FINAL PRESENTATION: Ultra-Reliable Deepwater
Electrical Power Distribution System and Power
Components
08121-2901-01
Rixin Lai
GE Global Research
1
RPSEA Ultra-Deepwater Technology Conference
October 29-30, 2013
Lone Star College Conference Center
The Woodlands, Texas
rpsea.org
Project Overview
Project Cost Summary
Period of Performance
Project budget
$6,249,959
Project start date
11/24/2009
Spend to date
$6,053,520
Project end date
11/24/2013
Objective: Develop long distance DC based transmission &
distribution architecture and components for deep water fields
Components
Characteristics
Onshore power generation unit 60 Hz. Minimum 200 MVA
2
Compressor loads (4 )
10 MW, 6.6 kV, 0.85 PF, 85%
efficiency
Pump loads (4)
2.5 MW, 6.6 kV, 0.85 PF, 85%
efficiency
Transmission distance
100 to 160 miles ( approx. 160
to 250 km)
Distribution distance
6.25 miles (10 km)
Field Scenario
Modular Stacked DC Architecture
o Engage sending end
o Establish link current (current
control mode)
o Engage receiving end (voltage
control mode)
o Engage load (dc current remain
the same, dc terminal voltages
vary with the loading)
DC fault tolerance, distributed dc conversion, modular design
3
Phase II: Component Development
MSDC System Demonstration


4
Steady-state and dynamic control
Fault management
Thermal Management
& Packaging


Reliability
Power density
DC WM Connector


Insulation capability
DC operation
Technology demonstration and risk mitigation for MSDC
MSDC Demonstration
4x4 full system operation
• Complete full system simulation and fault analysis
• Design and demonstrate bypass operation for fault protection
• Verify steady state and transient operation of MSDC
architecture in the lab demonstrator.
5
Cooling and Packaging
Multi-phase cooling




Pressure vessel partially filled
Power components immersed
Condensation on internal surface in
the vapor space
Passive, high reliability
Scaled down feasibility demonstration
Condensation
Evaporation
clear tank
Condens
er
diode
subcooled
fluid
6
heat
sink
• Optimize heatsink design, demonstrate multi-phase cooling
• Develop the hybrid packaging concept
DC Wet-Mate Connector
Wet-mate chamber
Cable Termination Chamber
Steel shell
Oil
Oil
Epoxy
Support
Epoxy
Epoxy
Copper
Cable
insulation
Key focus:
• Resistivity of materials
• DC stress control
• Interface insulation capability
• Effect of moisture
• Modeling and concept design
7
Oil
Stress
cone
Copper
Axis of symmetry
Oil
Epoxy
Material characterization
System Simulation
8
System Analysis Approach
The hierarchical combination of hardware demo and simulation can:
• Study closely the T and D cable impact to system operation;
• Investigate both steady-state and transient behaviors;
• Verify overall system control, protection, and fault ride-through.
9
System Analysis Approach
The hierarchical combination of hardware demo and simulation can:
• Study closely the T and D cable impact to system operation;
• Investigate both steady-state and transient behaviors;
• Verify overall system control, protection, and fault ride-through.
PSCAD power system model
10
System Analysis Approach
The hierarchical combination of hardware demo and simulation can:
• Study closely the T and D cable impact to system operation;
• Investigate both steady-state and transient behaviors;
• Verify overall system control, protection, and fault ride-through.
PSCAD power system model
PLECS power electronic system model
11
System Analysis Approach
The hierarchical combination of hardware demo and simulation can:
• Study closely the T and D cable impact to system operation;
• Investigate both steady-state and transient behaviors;
• Verify overall system control, protection, and fault ride-through.
PSCAD power system model
PLECS power electronic system model
Scaled-down hardware demo
12
System Analysis Approach
The hierarchical combination of hardware demo and simulation can:
• Study closely the T and D cable impact to system operation;
• Investigate both steady-state and transient behaviors;
• Verify overall system control, protection, and fault ride-through.
PSCAD power system model
Large system EMT simulation with detailed cable model
PLECS power electronic system model
Detailed control, protection simulation
Scaled-down hardware demo
13
Verification
Test Result vs. Simulation Result
Test waveform
PLECS waveform
10ms/DIV
20 ms
~17%
20A
~15%
20 ms
ISE [20A/DIV]
ISE [10A/DIV]
IG [20A/DIV]
~25%
~25%
IH [10A/DIV]
IH [20A/DIV]
PSCAD
waveform
10ms/DIV
I
~17% SE
[20A/DIV]
ISE
E
F
20 ms
IH
H
Demo system reflects
the major system
transient behaviors.
Scaled-down Demo
~25%
14IH
[20A/DIV]
10ms/DIV
G
Full-scale PSCAD
PSCAD Simulation for Fault Analysis
PSCAD is used due to its accurate cable modeling capability.
duty
40 [mH]
SE_converter V_CM_P
10 [kohm]
#1
1 [Mohm]
RLC
#2
C1
VSE
Cable2
S1 A1
C
Cable2
Cable2
A1 S1
C2
C1
C2
S2 A2
A2 S2
0.01 [ohm]
10 [kohm]
duty
ISE
IRE
10 [mH]
VRE
10 [mH]
V_SHEATH
C1
Cable3
S1 A1
C
Cable3
C1
Cable3
A1 S1
V_RE_CM_P
C2
S2 A2
C1
Ia
4.5
Compressor1
stop
C2
Cable4
S1 A1
A2 S2
C
Cable4
Cable4
A1 S1
C2
C1
6.0
Compressor2
stop
C2
S2 A2
A2 S2
SE_converter2
#1
1 [Mohm]
Eb
#2
C1
Cable5
S1 A1
C
Cable5
Cable5
A1 S1
C2
C1
Ib
7.5
Compressor3
stop
C2
S2 A2
A2 S2
duty
C1
SE_converter3
1 [Mohm]
#1
#2
Cable6
A1 S1
Cable7
S1 A1
Cable7
A1 S1
0.5
Pump1
1 [Mohm]
Cable8
S1 A1
A2 S2
C
Cable8
Cable8
A1 S1
C2
duty
C1
C2
S2 A2
C1
9.0
Compressor4
A2 S2
C
Cable7
C2
SE_converter4
C1
C2
S2 A2
C1
#2
C
Cable6
C2
duty
#1
Cable6
S1 A1
C1
1.5
Pump2
C2
S2 A2
A2 S2
SE_converter5
C1
1 [Mohm]
#1
#2
Cable9
S1 A1
C
Cable9
duty
ISE
SE_Control
duty
C1
VSE
Cable10
S1 A1
SE_converter6
1 [Mohm]
#2
40 [mH]
Base-line system
•
•
•
•
15
PSCAD model
6 SE-end and 8 RE-end modules;
4 compressor (12.5 MW) and 4 pump (2.5 MW) loads;
180 km Transmission and 10 km Distribution cables;
400 A link current, ~+-80 kV system voltage.
2.5
Pump3
A2 S2
C
Cable10
Cable10
A1 S1
C2
V_CM_N
C1
C2
S2 A2
#1
Cable9
A1 S1
C2
C1
S2 A2
A2 S2
3.5
Pump4
C2
V_RE_CM_N
Fault Analysis
Faulty Type
SE-end
Terminals
Typical faults:
open-circuit, shortcircuit, etc.
Ground
Fault
Inside
module
RE-end
Terminals
D., T.,
Cables
AC Load
Inside
module
Terminals
Highimpedance
grounding
Lowimpedance
grounding
May jeopardize key components
Trans. Cable OC fault
16
SE-end
May lose part of the production
RE-end
AC Load
Minimal impact to the rest of the system with bypass
Bypass Operation
Occurs @ 1s
Distribution cable
Bypass of a compressor load (27 kV)
No.1
M
IRE1
400A
Current which flows through the converter
M
0.55
ICON1, ICON2, ICON3
Transmission cable
IRE2
0.5
IRE (kA)
No.2
No.3
M
IRE3
0.45
No.4
M
0.4
0.35
0.79
17
0.8
0.81
0.82
0.83
0.84
Time (sec)
0.85
0.86
0.87
~35% current overshoot due to the cable energy
storage.
System can continue operation without interruption.
Ground Fault at Cable Terminal
ICON1
• Current spike occurs;
• Current varies with locations.
ICON2
• Cables discharge and
discharge loops are different.
ISE
IRE
ICON3
1.4
IRE
1.2
Current (kA)
1
0.8
0.6
ISE
0.4
0.2
ICON1,2,3
0
18
-0.2
18.95
<0
19
19.05
Time (sec)
19.1
Ground Fault at Cable Terminal
VCMP1
100
50
GF point
VCMP1
VCM (kV)
0
VCMP2
-50
VCMN1
-100
-150
-200
18.95
19
19.05
Time (sec)
19.1
VCMN2
19.15
100
50
VCM (kV)
0
VCMP2
VCMN1
-50
Transient voltages vary with locations
-100
VCMN2
-150
-200
18.95
19
19
19.05
Time (sec)
19.1
19.15
Cables are discharged w/ different time
constant.
Low Impedance Grounding
80
VCMP
60
VCM (kV)
40
20
VCMP
0
-20
-40
VCMN
-60
-80
0
5
10
Time (sec)
15
20
GF results in production loss.
NO voltage polarity reverse.
20
VCMN
Ground Fault at Load Side
Single-phase GF @ motor side
0.8
15
Ac current
0.6
Motor voltage
10
6.6 kV rms
0.4
5
Vac (kV)
0.2
0
-0.2
0
-5
-0.4
-10
-0.6
-0.8
9.97
21
9.98
9.99
10
Time (sec)
10.01
10.02
10.03
-15
9.97
9.98
9.99
10
Time (sec)
10.01
System can ride-through this without any transient
10.02
10.03
Bypass Protection
22
Why Bypass is Needed
DC choke
10 km dc cable
180km dc cable
M
180km dc cable
DC choke
Any open-circuit failure
M
M
M
Vs
Cascading damage
IRE
Other loads shut
down
M
M
M
M
MSDC system
IRE
M
M
M
M
Vs
Fast-speed bypass is a
critical protection device
23
Current Source, Series-Connected
Power System
23
Isolation and Protection for Distribution Cable Fault
C1, P1
P4
P1
C4
C1
Bypass circuit at Switch Hub
Cable fault
G
1
C2, P2
2
Subsea
Switch hub
C3, P3
C2
16
P2
C3
P3
24
Bypass Circuit Requirement
Design objective:
High-voltage solid-state bypass for open circuit protection
Design target:
•Fast detection and bypass reaction (µs range)
•Mini. circuit component count, high reliability
•Path to get to higher voltage
Implementation at the
converter module
25
Bypass Circuit Concept
A way of fast triggering is required even w/o the control
power
OV protection using Breakover
Breakover Diode I/V curve
OV protection
threshold
26
Diode
Bench Test
Iscr
Vscr
Open Circuit
Current
Source
Single thyristor
27
Two thyristors series connection
Detection and turn on time is managed within a few μs
Demo System Test
28
Scaled Down Test System
Benchmark System:
8 loads, 400A,160 kV dc bus
29
Lab demo System
4 loads, 40A, 2.4kV dc bus
System control and operation methods can be verified as
well as fault protection and dynamic behavior.
Lab Demo System
4 SE modules
4 RE
modules
4 regenerative
motor loads
Power
flow
30
System is running in pump-back mode.
Lab Demo Hardware
180 km 2-pole
Cable Emulator
10 km
distribution
cable
emulator
Input
transformer
Rec. end
module 1&2
Sending
end Power
stack
480V
power
suppl
y
31
Control Architecture
GE Mark VI Control
Rack # 1
•All sending end modules
are synchronized to
achieve higher
performance
GE Mark VI rack
Optical Fiber
Rack # 1
Control Room
Rack # 2-5
• one for each receiving end
module
Rack # 2 - 5
PC Toolbox
• No communication between controllers.
• Sending and receiving end modules work independently.
32
Control Algorithm – Sending End
ISE
Total SE
Modules
+
VSE Vcable
Total RE
Loads
-
33
Cable terminal voltage is measured and used as feedforward to improve system dynamic performance.
Control Algorithm – Receiving End
Current
source
34
Vdc_P
+
VRE
+
+
-
-
Vdc_N
Implementation of the Bypass Protection Circuit
• Fast reaction can minimize
the impact of fault on the
system operation.
35
Test for Distribution Cable Open Circuit Fault
M
M
M
Bypass
device
Open circuit fault
emulator
IGBT
M
36
• Bypass switch in the
switch hub can clear
distribution cable open
circuit fault.
• Cable open circuit fault is
emulated by turning off
IGBT.
Test Result – System Startup
37
SE Voltage
(50V/div)
Quadratic Loads
SE Current
(20A/div)
2A/s
Vse [50V/DIV]
Ise [20A/DIV]
Link current is built with controlled slope.
Test Results – Full Power Ramp Up
SE Voltage
(500V/div)
RE Voltage
(500V/div)
SE Current
(20A/div)
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
38
Constant link current
Loads enabled at different times
4 RE modules are enabled at different times.
Full Power – Steady State
SE Voltage
(500V/div)
RE Voltage
(500V/div)
72kW delivered
to receiving end
SE Current
(20A/div)
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
39
4 RE modules are working independently.
Load Variation
SE Voltage
(500V/div)
RE Voltage
(500V/div)
SE Current
(20A/div)
#4 module
ramp down
#4 module
ramp up
Constant link current
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
40
No interference between different modules.
Different Loading Condition
SE Voltage
(500V/div)
RE Voltage
(500V/div)
SE Current
(20A/div)
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
41
Constant link current
Different operation speeds
4 RE modules are working under different load
conditions.
Load Step Change
SE Voltage
(500V/div)
RE Voltage
(500V/div)
SE Current
(20A/div)
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
42
#4 module 100%
load step
change
Constant link current
#4 module restart
No impact on other modules with 100% load step
change.
Full Power Ramp Down
SE Voltage
(500V/div)
Quadratic Loads
RE Voltage
(500V/div)
SE Current
(20A/div)
Constant link current
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
43
4 RE motor loads are ramp down at different times.
Fast Shut Down
SE Voltage
(500V/div)
Loads shut down at different times
RE Voltage
(500V/div)
SE Current
(20A/div)
Constant link current
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
44
No impact on the link current.
System can restart at any time.
Test Under Fault Condition
• One load trip
 The faulty module is detected and bypassed
 The rest part of the system can ride through the fault.
• Cable open circuit fault
 Distribution cable open circuit fault emulated
 Fault is detected and bypassed.
 The whole system can ride through the fault.
45
One Load Tripped by Fault
SE Voltage
(500V/div)
RE Voltage
(500V/div)
#3 module input
current (20A/div)
#4 module input
current (20A/div)
SE Current
(20A/div)
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
46
#3
module
tripped
#3 module bypassed
20% overshoot in module input current
20% overshoot in link current
The system can ride through the fault in receiving end
module.
Distribution Cable Open Circuit Fault
Bypass switch
Voltage
(200V/div)
RE current
(20A/div)
Bypass switch
current (20A/div)
SE Current
(20A/div)
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
47
Fault is detected
Cable open circuit fault
Fault is bypassed
No impact on link current
No impact on loads
The system can ride through the fault in receiving end
module.
Distribution Cable Open Circuit Fault
Bypass switch
Voltage
(200V/div)
RE current
(20A/div)
Bypass switch
current (20A/div)
SE Current
(20A/div)
#1 module load
current (100A/div)
#2 module load
current (100A/div)
#3 module load
current (100A/div)
#4 module load
current (100A/div)
48
30µ
s
Fault happens
Fault cleared
Fault can be detected and bypassed within 30µs.
Conclusion
 Fully demonstrated the feasibility and the benefit of
MSDC architecture through simulation and lab
experiments.
 Verified phase change cooling approach, developed
hybrid packaging concept
 Characterized material insulation strength under DC
stress, developed DC connector concept design.
Next Step
• Prototype development according to customer need:
marinized package addressing HVDC insulation
requirement and cooling challenges; DC connector
prototyping; switch hub development; etc.
49
Contacts
PI: Rixin Lai
GE Global Research
lai@ge.com
540-921-7867
50
RPSEA PM: James Pappas
jpappas@rpsea.org
281-690-5511