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HARMONIC ANALYSIS OF
SELECTED DG DEVICES
Pradipta Kumar Tripathy, Durgesh P. Manjure, Dr. Elham B. Makram
CLEMSON UNIVERSITY ELECTRIC POWER RESEARCH ASSOCIATION
Clemson University, Clemson, SC 29634
Power System 2002 Conference: Impact of Distributed Generation
March 13-15, 2002
Clemson, SC
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OUTLINE

Introduction

Background

Modeling

Results

Conclusion & Future Work
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INTRODUCTION
Objective
To study the effect of Distributed Generation on distribution systems with respect to
harmonic distortion.
Outline of Research

Literature review

Case studies on the impact of different types of DG in residential, commercial,
and industrial systems to the distribution system
Methods Used

Time domain method for simulation
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BACKGROUND
Harmonic Sources in Power Systems
 Saturable devices
 Nonlinear loads
 Power electronic devices
Harmonics in typical DG systems
 Microturbines
 Wind Turbines
 Photovoltaics
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A TYPICAL RESIDENTIAL PV SYSTEM
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MODELING OF PV SYSTEM
Circuit components used for modeling the PV system are




A constant voltage DC source
A single phase inverter
An isolating transformer
A single-tuned filter
T1
D1
T3
D3
L
Vpv
C
T4
D4
T2
D2
T1
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MODELING OF RESIDENTIAL SYSTEM
Residential system is modeled by considering four typical houses.
Loads considered in each house:
Linear Loads (assumed)
 Incandescent light
 Refrigerator load
Nonlinear Loads
 Compact Fluorescent Light
 Television Load
 Heat pump
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CASES STUDIED
Case 1:
Harmonic distortion in the presence of DG as a standalone unit supplying
residential loads
Case 2:
Harmonic distortion in the distribution system due to residential system
loads alone
Case 3:
Combined effect of residential loads and DG on distribution system
harmonics
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TEST SYSTEM USED FOR CASE 1
Load current
T1
D1 T3
Load voltage
D3
L
Vpv
Filter
C
T4
D4 T2
D2
Isolation Transformer
PV System
House1
House2
House3
House4
Residential loads
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RESULTS FOR CASE 1
Load current
Magnitude (amperes)
Magnitude (volts)
Load voltage
150
100
50
0
-50
-100
-150
4.82
4.84
4.86
4.88
4.9
60
40
20
0
-20
-40
-60
4.83
4.85
Harmonic distortion in load voltage
30
25
20
15
10
5
00
5
10 15 20 25
Harmonic Order
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4.89
Time(seconds)
30
Harmonic distortion in load current
25
Magnitude (%)
Magnitude (%)
Time(seconds)
4.87
20
15
10
5
00
5
10 15 20 25
Harmonic Order
30
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TEST SYSTEM USED FOR CASES 2 & 3
12.47 kV/4.16 kV
Primary current
Primary current
Primary voltage
Primary voltage
4.16 kV/0.208 kV
Single phase loads
12.47 kV
Substation
12.47 kV/4.16 kV
Three phase loads
4.16 kV/0.208 kV
Load current
voltage
LoadLoad
current
Load voltage
Line reactor
House1
House2
House3
House4
Residential loads
PV System
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Isolation transformer
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RESULTS FOR CASES 2 & 3
10
9
8
7
6
5
4
3
2
1
0
Load voltage without PV
Load voltage with PV
Comparison of load current
3
5
7
9 11 13 15 17 19 21 23 25
Harmonic order
Magnitude (%)
Magnitude(%)
Comparison of load voltage
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45
40
35
30
25
20
15
10
5
0
Load current without PV
Load current with PV
3
5
7
9 11 13 15 17 19 21 231225
Harmonic order
RESULTS FOR CASE 2 & 3
Comparison of primary voltage
Primary Voltage without PV
Primary Voltage with PV
4.5
Magnitude (%)
4
3.5
3
2.5
2
1.5
Comparison of primary current
1
0.5
Primary current without PV
Primary current with PV
40
3
5
7
9 11 13 15 17 19 21 23 25
Harmonic order
35
Magnitude (%)
0
30
25
20
15
10
5
0
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5 7 9 11 13 15 17 19 21 23 25
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Harmonic order
RESULTS FOR CASE 2 & 3
Comparison of THD
THD(%)
Residential system Residential system
fed by distribution fed by distribution
system
system and PV
system
Load current
49.3
44.14
Load voltage
11.9
7.2
Primary current 38.4
21.9
Primary voltage 5.1
3.1
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CONCLUSIONS

Harmonics produced on the load side by the PV system were
not significant compared to the high current distortion caused
due to the household nonlinear loads.

Harmonic distortion injected to the distribution system
decreased after connecting the PV system due to harmonic
phasor cancellation.

Results presented are for the specific scenario discussed, and
could change with varying nonlinear loads and/or varying DG
types and sizes
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FUTURE WORK

Impact of varying levels of DG penetration on harmonic
propagation, in the presence of nonlinear loads

Modeling of other types of DG

Effect of DG on harmonic distortion in case of commercial and
industrial systems

Combined effect of PV and microturbine system
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