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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 29, NO. 6, NOVEMBERDECEMBER 1993
Harmonic Filter Design Using Actual Recorded Data
Elham B . Makram, Senior Member, IEEE, E. V. Subramaniam, Member,
IEEE, Adly A. Girgis,
Fellow,
IEEE, and Ray Catoe,
Member,
IEEE
Abstract-This paper presents a study of harmonic filters
design to minimize harmonic distortion caused by a harmonic
source such
as
drives. Several types of shunt harmonic filters
are presented. The analysis includes the basic principles, the
application of the 2-bus method and the economic aspects for
harmonic filter design. Off-line steady state simulation programs,
namely,
V-HARM nd HARMFLO
are used to model loads, to
study variation of the harmonics and to evaluate the effect of
harmonic filters at various buses in the system. Several existing
utility systems are used
as
test cases to check the performance of
the filter. The major objectives in this study are i) to improve
the power factor, (U) to reduce current and voltage distortion
to standard limits, and
i)
to reduce resonance problems at
other buses, if any. The paper also reports the transient analysis
of harmonic filters using Electromagnetic Transients Program
EMTP) which is essential to determine proper ratings of the
filter components.
I. INTRODUCTION
Due to the rapid development of electronic and semiconduc-
tor devices, harmonic problems have become a major concem
for present day engineers. Some of the sources of harmonics
are
[
11: a) tooth ripples or ripples in voltage waveform of rotat-
ing machines, b) flux distortion in the synchronous machines,
c) transformer magnetizing currents, d) network non-linearities
from loads such as static power converters, welders, arc
furnaces, voltage controllers and frequency converters, and e)
static-var compensators as suppliers of continuously variable-
var sources.
The harmonic filtering is one of the solutions to prevent
the troublesome harmonics from entering the rest of the
system. There are basically two types of filters: i) passive,
where the filter components are passive elements such as
resistor, inductor, and capacitor, and ii) active, where the
filter has a controlled current or voltage source. Among the
passive filters, there are two approaches to suppress undesired
harmonic currents; a) using a series impedance to block them,
b) diverting them by means of a low impedance shunt path.
The former is called a series filter and the latter is called
a shunt filter. Series filters are not commonly used because
they must carry full load current and be insulated for full
line voltage. These factors make a series filter more expensive
than shunt filters. In comparison with series filters, shunt filters
carry only a fraction of the current and are also less expensive.
Paper ND 19-93 approved by the Rural Electric Power Committee of the
IEEE Industry Applications Society
for
presentation at the 1992 Rural Electric
Power Conference. Manuscript released for publication March 17, 1993.
E. B.
Makram,
E.
V. Subramaniam, and A. A. Girgis are with
the
Department of Electrical and Computer Engineering, Clemson University,
Clemson, SC 29634-0915.
R. Catoe is with Duke Power Company, Charlotte, NC 28242.
IEEE Log
Number 9212396.
Reference
[ 2 ]
suggested three simple filter structures: a single
branch
of
series RLC (or single tuned filter) connected to the
bus where filtering was desired, a single branch in parallel with
a capacitor bank, say for power factor correction, and three
separate branches of tuned filters connected on the same bus.
The test system had several distributed non-linear loads (six-
pulse converters connected to battery chargers). The dominant
harmonic in this case was the fifth and the proposed filter was
a single tuned branch tuned to a frequency of
300
hertz. A
fixed quality factor
of
50 was used for the filter inductor.
References
[3,
41 suggested the use of second order high
pass filters. The advantage of a second order high pass is
that it provides a constant impedance to the harmonic currents
above a certain comer frequency. It also helps in reducing
commutation notches and it requires less total capacitance
than the notch filter. The disadvantage is the significant power
losses (both fundamental and harmonic) in the high pass
resistor.
Reference [5] presented a filter design scheme where the
filter was not directly connected through a transformer. It
suggested that
in
order to obtain the same filtering action as
before (filter directly connected), the RLC filter components
would have to change. The condition was that the impedance
versus frequency functions measured from the bus should
remain constant.
Reference [6] suggested the use of series inductor and
a second order high pass filter. The advantage
of
using a
series inductor is that it reduces high frequency harmonics,
control of di/dt during commutation and notch depth reduction.
The final filter design consisted of a series inductor equal to
system impedance, a three section filter, one tuned to the fifth
harmonic to provide general plant load power factor correction.
Two other filters were tuned to the fifth harmonic with a 0.1
ohm high pass resistor. Results showed that sectioning of filters
reduced the total power loss and reduced the voltage distortion
to standard limits.
Reference [7] showed the effectiveness of harmonic filters
and protection reactance in compensating the reactive power.
Also the effectiveness of the protection reactance (or converter
transformer reactance) in reducing voltage notch and distortion
factors was discussed. A smaller commutation angle, leads to
higher harmonic contents. The filters used were fifth, seventh,
eleventh harmonics. A seventeenth harmonic high pass filter
was also inserted on two sides of the protection reactance
(one on the supply side of the protection reactance, and
the other on the a.c. side of the converter). The voltage
notch dimensions were affected by location of filter and
the ratio of the protection and equivalent supply reactance.
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HARMONIC FILTER DESIGN
USING
ACTUAL RECORDED DATA
Reference [8] demonstrated the use of non-linear resistance
for filter design. The resistance was connected in parallel
with the filter inductor. This method may be effective in
controlling the parallel resonance conditions. In this paper,
analysis
of
different types of shunt filters has been studied.
Design considerations and economic aspects
of
single tuned
shunt filters are presented. Performance of each filter design is
tested using actual recorded data in a local utility systems. A
method to reduce resonance that may occur due to the presence
of the filter is also suggested.
11. ANALYSISF
SHUNT FILTERS
Several types of shunt filters were described in many
references
[9].
Single tuned filter is the most commonly used
filter. It supplies some or all of the fundamental frequency
reactive power required for power factor correction. The filter
components may be tuned to provide a low impedance shunt
path to a specific frequency. The quality factor of the inductor
determines the sharpness of tuning. A major disadvantage of
using single tuned shunt filters is the resonance problem that
often results when the filter is placed in a system.
The first order high pass filter is not normally used as it
requires a large capacitor and has excessive loss at fundamental
frequency. The second order filter provides good filtering
performance, but has higher fundamental frequency losses as
compared with the third order filters. However, a third order
filter has low losses at the fundamental frequency due to the
increased impedance at that frequency caused by the presence
of the capacitor in series with the high pass resistor. The
filtering action of a third order high pass filter is, however,
found to be less effective than a second order high pass filter.
The filtering performance of the C type filter lies in between
the second and third order types. The main advantage in the C
type filter is a considerable reduction in fundamental frequency
losses. The disadvantage of this filter is that it is more
susceptible to fundamental frequency deviations and filter
component value drifts. The double tuned filter can eliminate
two harmonics and its equivalent impedance is the same as
two parallel single tuned filters. This filter has the advantage
of reducing the power losses at fundamental frequency as
compared with two single tuned filters. Its main advantage
is in high voltage applications because of the reduction in the
number of inductors subjected to the line voltage.
111
FILTER PARAMETER
SELECTION
CRITERIA
The major criteria in filters design is to select a suitable
capacitor size that results in a reasonable power factor at
60
Hz. The value of the reactance is then tuned to the
offending harmonic. Although the common practice is to limit
the resistance of the filter to the reactors resistance, external
resistance may be added to modify the sharpness of tuning or
to change the bandwidth of the impedance versus frequency.
1) Fundamental Frequency Reactive Power Compensation
Consider the parameters X C f , X L f , R L f are the fun-
damental frequency capacitive, inductive and resistive
components of a single tuned filter respectively. Qf is
1177
the total reactive power to be supplied by the filter. Thus
w = 2 T f n
= 2 ~ n .o (1)
where f o is the power system fundamental frequency
and f is the tuning frequency of the filter. At the tuning
frequency, the capacitive and inductive components of
the filter become equal. That is
or
3)
Thus
(4)
JF-G
wo
=
w =
Assume
R L f
(resistance of the coil) is small, then
the fundamental frequency reactive power can be given
by
IT712
5 )
I
Q f
=
X L f - X C , )
where
VI
is the magnitude of the fundamental voltage at
the bus where the filter is located. Then, the total reactive
power of the filter can be obtained by substituting
equation 3) into equation
(5)
as
and
Thus
n X L f
RLf =
where Q is the quality factor of the coil. If the value of
reactive power to be supplied by the filter is known, the
capacitive component can be calculated using equation
6). The value of inductive reactance can then be calcu-
lated using equation (7). Using a standard manufacturers
tables for the values of quality factor of different coils,
R L ~
an be calculated from equation (8).
2 ) Calculation of Filter Parameters
Using
Z-Bus Method
The bus impedance matrix (Z-bus) can be used as a
tool to define and select filter parameters. The method
is suitable in cases where the line current distortion is
very high as compared with bus voltage distortion. This
may be true in most of distribution systems.
Consider an example system as shown in Figure 1.
This consists of a four-bus system i
j ,
k and m with an
injected harmonic current source at bus k . Assume that
line k-m) has the highest percentage current distortion.
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 29, NO. 6, NOVEMBERDECEMBER
1993
Using the 2-bus algorithm for this system, the filter
impedance can be included at bus k by adding a link
from bus
k
to ground then apply Kron s reduction [lo].
The final 2-bus matrix is,
where
v 2
and z k k = driving point impedance before the filter
impedance 2,) is added.
Each element in the impedance matrix is a function of
frequency.
Now, using 2-bus matrix before the filter is placed, the
voltages at buses k and m can be obtained as
v m
= Z k m I k (10)
v k = Z k k I k (11)
where
I k
is the injected current at bus
k ,
vm
nd
v k
are
the voltages at buses
m
and
k
respectively. Also, the
current in the line
k
-
m
is given by
b k m L k m
where z k m is the impedance of the line k - m.
Similarly, the voltage equations after filter is placed,
using Z b u s are obtained as
and the current in the line k - m) is
where Z k m is the impedance of the line between
k
and m. By substituting the value of
Lm
and Z L k into
equation (15), I k m can be obtained as:
substituting equation (12) into equation (16) yields
Equation (17) can be used to calculate the single tuned
shunt filter impedance based on the desired percentage
reduction of the harmonic current components. There-
fore, any standard capacitor size may be selected then the
corresponding inductor can be calculated based on the
tuned frequency. External resistance may be added based
on equation (8). This gives the flexibility in selecting the
filter capacitor size and would be useful in cases where
power factor correction is not required at the filter bus.
3)
Economic Aspects
in
Filter Design: for Single Tuned
Filters Cost
is an important criterion in any filter s
design. Single tuned filters are the least expensive type.
Damped filters have a large resistance and high rating
of its capacitance. These factors make a damped filter
more expensive than a single tuned filter.
Total voltage across a single tuned filter can be written
as.
or
(19)
n2
v , s v . -
n2-
I )
where
VL
Vc,
V
are the fundamental voltages across
the filter inductor, capacitor and at the filter bus respec-
tively. The fundamental and harmonic reactive power in
the filter components can be obtained by applying the
following equations.
Thus,
the harmonic capacitive reactive power can be
obtained as:
where I f n is the current through the filter at the tuned
harmonic frequency. The fundamental inductive reactive
power can be obtained as:
By substituting for Q f from equation (18) into equation
(20), results
Harmonic inductive reactive power can be obtained sim-
ilarly as the capacitive power since at tuning harmonic
frequency n, Xc, XL~).
The total cost (TC) is then given by
n2
TC = Q f . ;li..~}
Therefore, the total cost can be written as
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M A W
t al.: HARMONIC
FILTER
DESIGN USING
ACTUAL
RECORDED DATA
' r
-l-
I t
Y
Fig. 1 Four Bus
Example
System with
Harmonic
Current Source.
where
Jc, JL
are the unit cost of the capacitor and
inductor respectively in (kvar),
n
s the tuning harmonics
frequency, and Q f is the filter size determined by its
supplied reactive power.
A . Minimum Filter
A minimum filter is a filter which has minimum cost. These
filters are used when reactive power compensation is not an
important criterion. The minimum filter can be obtained
as
Therefore,
L
Q2f
=
or Q f
=
The minimum cost after substituting the value of Q f from
equation (26) into equation (25) is
Tcmi
2 d T Z C (27)
However, a minimum filter which appears to
be
ideal from an
economic point of view may not be very effective in reducing
the voltage or current distortion below specified limits. It
would then be necessary to consider the next available filter
size and evaluate the filter s performance.
Iv . SELECTION OF
FILTER
T Y P E
A
filter is designed based on the harmonic contents of
voltage and current obtained either from simulation programs
or actual recorded data at the harmonic source. Most of
the waveforms have a large percentage of distortion at the
lower harmonics. Therefore, single tuned filters are designed
to eliminate these harmonics. Since the magnitude of har-
monic currents decreases as the harmonic order increases, a
damped or high pass filter is recommended to screen out a
broad range of higher order harmonics. These filters provide
high impedance (capacitive) at lower harmonics and constant
resistive impedance at higher harmonics. The parameters of
these filters can be obtained similar to the single tuned filter
except the value of the resistance which can be obtained as
where Q (quality factor) has a value between 0.5 to 2.0.
The number of filter branches can be selected based on
the percentage of the harmonic components of voltage and
current. The fundamental frequency reactive power is usually
divided equally among the various filter branches but this may
not be always true. It may also,be necessary to place filters
elsewhere in the system to reduce resonance problems (series
or parallel), if any.
v . EXAMPLESF HARMONIC FILTER DESIGN
The steady state analysis of harmonic filters are performed
using two simulation programs, V-HARM which was devel-
oped by McGraw Edison [ l l ] and HARMFLO which was
developed by EPRI [12]. Two utility systems are used as
examples. The first system is 44 KV and the second system
is 12.4 KV. Details of these systems data can be shown in
reference
[
131.
A single line diagram
for this system is shown in Figure 2. This system serves mainly
industrial customers. There are larger numbers of capacitor
banks located at the 44 KV bus, bus 2L, bus 3L, and bus
4L.
This
system has two 1250 h.p. d.c. drives, each is fed by
a six-pulse converter. The converters are connected through
two similar transformers, one is connected wye-wye and the
other is connected delta-wye. The current produced by a p-
pulse converter is rich in harmonics of the order
I p
where
I
=
1 , 2 , . .
. However, in this system, two identical
transformers have been deliberately placed and phase shifted
by 30 degrees in order to cancel off certain harmonics such
as the 5th, 7th, 17th, 19th etc. These harmonics circulate
between the two transformer banks but do not appear on
the a.c. side. Near to perfect cancellation is ensured if both
drives are operating under similar loading conditions and have
similar firing angles. Thus, the system (utility side), sees an
equivalent 12-pulse converter with its characteristic harmonics
such as Ilth, 13th, 23rd and 25th. This is considered as the
best case when the
two
drives are in operation. The worst case
is considered when only one of the two drives is in operation
since no harmonics cancellation takes place.
The dominant harmonic components at the drives bus are the
5th and the 1 th. The magnitude of these components are based
on the worst case condition (one drive is in operation at full
load). Therefore, two single tuned shunt filters are designed at
bus 7L using the above analysis.
These filters parameters are:
5th Harmonic Filter
QC5 = 600 KVAR
XC5 = 28.843 ohm
XL5 = 1.252
ohm
tuned to 4.8 Hz
R5 = 0.2087 ohm
Q
=
30
Example
1
44 KVSystem)
1 th = Harmonic Fliter
QC l l = 300 KVAR
XCll = 57.685
XLll = 0.517 ohm
tuned to 10.56 Hz
R11
=
0.1897
ohm
Q = 30
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APPLICATIONS,VOL.
29,
NO. 6,
NOVEMBEWDECEMBER
1993
4 . 1 6 K V \ .
KVBUS
T
BUS IL
4 . 1 6 K V
1 2 . 5 K V
BUS4L
5 3
0 . 6 K V
n l
M K V
BUS BUS 4 BUS 6 DRIVE BUS
V O L T A G E D I ST O R T I O N AT V A R I O U S BUBB8
e
Fig.
3.
Voltage Distortion at Different Buses with and without the Filters.
The performance of the filters are tested using HARMFLO
and V-HARM programs. The harmonic distortion of voltage
and current before and after the filters are placed can be shown
in Figures 3 and 4.
This system serves rubber
and steel plants which have d.c. motors fed from 6-pulse
converters (cl, c2, c3) as shown in the single line diagram
of Figure
5.
Detail system parameters is in reference [13].
Actual recorded voltage and current waveforms are obtained
for each site of the plants.
First, the HARMFLO program is used to model the d.c.
drive using manufacturer s data for the armature resistance and
inductance. Second, V-HARM was used to define resonance
problems in the system. Previous analysis used to design the
Example 2
12.47
KV
5 ,
B 4
2
n
LINE
3 LINE
6
CVRRENT
THD
I N V AR IO U S L I N S S
Fig. 4. Current Distortion in Selected Lines with and without the Filters.
S V B
21
1 7 . 9 2 t j 7 9 . 2 4
20
= 1.664+j33.28
I
I
l 2
7-
1 2 . 4 7 K V
2=5.5
-
0 . 4 8 K V
6-PULSE
DRIVE
I
J
Fig. 5. Single Line Diagram of 12.47 KV System (Example
2 .
filter based on the recorded data at the sources (cl, c2, c3)
buses, the fifth harmonic is found to be dominant. The filter
is located at bus 11 (Figure
5)
with the following parameters:
Q c
X
=
86.39 ohm
X L
= 3.7496 ohm
Filter is tuned to 4.8 Hz
Q = 30
R
= 0.6249
ohm
= 1800 kVAR (3-phase rating)
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MAKRAM
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1181
One 5th i l t e r a t b u s
. i t h o u t f i l t e r
6
X
I
2
0
b u s2 b u s l l bus13
VOLTAOB
DISTORTION AT
VARIOUS BUSB
Fig.
6.
Voltage Distortiofi at Different Buses with and without the 5th Filters.
One 5 t h filler a t b us 1 1
w i t h o u t f i l l e r
n
X
O
3-4
5 7
12-13
C U R R E N T DISTORTION
IW VARIOUS
LINES
Fig. 7. Current Distortion in S electe d Lines with and without the 5th Harmonic
Filters.
The performance of this filter is tested using V-HARM and
HARMFLO programs. The percentage voltage and current
distortion before and after the filter is placed can
be
shown
in Figures 6 and 7.
VI. NATURE
OF
ACTUAL RECORDED HARMONIC
DISTORTION
Example 2represents an application of a six pulse drive
to an industrial process. In this case, the drive is used in
conjunction with a 230 horsepower DC motor for a mixing
process. The torque required by the DC motor varies during
the mixing process; therefore, the harmonic content of the
current waveform also varies with time. Three separate modes
of operation were observed while taking the measurements.
The first mode will be referred to
as
the idle mode. During
the idle mode, the mixing process is between manufacturing
runs. Because a relatively small amount of torque is required
from the
DC
motor, the content of the harmonics is also small.
The second observed mode of operation is the run mode.
This mode represents the process at full speed. During the
run mode, there is a slight variation in the magnitude of the
fundmental and harmonic currents. This variation is due to
changes in the torque required to drive the process. Although
the magnitudes vary, the current waveforms at different times
have the same relative harmonic content. Because there is only
a slight variation in the current magnitudes during the run
0.97 1.07 1.17
1.27
1.37 1.47
T i n e
m a )
XlE?)
Fig.
8.
Idle Mode for Example 2.
0.76
0.39
1
.81
-0.36
-0.73
0.88
9.99 19.98 29.97 39.96
49.95
f i l s
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IEEE TRANSACTIONS ON
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APPLICATIONS, VOL. 29,
NO. 6, NOVEMBERDECEMBER
1993
The EMTP is based on a time domain solution for transient
analysis. Several models are available in the EMTP for the
user to represent transmission lines such as lumped parameters,
pi-models, mutually coupled lines, distributed parameters,
transposed and untransposed lines.
Comparisons between capacitor switching and filter switch-
ing are made using the above two examples. It is found
that switching a harmonic filter designed for power factor
corrections was less troublesome than switching a capacitor
for the same purpose. This is due to the presence of the filter
inductor which prevents the sudden inrush current.
VIII. CONCLUSION
This paper has presented the steady-state and transient
analysis of harmonic filters designed for two actual utility
systems. In both analyses, at the bus where the filter is to
be placed the filter capacitor can be calculated based on
the power factor correction. If the power factor is high,
then the 2-bus method can be used to determine the filter
components. An optimal harmonic filter was close to satisfying
each design criteria and the available manufacturers standard
values. Resonance problems were minimized by converting an
existing capacitor bank into a C type filter. Investigations
were made to determine the case which gives the highest
magnitude of harmonic distortion. Switching filters in the
presence of capacitors showed that it would be better to switch
the filters first and then switch capacitors. Also, the maximum
overvoltage at the filter bus was determined in order to rate
the filter components properly. Harmonic filter design for time
varying harmonics is in progress at this stage.
ACKNOWLEDGMENT
This research was funded by Duke Power and Clemson Uni-
versity Electric Power Research Association. Many individuals
have significantly contributed to the progress of this project.
The discussions and recommendations of John Dalton, Ron
Adams, Steve Whisnat, Alan Frivette, and Melvin Chine have
been invaluable for this project to be completed. Also, the
plots obtained by Veer Pamulupati (graduate student) have
been useful.
REFERENCES
R. C. Duran, Chung Du ck KO, Analyzing and Con trollling Harmonic
Distortion Distribution Feeders, International Conference on Harmon-
ics in Power Systems, Worcester Polytechnic Institute, October, pp.
22-23, 1984.
G. T. Heydt, W. M. Grady, Distributed Rectifier Loads in Electric
Power Systems, IEEE Transactions on Power Apparatus and Systems,
PAS 103, No. 9, Sept. 1984, pp. 2452-2459.
Peter W. Hammond, A Harmonic Filter Installation to Reduce Voltage
Distortion from Static Power Converters, IEEE T ransactions on Industry
Applications, Volume 24, No. 1, JanuaryFebmary 1988.
D. A. Gonzalez, J. C. McCall, Design of Filters to Reduce Harmonic
Distribution in Industrial Power Systems, Conference Record, 1985,
IEEE-IAS Annual Meeting, Toronto, pp. 361.
Andras M. Dan, Through Transformer Fitted Harmonic Filter Group,
International Conference on Harmonics in Power System, Worcester,
October, 1984, pp. 174-177.
Allan Ludbrook, Harmonic Filters for Notch Reduction, IEEE Trans-
actions on Power Systems, 1986, pp. 1043-1047.
Gian Carlo Montanari and Mauro Loggini, Filters and Protection
Reactance for Distortion Compensation in Low Voltage Plants, IEEE
Transactions on Power Systems, 1988, pp. 1488-1496.
Mauro Loggini, Gian Carlo Montanari, Enrico Tironi, Dario Zaninelli,
Non-Linear Resistance for Filter Design, 3rd International Co nference
on Harmonics in Power Systems, 1988, pp. 170-176.
B. R. Anderson, P. J. Brassington, K. Mitchell, Interfacing of A. C.
Systems with HVDC Schemes: A Comparison of Filter Types; GEC
Transmission Distribution Projects Ltd, Strafford, England , pp. 158-163.
Paul M. Anderson, Analysis of Faulted Power Systems, Iowa State
University Press., Ames, IA, 1981.
The Power Verdict Series, V-HARM Users Manual: Version 3.40,
McGraw-Edison P ower Systems, July 1987.
The HARMFLO Code: Version 4.0, Users Guide, EPRI Research
Project 2444-1, Purdue University, November 1986.
E. V. Subramaniam, Off Line Harmonic Filter Design Ms.c. Thesis,
Clemson University, Clemson, SC, August 1990.
Elham B. Makram
(SM 82 was born in Assuit,
Egypt. She received the B. S . degree in Electrical
Engineering from Assiut University, Egypt in 1969.
She received the M.
S.
and Ph.D. degrees from Iowa
State University in 1978 and 1981, respectively.
From 1970 to 1976, she was an engineer in power
system planning in Assuit, Egypt. From 1978 to
1981, she was a research assistant at Iowa State
University. From 1981 to 1983, she was a Senior
Project Engineer at Siemens-Allis, Inc., in Raleigh,
NC. From 1983 to 1985, she was an Assistant
Professor at North Carolina A T State University. She is presently an
Associate Professor of Electrical and Computer Engineering at Clemson
University, Clemson, SC. Dr. Makram is a senio r member, a memb er of ASEE,
Sigma Xi, NSPE, and C IGRE. S he is a registered Professional Engineer. She
is the recipient of the 1991 Alumni Research Award at Clemson University
and the SWE 1993 Distinguished Engineering Award.
E. V. Subramaniam was born in Bombay, India
in 1966. He received his Bachelor of Technology
(B. Tech.) in Electrical Engineering from the Indian
Institute of Technology, Madras, India in 1988.
He received the M. S. degree in Electrical and
Computer Engineering from Clemson University,
Clemson, S C in 1990. He is presently working
as
a
consultan t Engineer at Scott Scott Associates in
Seattle Washington. He is a member of IEEE and
Power Engineering Society.
Adly A.
Girgis is a Fellow of the IEEE. He received
the B.
S .
(with distinction first class honors) and
the M. S. degree in Electrical Engineering from
Assuit University, Egypt. He received the Ph.D.
degree in Electrical Engineering from Iowa State
University. He taught at Assuit University, Egypt,
Iowa State University and North Carolina State
University.
Dr.
irgis oined Clemson University in 1985.H e
is currently D uke Powe r Distinguished Professor of
Power Engineering in the Electrical and Computer
Engineering Departmentand the Director of Clemson University Electric
Power Research Association. Dr. Girgis has published more than ninety
technical papers and holds four U.S. patents. He is the recipient of the
1989 McQueen Quattlebaum-Faculty Outstanding Achievement Award, and
the 1990 Edison Electric Institute Power Engineering Education Award and
the 1991 Iowa State Professional Achievement Citation in E ngineering Award.
His present research interests are real-time computer applications in power
system control, instrumentation and protection, signal-processing, and Kalman
filtering applications. Dr. Girgis is a member of Phi Kappa Phi, Sigma Xi,
and is a registered Professional Engineer.
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MAKRAM et
al :
HARMONIC FILTER DESIGN USIN G ACTU AL RECORDED DATA
Ray
C.
Catoe,
Jr.
received the B.S. degree with honors in electrical
engineering from North Carolina State University, Raleigh, NC in 1982.
From 1982 to 1992 he was
a
power quality engineer with Duke Power
Company in Charlotte, NC. His major areas
of
responsibililty included
specialized testing, training, and resolving power quality problems for large
industrial customers. He is presently employed as a technical sales engineer
with Jake Rudisill Associates in Charlotte, NC.
Mr. Catoe is a member of the Power Engineering Society; Eta Kappa Nu;
and Tau Beta Pi.
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