OTC 24183
Modular Stacked DC Transmission and
Distribution System for Ultra-deepwater Subsea
Process
R. Lai, D. Zhang, M. Harfmon Todorovic, L. Garces, R. Gupta, S. Chi, D. Dong, C.
Sihler, GE Global Research, S. Gunturi, GE Transportation, S. Rocke, K. Elgsaas,
GE Oil & Gas, R. Datta, Arizona State University, J. Song-Manguelle,
ExxonMobil, M. Alford, M. Haji, Chevron, J. Pappas, RPSEA
Slide 2
Trend for Subsea Processing
Increasing demand for electrical power to subsea
installations:
• Deep waters: 3000 m
• Long step-outs: 50-500 km
• Power: 100 MW with variable speed loads
• Power supply from shore or floating facility
Turbomachinery on
the seabed
Subsea electrification
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 3
AC Transmission System
AC (50/60 Hz)
• Known technology
• Limited step-out, var compensation required
Low frequency AC (e.g. 16.7 Hz)
• Extended step-out, reduced transmission losses
• Onshore frequency converter required
• Increased size of transformers and switchgear
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 4
Modern DC Transmission System
High voltage DC (voltage source HVDC)
• Low transmission losses, very long step-outs
possible
• Bulky equipment, difficult to install subsea
• Point-to-point transmission only, with AC
distribution
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 5
Proposed Modular Stacked DC (MSDC)
• Current source system
• Onshore/topside rectifier
• Subsea inverter modules
connected in series
• Adjustable inverter output
frequency driving pump or
compressor motors
• Each inverter comprises a
number of MSDC modules
depending on the power
requirement
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 6
DC System Operation Principle
Voltage source system
i1
iT
+
vT
K1
Current source system
(MSDC)
in
i2
K2
L1
Kn
+
L1
L2
K1
Ln
-
iT
-
v1
K2
L2
v2
Kn
Ln
vn
vT
• Constant voltage, adjustable
current
• Constant current, adjustable
voltage
• Loads are parallel connected
• Loads are series connected
• Protection devices in series
with the loads
• Protection devices parallel to
the loads
• With more than one load,
HVDC circuit breakers are
required
• HVDC circuit breakers
replaced by bypass switches
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 7
MSDC Operation
• Engage sending end
• Establish link current
(current control mode)
• Engage receiving end
(voltage control mode)
• Engage load (dc current
remain the same, dc
terminal voltages vary with
the loading)
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 8
Modularization of MSDC
•
Inverter comprises modules connected in series
•
Fixed module rating, the number of modules depends on
power requirement
•
Redundancy achieved by adding one or more extra modules
to the inverter
•
Reduced qualification costs (standardized module)
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 9
Comparison of MSDC and AC
132 kV / 50 Hz
~
=
=
=
=
=
~
~
~
~
M
M
M
M
MSDC has cost benefit even for medium step-out distance (~50km)
pump applications due to simpler architecture and modular design.
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 10
Comparison of HVDC and MSDC
G
Onshore or Topside
G
Onshore or Topside
• Multiple stages of power
conversion
• Requires AC Switch gear for
distribution
• Bulky centralized converter
• Impracticality of marinization
• With more than one load,
HVDC CB are required
•
•
•
•
•
•
Reduced conversion stages
Modular and scalable
Eliminates AC switchgear
Lower cost and size
Fault tolerant
For more than one load,
bypass switches are required
Conventional HVDC
Subsea HVDC Station
M
M
GE Modular
Stacked
MVDC/HVDC
M
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
M
Cable Connection with Switch Hub
C1, P1
Subsea
Switch hub
P4
P1
C4
C1
• Enable bypass and isolation for distribution cable fault
G
1
C2, P2
C3, P3
2
C2
16
P2
C3
P3
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 12
Technology Demonstration - RPSEA
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 13
System Simulation
• +/- 80 kV, 400 A link current
• 180 km transmission cable, 10 km distribution cable
• 4 X10 MW compressors loads, 4 X 2.5 MW pump
loads
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 14
Simulation Results
Compressor Load
Link Voltage
Pump Load
Link Current
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 15
Lab Scale Prototype
4 RE modules
4 motor loads
Power
flow
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 16
Lab Scale Prototype
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 17
MSDC Lab Demo – Functional Test Results
System start-up: build transmission line current
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 18
MSDC Lab Demo – Functional Test Results
Ramping up motor loads
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 19
MSDC Lab Demo – Functional Test Results
Steady state waveforms
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 20
MSDC Lab Demo – Functional Test Results
Step change and ramp down of motor loads
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 21
Summary
• MSDC is considered to be a strong future
alternative to subsea AC as well as HVDC
transmission and distribution
• The system operation and control concept have
been verified through the RPSEA program
• Further development and qualification of MSDC
required, including development of key components
such as subsea DC connectors
• Development will be based on oil and gas company
needs
OTC 24183 • MSDC Power System for Subsea Process• Rixin Lai
Slide 22
Acknowledgements / Thank You / Questions
Funding for this project is provided by the Research Partnership to Secure
Energy for America (RPSEA) through the “Ultra-Deepwater and
Unconventional Natural Gas and Other Petroleum Resources” program,
authorized by the U.S. Energy Policy Act of 2005.
Rixin Lai
GE Global Research
(518) 387-5453
lai@ge.com
James Pappas
RPSEA
(281) 690-5511
jpappas@rpsea.org