DC/DC converters and DC hubs in DC transmission Grids

1
DC/DC converters and DC hubs in
DC transmission Grids
Dragan Jovcic
Aberdeen HVDC Research center,
University of Aberdeen, UK
[email protected]
2
Overview:
1. Role of DC/DC converters and DC hubs in DC grids,
2. Isolated MMC-based DC/DC converter,
3. Thyristor LCL DC/DC converter,
4. IGBT LCL DC/DC converter,
5. IGBT LCL DC hub,
6. Aberdeen DC grid demonstrator
3
1. DC/DC converters and DC hubs in DC grids,
The role of DC/DC converters:
• DC voltage stepping (transformer),
• Power, voltage or current regulation (regulator),
• DC fault isolation and fault current limiting (DC Circuit Breaker),
• Interconnecting DC grids of different manufacturers (firewall).
The role of DC hubs (multiport DC/DC):
• Connecting multiple DC systems of different voltage,
• More cost effective than multiple DC/DC converters,
• Central power flow balancing and DC fault management,
4
1. DC/DC converters and DC hubs in DC grids
DC/DC 1 (Cb-E1) achieves:
• Voltage stepping 200kV/400kV,
• Power flow control,
• Improves stability,
DC/DC 2 (Cb-B1) achieves:
• Power flow control,
• Improves stability,
Figure 1. CIGRE B4.57, B4.58 DC grid benchmark [1]
[1] T K Vrana, Y Yang, D Jovcic, S Dennetière, J Jardini, H Saad, „The CIGRE B4 DC Grid Test System”,
ELECTRA issue 270, October 2013, pp 10-19.
5
1. DC/DC converters and DC hubs in DC grids
Onshore Offshore
1.0GW
I14
1
DC CB14_4
1.0GW
(1.56kA)
±320kV
DC Cable 45
100km, 1GW
1.0GW
AC2
Idc2 2
Zac2 AC CB2
DC Cable 25
300km, 1.0GW
I56
Idc3
Offshore DC
platform 2
1.0GW
5
Idc5
DC/DC 5
1.0GW
3
I36
(2.0kA)
VSC5
±250kV 1.0GW
0.0GW
DCCB56_6
1.0GW
1.0GW
Zac3 AC CB3
VSC4
1.0GW
0.0GW
DC CB25_5
1.0GW
±250kV
Idc4
±320kV
I25
DC Cable 56
100km,1.0GW
AC3
DC/DC 4
1.0GW
DCCB45_5
1.0GW
(2.0kA)
VSC2
1.0GW
1.0GW
(1.56kA)
DC Cable 14
300km,1.0GW
I45
VSC1
1.0GW
4
DC/DC achieves:
• Voltage stepping 250kV/320kV,
• Power flow control,
• DC fault current limiting
• DC fault isolation,
100km
Idc1
Zac1 AC CB1
100km
AC1
Offshore DC
platform 1
1.0GW
6
Offshore DC
platform 3
Idc6
(1.56kA)
(1.56kA)
VSC3
1.0GW
±320kV
DC Cable 36
300km, 1.0GW
DC CB36_6
±320kV
1.0GW
VSC6
1.0GW
300km
Figure 2. Three HVDC systems interconnected with 2 DC/DC converters [2]
[2] D Jovcic, M.Taherbaneh, J.P.Taisne, S.Nguefeu, “Topology assessment for 3 + 3 terminal offshore DC grid
considering DC fault management” IET Generation Transmission and Distribution, Vol9, issue 3, Feb 2015, pp221-30,
6
1. DC/DC converters and DC hubs in DC grids
DC/DC achieves:
• Voltage stepping,
• Power flow control,
• DC fault current limiting
• DC fault isolation,
Figure 3. Three radial DC grids interconnected with DC/DC converters [3]
[3] D Jovcic, M.Taherbaneh, J.P.Taisne, S.Nguefeu, “Offshore DC Grids as an Interconnection of Radial Systems:
Protection and Control aspects” IEEE Transactions on Smart Grids, Vol 6, issue 2, March 2015, pp 903-910, DOI: ,
7
1. DC/DC converters and DC hubs in DC grids,
Terminal 1
+400kV
I1
220kV
300km
Pac1,Qac1
LCC1
DC
substation 3/4
+400kV I13 1.0GW
V1
1
66kV
Pac2,Qac2
+50kV
0.2GW
Vac2
Iac2d,
Iac2q
0.2GW
Terminal 2
I2 +50kV P2
-400kV
DC/DC
2
(type 2)
V2
200km
I2a
fs2
-50kV
V2a
3
V3a 500km
-200kV
fs3
-400kV I12
Vac1
I3
+200kV
I3a
V1b
V1a
600
Terminal 3
DC/DC
3
(type 1)
1000km
1.0GW
P3
220kV
Pac3,Qac3
0.6GW +120kVI
4a
DC/DC
4
(type 1)
1
Vac3
fs4
+120kV 0.6GW
-120kV
1.6
1.8
Control system summary
-120kV
Converter controller
LCC1
PI control of V1 (1), with inner I1 control,
LCC3
PI control of Qac3 (3), with minimum override,
LCC4
PI control of Qac4 (4), with minimum override,
VSC2
PI control of Pac2 (My), and PI control of Qac2 (Mx) with inner Iac2d and Iac2q control,
DCDC2 PI control of V2a (fs2),
DCDC3 PI control of P3, with droop V1b (fs3),
DCDC4 PI control of P4, with droop V1b (fs4),
2.2
2.4
2.6
2.8
3
200
Fault on V4
Vac4
V4
100
0
Fault on Vac4
P4 Power reversal
-100
-300
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
2.2
2.4
2.6
2.8
3
time [s]
220kV
4
V4
2
time [s]
I4
Pac4,Qac4
LCC4
VSC2 -50kV
Mx My
Figure 4. DC grid with 3 DC/DC converters [4]
1.4
-200
Terminal 4
V4a
1.2
300
-200kV
400km
0
-200
-600
P4
I14
200
-400
LCC3
V3
P4
P4ref
400
Voltage [kV]
DC
substation 2
860
Voltage [kV]
P1
Power [MW]
+200kV
1.8GW
V1ref
V1
840
820
800
780
760
Vac4
740
1
1.2
1.4
1.6
1.8
2
time [s]
DC/DC achieves:
• Voltage stepping,
• Power flow control,
• DC fault current limiting
• DC fault isolation,
• DC voltage reversal
[4] D Jovcic and B.T Ooi, “Developing DC transmission network using DC transformers” IEEE Transactions on
Power Delivery, Vol. 25, issue 4, October 2010, pp 2535-2543.
8
1. DC/DC converters and DC hubs in DC grids,
1000MW
+250kV
345kV
345kV
CIGRE benchmark 1000MW HVDC
Idcr
Idci
dcinv
 dcrec
Y
230kV
 Y
230kV
Vdc
Lhp
Rhp
33kV
L13 C
13
Lact L
11 C11
Pact,Qact
L7
L5
Y Y
Chp
L23 C
23
33kV R
act
dcinv
 dcrec
Y Y
25MW Idct1
+22kV
It1
25MW
Ltap
Vdct1
Rg
Cf1
Lf1
 dct
+250kV
It2
Cf2
Lf1 Cf1
Qactc
V
C7 V actc
act
C5
-250kV
DC/DC type 1
-22kV
Rf2
Vdct2
 - Firing angle,
f - operating frequency
Cf2
-250kV
fs
Idct2
Rf2
Figure 5. Taping on HVDC using DC/DC converters [5]
DC/DC achieves:
• Voltage reduction,
• Power flow control,
• DC fault current limiting
• DC fault isolation,
• DC voltage reversal
[5] D Jovcic and B.T Ooi, “Tapping on HVDC lines using DC transformers” Electric Power Systems Research 81
(2), January 2011, pp 561-569.
9
1. DC/DC converters and DC hubs in DC grids,
1GW
AC1
Zac1 AC CB1
4
1
Idc1
I1H
I 4H_
_1
VSC1
1.0GW
1GW
Idc2
AC2
Zac2 AC CB2
DC
I2H
I2H_2
DC Cable 2
1.0GW
VSC2
1.0GW
±250kV
Idc3
Zac3 AC CB3
3
(1.56kA)
VSC3
1.0GW
I2H_H2
H3
I 4H_
DC Hub
_H
1
1
2
3
I 3H_
5
3
I 3H_
±320kV
4
ble
Ca W
C
D .0G
1
H4
4
6
1GW
4
I 4H
I5H-H5
I6H
I5H
5
I5H-5
_6
DC
3
ble
Ca W
DC .0G
1
C
1.0 able
GW 6
1.0GW
_H
6
6
VSC5
1.0GW
1.0GW
Idc6
(1.56kA)
W
1G
±320kV
±320kV
300km
Figure 6. 6-terminal DC grid with a DC hub [2]
Offshore DC
platform 2
Idc5
±250kV
I6H
VSC4
1.0GW
(2.0kA)
DC Cable 5
1.0GW
I6H
I 3H
1GW
AC3
I1H
C
1.0 able
GW 1
2
(2.0kA)
Offshore DC
platform 4
I1H
±320kV
Idc4
(1.56kA)
1G
W
(1.56kA)
Offshore DC
platform 1
1.0GW
100km
Offshore
VSC6
1.0GW
100km
Onshore
DC hub achieves:
• Voltage stepping (each line has different dc voltage),
• Interconnecting different vendors,
• Power flow control,
• DC fault current limiting
• DC fault isolation,
Offshore DC
platform 3
10
1. DC/DC converters and DC hubs in DC grids,
Glasgow
≈
=
≈
=
≈
=
≈
=
≈
=
1GW×5
Firth of Forth
DC hub
≈
=
≈
=
≈
=
≈
=
≈
=
1GW×2
1GW×5
1GW×5
≈
=
≈
=
≈
=
≈
=
≈
=
Hull
1GW×5
≈
=
≈
=
≈
=
≈
=
≈
=
Norway
Dogger
Bank
DC hub
1GW×5
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
1GW×5
1GW×2
1GW×4
East
Anglia
DC hub
≈
=
≈
=
≈
=
≈
=
≈
=
1GW×3
1GW×10
1GW×5
London
1GW×5
Baltic Sea 1GW×10
Germany
≈
=
≈
=
≈
=
≈
= 1GW×5
≈
=
1GW×5
≈
=
≈
=
≈
=
≈
=
≈
=
1GW×2
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
≈
=
DC hub achieves:
• Voltage stepping (each line has
different dc voltage),
• Interconnecting different vendors,
• Power flow control,
• DC fault current limiting
• DC fault isolation,
Germany
≈
=
≈
=
Belgium
Figure 7. North sea Supegrid with 4 DC hubs [6]
[6] D Jovcic and W.Lin “Developing Offshore DC Supergrid With Multiport Reconfigurable DC Hubs” CIGRE
Belgium Conference, Brussels, March 2014.
11
2. Isolated MMC-based DC/DC converter,
•
•
•
Operating frequency: 300-500Hz,
Limits DC fault current, but one MMC must be blocked,
Isolates DC faults
MMC1
Rdc1
½Vdcs1
MMC
Submodule
S1
S2
MMC2
SM1
SM1
SM1
SM1
SM1
SM1
SM2
SM2
SM2
SM2
SM2
SM2
SMN
SMN
SMN
SMN
SMN
SMN
LS1
R1
Vdc1
LS1
R1
LS1
R1
L
Rac LB Va
L
Rac LB Vb
Rac LB
Vc L 
iaca1
iacb1
½Vdcs1
VSM
CSM
Rdc1
idc2
idc1
R1
LS1
R1
LS1
R1
LS1
iacc1
Tr
LS2
R2
½Vdcs2
LS2
R2
iaca2
iacb2
iacc2
n:1
Fault 2
LS2
R2
Rdc2
Vdc2
½Vdcs2
R2
LS2
R2
LS2
R2
LS2
SM1
SM1
SM1
SM1
SM1
SM1
SM2
SM2
SM2
SM2
SM2
SM2
SMN
SMN
SMN
SMN
SMN
SMN
Fault 1
Rdc2
Figure 8. Isolated MMC-based DC/DC converter [7]
[7] D Jovcic and H Zhang, “Optimal Control and DC Fault Ride-Through of Transmission Level, MMC-Based,
Isolated DC/DC Converter” IEEE PES GM 2016, Boston, July 2016.
12
Active power(pu)
DC voltage(kV)
2. Isolated MMC-based DC/DC converter,
600
400
200
Vdc1
Vdc2
0
(a)
1
0.5
0
Pdcref
-0.5
2
0.6
0.4
M1ref,M2ref
0.2
AC voltage(kV)
dq current(pu)
0.8
M1
M2
0
-2
Idref
Id
(c)
600
v
v
a
400
b
4
v
c
200
0
-200
i
i
aca1
0
-2
Arm current(kA)
Arm current(kA)
MMC1
acc1
-2
MMC2
2
0
-2
(h)
MMC1
2
1.5
1
1.2
1.4
Time(s)
Capacitor voltage(kV)
Capacitor voltage(kV)
i
0
(g)
(i)
acb1
(f)
2
0.8
Iq
2
(e)
0.6
Iqref
(d)
AC current(kA)
Control index
1
1
0.4
Pdc
(b)
MMC2
2
1.5
1
0.4
0.6
0.8
1
(j)
Figure 9. Isolated MMC-based DC/DC converter response to DC faults
1.2
1.4
Time(s)
13
3. Thyristor LCL DC/DC converter,
•
•
•
•
Operating frequency: 200-500Hz, no transformer,
Only for relatively low stepping ratio 0.5-2
Limits DC fault current, and isolates DC faults
Voltage or current polarity reversal
High voltage circuit L2/2 Lf2/2
Lf1/2 L1/2 Low voltage circuit
I1
T1
I1s
T6 T8 I
2s
2Cr
2Cf1
V1
Ic
Vcr1
2Cf1
T2
Vcr2
Vc
T1
fs
I2
2Cf2
V2
2Cf2
2Cr
Lf1/2 L1/2
filter
T5 T7
T2
T6 T8 T5 T7 L2/2 Lf2/2
fs 2up 2down
filter
controller
Figure 10. Thyristor LCL DC/DC converter [8]
[8] D.Jovcic, “Bidirectional high power DC transformer” IEEE Transactions on Power Delivery Vol. 24, issue 4,
October 2009, pp 2276-2283..
14
3. Thyristor LCL DC/DC converter,
•
•
•
•
•
Prototype: 30kW, DC/DC 200V/900V, 40kg,
Operating frequency: 580Hz, no transformer,
In house developed Litz-wire inductors,
Power reversal using voltage or current polarity reversal
DC fault tolerant
Figure 11. Thyristor LCL DC/DC converter prototype [9]
[9] M. Hajian, J. Robinson, D Jovcic and B. Wu “30kW, 200V/900V thyristor LCL DC/DC converter laboratory
prototype design and testing ” IEEE Transactions on Power Electronics, vol 29, issue 3,2014, pp 1094-1102.
15
4. IGBT-based LCL DC/DC converter,
•
•
•
•
Operating frequency: 500-1000Hz, no transformer,
Any stepping ratio,
AC current in phase with voltage on both bridges,
Limits DC fault current, and isolates DC faults
I1 IDC1
IDC2 I2
S5
+
I1ac
I2ac
V1ac L1 Ic C Vc L2V2ac
C2 -
V1 +
C
- 1
V1
S1
S3
C
+
C1
-
L1
S4
S2
S7
V2
C2 +
L2
V2
S8
S6
-
Figure 12. IGBT LCL DC/DC converter [10]
[10] D Jovcic, and L Zhang, “LCL DC/DC converter for DC grids” IEEE Transactions on Power Delivery, vol 28, iss
4, 2013, pp 2071-2079.
16
4. IGBT-based LCL DC/DC converter,
•
•
•
•
•
Prototype: 30kW, DC/DC 200V/900V, 30kg,
Operating frequency: 1700Hz, no transformer,
In house developed Litz-wire inductors,
Power reversal using current polarity reversal,
DC fault tolerant,
Figure 13. IGBT LCL DC/DC converter prototype [11]
[11] M Hajian and D Jovcic “30kW, 200V/900V LCL IGBT DC/DC converter prototype design and testing” IEEE
ISGT Europe 2014, Istanbul, October 2014.
17
4. IGBT-based LCL DC/DC converter,
•
•
•
•
•
1GW, DC/DC ±250 kV/±320 kV,
Operating frequency: varied 300-700Hz,
Number of cells: varied 40-200,
Design for best efficiency (onshore):
Total losses 1.6%, Total weight: 1293ton,
Design for low weight (offshore):
Total losses 2.7%, total weight: 585ton,
Operating frequency (Hz)
Ccell (µF) (MMC1, MMC2)
300
1660, 1000
500
1000, 600
700
700, 420
Larm (mH) (MMC1, MMC2)
LCL inductors (mH) (L1, L2)
LCL capacitor (µF)
Total weight1 (103 kg)
Total volume (m3)
LCL inductors total losses (MW)
MMCs total power losses (MW)
DC/DC total power losses (MW)
DC/DC total power losses (%)
8, 12
65, 71
5
1293
1118
0.37
15.73
16.1
1.61
5, 7
39, 42
3
775
672
0.33
21.37
21.7
2.17
3, 5
28, 30
2.1
585
504
0.22
27.21
27.4
2.74
Figure 14. IGBT MMC-based LCL DC/DC converter [12]
[12] A. Jamshidifar, M. Hajian, D Jovcic and Y. Audichya, “Optimal Design of High power MMC-based LCL DC/DC
Converter” IEEE PES GM 2016, Boston, July 2016.
18
600
5. IGBT-based LCL DC hub,
vcA- vcC(kV)
0
Any number of ports. Each port has different DC voltage level.
Number of phase depends on power level and reliability requirements.
330MW per phase.
A phase can be connected/disconnected on the fly. Redundant phase
increases reliability.
Fault on any DC line will not affect operation.
vcB
vcC
-400
-600
0.999 0.9995
200
V1dc
V1dc
C1d
S1_1
S3_1
S5_1
S7_1
L1
v1
C1d
S2_1
S4_1
S6_1
S8_1
CB3A
CB1B
CB1C
CB1D
CB3B
120
100
0.9
vcB
vcC
S1_2
S3_2
S5_2
S7_2
L2
CB2A
v2
C2d
S2_2
S4_2
S6_2
S8_2
1.1
1.15
1.2
P1dc
P2dc
P3dc
P4dc
0.95
1
1.05
1.1
1.15
1.2
L3
S1_3
S3_3
S5_3
S7_3
C3d
S4_3
S6_3
S8_3
C3d
S3_4
S5_4
S7_4
C4d
S4_4
S6_4
S8_4
C4d
V3dc
v3
C3
V3dc
S2_3
Bus_D
ignd
CB2B
CB2C
CB2D
V2dc
1.05
Time(s)
Time(s)
Bus_C
Port 2
C2d
1
CB3D
Bus_B
vcD Bus_G
V2dc
0.95
4
3
2
1
0
-1
-2
-3
-4
CB3C
Bus_A
vcA
C1
Time(s)
140
Port 3
CB1A
1.0005 1.001 1.0015 1.002 1.0025
160
0.9
Port 1
1
180
Pidc(pu)
•
vcA
200
-200
Δφ(deg)
•
•
•
•
400
C2
Port 4
CB4A
S1_4
L4
V4dc
CB4B
CB4C
CB4D
C4
v4
S2_4
V4dc
Figure 15. 4-phase IGBT LCL DC hub [13]
[13] W Lin and D Jovcic, “Reconfigurable Multiphase Multi GW LCL DC hub with high security and redundancy”,
Electric power Systems Research, Elsevier, Vol 110, May 2014, pp. 104-112
19
5. IGBT-based LCL DC hub,
•
•
•
•
•
3-port DC hub prototype: 3x30kW: DC/DC/DC 200V/900V/900V.
Operating frequency: 2000Hz.
Port1: 5-level, 2-phase, MMC, 200V DC (16 cells).
Port2: 5-level, 2-phase, MMC, 900V DC (16 cells).
Port3: PWM, 2-phase, 900V DC.
Figure 16. 3x30kW LCL DC hub prototype
20
6. Aberdeen DC grid demonstrator
•900V and 200V DC bus with DC fault
hardware,
• 30kW 200V VSC converter
• 30kW 900V VSC converter,
• 30kW 200V LCC converter,
• 30kW 900V LCL VSC converter
• 30kW 200V/900V Thyristor DC/DC
converter
• 30kW 200V/900V IGBT DC/DC
converter
• 3x30kW DC hub, 200V/900V/900V
Figure 17. Aberdeen DC grid
21
6. Aberdeen DC grid demonstrator
Figure 18. Aberdeen DC grid photo.
22
Funding support for research results presented:
• EPSRC (Engineering and Physical Sciences Research Council) grant no: EP/H010262/1,
• EPSRC (Engineering and Physical Sciences Research Council) grant no: EP/K006428/1
• ERC (European Research Council), Starting Grant no: 259328,
• Scottish Enterprise, Proof of Concept award,
• Royal Academy of Engineering, Global Research Fellowship,
• RTE (Réseau de Transport d'Électricité), France,
• SSE (Scottish and Southern Energy), UK,
Dragan Jovcic
University of Aberdeen, UK
[email protected]
Dragan Jovcic and Khaled Ahmed “High-Voltage Direct Current
Transmission: Converters Systems and DC Grids” Wiley, 2015
1
Towards Application of Global Energy
Interconnection - a Demonstrator of DC
Grid with DC/DC Converters
Liangzhong Yao
China Electric Power Research Institute
[email protected]
2016 IEEE Power & Energy Society General Meeting
July 17-21, 2016, Boston, USA
Outline
1
Background
2
Key requirements
3
Challenges
4
Dynamic tests by a DC grid demonstrator
5
Conclusion and prospect
1. Background-Why HVDC
2/3 coal, wind and solar
resources are distributed
in
the
North
and
Northwest
More
than
2/3
power demand is
concentrated in the
East and Middle East
Status:
 By the end of 2015,
wind
power
installed
capacity
exceeded
129GW,
solar
power
installed
capacity
arrived 43GW.
Load
center
Photovoltaic
Wind power
Coal


Hydropower

Power demand area
4/5 hydropower
Southwest
Characteristics:
is
distributed
in
the
Large-scaled
centralized develop
Onshore and
offshore
Power supplies and
loads are distributed
reversely with a
remote distance
1. Background-Why HVDC
Technical advantages of HVDC (compared with HVAC)
 Lower loss with long transmission distance
 Lower cost with long transmission distance
• >800km (onshore)
• >50km (submarine cable)
 Larger transmission capacity with smaller
transmission
channel.
The
transmission
channel of AC system is 3 times larger than that
of DC system with the same transmission
capacity
 DC power can be controlled and the control is
independent of that of AC system
 Realizing the interconnection of AC systems with
different frequency (50-60Hz)
 Without increasing the short circuit current level of
AC systems
 Providing damping for AC systems
 Isolating the faults and power oscillation in AC
systems
 Achieving stable operation at a low power level
 etc
cost
DC
converter
substation
AC
substation
Break
even
point
distance
Fig. AC vs DC
1. Background- Status of LCC HVDC in China
 The development situation of LCC-HVDC
Total 23 HVDC projects (6 UHVDC, 3 B-TB ) in operation (2014)
 8 UHVDC/HVDC lines from hydro-plants
in Southwest sending hydro-power over
2,000 km separately to the coast area of
ECPG and SCPG
Thermal Base
3000MW
7 HVDC Terminals
31.76 GW
2500MW
1800MW
7200MW
10000MW
Hydro Power Base
9000MW
2000MW
3000MW
DC ±400~500kV
DC ±660kV
DC ±800kV
Hydro
plants
8 HVDC Terminals
1. Background- Status of LCC HVDC in China
 The situation of VSC-HVDC projects

The commercial projects have been realized in the world, and
main enterprises are ABB, SIEMENS and ALSTOM

The demonstration projects have been constructed in China, and
the main companies are SGCC and CSG
Project
Time in operation
Basic profile
MMC
Transmission capacity: 20MW
DC voltage: ±30kV
DC cable length: 8.6km
Nanhui HVDC project
2011.07




Zhoushan 5-terminal
HVDC project
2014.07



MMC
Longest distance: 40km
DC voltage: ±200kV
2015.12




MMC
Distance: 10.7km
Transmission capacity: 1000MW
DC voltage: ±320kV
2013.12



MMC
Transmission capacity: 200MW
DC voltage: ±160kV
Xiamen HVDC project
Nanao 3-terminal
HVDC project
1. Background - Global Energy Interconnection
 Global Energy Interconnection – A way for clean energy sharing
 The Global Energy Interconnection GEI = UHV Grid + Smart Grid + Clean Energy
(GEI) is a globally interconnected
strong and smart grid backboned by
UHV grids. It is the basic platform for
large-scale development, allocation and
utilization of global clean energy.
GEI can realize two replacements.
 Clean
Energy
Replacement:
Replacing fossil energy with clean
energy like solar and wind at Supply
Side.
 Electricity Replacement: Replacing
direct consumption of fossil energy
with electricity at Consumption Side.
Challenges:
 Wide area grid interconnection
 Long distance transmission
DC grid technology is one of the
effective ways to meet the
requirements for transboundary
transmission
and
wide-range
accommodation of renewable
energy power globally
Outline
1
Background
2
Key Requirements
3
Challenges
4
Dynamic tests by a DC grid demonstrator
5
Conclusion and prospect
2. Key Requirements of DC Grid
AC Grid
1. Power supplies (50Hz/60Hz
synchronous power supplies)
2. AC loads
3. Grid structure (radial or meshed
network)
4. Transformer (step-up, step-down)
5. Substation (power collection and
distribution)
6. Series/parallel compensation (seriesconnection controls active power,
parallel-connection controls reactive
power/ voltage)
7. Operation and control (active
power/frequency, reactive
power/voltage, stability)
8. AC circuit breaker
9. Fault protection, system recovery
10.……
DC Drid
1. DC power supplies (LCC or VSC
converters)
2. DC loads
3. Grid structure (series-connection,
parallel-connection?)
4. DC Transformer (step-up, stepdown?)
5. DC Substation (power collection
and distribution?)
6. Series-connected DC power flow
controller (DC power control of DC
lines)
7. Operation and control (start/stop,
power/voltage, stability)
8. DC circuit breaker
9. Fault protection, system recovery
10.……
2. Key Requirements of DC Grid
A comparison in short currents between AC and DC
 Respond time/speed: AC in second scale， and DC in millisecond scale (EMC )
 Overload capability: AC device can have large overload capability in seconds, DC is limited
Key Challenges:
 Overload
capability
 Storage &
Inertia
Shout circuit characteristics
current of AC Grid
2 times，10ms
1.3 times ，500ms
 DC grid
structure,
operation and
protection
DC Fault Ride Through Capability
2. Key Requirements- Grid Structure
1. Zhoushan 5-terminal HVDC
demonstration project
2. Typical DC grid by CIGRI B4
3. Super grid interconnected by
DC hub in Europe
5. 3-voltage level 4-terminal DC
system with DC hub
6. 2-voltage level DC system
with DC/DC converter
DC
AC
±200kV直流输电系统
DC
AC
kV
DC
AC
DC
AC
DC
AC
4. 4-terminal DC system with
DC/DC converter
0.5[ohm]
#1 #2
gsVSCp
hvVSCp
dc-v-fixed
ac-v-fixed
#1 #2
lvVSCp
Ulowp
dc-v-fixed
Ig
faultac A->G
Ipos
BRKNeg
Timed
Fault
Logic faultac
#1 #2
gsVSCn
hvVSCn
dc-v-fixed
BRKDCn
0.5[ohm]
ac-v-fixed
#1 #2
lvVSCn
Ulown
dc-v-fixed
BRKNeg Ineg
DCPMSG
2. Key Requirements- Grid Structure
7. DC grid with 4-port DC hub
8. DC grid with 5-port DC hub
9. 2-voltage level 5-terminal
DC grid with DC/DC converter
DC/DC converter
690 V
60 kW
30 kW
I3dc
I1dc
300 V 30 kW
DFIG
AC
端口
端口
WF1
VSC3
DC
DC
1
3
电缆 3 U
U vsc1 = ±400 V 电缆 1
vsc3 = ±300 V
U port1 = ±400 V B2B U port3 = ±300 V
U port2 = ±400 V dc-dc U port4 = ±150 V
DC
I2dc
60 kW
电缆 4 30 kW
端口
端口
690 V
300 V 30 kW
DC 2
4 I4dc
DFIG
电缆 2
U vsc2 = ±400 V
AC
．
330kV
GSVSC
VSC5
Vvsc1=±400kV
1GW
±30kV
AC
DC
AC
.
Vport1=±400kV
Vport4=±250kV
Vport2=±400kV
Vvsc2=±400kV
I2dc
DC cable 2
Port 2
Port 4
DC cable 4
220kV
DC cable 6
DC
DC
0.5GW
P3
DC/DC3
Receiving side
DC bus
Vvsc2=±400V
±80kV直流输电系统
Vd4
AC
0.5GW
0.5GW
Vd1
DC
海上风电场2（WF2）
DC
.
交流电网2
AC
AC
DC
DC
DC cable7
Pend2
DC
GSVSC2
±80kV
DC
DC/DC2
±30kV
AC
Vvsc2=±500kV
DC
AC
AC
DC
± 500kV 端口1
1GW
± 160kV
端口2
± 320kV
Grid
LCC
750kV
Vvsc3=±400kV
西北新能
源基地
.
8GW
± 800kV
8GW
LCC1
LCC2
± 800kV
± 800kV
LCC-HVDC输电系统
WF1
海上风电场1
± 250kV
500MW
500MW
端口4 端口1
端口2
电缆8
DC/DC5 ± 200kV 直流风场
电缆10
海上直流系统
端口2
DC
VSC3
± 160kV
DC/
DC4
DC/DC3
AC
AC
DFIG
陆上电网2
VSC2
± 500kV
0.5GW
220kV
DC
VSC6
WF2
VSC4
Vvsc3=±250kV
VSC2
电缆6
DC/DC2
端口3
端口1
± 320kV
PMSG
0.5GW
0.75GW
电缆3
330kV 1.3GW
I4dc
.
± 320kV
端口2
500MW
220kV
DFIG
电缆9
电缆7
电缆5
端口11GW 端口2 ± 320kV
2GW
500kV
0.8GW
1GW
220kV
端口1
电缆2 ± 500kV 电缆4
Port 1
DC cable 1
VSC1
AC
DC
DC/DC1
GSVSC1
VSC1
± 500kV
Vport3=±320kV
DC
HUB
DC
DFIG
DC
±160kV
1GW
Vd1
DC
DC
DC/DC1
交流电网1
Vvsc3=±320kV
500MW
1GW
电缆1
VSC3
Vport5=±400kV
220kV
海上风电场1（WF1）
2GW
500kV
WF1
Port 3
DC cable 3
Vd3
陆上电网1
Pend1
1.5GW
DFIG
I3dc
DC cable 5 Port 5
12. Typical DC grid with
multiple voltage level
直流环网
1GW
.
220kV
AC
Converter station 2
Converter station 3
11. Hybrid DC grid with 5-port
DC hub
DC
AC
DC
l23=80km
DC
AC
0.75GW
l24=125km
AC
1GW
220kV
Converter station 4
l12=200km
l13=160km
1GW
陆上电网3
Pend3
AC
Converter station 1
±160kV直流输电系统
0.75GW
220kV
DC
l14=160km
DC
U vsc3 = ±150 V
10. 3-voltage level 5-terminal
DC grid with DC/DC converter
DC
Converter station 5
WF2
VSC4
AC
AC
DC
VSC1
VSC2
DC
l45=250km
500kV
交流电网3
海上风电场2
2. Key Requirements- Grid Structure
 A Example: Multi-voltage level DC grid mixed with VSC and
LCC converters
直流环网
2GW
500kV
±500kV
线路1
1GW
500MW
DC/DC1
交流电网1
VSC1
端口1
± 500kV
线路2
DC/DC6
线路3
交流电网2
VSC2
± 500kV
1GW
线路6
DC/DC2
± 500kV 端口1
± 160kV
± 320kV
线路4
8GW
端口2
± 320kV
西北新能
源基地
± 800kV
LCC-HVDC输电系统
海上风电场1
± 250kV
500MW
500MW
端口4
端口2
端口1
线路8
DC/DC5 ± 200kV 直流风场
线路10
海上风电场2
Characteristics:
8GW
500kV
LCC2
LCC1
± 160kV
海上直流系统
DC/DC3
± 800kV
VSC3
DC/
DC4
端口2
750kV
端口3
端口1
端口11GW 端口2 ± 320kV
2GW
500kV
线路7
线路5
± 320kV
端口2
500MW
220kV
DFIG
线路9
WF1
± 800kV
交流电网3
A DC grid structure of multi-voltage level
 DC grid mixed with VSC and LCC
converters
 DC grid with multi-voltage level
using DC/DC converters
 Large-scale
renewable
energy
integration
 Integration of multi-type power
electronic equipment
2. Challenges- DC Equipment
 Equipment 1：A type DC/DC converter
±500kV
线路1
1GW
500MW
DC/DC1
端口1
DC/DC6
端口11GW 端口2 ± 320kV
± 500kV 端口1
GW
线路6
DC/DC2
端口3
端口1
± 160kV
± 320kV
线路4
线路3
线路7
线路5
± 320kV
端口2
VSC3
± 160kV
500MW
220kV
DFIG
线路9
WF1
海上风电场1
DC/
DC4
端口2
± 320kV
Typical network topology
± 250kV
500MW
500MW
端口4
端口2
端口1
线路8
DC/DC5 ± 200kV 直流风场
线路10
海上直流系统
海上风电场2
DC/DC3
端口2
± 800kV
8GW
500kV
LCC2
输电系统
± 800kV
交流电网3
Technical requirements:
 Realizing the interconnection of pseudo
bipolar DC systems and real bipolar DC
systems
 Realizing the transformation of voltage level
 Realizing the bidirectional power flow
Typical topology of A type DC/DC
converter
Prototype
2. Challenges- DC Equipment
 Equipment 2：B type DC/DC converter
0kV
路1
1GW
500MW
DC/DC1
端口1
DC6
线路5
± 320kV
端口2
端口11GW 端口2 ± 320kV
线路6
DC/DC2
00kV 端口1
VSC3
端口3
端口1
± 160kV
± 160kV
± 320kV
线路4
路3
线路7
500MW
220kV
DFIG
线路9
WF1
海上风电场1
DC/
DC4
端口2
± 320kV
± 250kV
500MW
500MW
端口4
端口2
端口1
线路8
DC/DC5 ± 200kV 直流风场
线路10
海上直流系统
海上风电场2
DC/DC3
端口2
0kV
电系统
8GW
500kV
LCC2
± 800kV
Typical network topology
交流电网3
Prototype
Technical requirements:
 Connecting multiple DC systems with different voltage level
 As a super node, facilitating to form a DC grid without DC
circuit breaker
 Ports can control the DC voltage or power
 If one port is out of operation, the rest ports can keep
running
 Achieving free distribution of power among ports
 Playing the role of DC circuit breaker in DC grid
B type DC/DC converter without bus
2. Challenges- DC Equipment
 Equipment 3：C type DC/DC converter
直流环网
2GW
500kV
±500kV
线路1
1GW
DC/DC1
交流电网1
VSC1
端口1
± 500kV
线路2
DC/DC6
线路3
交流电网2
VSC2
± 500kV
± 320
线路4
端口11GW 端口2 ± 320
2GW
500kV
线路
± 320kV
端口2
± 500kV 端口1
1GW
线路
DC/DC2
± 320kV
DC/DC3
端口2
750kV
8GW
± 800kV
西北新能
源基地
± 800kV
8GW
LCC2
LCC1
LCC-HVDC输电系统
± 800kV
Typical network topology
Technical requirements:
 Realizing the interconnection of DC systems with
different voltage level
 Through medium/high frequency AC transformer to
match the difference between DC voltage level and
realize a high ratio output
 Controlling the DC voltage or power of ports
 Playing a role in the fault isolation in DC grid
C type DC/DC converter (threephase two-level topology)
Prototype
C type DC/DC converter (single
phase MMC topology)
2. Challenges- DC Equipment
 Equipment 4：D type DC/DC converter
直流环网
2GW
500kV
±500kV
线路1
1GW
DC/DC1
交流电网1
VSC1
端口1
± 500kV
线路2
DC/DC6
线路3
交流电网2
VSC2
± 500kV
± 320
线路4
端口11GW 端口2 ± 320
2GW
500kV
线路
± 320kV
端口2
± 500kV 端口1
1GW
线路
DC/DC2
± 320kV
DC/DC3
端口2
750kV
± 800kV
8GW
西北新能
源基地
8GW
LCC2
LCC1
± 800kV
LCC-HVDC输电系统
± 800kV
Typical network topology
Technical requirements:
 Realizing DC line power redistribution (power
Flow controller
 Fine adjusting current
 High requirement of insulation
 Small capacity design
 Needing to consider reliable bypass technology
Internal topology of D type DC/DC converter
Prototype
2. Challenges- DC Equipment
 Equipment 5：E type DC/DC converter
直流环网
2GW
500kV
±500kV
线路1
1GW
DC/DC1
交流电网1
VSC1
端口1
± 500kV
线路2
DC/DC6
线路3
交流电网2
VSC2
± 500kV
± 320
线路4
端口11GW 端口2 ± 320
2GW
500kV
线路
± 320kV
端口2
± 500kV 端口1
1GW
线路
DC/DC2
± 320kV
DC/DC3
端口2
750kV
8GW
± 800kV
西北新能
源基地
± 800kV
8GW
LCC2
LCC1
LCC-HVDC输电系统
Technical requirements:
 Realizing the interconnection of VSC based DC
system and LCC based DC system
 The LCC side need to realize voltage polarity
reversal to meet the requirement of power reversal
in LCC based DC system
 Realizing the bidirectional power flow
± 800kV
Typical network topology
Internal topology of E type DC/DC converter
Prototype
2. Challenges- DC Equipment
 Equipment 6：DC circuit breaker
Technical requirements:
 Rapidness of detection
 Accuracy of recognition
 Timeliness of response
Topology of mechanical DC circuit breaker
Topology of solid-state DC circuit breaker
Technical difficulties:
 Due to no zero-crossing in DC current,
the arc extinguishing is difficult
 Due to high rising speed of DC fault
current, the fault locating is difficult
 Energy storage in the smoothing reactor
and capacitor during fault is large
Development level currently:
Topology of hybrid DC circuit breaker
 320kV/16kA/5ms
 180kV/7.5kA/2.5ms
 200kV/15kA/3ms
2. Key Requirements- Control Strategies
 Coordinated operation, control and protection
Master-slave
control
DC voltage
control
technologies
Voltage-margin
control
Voltage-droop
control
Voltage-droop
control with
voltage margin
Control
technologie
s of DC grid
DC power
control
technologies
Power control of
converter station
Fast power
transfer of DC
power flow
controller
DCCB
DC fault
protection
technologie
s
Selfblocking
ACCB
2. Key Requirements - Technical Standards
 Reliability evaluation and standard system
Standard category
system
Standard content
DC voltage level
Maximum power loss
Maximum DC line power
Interconnection protocol of different DC grid
Short capacity of AC system
Control and
protection
Power control mode of DC lines
Start and stop timing and control mode of converter station
Fault mechanism (including fault current limit, over voltage limit,
etc.)
Installation location of fault clearing devices
Fault selection and protection division
Protection acting time
equipment
Parameters of AC/DC converter
Parameters of DC cable
Parameters of DC over-head line
Parameters of DC/DC converter
Parameters of DC circuit breaker
Parameters of communication system
CIGRE:
1) B4-52 HVDC Grids Feasibility Study (2009-2012)
2) B4-56 Guidelines for Preparation of Connection
Agreements or Grid Codes for HVDC Grids (20112014)
3) B4-57 Guide for the Development of Models for
HVDC Converters in a HVDC Grid (2011-2014)
4) B4-58 Devices for Load flow Control and
Methodologies for Direct Voltage Control in a
Meshed HVDC Grid (2011-2014)
5) B4/B5-59 Control and Protection of HVDC Grids
(2011-2014)
6) B4-60 Designing HVDC Grids for Optimal
Reliability and Availability Performance (2011-2014)
7) B4/C1.65 Recommended voltage for HVDC
Grids (2013-2015)
CENELEC:
1) European Study Group on Technical Guidelines
for DC Grids (2010-2012)
2) New TC8X WG06 (2013-)
IEC:
1) TC-57 (WG13
Management
and
Exchange
CIM) Power Systems
Associated
Information
Outline
1
Background
2
Key requirements
3
Challenges
4
Dynamic tests by a DC grid demonstrator
5
Conclusion and prospect
3. Challenges
 Technical issues to be focused and studied
 Research on equivalent modelling and simulation of DC grid
• Topology, control and modelling of high-power, high-voltage, modular and high efficiency DC
power generation unit
• Dynamic simulation and equivalent modelling of key equipment in DC grid which can reflect
the electromagnetic transient characteristics
 Research on operation and control of DC grid, including
• Voltage control and power control
• Power dispatch and distribution of DC grid
 Research on fault protection of DC grid, including
• Economical, efficient and reliable fault current blocking methods (DC circuit breaker,
DC/DC converter, etc.)
• Protection configuration of meshed DC grid (protection configuration, protection
coordination, operating recovery of healthy part)
DC Grid protection needs to meet the requirements of :
•
•
•
•
Sensitivity, which can detect the occurrence of fault;
Selectivity, which can identify the fault area and isolate the healthy area;
Fast, which can isolate the fault quickly;
Reliability, which can clear the fault reliably (main protection, backup protection, regional
protection, etc.);
• Restorability, which can recover from fault with shortest time and lowest loss.
3. Challenges
 Technical Challenges
 Computation speed – need to solve the problem of low computation
speed for large-scale electromagnetic transient simulation
 Real-time simulation of the electromagnetic transient process of complex
systems, enhancing simulation accuracy
 Coordinated simulation technology between AC and DC grids
 Electromagnetic transient co-simulation technology in multiple time scale for
complex AC (electromechanical) / DC (electromagnetic) hybrid power grid
 Fast co-simulation technology of multiple power electronic devices
 Dynamic simulation technology based on real-time simulation platform
 Source / grid coordinated operation, control and protection technology
 Co-operation technology of renewable energy power generation unit and
DC grid
 Co-operation technology of energy storage unit and DC grid
 Coordinated operation strategies for meshed DC grid with multiple voltage
levels
 Development of key equipment for DC grid (DC/DC converter, DC circuit
breaker, DC fault current limiter)
 Equivalent dynamic simulation test of complex DC grid
Outline
1
Background
2
Key requirements
3
Challenges
4
Dynamic tests by a DC grid demonstrator
5
Conclusion and prospect
4. Dynamic tests by a DC grid demonstrator
 Introduction of the DC grid test system
Location: CEPRI
Nanjing
Area: 300 m2
Equipment: 32
System
design and
research
System
scheme
discussion and
formulation
Development
of system
devices
Communicatio
n function test
of single
device
Local system
integrated
test
System
integrated
test
4. Dynamic tests by a DC grid demonstrator
 Introduction of DC grid test system
Objectives & Characteristics:
DC grid demonstrator
with multiple voltage levels test system
1. Simulate renewable power collection and
transmission
2. Meshed topology, real bi-polar operation
3. Multiple voltage levels
4. Controllability of DC power flow
5. Interconnection of VSC-HVDC and LCCHVDC
6. Consider different DC/DC converters
4. Dynamic tests by a DC grid demonstrator
Introduction of control platform:
The control platform of test system can achieve independent displaying of global
display and operation on double screen, real-time operating of equipment and
refreshing display, dynamic refreshing of main interface data and power flow, accurate
and fast executing of multiple operating modes, query displaying and real-time
refreshing of real-time / historical curve, query displaying and export of data report.
Displa
4. Dynamic tests by a DC grid demonstrator
DC voltage control
 Example Test 1
VSC1
Power control
Objective: to verify the
performance of DC/DC converter
C type DC/DC converter
VSC2
DC voltage controlDC voltage control
Parameters of DC/DC converters:




60kW stable operation
62A DC current
60kW ~ -45kW power flow reversal
Response time 460ms
Rated power: 60kW
Rated input voltage: DC ±400V (± 10%)
Rated output voltage: DC ±800V (± 10%)
Control mode: DC voltage, power, DC
current
-45kW stable operation
51A DC current
4. Dynamic tests by a DC grid demonstrator
VSC
 Example Test 2
LCC1
D type DC/DC converter
Parameters of D type DC/DC converter
VSC side
LCC side
±800V
Rated DC Voltage
±900V
50A
Rated DC current
45A
8个半桥子模块
单相子模块数
8个全桥子模块
200V
子模块电容电压
225V
12
桥臂电抗总数
12
LCC2
Objective:
to verify the performance of
DC/DC converter
Operating mode 1 waveform Operating mode 2 waveform
Outline
1
Background
2
Key requirements
3
Challenges
4
Dynamic tests by a DC grid demonstrator
5
Conclusion and prospect
5. Conclusion and prospect
Conclusion:
 DC grid technology is an effective way to solve the problems of the
centralized integration of large-scale renewable energy with long
transmission distance, and it is also an effective solution for
implementation of global energy interconnection in the future.
Combined with China’s national gird conditions, one of its
development modes in the future will be the multi-voltage level DC grid
mixed with VSC and LCC based DC converters.
 CEPRI has carried out the basic theoretical research, and developed a
DC demonstration grid with multi-voltage level using various DC/DC
converters. Through dynamic tests carried out on the scaled-down DC
grid demonstrator, the feasibility of multi-voltage level DC grid is
verified.
5. Conclusion and prospect
Prospect:
 DC grid contains a large number of power electronic equipment
( i.e. DC converters) , and its dynamic response speed is very fast.
Therefore the system simulation modeling, coordinated operation
and fault treatment methods of DC grid are very complex.
 The requirements for secure, economic, and reliable operation of
the DC grid impose big challenges on the functions of DC
equipment, including the characteristics of operation and control,
and the methods of DC equipment/grid protection. Thus, it is
necessary to carry on the related research work in the future. For
example, the problems associated with reducing the loss of
converter, improving the operation reliability, protection of DC fault,
simulation modeling and operation and control technologies, etc.
Thank you for your attention!
Liangzhong Yao
China Electric Power Research Institute
[email protected]
2016 IEEE Power & Energy Society General Meeting
July 17-21 2016, Boston, USA
1
HVDC Grids
Magnus Callavik, ABB Power Grids
IEEE PES GM Boston, 2016-Jul-19
DC transmission Systems with DC/DC converters
Panel Paper 16PESGM1881-DC grids
2
Outline
• Why and when HVDC Grid and Multiterminal HVDC
• Status of HVDC Grid Components
–
–
–
–
–
Voltage source converters (VSC)
Cable systems and overhead lines
Breakers
DC – DC converters
Offshore developments
• Examples of ongoing work on HVDC grids
3
HVDC and HVDC Grids Benefits
• Technology advances in large power, longer
distance, lower losses, voltage support
– 0-3000 km, 0.05-13 GW, <1% losses/ station, VSC
• Energy system with large renewable integration
from remote and offshore locations
– Balance load and demand over long distance
• Market driven interconnection between grids
• Resilient grid zones, black start, handle n-1
HVDC – High voltage direct current. VSC – voltage source converters
http://abbtv.inside.abb.com/2015/12/04/turning-on-the-lights-in-thealand-islands-finland-hvdc-light-black-start-demonstration/
4
Market driving interconnections and
offshore wind connections
HVDC a future solution for

Energy trading

Security of supply

Integration of renewables

Balancing of intermittent power

Closing nuclear and fossil

Optimizing total grid efficiency
HVDC planned or
under discussion
5
NordLink and North Sea Link
NordLink Interconnecting Germany-Norway
1 400 MW Bipole
North Sea Link UK-Norway
1 400 MW Bipole

Interconnecting German wind & solar
with Norwegian hydro

Interconnecting Norwegian and British
energy markets, better use of renewables

± 525 kV, 623 km mass impregnated cables

VSC to support grid connection points
Integration of renewable power and energy markets
Fig. 1. http://spectrum.ieee.org/video/energy/renewables/nordlink-a-landmark-project-enabling-a-more-interconnected-europe
HVDC power increase by
higher voltage and current
LCC UHVDC (Classic). 8-13 GW / bipole
>150 links since 1954




Voltage increase up to 1100 kV
Current increases 4.5-5.0-6.25 kA.
Further increase in peak power?
Reactive power consumption may be challenging
VSC HVDC (HVDC Light)
>20 since 1999




First 500 kV bipoles with cables
Voltage increase for converters straightforward
Current increase would be beneficial
Cables at 2.6 kA, 525 kV
[MW]
[MW]
1 400
1 000
10 000
8 000
6 000
?
800
500
1100 [kV]
200
320
500
[kV]
Loss minimization is always important. At higher currents also for cooling design
1.
Dark blue in construction or operation. Light blue released
2.
Examples Hami-Zhengzhou 8 000 MW (LCC, 2014). EWIC NordLink 1400 MW (VSC, award 2015)
7
HVDC distances are stretched

Marine link up to 700 km between
Continental, British and Nordic grids
NSL
NordBalt

Future: Radii of 1000-2000-3000 km
equals 500 – 800 – 1100 kV UHVDC
8
Difference between Links and Grids
• Scale and density in favor of grids (always)
– HVDC Grids enable more benefits as transmission
capacity and voltage support functions improves
– Make sense to grid connect as density increase
• However, a single link is easier to plan, justify
economically, regulate, build and operate
– Better planning tools, scenario studies, grid codes
on DC side, technology guidelines
– Make new links future grid-enabled
9
DESIGN Grid example
• An attempt for a step-wise
approach to prepare
regulative framework
• A five line, e.g. each link 2
x 2.5 GW connected into a
network system
• Decouple wind and grid
• Create a starting point
• Proposed by KU Leuven,
Ronnie Belmans
10
Joint activities towards HVDC Grids
• Friends of the Supergrid
– Technology roadmap 2012-2030
• CENELEC TC8X-WG06
– Multiterminal (radial) guidelines, pre-standard
• EU framework programs, approx. 100 MEUR
– BestPath 2015-2018 (e.g. multivendor HVDC)
– Promotion 2016-2019 (offshore grids)
• Multiple CIGRE working groups (not only B4)
Key components of HVDC
transmission systems
Converters
Conversion of AC to DC
and vice versa
‫‫‬Three
High power semiconductors
Silicon-based devices
for power switching
manufacturing perspectives in HVDC technologies. HV testing. Clean room, cables
HV Cables
Underground and marine
transmission of power
12
HVDC Cable Systems
Rapid development of extruded cables
It is a cable system, CIGRE TB 496

2014: 525 kV rated voltage

Cables and accessories

Installed 80 kV in 1999. 320 kV 2015

2600 A

Sea,‫‫‬land,‫‫‬cupper,‫‫‬aluminum,…

ABB awarded close to 6000 km
Cable system with terminations,
prefab joints and factory vulcanized joint
Both MI and Extruded DC at 525 kV.
There are benefit to raise the voltage even further for certain applications
13
Hybrid HVDC Breaker
Fault clearance < 5 ms. Losses <0.01%. Scalable concept. First 320 kV, next level 500 kV
Hybrid HVDC Breaker
HVDC Breaker
Main Breaker
Current Limiting
Reactor
Residual
DC Current
Breaker
Ultrafast Disconnector
Load Commutation Switch
Hybrid concept: Mechanics
and power electronics
VSC
voltage source converter
Artist
impression
Flexible multiple protection zone HVDC can be designed and planned for
14
HVDC Grids Control & Protection
HVDC Grids simulation

Hardware-in-the loop real time
simulation of multiterminal grids
with breakers and several
protection zones

VSC-HVDC based. Ultra-fast
breaker are needed. Protection
works!
Hybrid HVDC Breaker

Developments in VSC-HVDC
ratings and density in the grid
leads the way
Main Breaker
Current Limiting
Reactor
Residual
DC Current
Breaker
Ultrafast Disconnector
Load Commutation Switch
15
Friends of the Supergrid (FOSG) Roadmap
http://www.friendsofthesupergrid.eu/
16
FOSG Roadmap, cont.
17
FOSG Roadmap cont.
18
(HV)DC-(HV)DC converters
• Connect and protect two HVDC system voltage levels
– Voltage ratio typically <3 (cf. HVAC typically 1.4-2)
• Fit HVDC systems of slightly different voltage
– Voltage ratio difference 10-30%, e.g. 500-550 kV
• Tap/feed-in a small load/generation to a high power
– Voltage ratio may be >5
• Special compact offshore solutions
• Connect monopole (MP) and bipole (BP) DC systems
19
DC-DC converter preferences
Inverter
Rectifier
• Using state-of-the-art VSC multilevel components, since it is a
relatively small DC-DC converter market near term
• Optimized on losses and availability and cost
• Scalable and handle both mono- and bipoles
• Provide insulation of two grids
• Low technology barrier, e.g. could be built today
• Available for planning and simulation studies already today
Points towards front-to-front converters (DC-AC-DC)
20
DC-DC converters preferences II
NB. HVDC grids are preferably built on
similar voltages, cf. CIGRE B4.C1.65
• In the longer term, more advanced
DC-DC converter topologies could
emerge from today’s technologies
• Special considerations for MV-MV,
MV-HV schemes and tapping and
infeed converters
• Boosting voltage is a special
application when grids of equal
voltage are connected to steer
power flow in meshed grids and to
maintain power capacity overall
21
Offshore converters: Dolwin Beta
1) Construction
in Dubai
Dolwin Beta platform. 900 MW
3) Installation of electrical equipment in
Haugesund, Norway
2) Transport
to Norway
Worlds largest offshore connection platform
22
Dolwin Beta at sea
Left: The wind turbines are seen far in the distance.
Mid and Right: Compare the size of two persons leaning on the fence
70 x 100 x 100 (w x l x h). 23000 tonnes
Worlds largest offshore connection platform
DolWin2 installation
DolWin2 Sailout
DolWin1 handover
23
Why start now?
• More and more HVDC links in the AC grid
• HVDC links are closer to each other
• First multiterminal systems are emerging
– Projects under discussion in Europe, constructed
and in planning in China
• The rating of VSC-HVDC increases to 3 GW
• The renewable generation increase
• Uniformity of HVDC grid codes emerging
24
Concluding remarks
• HVDC transmission technologies enable
– Integration of energy markets over long distance,
across sea, and non-synchronized grids
– Integration of renewable ´generation over long
distance and over time zones
– Transmission between regions for grid resilience
– Ever increasing power capacities
– Asset optimization solutions
– Grids, and DC-DC converters, can be planned for
25
1
DC/DC converters and their role
in future grids
Dr. Ervin Spahic
Head of Future Technologies,
Transmission Solutions, Energy Management,
Siemens Germany
Page 2
HVDC Europe today
PtP no grids
7/8/2016
Dr. Ervin Spahic
Page 3
HVDC Europe 2020+
PtP, no grids, several multiterminals
7/8/2016
Dr. Ervin Spahic
Page 4
HVDC Europe 2030+
several multiterminals, grid
7/8/2016
Dr. Ervin Spahic
Page 5
HVDC Europe
Look into the future - vision
Existing/executed projects
Projects up to 2025
Projects beyond 2025
Vision DC Overlay grid
* Projects from TYNDP from
ENTSO-E, MedGrid, Desertec,
FOSG…
7/8/2016
Dr. Ervin Spahic
Page 6
HVDC grids
Possibilities at the example of Germany
Major questions to be answered:
1. Need for the new transmission lines?
2. Economic benefits of DC links and
grids?
3. Technical benefits?
Existing and planned HVDC links
Possible HVDC links
7/8/2016
Dr. Ervin Spahic
Page 7
HVDC grids
Allready considered in DENA grid study II
Existing and planned HVDC links
Possible HVDC links
7/8/2016
Dr. Ervin Spahic
Page 8
HVDC grids
Answers - example
Transmission grid in 2022 with and without HVDC
2022 AC grid
2022 AC grid
incl. HVDC PtP
2022 AC grid
incl. HVDC terminal
2022 AC grid
incl HVDC grid
3,5 %
2,8 %
2,8 %
2,1 %
Overloadings
(number of congestions)
11
6
5
0
Voltage
(number of critical regions)
8
2
2
0
22,2 Gvar
2,3 Gvar
3,6 Gvar
0
Number of converter
stations
0
8
9
12
Length of HVDC lines
0 km
3103 km
2706 km
3980 km
(n-1 secure)
Losses total
Reactive power demand
Source: Spahic et. al. „Energiewirtschaftliche Tagesfragen“, Dezember 2012
7/8/2016
Dr. Ervin Spahic
Page 9
HVDC grids
A scenario for a step by step evolution
•
Subsequent stage
The small HVDC Grids
become interconnected
•
Full Bridge MMC
in combination with
fast disconnectors provide
reliable and cost efficient
fault clearing and fast recovery
•
Subsequent stage
The small HVDC Grids
become interconnected
•
Full Bridge MMC provides increased DC voltage control range as needed for longer transmission
distances
•
Selectivity between sub grids may need additional fast switching devices, like fault current
limiters or DC Breaker
The expected step by step growth of HVDC Grids
requires standardisation of HVDC Grid design and operating principles.
7/8/2016
Dr. Ervin Spahic
Page 10
HVDC grids
A scenario for a step by step evolution
•
Subsequent stage
The small HVDC Grids
become interconnected
•
•
Full Bridge MMC
in combination with
fast disconnectors provide
reliable and cost efficient
fault clearing and fast recovery
DC/DC
DC/DC
Subsequent stage
Need for DC/DC
converters???
The small HVDC Grids
become interconnected
•
Full Bridge MMC provides increased DC voltage control range as needed for longer transmission
distances
•
Selectivity between sub grids may need additional fast switching devices, like fault current
limiters or DC Breaker
The expected step by step growth of HVDC Grids
requires standardisation of HVDC Grid design and operating principles.
7/8/2016
Dr. Ervin Spahic
Page 11
HVDC Auto Transformer
A Single Stage HVDC-DC Converter
Within the AC Grid distinct voltage levels, suited to the transferred power
level and connected via transformers have proven useful
à For the success of HVDC grids a similar component, a HVDC-DC
converter, is necessary to support distinct HVDC voltage levels
±
P2
±
State of the art: Front-to-Front HVDC-DC converter
• Reverse Back-to-Back link with two stage energy conversion through
full AC link
320kV
DC AC
P1
DC AC
±
320kV
±
500kV
AC
Netz
500kV
GND
GND
DC AC
New Technology: HVDC Auto Transformer
• Single stage energy conversion with partial AC link
• Series connected DC-AC converters
• Partial energy conversion
• Twice as efficient as Front-to-Front solution
• Lower footprint and converter effort
• Full DC-AC capability
7/8/2016
N1
DC AC
N2
Dr. Ervin Spahic
Page 12
HVDC Auto Transformer
A Single Stage HVDC-DC Converter
±
500kV
P2
281MW DC AC
±
320kV
281MW
P1
500MW DC AC
281MW
AC
Netz
0MW
1124MW
GND
500MW DC AC
GND
1124MW
281MW
N1
281MW DC AC
281MW
N2
7/8/2016
Dr. Ervin Spahic
Page 13
HVDC Auto Transformer
A Single Stage HVDC-DC Converter
±
500kV
P2
281MW DC AC
±
320kV
P1
500MW DC AC
562 MW
281MW
0MW
562
MW
GND
500MW DC AC
AC
Netz
GND
1124MW
0MW
N1
281MW DC AC
281MW
N2
7/8/2016
Dr. Ervin Spahic
Page 14
HVDC Auto Transformer
A Single Stage HVDC-DC Converter
±
500kV
P2
281MW DC AC
±
320kV
P1
500MW DC AC
0 MW
281MW
281MW
1124
MW
GND
500MW DC AC
AC
Netz
GND
1124MW
281MW
N1
281MW DC AC
281MW
N2
7/8/2016
Dr. Ervin Spahic
Page 15
HVDC Auto Transformer
A Single Stage HVDC-DC Converter
±
500kV
P2
281MW DC AC
±
320kV
P1
500MW DC AC
1562
MW
281MW
500MW
AC
Netz
438
MW
GND
500MW DC AC
GND
1124MW
500MW
N1
281MW DC AC
281MW
N2
7/8/2016
Dr. Ervin Spahic
Page 16
HVDC Auto Transformer
A Single Stage HVDC-DC Converter
±
500kV
P2
281MW DC AC
±
320kV
0MW
P1
500MW DC AC
500MW
AC
Netz
1000
MW
1000MW
GND
500MW DC AC
GND
0 MW
500MW
N1
281MW DC AC
0MW
N2
7/8/2016
Dr. Ervin Spahic
Page 17
HVDC Auto Transformer
Advantages
Within the AC Grid distinct voltage levels, suited to the transferred power
level and connected via transformers have proven useful
à For the success of HVDC grids a similar component, a HVDC-DC
converter, is necessary to support distinct HVDC voltage levels
P2
DC AC
P1
à Single stage voltage conversion
à Lower losses (~ 50%)
à Less installed conversion power
à Lower footprint
à Same functionality as Front-to- Front topology
(except for galvanic isolation)
DC AC
GND
AC
Netz
GND
DC AC
à Based on MMC Technology
à Subconverters are state of the art MMC converters
à Know an proven technology
à Same Submoldules
à Full DC Fault resilience with Fullbridge Submodules
à Optimal for DC grid integration
à No additional DC breaker needed
7/8/2016
N1
DC AC
N2
Dr. Ervin Spahic
Page 18
HVDC Auto Transformer
Modular design
Possible two stage approach:
• 1st stage: bipole DC-AC converter
feeding connecting the OWF with
the AC grid
P1
±
320kV
AC
Grid
DC AC
GND
GND
DC AC
N1
7/8/2016
Dr. Ervin Spahic
Page 19
HVDC Auto Transformer
Modular design
±
500kV
P2
DC AC
P1
±
320kV
AC
Grid
DC AC
GND
Possible two stage approach:
• 1st stage: bipole DC-AC converter
feeding connecting the OWF with
the AC grid
• 2nd stage: extension to HVDC-DC
auto transformer for connection to
a e.g. 500kV DC transmission line
GND
DC AC
N1
DC AC
N2
7/8/2016
Dr. Ervin Spahic
Page 20
Implementation of DC/DC converters – stage 1
Example for offshore wind farm
Onshore Wind and
Solar Power
Offshore Wind Power
AC
DC
AC
DC
±
AC
DC
200kV
AC
DC
±
320kV
400kV
DC
DC
AC
7/8/2016
±
AC
Dr. Ervin Spahic
Page 21
Implementation of DC/DC converters – stage 2
Example for offshore wind farm
AC
DC
AC
DC
±
DC
DC
200kV
AC
DC
DC
±
DC
DC
±
±
320kV
AC
400kV
DC
AC
DC
AC
500kV
Extension to a multi terminal DC grid using HVDC-DC
converters to equalize volatile generation
7/8/2016
Dr. Ervin Spahic
Page 22
Implementation of DC/DC converters - stage 3
Example for offshore wind farm
AC
DC
AC
DC
±
DC
DC
200kV
AC
DC
DC
±
DC
DC
±
±
320kV
AC
400kV
DC
AC
DC
500kV
Long distance DC transmission to
remote load centers
7/8/2016
DC
AC
Dr. Ervin Spahic
23
DC/DC converters and their role
in future grids
Dr. Ervin Spahic
Head of Future Technologies,
Transmission Solutions, Energy Management,
Siemens Germany
1
Samuel NGUEFEU, RTE − France
Update on the roadmap of a TSO
anticipating future DC networks
Panel session on DC transmission
systems with DC/DC converters
July 19, 2016
2
CONTENTS
•
•
•
•
•
•
•
Overview of French HVDC systems and projects
From point-to-point links to meshed DC grids
Mapping of ongoing projects @RTE, with multiple partners
5-terminal « TWENTIES » Hybrid mock-up
250V-400V DC-DC converter between terminals 1 and 2
Simulation results, to be confirmed by experimental tests
Appendix
DC transmission systems with DC/DC converters
Overview of French HVDC systems and projects
FAB: France
Aldernay Britain
2*700 MW - 2022
Cross–Channel
2 GW 1986; 2015
IFA 2
1000 MW - 2020
Eleclink
1000 MW –2018
In operation
Decided/Under construction
Proposal/planning
Granted merchant interconnector
Celtic
Interconnector
700 MW - 2025
Piémont Savoie
2*600MW 2019
France Espagne
Golfe de Gascogne
2*1000 MW - 2022
Midi Provence
1000 MW - 2020
France Espagne
2*1000MW - 2015
4
From point-to-point links to meshed HVDC grids
Specific DC grid Components
• AC-DC converter structures
• Breakers, disconnectors, limiters
• DC-DC converter structures
• Prototypes + low scale testing
Control and Protection
• f/P, Udc/P, Udc/Idc droop controllers
• Fault detection algorithms
• System Protection strategy
DC grid topologies
• Large enough (> 10 substations)
• CAPEX and OPEX comparisons
Investigation methods and tools
• Offline Static/dynamique simulations
• Real-time interoperability (SMARte)
• Contribution to pre-standardisation
5
Mapping of ongoing projects @ RTE, with multiple partners
• Hybrid DC CB
• Current Limiter
• Mechanical Breaker
• DC-DC Converter
(and DC Hubs)
• AC-DC Converters
Development of
EMTP models
for specific
components
• DC Fault detection
Algorithms and
Protection systems
• DC voltage and
Power Flow control –
System stability
• Steady-state studies
• Dynamic studies
• Relevant Control and
Protection strategies
Pre-STANDARDIZATION
CENELEC
ENTSO-E
CIGRE B4- WG
Project 1
Elaboration of
functional
building blocks
Elaboration and
simulation of 3
large HVDC grid
topologies
Comparison of
performances
and costs
Project 2
AC-DC innovative structures:
HB, FB, Mixed-Cell, AAC, etc.
Projects 3a + 3b
PROMOTioN
Project 5
Innovative DC grid voltage
and power flow controllers
- Diode-Unit converter stations
- Prototypes of switchgear devices;
- Protection system interoperability
- DC-DC Prototype testing on
low scale DC grid mock-up
- MMC Prototype testing and
validation versus FPGA models
Project 4
Development and
Implementation of protection
algorithms for DC grids
BEST PATHS (Demo 2)
Interoperability assessment with
EMTP-RV and the HYPERSIM
simulators of ABB, GE-ALSTOM and
SIEMENS converter stations
6
General overview of the 5-terminal « TWENTIES » mock-up
Udc = ±125V, Idcnom = 10A
Uac = 125V
Low voltage DC cables
1
3
2
AC Grid and
windfarms simulation
4
RT simulated VSC
5
Real VSC
DC Breaker and
protection algorithms
SCADA system
7
Five terminal DC grid with embedded 250V-400V DC-DC converter between terminals 1 and 2
1,7 kHz IGBT based LCL DC transformer
with no internal AC transformer employed.
Also operable in 400/400 V configuration.
FLV2
Starting sequence.
Normal operation, including Power reversal in
DC-DC Converter.
System behaviour during pole-to-pole faults.
Improved DC grid with 2 protection zones.
Symmetrical monopolar configuration
8
DC grid with embedded 250V/400V converter simulation:
Voltages’ results with two successive DC faults FHV1 and FLV2
a- 400V protection zone voltages
DC fault isolation from either side of
the DC-DC converter.
b- 250V protection zone voltages
9
DC grid with embedded 250V/400V converter simulation:
Powers’ results with two successive DC faults FHV1 and FLV2
c- Master terminals powers
Fault isolation using inherent property
of DC-DC converter (the fault is not
transferred to the other side when the
converter is in open loop).
Transient dc fault is studied and
results show nice recovery of the dc
grid after dc fault is removed.
d- Slave terminals powers
10
DC grid with embedded 250V/400V converter simulation:
Converter variables (DC faults FHV1 and FLV2)
internal ac
currents
internal ac voltage
11
DC grid with embedded 250V/400V converter simulation:
Converter variables (DC faults FHV1 and FLV2)
a- power port variables
b- power balancing port variables
12
DC grid with embedded 250V/400V converter simulation:
Voltages’ results with two successive DC faults FHV2 and FLV2
a- 400V protection zone voltages
Applying the fault at HV2 (instead of
HV1) leads to very similar results.
b- 250V protection zone voltages
13
DC grid with embedded 250V/400V converter simulation:
Powers’ results with two successive DC faults FHV2 and FLV2
c- Master terminals powers
d- Slave terminals powers
Thank you for your attention
15
Annexes
DC transmission systems with DC/DC converters
16
BEST PATHS: Interoperability of Multivendor VSC HVDC grids
HYPERSIM
Control and
Protection Replica
Objectives:
Real-Time
Simulator
Demonstrate the interoperability
of VSC-HVDC converters from
three
different manufacturers,
associated in the same multiterminal DC grid.
ABB
Develop a testing methodology
based on a Hypersim dedicated
vendor independent platform.
SIEMENS
GE-ALSTOM
17
Contributions to CIGRE, ENTSO-E and CENELEC « HVDC grids« WG
- B4-52 (HVDC Grids)
- B4-56 (HVDC Grid Codes),
- B4-57 (Converter Models for HVDC Grids),
- B4-58 (Load Flow and DC voltage Control
- B4-59 (Control and Protection of HVDC Grids)
- B4-60 Optimal Reliability and Availability.
- B4-72 DC grid Benchmark models
ENTSO-E: HVDC Connection and DC connected Offshore Power Park Module
Requirements (HVDC Code).
Work start beginning 2012. Draft for Assembly approval sent out 15 April 2014.
The drafting team has to formulate the requirements that must be met for the connection
of Offshore Power Park Modules, that are
o E: Radial DC Offshore Connection and AC Collection
o F: Hybrid AC/DC Offshore Solution
o G: Meshed Multiterminal DC-Offshore, AC Collection
o H: Meshed Offshore DC, DC Collection
These requirements are to be functional in nature and build upon the high level
requirements set out in the ACER Framework Guidelines on ‘Electricity Grid
Connections’.
To extend the work recorded in FprTR 50609:2013 "Technical Guidelines for Radial HVDC Networks«, reference
CLC/TC 8X 24711, the CENELEC CLC/TC8X/WG6 WG has been launched in April 2013. RTE leads subgroup 1
(Coordination of HVDC Grid system and AC systems) and participates to subgroup 2 (HVDC Grid Control), 3
(HVDC Grid protection) and 5 (Models and Validation). prTS expected by end of 2016.
DC transmission systems with DC/DC converters
18
Ongoing developments
Based on large DC grid topologies
with more than 10 stations and several
lines and cables, similar to the CIGRE
benchmark model…
CIGRE HVDC Grid Benchmark
Benchmark Rev. 11
DC Overhead
DC Cable
AC Overhead
AC Cable
A0
C
1
A1
Develop a DC grid model using HBMMC
and
Hybrid
DCCBs
+
conventional protection system
C2
Investigate the strategy of simultaneous
disconnection of all DCCB
Develop a DC grid model using HBMMC
and
Hybrid
DCCBs
+
mechanical DCCBs and DC-DC
Converters or DC Hubs
Develop a DC grid model using FBMMC and some DC switches
D1
B
0
B4
B
1
E1
B
5
B2
B3
B
6
Performance and Cost Comparisons
Pros and cons of next 3 topologies will be listed at
the end of the developments
F1
19
Example (1) of HVDC grid topology with HB-MMC and Hybrid DCCB
(km)
800
A1
750
C1
Ba-A1
800MVA
Ba-A0 309
200km
SA0
618
1200MVA809
=
200km
309
809
1200MVA
Cb-A1-2
=
800MVACm-C1
50km 107
±400kV
Bb-C2
600
200km
1200MW
400
800MVA
500 Cb-D1-1
±400kV
Bb-D1
=
1000
500 Cb-D1-2
=
1000
Bo-D1
800MVA
B1
175
=
±400kV
783 Bb-B2-1
±400kV
1200MVA
=
Cb-B2-2
Cm-B2
Bm-E1
100 Cm-E1
±400kV
Bb-B2-2
1200MW
200km
200km
=
Cb-B2-1
800MVA
= Cb-B1-2
1200MVA
±400kV
Bb-B1
562
120
0
200 MW
km
783
1200MVA
Ba-B2
B2
B3
F1
50 100 150 200 250 300 350 400(km)
1200
150
100
750
= Cb-B1-1
Ba-B1
1580
300km
1200MW
790
300km
1200MW
SB0
200km
E1
188
750
448
250
200km
1200MW
±400kV
Bb-B4
200km
Ba-B0
1200MW
200km
620
350km
B4
300
50
450k
m
800M
W
12 447k
00 m
MW
D1
400km
1200MW
OFFshore
450
Cb-C2
800MVA
0
1200MW
400km
ONshore
500
200
619
980
550
350
1600MW
300km
619
500
Bo-C2
=
650
600
500
=
±400kV 600
Bb-A1
1000
Bm-C1±400kV
392
200km
800MW
Cb-A1-1
C2
700
0
Bm-A1
±400kV
= Cm-A1
0
392
= AC/DC Converter Station
Hybrid DC CB
DC Cable
DC Overhead line
200MVA Bo-E1
100
M
319
103
0
=
1300
Bm-B2
±400kV
200km
89
200km
86
800MW
200km
0
Bm-B3
800
Ba-B3
±400kV
= 1200MVA
900Cm-B3
808
1200MW
200km
Bm-F1
497
±400kV
=
500
Cm-F1
800MVA
Bo-F1
20
Example (2) of HVDC grid topology with FB-MMC and Mechanical DCCB
Ba-A1
800MVA
FB MMC
Mechanical DCCB
DC Cable
DC Overhead line
(km)
800
A1
750
C1
Ba-A0 309
200km
SA0
1200MVA
C2
700
Cm-A1
Cb-A1-1
809
Bm-C1
Cm-C1
800MVA
Bb-C2
Bb-A1 600 200km
1200MW
1618
OFFshore
500
Bb-D1
450
B4
800MVA
500
800MVA
B1
1000
Bo-D1
1000
300
Ba-B0
200km
2800MW 620
Ba-B1 750
188
Bb-B4
(200)
250
200
Cb-D1
500
D1
400
350
Cb-C2
800MVA Bo-C2
0
ONshore
500
600
600
550
500
392
200km
800MW
107
Cb-A1-2
1000
650
0
1200MVA 809
200km
309
618
Bm-A1
0
E1
1200MVA750
SB0
150
1200MVA
175
Cb-B1-1
Bb-B1
120
0
200 MW
km
562
Cb-B1-2
Bm-E1
1200
100
100
100
1200MVA
Ba-B2
50
B2
B3
F1
50 100 150 200 250 300 350 400(km)
Cb-B2-1
Cb-B2-2
103
782
Cm-E1 Bo-E1
200MVA
Bb-B2-1
M
782
319
Bb-B2-2
0
Bm-B2
Cm-B2
1300
200km 0
800MW 800
800MVA
89
Ba-B3
86
900
Bm-B3
Cm-B3
1200MVA
1200MW 800
200km
Bm-F1
497
Cm-F1 Bo-F1
800MVA
500
21
Example (3) of HVDC grid topology including DC-DC Converters
A1
750
800MW
50km
(km)
800
C1
650
OFFshore
500
450
D1
350
B4
=C
D
C
D=
400
B1
200km
150
B2
B3
F1
50 100 150 200 250 300 350 400(km)
MW
800
50
200km
100
103
448
E1
790
300km
1200MW
790
1200MW
300km
250
200
500
00
1200
M
730k W
m
300
12
MW
00
12 50km
4
450
ONshore
20
28 0MW
0k
m
550
4
1 47
44200Mkm
7
12 k m W
97
00
1
MW
97
1
600
800MW 300km
800MW 300km
500
C2
700