Presentation - POWER TRANSFORMERS: Saturation ...

POWER TRANSFORMERS:
Saturation Compensation Modeling,
Simulation, and Experiments
John Thomas, Dr. David Cope
Engineering Matters, Inc.
23 Farwell Street
Newton, MA 02460
www.engineeringmatters.com
14 October 2003
1

Engineering Matters ®
Short Form Resume
• Incorporated 1998
• Woman-Owned Small Business
• Won several Phase I and Phase II SBIRs
• Electromechanical Focus
– Specialty motors, robotics, electromagnetic
signature control and analysis
• Direct drive force feedback joysticks
– Several patents received
– Three high-performance versions available
• Ansoft user since 1984.
Engineering Matters ® 2

Engineering Matters ®
Design & Analysis Expertise
• Electromagnetics
– Motors
– Actuators
– Sensors
• Electrical design
– Power
– Analog and digital
design
• Systems integration
• Mechanical design
– Prototype
– Design for
Manufacturing
• Software design
– Firmware
– GUI/API
– Computer interfacing
• Control design.
Engineering Matters ® 3

Power Transformer Saturation
Progression
• Large scale common mode transformer currents, through
a series of physical interactions, cause many deleterious
effects. In some notable cases, these effects have led to
total system collapse.
SMD
EMP
ESP
σ
SMD = Solar Magnetic Disturbance
EMP = Electromagnetic Pulse
ESD = Earth Surface Potential
GIC = Ground-Induced Currents
VAR = Volts-Amps Reactive
GIC
Harmonics
Engineering Matters ® 4
B
HEAT
VAR
H

Reasons for interest in
transformer saturation
• Transformer DC current
causes half-cycle
saturation, generation of
harmonics, over-heating,
increased audible noise,
and mechanical stress.
• Results in decreased
transformer life.
DC Flux
Offset
φ(t)
t 1 t 2 t 3
t 4 t 5 t 6
Engineering Matters ® 5
t
t 1
t 2
t 3
B(H)
t 4
t 5
t 6
t
H
I mag

Ground-Induced Currents (GIC)
• Solar Coronal Mass
Ejections (CME) affect
utility operations
– Generates an Earth-surface
potential (1-10 V/km)
– Drives a quasi-DC ground
current (10-100A DC)
– Duration 2-4 hours.
• HEMP effects are more
intense than CME effects
– 10X voltage (10-100 V/km)
– 10X current (~1000A DC)
– 10-15 minutes/burst.
Two Causes:
Image credit: NASA
I
I/3 I/3
I/3
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I
I/3 I/3
I/3
I

Solar Magnetic Disturbances
• Solar magnetic
disturbances
(SMD) emit
coronal mass
ejections (CME)
that interact with
the earth’s
magnetic field.
Image credit: NASA
Engineering Matters ® 7

SMDs follow the
11 Year Sunspot Cycle
Measurement
period
March 2003
Image credit: Meteorological Satellite
Applications Branch, Air Force Weather Agency.
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Overall Electrical Schematic for
Source
Energy
Storage
60 Hz Filter
GIC Compensation
3φ Generator
a b c
GSU XFMR
Y-Y XFMR
Transmission Line
GIC injection
(simulated)
GIC injection
(simulated)
GIC injection
(simulated)
Earth ground
Single
Phase
XFMR
Single
Phase
XFMR
Single
Phase
XFMR
Phase A
Load
Tertiary Winding
Phase B
Load
Tertiary Winding
Phase C
Load
Tertiary Winding
GIC Compensation
GIC
Compensation
GIC Compensation
Engineering Matters ® 9

Ansoft Maxwell ® & Simplorer ®
• Three cases:
(1) No GIC (before),
(2) GIC (during),
(3) GIC with
compensation (after)
• Maxwell 2D
nonlinear Model
• Simplorer Model
– Block diagram &
circuit simulation
– Post processing
analysis.
Modeling
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Maxwell-Simplorer Linkages
Nonlinear Transformer Model
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Simplorer Block Diagram
Functionality of three circuits
(PLL, time delay switch, op-amps)
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Simplorer Results: Saturation
Compensation Control
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Simplorer Results: Closed-loop
Error Signal & Correction Current
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Simplorer Results:
Post-processing FFT
Before GIC
I 2n ~0
During GIC,
large I 2n
After GIC with
Compensation
I 2n ~0
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Maxwell 2D Results:
Transformer |B| plots
Before GIC During GIC
After GIC with
Compensation
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Sub-scale Mock-up Demo Unit
• Sub-scale
demonstration unit
built & tested
• Experimental
measurements
compared with
simulation results
Transmission
Lines
GIC
Injection
GSU XFMR
Filter
Filter
Step-down
XFMR
Generator
Load
Compensation
Circuits
Engineering Matters ® 17

Sub-scale Unit Measurements:
Error Signal & Compensation Current
Engineering Matters ® 18

Sub-scale Unit Measurements:
Primary currents for three cases
Before GIC
During GIC
After GIC with
Compensation
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Sub-scale Unit Measurements:
FFT Harmonic Amplitudes
Engineering Matters ® 20

Transformer Saturation
Compensation Summary
• Natural & man-made events can cause transformer
saturation which threatens power electric system
stability and reliability
• Regained transformer stability by automated
measurement and compensation
• Achieved very good comparison between
simulations and experiments
• Future work will extend SMPS capabilities to
higher power and voltage. More modeling and
simulation are needed.
Engineering Matters ® 21

Additional Projects of Interest
(designed with Maxwell® 3D)
• Force Feedback
Joystick (Direct drive,
wide bandwidth, very
rugged)
• MEMS OXC actuator
Engineering Matters ® 22

Robotic Design and System Integration—Power
Electronics, Vehicle design, Test Plan; RC, Motor
and Battery selection
Engineering Matters ® 23

Acknowledgements
The GIC-compensation project was
developed with funding from the
United States Army Space &
Missile Defense Command
Contract numbers DASG60-01-
C-0017 and DASG60-02-C-0066.
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Unconventional Alternative
• Geothermal
• Wave-action
• Human-effort
Power Applications
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Bill Powell working out in
Icelandic geothermal pool
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References
• Introduction to Geomagnetic Fields, Wallace Campbell, Cambridge
University Press, NY, 1997.
• “Geomagnetic Storms and Their Impact on Power System,”
Kappenman, John, G., IEEE Power Engineering Review, May 1996, p.
5.
• “Comparison of SS-GIC and MHD-EMP-GIC effects on power
systems,” Meliopoulos, A.P.S.; Glytsis, E.N.; Cokkinides, G.J.;
Rabinowitz, M. Georgia Inst. of Technol., Atlanta, GA, USA Power
Delivery, IEEE Transactions on, Pages: 194-207 Jan. 1994 Vol. 9
Issue: 1 ISSN: 0885-8977.
• "Geomagnetically induced Currents during Magnetic Storms", R.
Pirjola, Plasma Science, IEEE Transaction on, Vol. 28, No. 6, Dec.
2000, p. 1867.
Engineering Matters ® 27

Significant Power System
Outages (GIC & Other)
• GIC Storms:
– February 1986, March
1989, March 1991,
November 1991 and May
1992.
• GIC-Utility Events (place,
people affected, duration):
– North America: April 1940,
Sept. 1989, March 1991,
Oct 1991
– Quebec March 1989, 6M, 9
hr. massive outage
• General Outages (place,
people affected, duration):
– US August 2003, 50M, 16-
20 hr.
– London August 2003,
1.5M, 1 hr.
– Denmark & Sweden
September 2003, 5M, 4 hr.
– Italy September 2003, 57M,
9 hr.
Engineering Matters ® 28

March 13, 1989 GIC-related
Image credit: Kappenman
‘Events’
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