Upload
others
View
7
Download
0
Embed Size (px)
Citation preview
1 / 33
Use of FACTS and HVDC for Power
System Interconnection and
Grid Enhancement
Günther Beck, Wilfried Breuer,
Dusan Povh, Dietmar Retzmann,
Erwin Teltsch
Siemens Power Transmission and
Distribution (PTD),
Germany
2 / 33
0. Overview Interconnection of power systems with either AC or DC links may offer important technical,
economical and environmental advantages. In the future of liberalised power markets, these
advantages will become even more important: pooling of large power stations, sharing of
spinning reserve, use of most economic energy resources, as well as ecological constraints:
nuclear power stations at selected locations, hydro energy from remote areas, solar energy
from steppes and deserts, and connection of large off-shore wind farms.
Examples of large interconnected systems are the Western and Eastern European systems
UCTE (installed capacity 530 GW) and IPS/UPS (315 GW), which are planned to be
interconnected in the future. Up to now, the power systems in China are more separated:
China with 7 large inter-provincial grids and India with 4 large regional grids. However,
interconnections by AC and increasingly by DC are in progress in Far East, too.
Since the 60s, FACTS (Flexible AC Transmission Systems) and HVDC (High Voltage Direct
Current) transmission have developed into a mature technology with high power ratings.
Transmission ratings of 3 GW over large distances with just one bipolar DC transmission
system are state of the art in many grids today. In China, however, there are new transmission
schemes in the planning phase with ratings of 4 - 6 GW (at +/- 800 kV DC and 1000 kV AC).
Reason for such high ratings is the need for bulk power transmission corridors with 20 GW
for system interconnection.
In general, for transmission distances above 700 km, DC transmission is more economical
than AC transmission (≥ 1000 MW). With submarine cables, transmission levels of up to 600
- 800 MW over distances of nearly 300 km have already been attained, and cable transmission
lengths of up to 1,300 km are in the planning stage. As a multi-terminal system, HVDC can
also be connected at several points with the surrounding AC networks. FACTS is applicable
in parallel connection (SVC, Static VAR Compensator – STATCOM, Static Synchronous
Compensator) or in series connection (FSC, Fixed Series Compensation - TCSC, Thyristor
Controlled Series Compensation – TPSC, Thyristor Protected Series Compensation) or in
combination of both (UPFC, Unified Power Flow Controller) to control load flow and to
improve dynamic conditions. Rating of SVCs is up to 800 MVAr, series FACTS devices are
implemented on 550 and 735 kV level to increase the line transmission capacity up to several
GW.
3 / 33
In the paper, benefits of FACTS and HVDC for system interconnection and for grid
enhancement are depicted, and preferences of applications are explained. Study and project
examples are given.
1. Development of Power Transmission
The development of power systems follows the requirements to transmit power from
generation to the consumers. With an increased demand for energy and the construction of
new generation plants, first built close and then at remote locations from the load centers, the
complexity of power systems has grown. This development is schematically shown in Fig. 1.
To transport the energy from generation to consumers, the development of power systems
considers locations of expected load requirements on the one hand, and the suitable location
of power stations on the other hand. However, on a long-term basis, it can be expected that
the transmission systems will stagnate in their development, since an increasing part of power
generation will be transferred into the distribution or low voltage networks in the future [1, 3].
Since the load flows existing today can change considerably, this altering environment
decisively influences further development and optimization of transmission networks. The
ancillary functions required for smooth operation of the networks, such as frequency control,
load-flow control, reactive-power and voltage control, as well as the responsibility for system
Fig. 1: Development of Power Systems and per Capita Consumption
Isolated smallGridsIsolated smallGrids
System Interconnections
Demand for Power Quality
Increased Automation
More Investments in DistributionDecentralized Power Supplies
High Energy Imports
Use of new Technologies
per CapitaPower Consumptionper CapitaPower Consumption
Developing Countries Emerging Countries Industrialized Countries
Long - DistanceTransmission(HVAC, HVDC)
Long - DistanceTransmission(HVAC, HVDC)
Introduction ofhigher VoltageLevels
Introduction ofhigher VoltageLevels
Lifetime Extension, Monitoring
Right of Way Problems, Transmission Bottlenecks
Least-CostPlanning
High Investments in Transmission Systems
4 / 33
security, are in the hands of the system operator. To support the operation and to increase the
reliability of heavily loaded networks, FACTS and HVDC need to be installed. Higher
investments into grid interconnections must be made to achieve cost benefits.
Based on a large number of studies on power system development in different world regions,
the following general trends can be expected:
As listed below, power system interconnections offer the necessary benefits regarding these
constraints. They are generally valid and do not depend on the kind of the interconnection.
With the size of interconnected systems, however, the technical and economical advantages
diminish and the required additional investments for system enlargements increase. In
addition to that, the transmission costs increase with the transmission distance. Considering
the current transmission costs of about 1-2 Cents per kWh and 1000 km, the advantages of the
energy taken from the interconnected systems over very long distances would not be
economical any more. The reasonable distance to transmit power still economically could be
therefore in the range of up to 3000 km. These conditions, however, could possibly change if
strong political efforts will support the use of renewable energy in remote areas in large scale,
independent from production and transmission costs. Strategies for the development of large
Increasing Power Demand - from 3,560 GW in 2000 to 5,700 GW in 2020
Strong Environmental Constraints – Limitation for Power Plant Expansions
Natural Energy Resources far away from Load Centers
Severe Right of Way Constraints A strong Issue in many Countries, especially in Europe
Possibility to use larger and more economical Power Plants
Reduction of the necessary Reserve Capacity in the System
Utilization of most favorable Energy Resources
Flexibility of building new Power Plants at favorable Locations
Increase of Reliability in the Systems
Reduction of Losses by an optimized System Operation
5 / 33
power systems go clearly in the direction of hybrid transmissions, consisting of HVDC and
HVAC interconnections among regional sub-systems. Such interconnected systems have
significant technical and reliability advantages [3-6].
Fig. 2 shows schematically such a hybrid system using HVDC and FACTS. Power exchange
in the neighboring areas of interconnected systems offering most advantages can be realized
by AC links, preferably including FACTS for increased transmission capacity and for stability
reasons. The transmission of larger power blocks over longer distances should, however, be
utilized by the HVDC transmissions directly to the locations of power demand. HVDC can be
realized as direct coupler without a DC line – the so-called Back-to-Back solution (B2) or as
point to point long distance transmission via DC line. The HVDC links can strengthen the AC
interconnections at the same time, in order to avoid possible dynamic problems which exist in
such huge interconnections [3, 6].
Long-term developments in power industry depend on expectations for future political,
financial and technical conditions. For the last decade, however, the developments have been
strongly driven by the globalization, leading to deregulation and liberalization. The world
markets have been gradually opened, with different speed in different countries. This
transition of economies brought many advantages, but also disadvantages in some fields. At
Fig. 2: Large Power System Interconnections – Benefits of Hybrid Solutions
Large System Interconnections, using HVDCLarge System Interconnections, using HVDC
SystemA
SystemC
SystemE
SystemF
High VoltageHVDC B2B
SystemB System
D
SystemG
and FACTS
AC Transmission- via AC Lines
DC – the Stability Booster and“Firewall” against “Blackout”
HVDC - Long Distance DC Transmission
“Countermeasures”against large Blackouts
& FACTS
Large System Interconnections, using HVDCLarge System Interconnections, using HVDC
SystemA
SystemA
SystemC
SystemC
SystemE
SystemE
SystemF
SystemF
High VoltageHVDC B2B
SystemB
SystemB System
DSystem
D
SystemG
SystemG
and FACTS
AC Transmission- via AC Lines
DC – the Stability Booster and“Firewall” against “Blackout”DC – the Stability Booster and
“Firewall” against “Blackout”
HVDC - Long Distance DC TransmissionHVDC - Long Distance DC Transmission
“Countermeasures”against large Blackouts
“Countermeasures”against large Blackouts
& FACTS& FACTS
6 / 33
the same time, social and environmental aspects became more and more important, even if
they are, in some way, in contradiction with the globalization of the economy.
Fig. 3 shows the typical sharing of investments in power generation, transmission and
distribution. These values depend, however, on the specific structure of the systems. The
estimation of the requested investments in the power industry for the next 30 years is US$ 10
trillion, or roughly US$ 350 billion per year. Based on this, about US$ 70 billion per year
should be invested in power transmission [1].
Fig. 3: Investments in Power Industry
Investments in Power IndustryInvestments in Power Industry
~ 40 %~ 40 %~ 40 %~ 40 %~ 20 %~ 20 %
Generation Transmission DistributionGeneration Transmission Distribution
Depending on Grid StructureDepending on Grid Structure
Fig. 4: Transmission Systems – The “VIPs” of the Power Market
GenerationGeneration
Regulated Markets:one Owner - the Utility
Regulated Markets:one Owner - the Utility
Deregulated Markets:different Owners & Players
Deregulated Markets:different Owners & Players
or -neck-neck
for Cash-Flow &Return on Investments
DistributionDistribution
Transmissioncan be
Transmissioncan be
7 / 33
Although the sharing of transmission investments is only 20 % of the total sum, its
importance is in fact high: transmission can be the key for cash-flow and return on
investments, or just a bottleneck causing limitations and supply interruptions. Thus,
transmission systems are the VIPs of the power market, as shown in Fig. 4.
Fig. 5 shows the perspectives of DC transmission capacity worldwide. It can be seen that
China alone will be contributing significantly to this development because of its large
increase of economy (GDP) per year.
In Fig. 6 and 7, the transmission grid developments in China and India are depicted, leading
to very large hybrid interconnections with AC and DC solutions.
A large number of different FACTS and HVDC have been put into operation either as
commercial projects or prototypes. Fig. 8 gives an example of the Siemens applications
worldwide. Thus it appears that some areas are still “blank”, which is expected to change in
the future. In the figure, the number and the increase of large HVDC long-distance
transmission projects are also indicated.
The different technologies with FACTS and HVDC for grid enhancement using modern high
power electronics, as indicated in Fig. 8, are explained more detailed in the next sections.
Fig. 5: Development of DC Transmission: Worldwide installed Capacity
1970 1980 1990 2000 2010
60
50
40
30
20
10
0
GW
An additional 48 GW are expected from Chinaalone until 2020 !
Worldwide installed HVDC “Capacity”: 55 GW in 2005Worldwide installed HVDC “Capacity”: 55 GW in 2005
Sources: IEEE T&D Committee 2000 - Cigre WG B4-04 2003
This is 1.4 % of the Worldwide installed Generation CapacityThis is 1.4 % of the Worldwide installed Generation Capacity
8 / 33
Fig. 6: China goes Hybrid: AC plus 20 HVDC Interconnections
Sources: SP China, ICPS - 09/2001; State Grid Corp. China, 2003
In to
tal:
20
HVD
C In
terc
onne
ctio
ns
3 x B2B11 x HVDC Long Distance Transmissions
plus
…
plus
…
2005: 12 GW2020: 60 GW
and
Russian Power Grid
North Power Grid
Center Power Grid
LanchangjiangRiver
JinshajiangRiver
NWCPG
NCPGWangqu Plant
Yangcheng Plant
NECPG
SPPG
CSPGThree Gorges
ECPG
CCPG
Tailand Power Grid
SCPG
South Power GridHPPG
Russian Power Grid
North Power Grid
Center Power Grid
LanchangjiangRiver
JinshajiangRiver
NWCPG
NCPGWangqu Plant
Yangcheng Plant
NECPG
SPPG
CSPGThree Gorges
ECPG
CCPG
Tailand Power Grid
SCPG
South Power GridHPPG
Gezhouba-ShanghaiTianGuang3G-ECPG IGuiGuang I3G-Guangdong
Initially:
GuiGuang II
Gezhouba-ShanghaiTianGuang3G-ECPG IGuiGuang I3G-Guangdong
Initially:
GuiGuang II
Fig. 7: Grid Extension in India - Hybrid AC plus DC
R O U R K E LA
R A IP U R H IR M A
T A L C H E R
J A IP U R
N E R
E RW R
N R
S R
B 'S H A R IF
A LL A H A B A D
S IP A T
G A Z U W A K A
J E Y P O R EC H A N D R A P U R
S IN G R A U LI
V IN D H Y A -
2000
MW
2000MW
3000M W
10 0 0M W
5 00 M W
LU C K N O W
D IH A N G
C H IC K E N N E C K
K R IS H N A
T E E S T A
T IP A IM U K HB A D A R P U R
M IS A
D A M W E
K A T H A L-G U R I
L E G E N D
7 65 K V L IN E S 4 00 K V L IN E S
H V D C B /B
H V D C B IP O LE
E X IS T IN G / X P LA N X I P LA N
Z E R D A
H IS S A R
B O N G A IG A O N
D E V E L O P M E N T O F N A T IO N A L G R ID
K O L H A P U R
N A R E N D R A
K A IG A
M A N G A LO R E
P O N D A
IX P LA N
M A R IA N I
N .K .
K A H A L G A O N
R A N G A N A D I
S E O N I
C H E G A O N
B H A N D A R A
D E H G A M
K A R A D
L O N IK A N D
V A P I
G A N D H A R /
T A LAA R U N
B A N G L A
B A LLA B G A R H A 'P U R(D E L H I R IN G )
B A N G A LO R E
K O Z H IK O D E
C O C H IN
K A Y A M K U LA M
T R IV A N D R U M
P U G A LU R
K A Y A T H A R
K A R A IK U D I
C U D D A L O R E
S O U T H C H E N N A I
K R IS H N A P A T N A M
C H IT T O O R
V IJA Y A W A D A
S IN G A R P E T
P IP A V A V
L IM B D I
K IS H E N P U R
D U L H A S T IW A G O O R A
M O G A
U R I
B H U T A N
R A M A G U N D A M
S A T LU JR A V I
JU LLA N D H A R
D E S HN A G A R
V A R A N A S I
/U N N A O
M 'B A D
P U R N E A
K O R B A
N A G D A
S IL IG U R I/B IR P A R A
P H A S E - III
NIC
OB
AR
AN
DA
MA
N A
ND
LAKSHAD
WEEP
T E H R I
M E E R U T
B H IW A D I
B IN A S A T N A
M A LA N P U RS H IR O H I
K A W A S
A M R A V A T I
A K O LA
(B y 2 0 1 2 )
A G R A
S IR S I
C H A L
J E T P U RA M R E LI
B O IS A RT A R A P U R
P A D G H E
D H A B O L
K O Y N A
/B A R H
G 'P U R
H O S U R
Similar Perspectives … as in China
Source: Power Grid Corporation of India, 2003
9 / 33
2. Transmission Solutions with FACTS and HVDC
FACTS and HVDC use power electronic components and conventional equipment which can
be combined in different configurations for switching or controlling reactive power, and for
active power conversion. Conventional equipment (e.g. breakers, tap-changer transformers)
offer very low losses, but the switching speed is relatively slow. Power electronics can
provide high switching frequencies up to several kHz, but with an increase in losses. A view
on the different kinds of semiconductors is given in Fig. 9. In Fig. 10, the stepwise assembly
of the thyristors in modules and valve groups is shown.
Fig. 8: FACTS & HVDC worldwide – Example Siemens (ref. to Text)
SeriesFSC
NGH
TPSC
TCSC
SeriesFSC
NGH
TPSC
TCSC
Load FlowB2B
UPFC
CSC
Load FlowB2B
UPFC
CSC
2, 2 Tian Guang 2003Kayenta 1990
Serra de Mesa 1999Imperatriz 1999
Fortaleza 1986
••
•
•Samambaia 2002
•
Virginia Smith 1987
•Welsh 1995
•Acaray 1981
•••Dürnrohr 1983
Etzenricht 1993Wien Südost 1993
•Bom Jesus la Lapa 2002
•
Limpio 2003
•Ibiuna 2002
•3 Vincent 2000
•Jacinto 2000
•Funil 2001
2 Pelham, 2 Harker, 2 Central, 1991-1994
•
Nopala 2006
•
Atacama 1999
•
P. Dutra 1997
• Cerro Gordo 1999
•Chinú 1998
•Impala
•2 Adelanto 1995
•
Jember 1994
•3 Montagnais 1993
•
2 Kemps Creek 1989
•Brushy Hill 1988
•
•
Campina Grande 2000
2 Zem Zem 1983
•
••
•
•
Rejsby Hede 1997
•Sullivan 1995
•Paul Sweet 1998 •
Inez 1998
•
2 Marcy 2001-2003
Military Highway 2000
•Kanjin (Korea) 2002
•
Lugo 1985
Laredo 2000
•
Spring Valley 1986
••IllovoAthene•
Muldersvlei 1997
•
2 Tecali 2002
3 Juile 2002
•Barberton 2003•
Maputo 2003
•Milagres 1988
• 2 Yangcheng 2000
•2 Hechi 2003
•
•
Eddy County 1992
2 Dominion 2003
2 Chuddapah 20032 Gooty 2003
•
Lamar 2005
2 Midway 2004 Seguin 1998•
1994-1995
Porter 2006Dayton 2006
Nine Mile 2005
ParallelSVC
MSC/R
ParallelSVC
MSC/R
.
.Moyle MSC 2003Willington 1997
Hoya Morena,Jijona 2004
.Baish 2005,Samitah 2006 .
K.I. North 2004
Kapal 1994
Ghusais,Hamria,Mankhool, Satwa
1997
.
Siems 2004
Cano Limón 1997
• 2006
••
2, 2 Purnea2, 2 Gorakhpur
Status: 10-2005
•
••• Châteauguay 1984
Ahafo 2006
•
•
2 Lucknow 2006
•
3 Puti 2005
• Iringa, Shinyanga 2006
•
3, 2 El Dorado2006
STATCOMFlicker STATCOMSTATCOMFlicker STATCOM
•
Radsted 2006
•
• 2 Sabah 2006
Nebo 2007
9 Powerlink,Refurbishment2007
Devers 2006
•Benejama,Saladas 2006
La Pila 1999
•
•• •• •
•
Plus 16 Projects for HVDC Long Distance Transmission …
Plus 16 Projects for HVDC Long Distance Transmission …
8 alone between 2000 &2005 in 4 Continents8 alone between 2000 &2005 in 4 Continents
Fig. 9: High Power Semiconductors
Pellet of LTT Thyristor
Pellet ofGTO / IGCT
Assembly ofChips in IGBT
IGCT = Insulated Gate commutated Thyristor
IGBT = Insulated Gate bipolar Transistor
LTT = Light triggered Thyristor
10 / 33
Fig. 11: Use of Power Electronics for FACTS & HVDC - Transient Performance and Losses
More Dynamics for better Power Quality:
Use of Power Electronic Circuits for Controlling P, V & QParallel and/or Series Connection of ConvertersFast AC/DC and DC/AC Conversion
ThyristorThyristor
50/60 Hz
ThyristorThyristor
50/60 Hz
GTOGTO
< 500 Hz
GTOGTO
< 500 Hz
IGBT / IGCT
Losses
> 1000 Hz
IGBT / IGCT
LossesLosses
> 1000 Hz
Transition from “slow” to “fast”
Switching Frequency
On-Off Transition 20 - 80 ms
Transition from “slow” to “fast”Transition from “slow” to “fast”
Switching Frequency
On-Off Transition 20 - 80 ms
1-2 %1-2 %
4-5 %4-5 %
ThyristorThyristor
ModuleModule
Valve Group - Example Indoor for HVDC
ThyristorThyristor
Module
Valve Group - Example Outdoor for FACTS
Fig. 10: HVDC and FACTS - Advanced Power Electronics for High Voltage Systems
11 / 33
The dependency between transient performance and losses is depicted in Fig. 11. An example
of actual losses in a large HVDC project is given in section 5, Fig. 26.
Flexible AC Transmission Systems (FACTS) based on power electronics have been
developed to improve the performance of long distance AC transmission. The technology has
then been extended to the devices which can also control power flow. Excellent operating
experiences are available worldwide, and FACTS technology also became mature and
reliable.
Fig. 12 shows the principal configurations of FACTS devices. Main shunt connected FACTS
application is the Static Var Compensator with line-commutated thyristor technology, where
the maximum switching frequency in each phase element is limited by the “driving” system
frequency.
A further development is STATCOM using voltage sourced converters. Both devices provide
fast voltage control, reactive power control and power oscillation damping features (POD). As
an option, SVC can control unbalanced system voltages. The developments of FACTS
technologies are depicted in Fig. 13. Static Var Compensation is mainly used to control
system voltage. There are hundreds of these devices in operation worldwide. For decades, it
has been a well developed technology, and the demand on SVC is further increasing.
Fixed series compensation is widely used to improve the stability by reducing the
transmission angle in long distance transmissions. A huge number of these applications are in
operation. If system conditions are more complex, Thyristor Controlled Series Compensation
Fig. 12: FACTS - Flexible AC Transmission Systems: Support of Power Flow
SVC - Static Var Compensator (Standard for Parallel Compensation)
STATCOM - Static Synchr. Compensator (Fast SVC, Flicker Compensation)
FSC - Fixed Series Compensation
TCSC - Thyristor Controlled Series Compensation
TPSC - Thyristor Protected Series Compensation
GPFC - Grid Power Flow Controller (FACTS-B2B)
UPFC – Unified Power Flow Controller
TCSC/TPSC
FSC
60 Hz 60 Hz
ACAC
60 Hz 60 Hz
ACACACAC
GPFC/UPFC
AC AC
50 or 60 Hz60 Hz
GPFC/UPFC
AC AC
50 or 60 Hz60 Hz
ACAC ACAC
50 or 60 Hz60 Hz
/ UPFC
/ TPSC
/ STATCOMSVC
60 Hz60 Hz
ACAC
SVC
60 Hz60 Hz
ACAC
60 Hz60 Hz
ACAC
60 Hz60 Hz
ACACACAC
12 / 33
is used. TCSC has already been applied in different projects for load-flow control, stability
improvement and to damp oscillations in interconnected systems.
Special FACTS devices are UPFC (Unified Power Flow Controller) and GPFC (Grid Power
Flow Controller) [2, 5]. UPFC combines a shunt connected STATCOM with a series
connected STATCOM (= S3C, Solid State Series Compensator), which can exchange energy
via a coupling capacitor. The CSC (Convertible Synchronous Compensator) in Fig. 8 uses a
UPFC which can be switched over into different applications with either two STATCOMs or
two S³Cs. GPFC is a special DC back-to-back link, which is designed for fast power and
voltage control at both terminals. In this manner, GPFC is a “FACTS Back-to-Back”, which
is less complex and expensive than the UPFC.
For most applications in AC transmission systems and for network interconnections, SVC,
FSC, TCSC and GPFC/B2B are fully sufficient to match the essential requirements of the
grid. STATCOM and UPFC are tailored solutions for special needs.
The basic configurations of HVDC are depicted in Fig. 14 and 15. HVDC operates as power
flow controller; it “forces P to flow”. In hybrid system configurations with synchronous
frequencies over the whole grid, HVDC offers a highly effective control of power flow. In
addition to that, in case of system faults, HVDC can either support the grid recovery, or it can
automatically split the systems like a “Firewall”, which is very helpful for Blackout
1st Generation
MechanicallySwitched Devices
1st Generation
MechanicallySwitched Devices
VSC TechnologyGTO, IGBT, IGCT
3rd Generation
VSC TechnologyGTO, IGBT, IGCT
3rd Generation
Thyristor ControlledComponents
2nd Generation
Thyristor ControlledComponents
2nd Generation
Breaker DelayBreaker Delay 2 - 3 Cycles 2 - 3 Cycles 1- 2 Cycles 1- 2 Cycles Response TimeResponse Time V-Control
I-Control:< 1 Cycle
Slow VARsSlow VARs Fast VARsFast VARs
Fig. 13: FACTS – Technology Developments
13 / 33
prevention in case of cascading events [3]. For bipolar applications, a second set of converters
with negative voltage plus coupling transformers is provided.
For system interconnections, an additional benefit of the HVDC is its incorporated fault-
current limitation feature. HVDCPLUS is the preferred technology for interconnection of
islanded grids to the power system, such as off-shore wind farms. This technology provides
the so-called “Black Start” feature by use of voltage sourced converters. Voltage sourced
Fig. 15: HVDC - High Voltage DC Transmission: It forces P to flow
HVDC-LDT - Long Distance Transmission
B2B - The Short Link
Back-to-Back Station
60 Hz 50 Hz
AC AC
B2B - The Short Link
Back-to-Back Station
60 Hz 50 Hz
AC AC
Back-to-Back Station
60 Hz 50 Hz
ACAC ACAC
DC Cable
AC AC
Submarine Cable Transmission
DC Cable
AC AC
DC Cable
ACAC ACAC
Submarine Cable Transmission Long Distance OHL Transmission
DC Line
AC AC
Long Distance OHL Transmission
DC Line
ACAC ACAC
HVDC - High Voltage DC Transmission: It forces P to flowStandard with Thyristors (Line-commutated Converter)
AC/DC and DC/AC conversion by Power Electronics
HVDCPLUS (Voltage-Sourced Converter - VSC)
HVDC can be combined with FACTS
V-Control included
130 ≤ kV ≤ 800300 ≤ MW ≥ 4000
130 ≤ kV ≤ 800300 ≤ MW ≥ 4000
Rating LDT:
130 ≤ kV ≤ 800300 ≤ MW ≥ 4000
130 ≤ kV ≤ 800300 ≤ MW ≥ 4000
Rating LDT:
up to 1000 - 4000 km
... or with Cable/Line - the Long Distance Transmission
up to 1000 - 4000 km
... or with Cable/Line - the Long Distance Transmission
Filters Filters
Back-to-Back - the short Link ...Back-to-Back - the short Link ...
fA = 50 Hz Example fB = 60 HzfA = 50 Hz Example fB = 60 Hz
Power & Voltage ControlFault Current Blocking
13,8 ≤ kV ≤ 55030 ≤ MW ≤ 1200
13,8 ≤ kV ≤ 55030 ≤ MW ≤ 1200
B2B - Rating:
13,8 ≤ kV ≤ 55030 ≤ MW ≤ 1200
13,8 ≤ kV ≤ 55030 ≤ MW ≤ 1200
B2B - Rating:
Fig. 14: High Voltage DC Transmission – Basic Configurations
14 / 33
converters do not have the need of a “driving” system voltage; they can build up a 3 phase AC
voltage via the DC voltage at the cable end, supplied from the converter at the main grid.
3. Phase Shifting Transformer versus HVDC and FACTS
Phase shifting transformers have been developed for transmission system enhancement in
steady state system conditions. The operation principle is voltage source injection into the line
by a series connected transformer, which is fed by a tapped shunt transformer, very similar to
the UPFC, which uses VSC-Power Electronics for coupling of shunt and series transformer.
This way, overloading of lines and loop-flows in Meshed Systems and in parallel line
configurations can be eliminated. However, the speed of phase shifting transformers for
changing the phase angle of the injected voltage via the taps is very slow: typically between 5
and 10 s per tap, which sums up for 1 minute or more, depending on the number of taps.
As a rule of thumb for successful voltage or power-flow restoration under transient system
conditions, a response time of approx. 100 ms is necessary with regard to voltage collapse
phenomena and “First Swing Stability” requirements. Such fast reaction times can easily be
achieved by means of FACTS and HVDC controllers. Their response times are fully suitable
for fast support of the system recovery. Therefore, dynamic voltage and load-flow restoration
is clearly reserved to power electronic devices like FACTS and HVDC.
In conclusion, phase shifting transformers and similar devices using mechanical taps can only
be applied for very limited tasks with slow requirements under steady state system conditions.
4. FACTS Technologies and Applications
In this section, a more detailed description of FACTS technologies is given. Fig. 16 and 17
show the full range of applications, including actual ratings and voltage levels of today’s
solutions, as listed in Fig. 8.
Fig. 18 shows a site view of one of the 27 SVCs, which have been installed in the UK to
overcome transmission bottlenecks caused by deregulation [3]. The SVC control functions,
including options for specific tasks, such as unbalance control (not necessary in UK), are also
indicated in the figure. An increasing number of SVCs are also going to be installed in other
continents. In Fig. 19, an example of an SVC in South America is given. The SVC was
implemented to improve system stability of the large transmission grid. The installed
containerized solution offers additional benefits, such as reduction in installation and
15 / 33
commissioning time, as well as space and cost savings compared to conventional building
technologies.
Fig. 17: FACTS for Series Compensation
FSC
~
220 ≤ kV ≤ 800200 ≤ MVAr ≤ 800
Fixed Series Compensation
Protection
Circuit BreakersArresters
Capacitors
FSC
~
220 ≤ kV ≤ 800200 ≤ MVAr ≤ 800
Fixed Series Compensation
Protection
Circuit BreakersArresters
Capacitors
TCSC
~
220 ≤ kV ≤ 800100 ≤ MVAr ≤ 200
Thyristor Controlled Series Compensation
Thyristor ValvesControl & Protection
α
Capacitors
Circuit Breakers
TCSC
~
220 ≤ kV ≤ 800100 ≤ MVAr ≤ 200
Thyristor Controlled Series Compensation
Thyristor ValvesControl & Protection
α
Capacitors
Circuit Breakers
TPSC
~
220 ≤ kV ≤ 800100 ≤ MVAr ≤ 500
Thyristor Valves
Thyristor Protected Series Compensation
Protection
ILim
Capacitors
Circuit Breakers
TPSC
~
220 ≤ kV ≤ 800100 ≤ MVAr ≤ 500
Thyristor Valves
Thyristor Protected Series Compensation
Protection
ILim
Capacitors
Circuit Breakers
MSC / MSR
~
52 ≤ kV ≤ 80050 ≤ MVAr ≤ 500
Mechanical SwitchedCapacitors / Reactors
Reactors
SwitchgearCapacitors
MSC / MSR
~
52 ≤ kV ≤ 80050 ≤ MVAr ≤ 500
Mechanical SwitchedCapacitors / Reactors
Reactors
SwitchgearCapacitors
STATCOM
~
52 ≤ kV ≤ 80050 ≤ MVAr ≤ 800
Static Synchronous Compensator
GTO/IGBT ValvesControl & ProtectionTransformerDC Capacitors
STATCOM
~
52 ≤ kV ≤ 80050 ≤ MVAr ≤ 800
Static Synchronous Compensator
GTO/IGBT ValvesControl & ProtectionTransformerDC Capacitors
SVC
~
52 ≤ kV ≤ 80050 ≤ MVAr ≤ 800
Static Var Compensator
Reactors
Thyristor Valve(s)Control & ProtectionTransformerCapacitors
SVC
~
52 ≤ kV ≤ 80050 ≤ MVAr ≤ 800
Static Var Compensator
Reactors
Thyristor Valve(s)Control & ProtectionTransformerCapacitors
Fig. 16: FACTS for Parallel Compensation
16 / 33
In Fig. 20-21, the features and cost savings of series compensation due to grid enhancement
are summarized. The mentioned SSR (sub-synchronous resonances) topic is a critical issue
for large thermal generators with long shafts [7]. The flexibility of modern FACTS
technologies under extremely harsh environmental conditions is indicated in Fig. 21-22: the
operating range for FSC begins at -500 C, for TCSC it can reach up to +850 C. This is
Benefits:o Improvement of Voltage Qualityo Increased Stability
Voltage Control Reactive Power ControlPower Oscillation DampingUnbalance Control (Option)
Voltage Control Reactive Power ControlPower Oscillation DampingUnbalance Control (Option)
Fig. 18: SVC Pelham, NGC, UK - 400 kV/14 kV, -75/+150 MVAr
Fig. 19: SVC Bom Jesus da Lapa, Enelpower, Brazil - 500 kV, +/-250 MVAr Containerized Solution
Valves & ControlValves & Control Benefits:
o Improvement of Voltage Qualityo Increased Stabilityo Avoidance of Outages
17 / 33
necessary due to the outdoor installation on high voltage potential, with the isolated platform
mounted directly in series with the transmission line.
Fig. 21: 500 kV TCSC Serra da Mesa, Furnas/Brazil – Essential for Transmission
Current Control Impedance ControlPower OscillationDamping (POD)Mitigation of SSR(Option)
Current Control Impedance ControlPower OscillationDamping (POD)Mitigation of SSR(Option)
Benefits:o Increase of Transmission Capacityo Improvement of System Stability
Benefits:o Increase of Transmission Capacityo Improvement of System Stability
Up to 500 PODOperations per dayfor saving the System Stability
A System Outage of 24 h hours would cost 840,000 US $ *
Up to 500 PODOperations per dayfor saving the System Stability
A System Outage of 24 h hours would cost 840,000 US $ *
* 25 US $/MWh x 1400 MW x 24 hrs
> + 60 o C
up to 85 o
> + 60 o C
up to 85 o
Fig. 22: FSC at EHV 735 kV plus harsh Environment
Poste Montagnais, Canada - FSCPoste Montagnais, Canada - FSC
- 50 o C- 50 o C
Fig. 20: FACTS - Application of Series Compensation
TCSC/TPSCTCSC/TPSC FSCFSCα
~ ~
TCSC/TPSCTCSC/TPSC FSCFSCα
~ ~
α
~~~ ~~~~Damping of Power OscillationsLoad-Flow ControlMitigation of SSR
Controlled Series Compensation:
Damping of Power OscillationsLoad-Flow ControlMitigation of SSR
Controlled Series Compensation:Controlled Series Compensation:
Fixed Series Compensation:
Increase of Transmission Capacity
Fixed Series Compensation:Fixed Series Compensation:
Increase of Transmission Capacity
18 / 33
For Thyristor Protected Series Compensation TPSC, innovative developments in Thyristor-
Technology have been applied: Light-triggered Thyristors (now state of the art for FACTS
and HVDC) by means of a special heat-sink to enable a very fast self-cooling of the valves
within half a second only. By these means, TPSC is fully suitable for multiple fault
conditions, as it is often the case under hot climate conditions due to brush-fires leading to
repetitive line faults. In the TPSC, the thyristor replaces the conventional MOV (zinc oxide
arrester) for fast capacitor protection against over voltages due to short-circuit currents.
During faults, the MOV heats up heavily. Due to an upper temperature limit, the MOV must
cool down before the next current stress can be absorbed. Cool-down requires a substantial
amount of time, time constants of several hours are typical. During this time, the series
compensation must be taken out of service (bypass-breaker closed) and consequently the
power transfer on the related line needs to be reduced dependent on the degree of
compensation, leading to a significant loss in transmission capacity. Thus it appears that by
using the TPSC with fast cooling-down time instead of conventional series compensation with
MOV, a significant amount of money for each application can be saved.
Fig. 23 shows a site-view of one of the 5 TPSCs, installed at 500 kV in California, USA (ref.
to Fig. 8).
In Fig. 24, two projects with series compensation in China are presented. The picture a) gives
a view of one phase element of the two Pingguo TCSCs. The 3D view b) demonstrates how
Fig. 23: TPSCs Vincent and Midway/USA: 5 TPSC Systems at 500 kV - fully proven in Practice
Outdoor Valves on a PlatformLTT Thyristors, self-cooled
TPSC Technology: Outdoor Valves on a PlatformLTT Thyristors, self-cooled
TPSC Technology:
19 / 33
easily series compensation can be mounted to the existing line: when the installation is
finished (besides the line), a line interruption and a jumper connection to the platform is
made, with an actual power transmission interruption of only 1-3 days.
5. HVDC for Interconnection and Transmission Optimization
During the developments of East-West Grid interconnection in Europe, three B2B projects
have initially been installed. One of them is shown in Fig. 25. All 3 projects led to fast and
more than full return on investments by energy trading. With the upcoming synchronous
extension of UCTE, however, they were taken out of service.
The low losses of the thyristor technology in comparison with VSC devices (ref. to Fig. 11),
are depicted in Fig. 26 for the Etzenricht installation shown in Fig. 25. Similar – and even
lower – losses have been achieved with the new HVDC installations. Especially in very large
DC transmission projects with 3 GW and more, minimal losses are an important issue for the
investors.
Fig. 24: China goes ahead – Transmission Enhancement with FACTS a) Photo of Pingguo TCSC, commissioned in June 2003 b) 3D View on Fengjie 500 kV Fixed Series Compensation, China 2x 600 MVAr, Line Compensation Level 35%
Commercial Operation in June 2006Commercial Operation in June 2006
Enhancement of Chinas “Central Transmission Corridor”Enhancement of Chinas “Central Transmission Corridor”
b)
a)
20 / 33
After the Blackout in the United States, new projects with high voltage power electronics are
smoothly coming up. Siemens PTD has been awarded a contract by Neptune Regional
8000 kW of Losses equals1.33% of 600MW
3%3%3%3%4%4%
37%37%
53%53%
AuxiliariesSmoothing ReactorFilter Circuits
Converter Valves
Converter Transformers
this sums up to …this sums up to …
Total B2B Losses: close to 1 % onlyTotal B2B Losses: close to 1 % only
Fig. 26: HVDC Losses – Example B2B Etzenricht
Fig. 25: Etzenricht, one of the initial Steps for East-West System Interconnection in Europe with 3 B2Bs – now replaced by synchronous Links (ref. to Text)
HVDC B2B - as Interconnector or Power-Flow Controller: Etzenricht, an Example from Germany
System Data:Rated Power: 600 MWDC Voltage: 160 kV DCDC Current: 3750 A AC Voltage: 420 kV
21 / 33
Transmission System LLC (RTS) in Fairfield, Connecticut, to construct an HVDC
transmission link between Sayreville, New Jersey and Long Island, New York. Neptune RTS
was established to develop and commercially operate power supply projects in the United
States. By delivering a complete package of supply, installation, service and operation from a
single source, Siemens is providing seamless coverage for the customer’s needs. The
availability of this combined expertise fulfills the prerequisites for financing these kinds of
complex supply projects through the free investment market. Siemens and Neptune RTS
developed the project over three years to prepare it for implementation. In addition to
providing technological expertise, studies, and engineering services, Siemens also supported
its customer in the project’s approval process. In Fig. 27, highlights of this innovative project
are depicted.
Another highlight of HVDC project development is shown in Fig. 28. Basslink HVDC
provides a submarine cable link across the Bass Strait between Tasmania and the state of
Victoria on the Australian mainland. Basslink Pty Ltd. was specially formed by National Grid
Transco (the world's largest independent transmission network operator) to run the project
titled Basslink. The advantages of this link lie on both sides of the water: gaining access to the
Australian electricity market, Tasmania can supply Victoria at peak load times with power
from hydro generating plants. Tasmania can top up its base load from the mainland grid and
Fig. 27: New HVDC Cable Link Neptune RTS, USA
Customer:
End User:
Location:
Project
Development:
Supplier:
Transmission:
Power rating:
Transmission dist.:
Neptune RTS
Long Island Power
Authority (LIPA)
New Jersey: Sayreville
Long Island: Duffy Avenue
NTP-Date: 07/2005
PAC: 07/2007
Consortium
Siemens / Prysmian
Sea Cable
600/660 MW monopolar
82 km DC Sea Cable
23 km Land Cable
Customer:
End User:
Location:
Project
Development:
Supplier:
Transmission:
Power rating:
Transmission dist.:
Neptune RTS
Long Island Power
Authority (LIPA)
New Jersey: Sayreville
Long Island: Duffy Avenue
NTP-Date: 07/2005
PAC: 07/2007
Consortium
Siemens / Prysmian
Sea Cable
600/660 MW monopolar
82 km DC Sea Cable
23 km Land Cable
Ed Stern, President of Neptune RTS: “High-Voltage Direct-Current Transmission will play an increasingly important Role, especially as it becomes necessary to tap Energy Reserves whose Sources are far away from the Point of Consumption”
Ed Stern, President of Neptune RTS: “High-Voltage Direct-Current Transmission will play an increasingly important Role, especially as it becomes necessary to tap Energy Reserves whose Sources are far away from the Point of Consumption”
22 / 33
also secure the base load in drought periods, when reduced hydro power is available. In
addition to that, Tasmania plans to set up wind farms to improve the production of electrical
power from regenerative sources further, ref. to Fig. 28.
The Basslink HVDC project shows that HVDC is fully suitable to match complex
transmission requirements even under environmental sensitive conditions. In Fig. 29 it is
shown that a combination of land cable, sea cable and overhead line was selected to match
both environmental constraints and cost issues.
For a long time, China has been benefiting from HVDC transmission by connecting clean and
low cost energy sources to the remote load centers, as indicated in Fig. 30 for the Tian-Guang
project (1800 MW) in South China. In Fig. 31 it is shown that a project termination for Gui-
Guang I (3000 MW) could be achieved 6 months ahead of schedule, which provides a large
amount of additional return on investments to the customer.
Fig. 28: Innovative Transmission Technologies for long Distances - Basslink HVDC
Benefits of HVDCBenefits of HVDC
Clean & Low Cost Energyover Long Distance – suitable
for Peak-Load Demand
Clean & Low Cost Energyover Long Distance – suitable
for Peak-Load Demand
Improvement of PowerQualityImprovement of PowerQuality
Improvement of localInfrastructuresImprovement of localInfrastructures
HVDC Cable (400 kV / 1500 mm2)
Metallic Return Cable (12/20 kV / 1400 mm2)
FO Cable (12 Fibers)
HVDC Cable (400 kV / 1500 mm2)
Metallic Return Cable (12/20 kV / 1400 mm2)
FO Cable (12 Fibers)
System Data:Rating 500 MWVoltage 400 kV DCThyristor 8 kV LTTTransmissionlength 370 km
System Data:Rating 500 MWVoltage 400 kV DCThyristor 8 kV LTTTransmissionlength 370 km
Cable Laying Vessel“Giulio Verne“
23 / 33
As a follow-up of the Gui-Guang I project, which is in full commercial operation, a new
contract for Gui-Guang II has been awarded to Siemens and its local partners with equal
transmission capacity of 3000 MW. Examples of system studies for projects with HVDC and
FACTS for system stability improvement in China and other continents are depicted in the
next section.
Sea Cable
Underground Cable
Converter Station
500 kV Substation
3.2 km 57.4 km 295 km
Transition Station
6.4 km
Underground Cable
Converter Station
Transition Station
220 kV Substation
1.7 km 2.1 km8.9 km
McGauransBeach
Five Mile Bluff
Bass Strait
Loy Yang Georgetown
Sea Cable
Underground Cable
Converter Station
500 kV Substation
3.2 km 57.4 km 295 km
Transition Station
6.4 km
Underground Cable
Converter Station
Transition Station
220 kV Substation
1.7 km 2.1 km8.9 km
McGauransBeach
Five Mile Bluff
Bass Strait
Loy Yang Georgetown
Fig. 29: Basslink HVDC - Optimization of the Transmission System
Operated by:South China Electric Power JVC (SCEP)
System Data:Rating 1800 MWVoltage +/-500 kVDCThyristor 8 kVLine Length 960 km
BenefitsBenefitsUse of Clean &Low CostEnergy
Use of Clean &Low CostEnergy
TianshengqiaoTianshengqiao
Guangzhou BeijiaoGuangzhou Beijiao
The Task: Connection of Hydro Generation to Remote Load Centers
Tian Hydro StationTian Hydro Station
Fig. 30: HVDC Long Distance Transmission Tian-Guang
24 / 33
6. System Studies for large Transmission Projects with HVDC and FACTS
Fig. 32-33 give an example of a large power system simulation of the Chinese grid [2], in
which both FACTS and HVDC have been integrated for grid interconnection and point to
point long distance transmission in a hybrid way.
Fig. 31: HVDC Long Distance Transmission Gui-Guang I
Rating: 3000 MWVoltage: ± 500 kV
Contract: Nov. 1, 2001Project terminated 6 Months ahead of Schedule by Sept. 2004
Thyristor: 5" LTT with integrated Overvoltage Protection
View of the Thyristor-Module
Project terminated 6 Months ahead of Schedule by Sept. 2004
Fig. 32: Use of HVDC and FACTS in a hybrid System in China
GuiyangNayong
AnshunAnshun
Huishui
Hechi
Lubuge
TSQ-ILuoping
HVDC TSQ
LiudongYantan
TCSC & FSCPingguo
Baise
TSQ-II
Nanning
Yulin
Laibin
Hezhou
Gaomin
Luodong
ZhaoqingConv. Stat.
BeijiaoConv. Stat.
Guangzhou
Wuzhou
TSQ Conv. Stat.
Yunnan
Guangxi
Guizhou
Guangdong
HVDC GuiGuang
AnshunConv. Stat.
Liuzhou
Zhaoqing
Beijiao
Zhengcheng
Guangxi
Pingguo
FSC
HVDC Converter Station
TCSC FSC
HVDC Converter Station
TCSCTCSC FSCFSC
Hydro Power StationHydro Power Station
Thermal Power StationThermal Power Station
25 / 33
Because of the long transmission distances, the system experiences severe power oscillations
after faults, close to the stability limits. In the recordings in Fig. 33 (upper part) oscillations
are depicted. The first case given is HVDC transmitting power in constant power mode, see
curve a. It can be seen that strong power oscillations occur. If, however, damping control of
HVDC Gui-Guang is activated (curve b ), the oscillations are damped very effectively. Using
series compensation with two TCSCs and two FSCs at Pingguo substation, the stability of the
overall system can be further increased (curve c ). The lower part of Fig. 33 shows that
without HVDC, the Pingguo TCSCs need more actions for damping: 1a) compared to 2a)-b).
Without series compensation and without HVDC damping, such a large power system would
be unstable in case of fault contingencies, thus leading to severe outages (Blackout) [3].
Fig. 33: China - Benefits of active Damping with HVDC & FACTS
2b)
2a)
1a)
POD Output Signal (pu) TCSC 1 (= TCSC 2)
POD Output Signal (pu) TCSC 1 (= TCSC 2)
POD Output Signal HVDC (%)
Fast and strong Action of HVDC with POD
HVDC not activeMore Action of TCSC required
Less Action of TCSC required HVDC active
2b)
2a)
1a)
POD Output Signal (pu) TCSC 1 (= TCSC 2)
POD Output Signal (pu) TCSC 1 (= TCSC 2)
POD Output Signal HVDC (%)
Fast and strong Action of HVDC with POD
HVDC not activeMore Action of TCSC required
Less Action of TCSC required HVDC active
5 10 15 200
0
600
900
1200
1500
-600
300
-900
-300
Time (s)
Powe
r flo
w in
one
line
Huish
ui-H
echi
(MVA
)
a
b
5 10 15 200
0
600
900
1200
1500
-600
300
-900
-300
Time (s)
Powe
r flo
w in
one
line
Huish
ui-H
echi
(MVA
)
a
b
Time / s
ab
c
5 10 15 200
0
600
900
1200
1500
-600
300
-900
-300
Time (s)
Powe
r flo
w in
one
line
Huish
ui-H
echi
(MVA
)
a
b
5 10 15 200
0
600
900
1200
1500
-600
300
-900
-300
Time (s)
Powe
r flo
w in
one
line
Huish
ui-H
echi
(MVA
)
a
b
Time / s
aabb
cc
Power Flow in one Line Huishui-Hechi (MW)
Dynamic Results
a – without Power Modulationb – with Power Modulation
of HVDC Controlc – further Improvements with
Pingguo TCSC/FSC
26 / 33
Similar studies have been carried out for large transmission projects worldwide. An example
of such studies is described in the following.
With the Mead-Adelanto and the Mead-Phoenix Transmission Project (MAP/MPP), a major
500 kV transmission system extension has been carried out to increase the power transfer
opportunities between Arizona and California, USA. The extension includes two main series
compensated 500 kV line segments and two equally rated Static Var Compensators, supplied
by Siemens, at the Adelanto and Marketplace substations - ref to Fig. 34. The SVCs enabled
the integrated operation of the already existing highly compensated EHV AC system and two
large HVDC systems. The SVC installation was an essential prerequisite for the overall
system stability at an increased power transfer rate.
An example of the intensive project testing with computer and real-time simulator facilities is
given in Fig. 35 for a fault application at Marketplace 500 kV bus. The figure shows the
computer test results with both SVCs active. The influence of the HVDC can be seen from
Fig. 34: HVDC plus SVC: Mead-Adelanto - USA
Increase of Transmission Capacity
Improvement of System Stability
Increase of Transmission Capacity
Improvement of System Stability
Upgrade of a large AC and DC TransmissionSystem with 2 SVCs& FSCs
Each SVC: 388 MVAr for Voltage and POD ControlEach SVC: 388 MVAr for Voltage and POD Control
27 / 33
the DC voltage E dc. Figure a) is with both SVCs only in voltage control mode (PSDC
blocked); Figure b) shows an improved damping with the PSDC function enabled.
In Fig. 36, a new FACTS application with SVC in combination with HVDC in Germany is
shown [2]. It is actually the first high voltage FACTS controller in the German network.
Reason for the SVC installation at Siems substation nearby the landing point of the Baltic
Cable HVDC were unforeseen right of way restrictions in the neighboring area, where an
initially planned new tie-line to the strong 400 kV network for connection of the HVDC was
denied. Therefore, with the existing reduced network voltage of 110 kV (see the dotted black
lines in Fig. 36, only a limited amount of power transfer of the DC link was possible since its
commissioning in 1994, in order to avoid repetitive HVDC commutation failures and voltage
problems in the grid. In an initial first step for grid access improvement, an additional
transformer for connecting the 400 kV HVDC AC bus with the 110 kV bus (see the figure)
was installed. Finally, in 2003 with the new SVC, equipped with a fast coordinated control,
the HVDC could fully increase its transmission capacity up to the design rating of 600 MW.
In addition to this measure, a new cable to the 220 kV grid was installed, to increase the
system strength with regard to performance improvement of the HVDC controls. In Fig. 37, a
photo of the Siems SVC in Germany is given.
1100
1000
900
800
700
400
200
0
1.4
1.2
1.0
0.8
0.6
400
200
0
E dc Adelanto (volts) Mkplc 500kV Bus Vlt (pu)
Adel Bsvc (Mvar) Mkplc Bsvc (Mvar)
a)E dc Adelanto (volts)
Mkplc 500kV Bus Vlt (pu)
Adel Bsvc (Mvar) Mkplc Bsvc (Mvar)
1100
1000
900
800
700
1.4
1.2
1.0
0.8
0.6
400
200
0
400
200
0
0 0 1010 2020Time (sec) Time (sec)
b)
a) Both SVCs in Voltage Control Mode
b) Both SVCs in Coordinated Voltage & Power Oscillation Damping Control Mode
Design by Computer StudiesDesign by Computer Studies
Fig. 35: Mead-Adelanto Studies – Comparison of SVC Voltage- and POD-Control Mode
28 / 33
In the same way as in the previous project cases, intensive studies, first with computer and
then with real-time simulator by using the physical SVC controls and simplified models for
the HVDC, have been carried out prior to commissioning.
Essential for enhanced Grid Access of the HVDCEssential for enhanced Grid Access of the HVDC
Fig. 37: The Solution – the first HV SVC in the German Grid at Siems Substation
Fig. 36: The Problem – no Right of Way for 400 kV AC Grid Access of Baltic Cable HVDC
Initially planned Connection
Grid Access denied
1
2
1 Initial Step for Grid Access Enhancement
2 and a new 220 kV Cable
2
2
Final Solution: new SVC with TCR & TSC100 MVar ind.200 MVar cap.
Now, the HVDC can operate at full Power Rating
Initially planned Connection
Grid Access denied
11
22
1 Initial Step for Grid Access Enhancement
11 Initial Step for Grid Access Enhancement
2 and a new 220 kV Cable22 and a new 220 kV Cable
22
22
Final Solution: new SVC with TCR & TSC100 MVar ind.200 MVar cap.
Final Solution: new SVC with TCR & TSC100 MVar ind.200 MVar cap.
Now, the HVDC can operate at full Power Rating
2003
1994
29 / 33
In conclusion of the previous sections, Table 1 summarizes the impact of FACTS and HVDC
on load flow, stability and voltage quality when using different devices. Evaluation is based
on a large number of studies and experiences from projects.
7. Innovative Transmission Solutions using High Voltage Power Electronics
Increasing generation in high load density networks on the one hand, and interconnections
among the systems on the other hand, increase the short-circuit power. If the short-circuit
current rating of the equipment in the system is exceeded, the equipment must be uprated or
replaced, which is a very cost- and time-intensive procedure. Short-circuit current limitation
offers clear benefits in such cases. Limitation by passive elements, e.g. reactors, is a well
Table 1: FACTS & HVDC – Overview of Functions & “Ranking”
HVDC (B2B, LDT)
UPFC(Unified Power Flow Controller)
MSC/R(Mechanically Switched Capacitor / Reactor)SVC (Static Var Compensator)STATCOM (Static Synchronous Compensator)
Load-Flow Control
Voltage Control: Shunt Compensation
FSC (Fixed Series Compensation)TPSC (Thyristor Protected Series Compensation)TCSC (Thyristor Controlled Series Compensation)
Variation of the Line Impedance: Series Compensation
Voltage QualityStabilityLoad Flow
SchemeDevicesPrincipleImpact on System Performance
Influence: no or lowsmallmediumstrong
Based on Studies & practical Experience
30 / 33
known practice. It reduces, however, the system stability, and there is an impact on the load-
flow.
By combining the previously mentioned 500 kV TPSC application with an external reactor
(see Fig. 38), whose design is determined by the allowed short-circuit current level, this
device can also be used very effectively as short-circuit current limiter (SCCL, ref. to [4, 7]).
This new device operates with zero impedance in steady-state conditions, and in case of short-
circuit it is switched within a few ms to the limiting-reactor impedance.
Fig. 39: FCL - Principles and Applications
Not available for HV Levels and Constraints on Protection Co-ordination
Not available for HV Levels and Constraints on Protection Co-ordination
Difficult or impossible at High Voltage LevelsDifficult or impossible at High Voltage Levels
Fault Current LimitationConventional Solution: Reactor
The new FACTS Solution: SCCL
Future Option: High-Temperature Superconducting FCL
Fault Current InterruptionIs-Limiter
Electronic Devices (“Small FACTS”)
Risk of Voltage CollapseRisk of Voltage Collapse
SCCL: no ConstraintsSCCL: no Constraints
Fig. 38: SCCL - an Innovative FACTS Solution using TPSC
Bus 1 Bus 2
AC AC
Bus 1 Bus 2
ACAC ACAC
SCCL SCCL SCCL SCCL SCCL SCCL
TPSCTPSCTPSCTPSCTPSCTPSC + ReactorReactor+ ReactorReactorReactorReactor
Thyristor Protected Thyristor Protected Series CompensationSeries CompensationThyristor Protected Thyristor Protected Series CompensationSeries Compensation
Use of proven TechnologyUse of proven Technology
The new Idea !The new Idea !
31 / 33
Fig. 39 gives a brief overview on today’s solutions for fault-current limitation, including the
new SCCL. Basically, there are two methods for fault-current reduction: limitation and
interruption. The constraints and benefits of the different solutions are indicated in the figure.
Fig. 40 shows the basic function and the operating principle of the SCCL, including a 3-D
view of the SCCL. In comparison with the TPSC site photo, it can be seen that the TPSC is
just complemented by an additional reactor for the current limitation. Further details on the
SCCL solution are described in [7].
8. Market and Reliability Issues
Table 2 summarizes the market expectations for FACTS and HVDC solutions today and in
the future. The market for series compensation, for SVC and for B2B for load-flow control is
actually large today and, as a result of liberalization and deregulation in the power industry, is
developing fast in the future. The market in the HVDC long distance transmission field is
further progressing fast. A large number of high power long distance transmission schemes
using either overhead lines or submarine cables projects have been put into operation or are in
the stage of installation.
Fig. 40: SCCL - Short-Circuit Current Limitation with FACTS
To Bus 2
Reactor
Thyristor Valve Housing
BYPASS Breaker
Capacitor Bank
To Bus 1
Communication
To Bus 2
Reactor
Thyristor Valve Housing
BYPASS Breaker
Capacitor Bank
To Bus 1
Communication
ImpedanceX
Zero Ohm for best Load Flow
Fast Increase of Coupling Impedance
t
ImpedanceX
ImpedanceX
Zero Ohm for best Load Flow
Fast Increase of Coupling Impedance
t
Just one additional X !Just one additional X !
32 / 33
Concerning reliability of high voltage power electronics, Table 3 gives an example of two
SVC projects installed in South Africa. Same high reliability is also achieved for HVDC as
Table 2: Markets for FACTS and HVDC
HVDC
UPFC
TCSC / TPSC
FSC
STATCOM
SVC
Series Compensation
Shunt Compensation
Combined Device
Power Transmission
MSC/R
HVDC
UPFC
TCSC / TPSC
FSC
STATCOM
SVC
Series Compensation
Shunt Compensation
Combined Device
Power Transmission
MSC/R
Excellent Market Upcoming Market Small Market
Table 3: Availability of Power Electronics – Example FACTS: close to 100 %- same for HVDC
Recordings from NATAL SVCs / RSA (2 TCR & 3 Filter)Guarantied Availability: 98 - 99 %
1h0036h409h402h13MDT in hrs
03h002h0010h15On-line Maintenance
162h00102h2680h000hOff-line Maintenance
1252Forced and deferred Outages
10010099.4599.9Availability (%)
1998199719961995Illovo SVC
1h0036h409h402h13MDT in hrs
03h002h0010h15On-line Maintenance
162h00102h2680h000hOff-line Maintenance
1252Forced and deferred Outages
10010099.4599.9Availability (%)
1998199719961995Illovo SVC
10h304h403h204h40MDT in hrs
0001h00On-line Maintenance
60h1562h0081h004h00Off-line Maintenance
2194Forced and deferred Outages
99.7799.9299.7199.78Availability (%)
1998199719961995Athene SVC
10h304h403h204h40MDT in hrs
0001h00On-line Maintenance
60h1562h0081h004h00Off-line Maintenance
2194Forced and deferred Outages
99.7799.9299.7199.78Availability (%)
1998199719961995Athene SVC
33 / 33
the technology applied uses the same components. Excellent on-site operating experience is
being reported, and the FACTS and HVDC technology became mature and reliable.
9. Conclusions
Deregulation and privatization is posing new challenges on high voltage transmission
systems. System elements are going to be loaded up to their thermal limits, and wide-area
power trading with fast varying load patterns will cause congestion. System enhancement will
be essential to keep the supply reliable and safe. Interconnection of power systems offers
many benefits for the operation of the grids. The performance of power systems, however,
decreases with size, loading and complexity of the networks. This is related to problems with
load flow, power oscillations and voltage quality. Such problems are even deepened by the
changing situations resulting from deregulation of the electrical power markets. The power
systems have not been designed for wide-area power trading with daily varying load patterns,
where power flows do no more follow the initial planning criteria of the existing network
configuration. Large blackouts in America and Europe confirmed clearly that the favorable
close electrical coupling might also include risk of uncontrollable cascading effects in large
and heavily loaded interconnected systems. FACTS and HVDC, however, provide the
necessary features to avoid technical problems in the power systems, and they increase the
transmission efficiency.
10. References
[1] U. W. Niehage, “Future Developments in Power Industry”, Key-Note Adress at AESIEAP, 28-05 September 2005, New Delhi, India
[2] L. Kirschner, D. Retzmann, G. Thumm, “Benefits of FACTS for Power System Enhancement”, 14-18 August, 2005, IEEE/PES T & D Conference, Dalian, China
[3] G. Beck, D. Povh, D. Retzmann, E. Teltsch, “Global Blackouts – Lessons Learned”, Power-Gen Europe, 28-30 June 2005, Milan, Italy
[4] W. Breuer, D. Povh, D. Retzmann, V. Sitnikov, E. Teltsch, “Benefits of Power Electronics for Transmission Enhancement”, 10-11 March 2004, Moscow, Russia
[5] W. Breuer, X. Lei, D. Povh, D. Retzmann, E. Teltsch, “Role of HVDC and FACTS in future Power Systems”, 18-22 October 2004, 15th CEPSI, Shanghai, China
[6] W. Breuer, X. Lei, D. Povh, D. Retzmann, E. Teltsch, “Solutions for large Power System Interconnections”, 18-22 October 2004, 15th CEPSI, Shanghai, China
[7] V. Gor, D. Povh, Y. Lu, E. Lerch, D. Retzmann, K. Sadek, G. Thumm, “SCCL – A new Type of FACTS based Short-Circuit Limiter for Application in High Voltage Systems”, CIGRÉ Report B4-209, Session 2004.