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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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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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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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IEEE TRANSACTIONS ON

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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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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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