vdc
2Idc
Vdc
Idc
Ground return
Idc
Vdc
2Idc
Vdc
Idc
Metallic return
Monopolar Con

gurations
Idc
Vdc
Ground return
Idc
Vdc
Metallic return

guration
Idc
Vdc
Vdc
Idc
Ground return

guration
Idc
Vdc
Vdc
Idc
Ground return
Idc
Vdc
Vdc
Idc
Metallic return

guration
Idc
Vdc
Vdc
Idc
Ground return
Idc
Vdc
Vdc
Idc
Metallic return
Bipolar con

gurations during faults
Vdc
Idc
HVdc cable fault

gurations during faults
Vdc
Idc
HVdc cable fault
Vdc
Idc
HVdc converter fault

From Point-to-Point to MTdc Networks
Table of Contents
The Thury System
Past
Present
Future

From Point-to-Point to MTdc Networks SACOI
Mainland
Italy
San Dalmazio
Lucciana
Corsica
Mediterranean
Codrogianos
Sardinia
Sea
200 kV dc overhead line
200 kV dc submarine cable
Electrode line
Converter stations
Insolator stations
Aerial view
1967: 6-pulse mercury-arc converters,
monopole, ground return.
Italy
200 MW
200 kV
1000 A
Corsica
50 MW
200 kV
250 A
Sardinia
200 MW
200 kV
1000 A
220 kV 220 kV
90 kV
Single line diagram [10]

Mainland
Italy
San Dalmazio
Lucciana
Corsica
Mediterranean
Codrogianos
Sardinia
Sea
Electrode line
Converter stations
Insolator stations
Aerial view
Line capacity: 200 MW @ 200 kV (300 km
OHL, and 120 km submarine [9]).
Italy
200 MW
200 kV
1000 A
Corsica
50 MW
200 kV
250 A
Sardinia
200 MW
200 kV
1000 A
220 kV 220 kV
90 kV

Mainland
Italy
San Dalmazio
Lucciana
Corsica
Mediterranean
Codrogianos
Sardinia
Sea
Electrode line
Converter stations
Insolator stations
Aerial view
1987: 1st MTdc HVdc network. Lucciana
converter in Corsica (thyristor / 50 MW) [10].
Italy
200 MW
200 kV
1000 A
Corsica
50 MW
200 kV
250 A
Sardinia
200 MW
200 kV
1000 A
220 kV 220 kV
90 kV

Mainland
Italy
San Dalmazio
Lucciana
Corsica
Mediterranean
Codrogianos
Sardinia
Sea
Electrode line
Converter stations
Insolator stations
Aerial view
1987: 1st MTdc HVdc network. Lucciana
converter in Corsica (thyristor / 50 MW) [10].
1992: Sardinian and Italian converter upgraded
to thyristor technology (from 200 to 300 MW).
Italy
200 MW
200 kV
1000 A
Corsica
50 MW
200 kV
250 A
Sardinia
200 MW
200 kV
1000 A
220 kV 220 kV
90 kV

From Point-to-Point to MTdc Networks Hydro-Quebec { New England
Phase I (Oct 1986): 2 terminals (Des
Cantons - Comerford). 172km / 450
kV / 690 MW [11, 12].
Aerial view [12]
Radisson
Nicolet
Des Cantons
Canada
Comerford
Sandy Pond
USA

kV / 690 MW [11, 12].
Phase II (1990): +3 converters.
Radission (2250 MW) and Sandy Pond
(2000 MW) [12]. Goal: power from La
Grande hydro plant to Boston.
Aerial view [12]
Radisson
Nicolet
Des Cantons
Canada
Comerford
Sandy Pond
USA

kV / 690 MW [11, 12].
1992: Nicolet (2138 MW), Montreal.
Aerial view [12]
Radisson
Nicolet
Des Cantons
Canada
Comerford
Sandy Pond
USA

kV / 690 MW [11, 12].
No dc breakers (dc-side contingencies
are dealt via control actions).
Single line diagram
Chissibi
Qu´ebec
Nemiscau
735 kV
735 kV
315 kV
1022 km
105 km
383 km
735 kV
735 kV
Sherbrooke
New England
345 kV
Legend
Generation
Islanding breaker
DC converter
Transformer
Decommissioned
6 16
12
La Grande-2A La Grande-2
La Grande-1
Radisson
2 250 MW
Nicolet
2 138 MW
Des Cantons
690 MW
Comerford
690 MW
Sandy Pond
2 000 MW
± 450 kV

kV / 690 MW [11, 12].
No dc breakers (dc-side contingencies
are dealt via control actions).
Initial 2 converters were
decommissioned after reassessment of
the additional bene

ts they would bring
to the three-terminal MTdc (ABB) [12].
Single line diagram
Chissibi
Qu´ebec
Nemiscau
735 kV
735 kV
315 kV
1022 km
105 km
383 km
735 kV
735 kV
Sherbrooke
New England
345 kV
Legend
Generation
Islanding breaker
DC converter
Transformer
Decommissioned
6 16
12
La Grande-1
Radisson
2 250 MW
Nicolet
2 138 MW
Des Cantons
690 MW
Comerford
690 MW
Sandy Pond
2 000 MW
± 450 kV

ts they would bring
to the three-terminal MTdc (ABB) [12].
Remaining 3 form a MTdc network
(1480 km of OHL).
Single line diagram
Chissibi
Qu´ebec
Nemiscau
735 kV
735 kV
315 kV
1022 km
105 km
383 km
735 kV
735 kV
Sherbrooke
New England
345 kV
Legend
Generation
Islanding breaker
DC converter
Transformer
Decommissioned
6 16
12
La Grande-1
Radisson
2 250 MW
Nicolet
2 138 MW
Des Cantons
690 MW
Comerford
690 MW
Sandy Pond
2 000 MW
± 450 kV

Why MTdc Networks with HVdc Classic didn't thrive?
Nowadays, the MTdc network can operate in three dierent con

gurations:
point-to-point link (e.g. between Radisson and Sandy Pond or Nicolet
and Sandy Pond);
multi-terminal HVdc network (all 3 terminals);
hybrid con

guration (pole outage at Radisson or Sandy Pont): 3
converters connected on one pole and 2 on the other pole.
Switchgear arrangement [13]
DUNCAN
ELECTRODE
DES CANTONS
ELECTRODE
LINE 1
LINE 2
RADISSON NICOLET DES CANTONS COMERFORD SANDY POND
DISCONNECT
RAPID DISCONNECT
COMMUTATION BREAKERS
DC CABLE

MTdc Network Topologies
Table of Contents
The Thury System
Past
Present
Future

MTdc Network Topologies Technology
HVdc Technology
CSC-MTdc: all the converter stations use the line commutated
current-source converter HVdc technology;
VSC-MTdc: all the converter stations use the forced commutated
voltage-source converter HVdc technology;

HVdc Technology
Hybrid-MTdc: when both HVdc technologies { CSC and VSC { are
used together.

HVdc Technology
Hybrid-MTdc: when both HVdc technologies { CSC and VSC { are
used together.
Note: Multiple infeed of HVdc lines into ac networks does not form a
MTdc network!
AC System 1 AC System 2
AC System 3

MTdc Network Topologies Series x Parallel
Multi-terminal dc network with monopolar HVdc stations
Idc
Vdc2
Vdc1 Vdc3
Vdc1+Vdc2+Vdc3+Vdc4 = 0
Vdc4
Series MTdc

Multi-terminal dc network with monopolar HVdc stations
Idc
Vdc2
Vdc1 Vdc3
Vdc1+Vdc2+Vdc3+Vdc4 = 0
Vdc4
Series MTdc
Vdc
Idc2
Idc1
Idc1+Idc2+Idc3+Idc4 = 0
Idc3
Idc4
Parallel MTdc

Parallel Connected MTdc networks
Radial

Parallel Connected MTdc networks
Radial Meshed

Comparison between series and parallel MTdc networks
Characteristic Series MTdc Parallel MTdc
Power Flow
Reversal
In CSC-MTdc power
ow reversal can easily be
achieved by inverting the converter voltages. With
VSC-MTdc it would not be easy to invert the
converters voltage polarity, thus power
ow reversal
would involve mechanical switches.
In CSC-MTdc the current direction cannot be
inverted, hence, there is need for mechanical
switches. In VSC-MTdc the current direction can
easily be inverted, hence power
ow reversal can be
achieved via control actions.
HVdc Terminal
Power Rating
Depends on converter voltage rating (cheaper for
smaller powers).
Depends on converter current rating.
Losses
Higher losses, which can be minimised by always
operating with the minimum current possible.
Lower losses.
Insulation
Is dicult in series connection as the voltages in the
MTdc network vary.
All converters need to be insulated to the rated
voltage.
DC Faults
A permanent fault in a transmission line would make
the whole MTdc network unavailable.
A permanent fault in a transmission line would only
make the aected terminal unavailable (in meshed
MTdc networks normal operation is still possible).
AC Faults Leads to overvoltages in the remaining terminals. Leads to overcurrents in the remaining terminals.
Protection
In series CSC-MTdc, dc faults can be handled via
control actions. VSC-MTdc will need dc breakers.
For clearing dc faults parallel MTdc networks will
need dc breakers.

MTdc Network Topologies Classi

cation
Classic VSC Hybrid
Homopolar Monopolar Bipolar
Parallel Series
Radial Meshed
HVdc
technology
Return
Path
MTdc
network
topology
Metallic Ground
HVdc
configuration
Classi

cation of MTdc transmission systems.

References
[1] E. W. Kimbark, Direct current transmission. Wiley-Interscience, 1971, vol. 1,
iSBN: 9780471475804.
[2] ABB AB Grid Systems - HVDC, HVDC Light - It's time to connect, ABB,
Ludvika, Technical Report, December 2012. [Online]. Available:
http://www05.abb.com/global/scot/scot221.nsf/veritydisplay/
2742b98db321b5bfc1257b26003e7835/$

le/Pow0038%20R7%20LR.pdf
[3] D. A. Woodford, HVDC Transmission, Manitoba HVDC Research Centre, pp.
1{27, March 1998, Last Accessed on 03 February 2013. [Online]. Available:
http://www.sari-energy.org/PageFiles/What We Do/activities/HVDC Training/
Materials/BasisPrinciplesofHVDC.pdf
[4] Working Group on HVDC and FACTS Bibliography and Records, HVDC
PROJECTS LISTING, IEEE Transmission and Distribution Committee: DC and
Flexible AC Transmission Subcommittee, Winnipeg, Technical Report, 2006.
[Online]. Available:
http://www.ece.uidaho.edu/hvdcfacts/Projects/HVDCProjectsListingDec2006.pdf
[5] R. S. Thallam, High-Voltage Direct-Current Transmission, ser. The Electrical
Engineering Handbook. CRC Press, 2000, ch. 61.3, pp. 1402{1416, iSBN:
9780849301858.

References
[6] M. P. Bahrman, DIRECT CURRENT POWER TRANSMISSION, ed., ser. Standard
Handbook for Electrical Engineers. Mcgraw-hill, 2006, ch. 15, pp. 1{34, iSBN:
9780071491495.
[7] V. Botan, J. Waldmeyer, M. Kunow, and K. Akurati, Six Inch Thyristors for
UHVDC Transmission, in PCIM Europe: International Exhibition and Conference
for Power Electronics, Intelligent Motion, Renewable Energy and Energy
Management. Nuremberg: Mesago, 2010, pp. 1{4. [Online]. Available:
c22b8e970d5455e3c1257af3004ef622/$

le/6Inch%20Thyristor%20for%20UHVDC%
20transmission.pdf
[8] Z. Kunpeng, W. Xiaoguang, and T. Guangfu, Research and Development of
800kV / 4750A UHVDC Valve, in 2nd International Conference on Intelligent
System Design and Engineering Application (ISDEA), 2012, pp. 1466{1469.
[9] J. Arrillaga, Y. Liu, and N. Watson, Flexible Power Transmission: The HVDC
Options. Wiley, 2007, iSBN: 9780470511855.
[10] V. Billon, J.-P. Taisne, V. Arcidiacono, and F. Mazzoldi, The Corsican tapping:
from design to commissioning tests of the third terminal of the Sardinia-Corsica-Italy
HVDC, IEEE Transactions on Power Delivery, vol. 4, no. 1, pp. 794{799, 1989.

References
[11] G. Morin, L. Bui, S. Casoria, and J. Reeve, Modeling of the Hydro-Quebec-New
England HVDC system and digital controls with EMTP, IEEE Transactions on
Power Delivery, vol. 8, no. 2, pp. 559{566, 1993.
[12] ABB. The HVDC Transmission Quebec - New England: The

rst large scale
mutiterminal HVDC transmission in the world. Last Accessed: 31 July, 2013.
[Online]. Available: http://www.abb.com/industries/ap/db0003db004333/
87f88a41a0be97afc125774b003e6109.aspx
[13] D. McNabbn, Feedback on the Quebec - New England Multiterminal HVDC Line:
20 years of Operation, in Cigree B4 Open Session. Paris: Cigree, 2010. [Online].
Available: http://b4.cigre.org/content/download/15754/604515/version/1/

The Modern VSC-HVdc Technology
Part II
Co-authors:

Introduction
Table of Contents
1 Introduction
Background
Comparison with CSC-HVdc
2 Voltage-Source Converter Technology
Initial Developments
Multi-level VSC technology
VSC Commissioning
3 VSC-HVdc Structure
AC Circuit Breakers
Transformers
Filters
Phase Reactors
DC Capacitors
Dr. R. Teixeira Pinto (TU Delft) MTdc Networks Tutorial: Part II August 25, 2014 2 / 22

Introduction Background
Previous HVdc systems used thyristor (only turn o).

VSC-HVdc uses self-commutating devices { e.g. GTO, IGBT (turn on
and o).

and o).
Therefore, VSC = more controllable sinusoidal voltages and currents
whereas CSC = much higher power ratings (and lower losses) [1].

and o).
1999: 1st commercial VSC (ABB). 50 MW Link between Gotland
island and Sweden [1].

and o).
Well stablished: 2010 at least 10 systems in operation [2].

and o).
Most projects are point-to-point, but control
exibility means VSC
technology eases implementation of MTdc networks (1st VSC-MTdc
network was built in China in 2013).

and o).
Most projects are point-to-point, but control
exibility means VSC
technology eases implementation of MTdc networks (1st VSC-MTdc
network was built in China in 2013).
Main converter topologies used: 2-level, 3-level and multi-level.

Introduction Comparison with CSC-HVdc
Characteristic CSC-HVdc VSC-HVdc
Converter Line-commutated current-source. Self-commutated voltage-source.
Switch Thyristor: turn on capability only. IGBT: turn-on and turn-o capabilities.
Age Old: First commercial project in 1954. New: First commercial project in 1999.
Projects Worldwide 146 15
Power Rating up to 8000 MW up to 1000 MW
Voltage Rating up to 800 kV up to 320 kV
Filters
Harmonic orders are low (e.g. 11-th and 13-th),
hence high

ltering eorts are needed.
Filters are tuned to higher frequencies and are,
therefore, smaller and cheaper.
Footprint Very high. Lower.
Control
Always consume reactive power (two-quadrant
operation).
Independent control of active and reactive power
(four-quadrant operation).
AC Network
Requirements
Needs a reasonably strong ac system to operate
(high minimum short-circuit ratio, e.g. SCR 3)
Can operate with a weak ac network or be used
to feed islands and passive ac networks providing
frequency control. Black start capability.
AC Faults
Presents commutation failure during ac faults. In
case of repeated commutation failures the
converter is blocked.
Can maintain active power transfer even under ac
faults, fault-ride through capable.
DC Faults
Is capable of extinguishing dc-side faults via
control actions.
Has no way of limiting dc-fault currents (because
of the free-wheeling diodes), therefore dc breakers
are needed.
Losses [% of Rated
Power]
0.7% 1.5% (two-level) or 1.0% (multi-level)
Communication
Special arrangements are needed to coordinate
the operation of converter stations.
Communication between the recti

er station and
the inverter station in theory is not necessary.
The control of each converter station operates in
an independent way.
Multi-terminal
Operation
Dicult since there is need for coordination
between the converters (current order
synchronisation) and power-
ow reversal involves
polarity changes through mechanical switches.
Easier to accomplish since there is little need for
coordination between the interconnected
converters and power-
ow reversal does not
involve mechanical switches.

Voltage-Source Converter Technology
Table of Contents
1 Introduction
Background
VSC Commissioning
AC Circuit Breakers
Transformers
Filters
Phase Reactors
DC Capacitors

Voltage-Source Converter Technology Initial Developments
2-level VSC
The Graetz bridge is the most straightforward VSC con

guration: each
phase can be connected either to the positive dc terminal, or the negative
dc terminal.
+
-
Vdc / 2
Vdc / 2
n
va
1
4
1'
4'
vb
3
6
3'
6'
vc
5
2
5'
2'
or
Vdc
Idc
ia ib ic
Circuit of the 3-phase two-level voltage-source converter.

2-level VSC
VSC consists of 6 valves. Each valve contains a switching device (IGBT)
and an anti-parallel diode.
+
-
Vdc / 2
Vdc / 2
n
va
1
4
1'
4'
vb
3
6
3'
6'
vc
5
2
5'
2'
or
Vdc
Idc
ia ib ic

2-level VSC
Series connection of IGBTs needed to handle the higher voltages. For ex-
ample, for 150 kV, at least a 100 IGBTss for each valve (if 3.0 kV IGBTs
are used).
+
-
Vdc / 2
Vdc / 2
n
va
1
4
1'
4'
vb
3
6
3'
6'
vc
5
2
5'
2'
or
Vdc
Idc
ia ib ic

2-level VSC
Several IGBTs in series: not an easy task. Standard wire-bond IGBT fail in
open circuit (bad for series connection).
+
-
Vdc / 2
Vdc / 2
n
va
1
4
1'
4'
vb
3
6
3'
6'
vc
5
2
5'
2'
or
Vdc
Idc
ia ib ic

2-level VSC
On early VSC-HVdc ABB used presspack IGBTs which fails in short-circuit
(good for series connection).
+
-
Vdc / 2
Vdc / 2
n
va
1
4
1'
4'
vb
3
6
3'
6'
vc
5
2
5'
2'
or
Vdc
Idc
ia ib ic

2-level VSC
Presspack IGBT drawback: only a few suppliers worldwide.
Wire-bond IGBT s many suppliers and bigger overall market. Siemens and
Alstom VSCs use wire-bound (maybe because ABB patented series connec-
tion of IGBTs?) [3].
+
-
Vdc / 2
Vdc / 2
n
va
1
4
1'
4'
vb
3
6
3'
6'
vc
5
2
5'
2'
or
Vdc
Idc
ia ib ic

3-level VSC
+
Vdc / 2
Vdc / 2
-
N
a 
1
4
1'
4'
1*
4*
1°
1°
diode clamping
+
Vdc / 2
Vdc / 2
-
N
a 
1
4
1'
4'
1*
4*
1°
1°
Vdc / 2

ying capacitor
Switching logic for the 3-level VSC.
Topology
Voltage Level
+Vdc=2 0 Vdc=2
Diode Clamping 1 4 4 1* 1*
4*
Flying Capacitor 1 1* 4 1* or 1 4* 4 4*
Lower dv=dt, less harmonics and lower
switching losses.
Most used topologies: NPC and CFC
(switching logic diers).
Total number of IGBTs ' 2-level VSCs.
However, 3-level NPC require more
diodes for clamping.
The three-level concept can be extended
to a higher number of voltage levels [4].
No NPC 3-levels for HVdc: complex
insulation and cooling design of valves
(option for B2B links - higher currents
and lower voltages).

Voltage-Source Converter Technology Multi-level VSC technology
Proposed in 2003 by Prof. Rainer
Marquardt (University of Bundeswehr -
Munich) [5, 6].
Applications: HVdc, STATCOM, Railway
and other large drives (tens of MW).
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
MMC (or M2C) topology.

Munich) [5, 6].
DC capacitors distributed in modules
(converter is built up by cascading
modules) [7].
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
B
A
MMC Submodule.

Munich) [5, 6].
modules) [7].
Each MMC module consists of two valves
3 dierent switching ways:
1 lower IGBT on and upper IGBT o: the
capacitor inserted into from A to B.
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
B
A
MMC Submodule.

Munich) [5, 6].
modules) [7].
Current from A to B (charging);
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
B
A
Charging.

Munich) [5, 6].
modules) [7].
Current from B to A (discharging)
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
B
A
Discharging.

Munich) [5, 6].
modules) [7].
2 upper IGBT on and lower IGBT o: bypassed
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
B
A
Bypassed.

Munich) [5, 6].
modules) [7].
2 upper IGBT on and lower IGBT o: bypassed
3 Both IGBTs o: blocked
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
B
A
Blocked.

Continuing...
The major challenge with the MMC is mainly a control problem: to
make sure that the capacitor voltages in all the submodules are
strictly controlled.
The control system is responsible for maintaining the average sum of
inserted submodules in the upper and the lower arm at a constant
level (voltage balancing).
The alternating voltage output is obtained by varying the dierence
between the number of inserted submodules in the upper and the
lower arms (switching frequencies as low as 150 Hz could be
achieved).
The MMC has low switching losses and its harmonic content is very
small (very small

lters) [8].
Smaller voltage steps involving only a few semiconductor devices in
the converter arm. Lower stresses on the phase reactor.

HVC Plus
IGBT (wirebond)
Siemens HVDC PLUS components [8].
For the submodules: o-the-shelf
wire-bonded IGBT modules with plastic
cases.

HVC Plus
A
B
Submodule Diagram
cases.
The submodule: half-bridge with a
bypass thyristor and vacuum switch
(wire-bond fail as an open circuit).

HVC Plus
Submodule Picture
cases.
MMC because ABB patented series
connection of IGBTs? [3].

HVC Plus
Submodule Picture
cases.
A 400-MW MMC ' 200
submodules/converter arm (depending
on voltage level)

HVC Plus
California
Livermore
Oakland
San Leandro Pleasanton
Richmond
Martinez
Concord
Antioch
Pittsburg
Vallejo
Novato
San Rafael
San
Francisco
Potrero Hill
Daly City
±200 kV (400 MW)
88 km
The Transbay project [9].
cases.
A 400-MW MMC ' 200
submodules/converter arm (depending
on voltage level)
Nov. 2010: 1st MMC for HVdc (Trans
Bay Cable project: 88 km / 200 kV /
400 MW [8, 9]).

HVDC Light
2
1
36
2
1
36
2
1
36
2
1
36
2
1
36
2
1
36
Double
submodule
CTL converter diagram
ABB HVDC Light components [8].
ABB Light 4th generation: Cascaded
Two-Level (CTL) converters (direct
voltages up to 320 kV) [10, 11].

HVDC Light
submodule IGBT (presspack)
CLT submodules: half-bridges with a small
number ( 8) series-connected IGBTs
(press-pack) [12].

HVDC Light
IGBT1
IGBT8
IGBT1
IGBT8
double submodule diagram
(press-pack) [12].
CTL converter con

guration (dierence = IGBT switches
inside the submodule).

HVDC Light
double submodule picture.
(press-pack) [12].
CTL converter con

guration (dierence = IGBT switches
inside the submodule).
July 2010: Awarded connection of
DolWin 1 OWF (Converter: 800 MW /
320 kV / 75 km submarine cable / 90 km
underground cable part). Will serve 2 400
MW OWFs (2nd to be connected later).

HVDC Maxsine
Vdc
SW1
A B
SW2
SW3
SW4
Diagram of a FBS.
Alstom HVDC Maxsine components
[8].
MMC topology, but might use full-bridge
submodules (FBS) [13, 3].

HVDC Maxsine
Vdc
SW1
A B
SW2
SW3
SW4
Diagram of a FBS.
[8].
O-shelf IGBTs: operated (rated) 2 kV
(3.3 kV) / 1.2 kA (1.5 kA) for safety.

HVDC Maxsine
FBS voltage output
Switches
(SW)
Output voltage
(vAB)
1 4 +Vdc
1 3 0
2 4 0
2 3 Vdc
[8].
FBS: Possible to invert dc-side voltage (for
Hybrid MTdc networks) and to fully
interrupt the dc fault currents.

HVDC Maxsine
Alstom HVDC Maxsine submodule [3].
[8].
Submodule: IGBTs, dc capacitor (oil free),
gate drives and a fast mechanical bypass
switch.

HVDC Maxsine
[8].
switch.
8 submodules form a power module (circa
160 kg / 150 x 65 x 30 cm) [3].

HVDC Maxsine
[8].
switch.
8 submodules form a power module (circa
160 kg / 150 x 65 x 30 cm) [3].
FBS: double the switching devices (more
costly).

Voltage-Source Converter Technology VSC Commissioning
Planning VSC-HVdc Links (2-3 years)
Application and Feasibility Studies:
Comparison of Line-Commutated Converter and VSC
Economic Justi

cation of a VSC Scheme
Comparing Alternative Termination Points for the VSC Scheme
Cable route and voltage options
Comparing the Selected Scheme with Alternative Solutions
Preparing an Outline Speci

cation of the VSC Transmission Project
Speci

cation Studies
Specifying the Performance Requirements for the VSC Scheme
AC System Data for the Design of the VSC Scheme
Modeling of VSC System
Load Flow, Short-circuit, Harmonic Performance Modelling
EM Transient Stability System Impact Modelling
Environmental Impact studies: Cable route and termination stations environmental impact
analysis, Audible EMF and EMC

Voltage-Source Converter Technology VSC Commissioning
Commissioning VSC-HVdc (1 year)
All equipment within the scope of supply shall be comprehensively tested and run for
trail period in order to demonstrate that it meets the speci

ed requirements.
Factory Acceptance Tests Equipment QA and component testing
Factory Acceptance Tests - Equipment QA and component testing
Control Veri

cation Tests with Real-Time Simulator: TSO and Owner witness
these tests.
Commissioning Tests: performed to con

rm, without undue disturbance to the
power system, that the system meets the performance speci

cations.
The on-site inspection and test activities:
Equipment tests;
Subsystem tests;
System tests;
Trial operation;
Acceptance tests.

VSC-HVdc Structure
Table of Contents
1 Introduction
Background
VSC Commissioning
AC Circuit Breakers
Transformers
Filters
Phase Reactors
DC Capacitors

VSC-HVdc Structure
Typical layout of a VSC-HVdc Station
HVDC Plus station layout [14] Aerial view of the Shoreham VSC [15]
The smaller footprint and more
exible control make VSC-HVdc systems
the most convenient choice for the connection of oshore wind farms [16,
17, 18].

VSC-HVdc Structure
HVDC Plus station layout [14] Aerial view of the Shoreham VSC [15]
VSC-HVdc transmission system: 2 converter stations (nowadays with multi-
level topology); an ac transformer; dc-side capacitors; and a dc cable or
overhead line.

VSC-HVdc Structure
AC
System Phase
Reactor
circuit
breaker
AC
Transformer
VSC
converter
station
DC LINE
DC Capacitor
Neutral point
grounding
AC
FILTERS
Single-line diagram of a VSC-HVdc transmission station.
Other components include: ac circuit breakers, surge arresters, ac-harmonic
and radio-interference

lters, transformers tap-changers, phase reactors, dc-
side harmonic

lters, dc chopper and braking resistor; and grounding equip-
ment [19, 1]. Some of these components are brie
y discussed next.

VSC-HVdc Structure AC Circuit Breakers
High-voltage ac circuit breaker [20]
(800 kV, breaking currents up to
63 kA in 2 cycles [20]).
Triple purpose: 1st it connects the ac
system to the converter station when,
during system start-up, the dc-side
capacitor is charged to the nominal
voltage.
2nd: disconnect the converters in case
of a contingency in the ac system.
3rd: VSC have no control means for
clearing dc-side faults.
SF6 GIS switchgear substituted traditional oil-based ac breakers.
Breaking times: circa 2 to 3 cycles. [21].
Interruption processes:
1 terminals are mechanically separated creating an electrical arc
2 arc is

nally quenched once there is a current zero crossing.

VSC-HVdc Structure Transformers
East West Interconnector Transformer.
Main task: adapt the ac system voltage
for the converter (e.g. 0.8 SPWM
modulation index).
Helps

ltering the currents and limiting
fault currents.
Decouples zero sequence harmonics (if
secondary side is not grounded).
Basic design principle (physical dimensions) [21]: Acu; Aco /
Sn
fJ'^ B
Main dierences with CSC-HVdc transformers [22]:
1 lower insulation requirements: produced ac-side voltage has null dc
oset w.r.t. to ground;
2 lower harmonic content in the current (lower stresses and losses);
3 No need for OLTC for control purposes (only to optimise operation and
reduce losses).
4 Standard two-winding transformers can be used.

VSC-HVdc Structure Filters
LCL

lter
Lg Lc
Cf
HVdc ac-side
capacitor bank
Negative eects of harmonics [19]:
1 Extra losses (heating) in components;
2 Overvoltages due to resonance;
3 Inaccuracy or instability of control systems;
4 Noise on voice-frequency telephone lines.
Smaller and cheaper

lters (PWM operation)
Very dicult to optimise

lter design (network
harmonic impedances are needed).
Simpler LCL

lter is usually used for low and
medium-power VSC applications [23].
Theoretically a high-pass

lter would be sucient. In
practice, 2 or 3 branches of tuned

lters may be
necessary [21]. A radio interference

lter may be
needed to avoid telecommunication disturbances [19].
The

lter capacitors reactive power are usually selected
between 10 and 20% the VSC rated power.

VSC-HVdc Structure Filters
Size matters...
Filtering greatly in
uences the total footprint of a HVdc converter station.
Aerial view (to scale from GoogleEarth) of a HVdc Classic and a VSC-HVdc converter stations.
Furnas HVdc Classic Station from the
Itaipu transmission system, in Brazil.
0.86 km2 (0.86 km x 1 km), 3150 MW,
600 kV [24]
VSC-HVdc station in Diele { part of
the BorWin1 HVdc transmission system
in Germany. 0.17 km2 (0.33 km x
0.50 km), 400 MW, 150 kV [25].

VSC-HVdc Structure Phase Reactors
HVdc Classic [26]VSC-HVdc
[27]
Air coil reactors for HVdc systems
(on LCC dc-side / on VSC ac-side).
Serves the following purposes: [1, 22]:
reduce the converter ac-side current
high frequency content;
help to avoid sudden change of polarity
due to valve switching;
decouple active and reactive power
control;
limit amplitude and rate-of-rise of
short-circuit currents.
Figures: an 800 kV reactor for UHVdc projects in China [26]; and 350 kV
reactor for the Caprivi VSC system in Africa (300 MW, monopole) [27, 28].
Typical impedance values are in the 0.10 - 0.15 pu range [29, 30].
Air coil is the most common technology (iron core also possible).
Main design aspects: rated current, impedance, insulation level, overall
losses, noise levels, thermal and dynamic stability [31].
A basic scaling rule for air coils is given by [21]: Co;M / In
p
L

VSC-HVdc Structure DC Capacitors
Dry: 750 F, 1210 V [32]
Oil: 1600 F, 2900 V [32]
HVDC Maxsine submodule
[13]
Energy storage (act as a voltage source).
Serve as a

lter for high frequency currents [1].
Larger capacitors, lower voltage ripples (costly).
Basic dimensioning rule: Co;M; Vo /
1
2
CdcV2
dc
Design: essential to consider the transient voltage
constraints.
Dry metallised

lm capacitors (more environmental
friendly, explosion safe, 2x the capacitance in 0.5x
the volume, self-healing, shorter production time
and simpler to install) [21].
Up to 10x more capacitors are needed in MMC
than 2-level VSC [33].
Ultimately, the dc capacitor can be characterised
by a time constant [34]: = CdcV2
dc

2Sn

References
[1] J. Arrillaga, Y. Liu, and N. Watson, Flexible Power Transmission: The HVDC
Options. Wiley, 2007, iSBN: 9780470511855.
[2] E. Koldby and M. Hyttinen, Challenges on the Road to an Oshore HVDC Grid,
in Nordic Wind Power Conference, 2009.
[3] Hans-Peter Nee and Lennart Angquist, Perspectives on Power Electronics and Grid
Solutions for Oshore Wind farms, Elforsk AB, Stockholm, Technical Report,
November 2010. [Online]. Available:
http://www.elforsk.se/Rapporter/?download=reportrid=10 96
[4] N. Flourentzou, V. Agelidis, and G. Demetriades, VSC-Based HVDC Power
Transmission Systems: An Overview, IEEE Transactions on Power Electronics,
vol. 24, no. 3, pp. 592{602, Mar. 2009. [Online]. Available:
http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=4773229
[5] A. Lesnicar and R. Marquardt, An innovative modular multilevel converter topology
suitable for a wide power range, in Power Tech Conference Proceedings, 2003 IEEE
Bologna, vol. 3, 2003, pp. 1{6.
[6] M. Glinka and R. Marquardt, A new AC/AC multilevel converter family, IEEE
Transactions on Industrial Electronics, vol. 52, no. 3, pp. 662{669, 2005.

References
[7] S. Allebrod, R. Hamerski, and R. Marquardt, New transformerless, scalable
Modular Multilevel Converters for HVDC-transmission, in IEEE Power Electronics
Specialists Conference (PESC), 2008, pp. 174{179.
[8] J. Dorn, H. Gambach, and D. Retzmann, HVDC transmission technology for
sustainable power supply, in 9th International Multi-Conference on Systems,
Signals and Devices (SSD), 2012, pp. 1{6.
[9] R. Adapa, High-Wire Act, IEEE Power and Energy Magazine, pp. 18{29,
Nov./Dec. 2012.
[10] L. Harnefors, A. Antonopoulos, S. Norrga, L. Angquist, and H.-P. Nee, Dynamic
analysis of modular multilevel converters, IEEE Transactions on Industrial
Electronics, vol. 60, no. 7, pp. 2526{2537, 2013.
[11] B. Jacobson, P. Karlsson, G. Asplund, L. Harnefors, and T. Jonsson, VSC-HVDC
transmission with cascaded two-level converters, in Cigree Session B4. Paris:
Cigre, 2010, pp. 1{8. [Online]. Available:
422dcbc564d7a3e1c125781c00507e47/$

le/b4-110 2010%20-%20vsc-hvdc%
20transmission%20with%20cascaded%20two-level%20converters.pdf
[12] J. Hafner and B. Jacobson, Proactive hybrid HVDC breakers { A key innovation
for reliable HVDC grids, Paper presented at the International Symposium on

EPE '14 ECCE Europe Tutorial #2 - Challenges on the Road to Future High-Voltage Multi-Terminal DC Networks

EPE '14 ECCE Europe Tutorial #2 - Challenges on the Road to Future High-Voltage Multi-Terminal DC Networks

Recommandé

Recommandé

Contenu connexe

Similaire à EPE '14 ECCE Europe Tutorial #2 - Challenges on the Road to Future High-Voltage Multi-Terminal DC Networks

Similaire à EPE '14 ECCE Europe Tutorial #2 - Challenges on the Road to Future High-Voltage Multi-Terminal DC Networks (20)

Dernier

Dernier (20)

EPE '14 ECCE Europe Tutorial #2 - Challenges on the Road to Future High-Voltage Multi-Terminal DC Networks