• Introduction: VSC-HVDC connections • VSC-HVDC structure and controller • VSC-HVDC connected OWF frequency control - Control strategy - Simulation results • VSC-HVDC interconnector frequency control - Control strategy - Simulation results • Conclusion and future works

1. Power System with VSC-
HVDC Interconnection
Frequency Stability Control Strategy
L.J. Cai
GEIRI Europe GmbH
Berlin, Germany

2. GEIRI
 GEIRI: Global Energy Interconnection
Research Institute
 Main Working Areas
 Offshore windfarm grid connection
 Offshore HVDC platform design
 Interconnection researches
 Participating research projects, i.e. Horizon
2020, Schaufenster Projects, BMWI Projects
etc.

3. 1GW 320kV VSC

4.  Introduction: VSC-HVDC connections
 VSC-HVDC structure and controller
 VSC-HVDC connected OWF frequency control
 Control strategy
 Simulation results
 VSC-HVDC interconnector frequency control
 Control strategy
 Simulation results
 Conclusion and future works
Contents

5.  Introduction: VSC-HVDC connections
 VSC-HVDC structure and controller
 VSC-HVDC connected OWF frequency control
 Control strategy
 Simulation results
 VSC-HVDC interconnector frequency control
 Control strategy
 Simulation results
 Conclusion and future works
Contents

6. VSC HVDC
OWF
Interconnection
Embedded

7.  Introduction: VSC-HVDC connections
 VSC-HVDC structure and controller
 VSC-HVDC connected OWF frequency control
 Control strategy
 Simulation results
 VSC-HVDC interconnector frequency control
 Control strategy
 Simulation results
 Conclusion and future works
Contents

8. :
:
:
:
:
:
Sub-
Module
Multi-
valve
Arm
ai bi ci cv
bv
av
armL armL armL
+
armL armL armL
-
dcV
bui
a
il
aui cui
b
il c
il
auv
+
-
dcI
+
-
l a
v
1SM au
2SM au
400SM au
1SM bu
2SM bu
400SM bu
1SM cu
2SM cu
400SM cu
1SM al
2SM al
400SM al
1SM bl
2SM bl
400SM bl
1SM cl
2SM cl
400SM cl
Cv C
1S
2S
p
n
1g
2g
(a)
+
1. Voltage balancing control
2. Circulating current control
3. Protections
…
VSC HVDC Structure

9. Cable/Line
MMC
Converter
PLL
Outer
Controller
Inner
Controller
Modulation
+ Banlance
θ
θ
V,θVf-
controller
Cable/Line
MMC
Converter
PLL
Outer
Controller
Inner
Controller
Modulation
+ Banlance
θ
θ
VSC HVDC Controller

10.  I
P
K
K s++
-
L
L
+
-
+
+
+
+
-
+ I
P
K
K s
+
-
-
ˆ
di
ˆqi
di
qi
gqv
gdv
ˆdv
ˆqv
Cable/Line
MMC
Converter
PLL
Outer
Controller
Inner
Controller
Modulation
+ Banlance
θ
θ
V,θVf-
controller
Inner Controller

11.  Voltage frequency control (Vf-control)
 DC-Voltage and AC voltgae/reactive power
control (Vdc-Vac-control)
 Active power control (P-control)
 Droop control (Droop, for multi-terminal
operation)
Cable/Line
MMC
Converter
PLL
Outer
Controller
Inner
Controller
Modulation
+ Banlance
θ
θ
V,θVf-
controller
Outer Controller

12.  I
P
K
K s+
+
-
0
2 s
acv
ˆacv
ˆf
ˆdv
ˆqv ˆv
dq
abc
ˆ
Cable/Line
MMC
Converter
PLL
Outer
Controller
Inner
Controller
Modulation
+ Banlance
θ
θ
V,θVf-
controller
V/f Controller

13. slow setpoint tracking
 I
P
K
K s
 I
P
K
K s+
+
+
+
+ +
+
-
-
acv
dcv
ˆ
di
ˆqi
ˆdcv
ˆacv
Cable/Line
MMC
Converter
PLL
Outer
Controller
Inner
Controller
Modulation
+ Banlance
θ
θ
V,θVf-
controller
Vdc/Vac Controller

14. VSC HVDC
OWF
Interconnection
Embedded

15.  OWF
OWF VSC-HVDC
OWF
3~
=
150kV
AC cable Offshore
converter
Onshore
converter
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system
3~
=
Converter
A
Converter
B
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system B
~
Onshore
power
system A
400kV
transmission
line
 Inter-
connection

16.  Introduction: VSC-HVDC connections
 VSC-HVDC structure and controller
 VSC-HVDC connected OWF frequency control
 Control strategy
 Simulation results
 VSC-HVDC interconnector frequency control
 Control strategy
 Simulation results
 Conclusion and future works
Contents

17.  OWF
GEIRI
OWF
3~
=
150kV
AC cable Offshore
converter
Onshore
converter
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system
Vf-control
Frequency
Controller
Vdc-Vac
Control

18. 3~
=
Offshore
converter
Onshore
converter
3~
=
+
-
VDCC
PDC
PAC
GEIRI

19. Trigger
-
+
fref
fonshore
PI
Controller
+
+
VDC_ref
Gradient
Limiter
VDC
-
GEIRI
 OWF
OWF
3~
=
150kV
AC cable Offshore
converter
Onshore
converter
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system

20.  Introduction: VSC-HVDC connections
 VSC-HVDC structure and controller
 VSC-HVDC connected OWF frequency control
 Control strategy
 Simulation results
 VSC-HVDC interconnector frequency control
 Control strategy
 Simulation results
 Conclusion and future works
Contents

21. OWF
3~
=
150kV
AC cable Offshore
converter
Onshore
converter
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system
Load A
500MW
GEIRI

22. OWF
3~
=
150kV
AC cable Offshore
converter
Onshore
converter
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system
Load A
500MW
GEIRI

23.  Introduction: VSC-HVDC connections
 VSC-HVDC structure and controller
 VSC-HVDC connected OWF frequency control
 Control strategy
 Simulation results
 VSC-HVDC interconnector frequency control
 Control strategy
 Simulation results
 Conclusion and future works
Contents

24.  OWF
GEIRI
OWF
3~
=
150kV
AC cable Offshore
converter
Onshore
converter
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system
3~
=
Converter
A
Converter
B
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system B
~
Onshore
power
system A
400kV
transmission
line
 Inter-
connection

25. GEIRI
Trigger
-
+
fref
fA
PI
Controller
+
+
Pref
Gradient
Limiter
3~
=
Converter
A
Converter
B
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system B
~
Onshore
power
system A
400kV
transmission
line
 Inter-
connection
Frequency
Controller
P-control Vdc-Vac
Control

26. 3~
=
Converter
A
Converter
B
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system B
~
Onshore
power
system A
400kV
transmission
line
GEIRI
P-control Vdc-Vac
Control
Frequency
Controller
Trigger
-
+
fref
fB
PI
Controller
+/-
+
VDC_ref
Gradient
Limiter
VDC
-
 Inter-
connection

27.  Introduction: VSC-HVDC connections
 VSC-HVDC structure and controller
 VSC-HVDC connected OWF frequency control
 Control strategy
 Simulation results
 VSC-HVDC interconnector frequency control
 Control strategy
 Simulation results
 Conclusion and future works
Contents

28. P Control
0 5 10 15
time (t)
0.8
0.85
0.9
0.95
1
0 5 10 15
time (t)
0
100
200
300
400
500
600
3~
=
Converter
A
Converter
B
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system B
~
Onshore
power
system A
400kV
transmission
line
Load A
500MW
 Inter-
connection
P

29. VDC Control
0 5 10 15
time (t)
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
0 5 10 15
time (t)
-800
-700
-600
-500
-400
-300
-200
-100
0
3~
=
Converter
A
Converter
B
±320kV
DC cable
400kV
transmission
line
=
3~
~
Onshore
power
system B
~
Onshore
power
system A
400kV
transmission
line
Load A
500MW
 Inter-
connection
P

30.  Introduction: VSC-HVDC connections
 VSC-HVDC structure and controller
 VSC-HVDC connected OWF frequency control
 Control strategy
 Simulation results
 VSC-HVDC interconnector frequency control
 Control strategy
 Simulation results
 Conclusion and future works
Contents

31.  Conclusion
 VSC-HVDC connected OWF frequency control
 VSC-HVDC interconnector frequency control
 Future works
 Coordinated control: OWF, VSC-HVDC and
onshore controllers
 VSC-HVDC voltage stability control
 VSC-HVDC oscillation stability control
 …
Conclusion

32. Thank you very much for your attention!