Harmonics Impact of Rooftop Photovoltaic Penetration Level on Low

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International Journal of Electronics and Electrical Engineering Vol. 4, No. 3, June 2016
Harmonics Impact of Rooftop Photovoltaic
Penetration Level on Low Voltage Distribution
System
Orawan Poosri and Chalie Charoenlarpnopparut
Sirindhorn International Institute of Technology, Thammasat University, Bangkok, Thailand
Email: orawan.poo@pea.co.th, chalie@siit.tu.ac.th
Abstract—Integration of increasing penetration level of
rooftop photovoltaic in the next few years may affect the
quality of low voltage distribution system in Thailand.
Harmonic current injected from rooftop PVs may cause
harmonic problem and affect power quality of grid.
Therefore, this research intends to study harmonic impact
of rooftop photovoltaic penetration level on low voltage
distribution system (400/230V) in urban area. DIgSILENT
PowerFactory program is used to simulate and analyze the
impact of rooftop PVs which connected in different
penetration level and two scenarios of background system,
such as balanced grid voltage, and polluted grid (with
THDv). The result of simulated model shows that the total
harmonic distortion voltage of the network is over the
standard due to the amount of PVs with inverter (which has
THDi<2%) connected to the system is more than 60%
penetration of rated power of transformer. 
malfunction or may be damaged. The utility needs to
study and analyze attentively the power quality issues for
the optimization of the penetration rooftop PV in LV
distribution network to minimize impact of rooftop PV.
There are several papers interested in harmonics
problem with PV systems [1]-[3]. They research some
factors which can influence the harmonic distortion of the
grid like radiance, environmental temperature, the control
method of the inverter, the imbalance of three-phase grid,
and the voltage harmonics of the grid. This paper uses
two factors as system loading level and some harmonics
of the grid (before PV will be connected to a network) for
analyzing the effect to harmonic output of PVs.
Index Terms—rooftop PV, distribution system, distributed
generator, harmonics impact of rooftop PV
A. Distribution System Model
I.
II.
INTRODUCTION
Currently, renewable energy resources as distributed
generators in power systems are growing up in many
countries around the world including Thailand due to
rising fuel price, high electricity price and environment
concerning. One of the most popular distributed
generators is solar or Photovoltaic (PVs) power generator.
In 2014, the government of Thailand encourages
residential and commercial units to install rooftop PVs
for producing and selling electricity through Feed-inTariff (FIT) which is proposed to attract many people for
participating in this campaign.
Grid connected PV systems use a power electronic
inverter, which injects harmonic current into the power
system, for changing DC to AC. However, the large
amount of the rooftop penetration connected into Low
Voltage (LV) distribution network, the large numbers of
inverters which cause harmonic current injected into the
grid also are massive in the network. The utility may face
the important issue as the harmonics problem in
residential network. Its disadvantage causes some
electrical devices and the local equipment in the
distribution network (like transformer, capacitor bank)
Manuscript received April 16, 2015; revised September 24, 2015.
©2016 Int. J. Electron. Electr. Eng.
doi: 10.18178/ijeee.4.3.221-225
221
SIMULATION SETUP
PEA residential low voltage networks are composed of
four wires with radial topology. It contains 250kVA
Distribution Transformer (DTR) power rating which was
connected in medium-voltage: low-voltage (22kV/400V).
The secondary side of DTR has 3 feeders and there are
159 households) (71 single phase loads and 88 three
phase loads) as shown in Fig. 1.
B. Residential Load Profile and Daily Curve Power of
Rooftop PV
Power output of Rooftop PV and the loading curve of
residential during 24 hours are shown in Fig. 2 and Fig. 3,
respectively.
C. Parameter of PV
 Size and connection type of PV
Single phase PV sizes 3kW with 2 types of inverter as
PV1 and PV2.
PV1 is represented rooftop PV with inverter type 1
release THDi less than 2%
PV2 is represented rooftop PV with inverter type 2
release THDi more than 5%
 Penetration level of Rooftop PV is the proportion
of installed power solar rooftop with the rated
power of transformer
%PV Penetration = Total PowerPV
Rated Power of TR
International Journal of Electronics and Electrical Engineering Vol. 4, No. 3, June 2016
Figure 1. Single line diagram of PEA low voltage distribution system.
TABLE I.
%PV
Penetration
BUSES SELECTED FOR INSTALLATION OF ROOFTOP PV
WITH 10, 20, …, 80% PV PENETRATION
Bus with PV connected
10
20
Feeder1-bus17,18,19,20,21,22,23,24
30
Feeder1-bus17,18,19,20,21,22,23,24,25,
26,27
Feeder2-bus11,21,24,25,34,70,91,93,95,
96,108,112,113,119
Feeder1-bus17,18,19,20,21,22,23,24,25,
26,27
Feeder2-bus21,34,70,108,112,113
40
Feeder1-bus17,18,19,20,21,22,23,24,25,
26,27
Feeder2-bus11,21,24,25,34,54,55,70,85,89,
90,91,92,93,94,95,96,97,108,112,113,119
50
Feeder1-bus17,18,19,20,21,22,23,24,25,
26,27
Feeder2-bus11,21,24,25,34,36,46,47,48,49,
50,51,52,53,54,55,70,85,89,90,91,92,93,94,95,96,9
7,108,112,113,119
60
Feeder1-bus17,18,19,20,21,22,23,24,25,
26,27
Feeder2-bus11,21,24, 25,34,36,46,47,48,49,
50,51,52,53,54,55,70,85,89,90,91,92,93,94,95,96,9
7,103,104,105,106,107,108,109,110,111,112,113,1
19
70
80
Figure 2. Daily output power of rooftop PV.
Figure 3. Dialy load profile of household.
Rooftop PVs will be installed to distribution system
with 10, 20, 30, 50, 60, 70, and 80% PV Penetration.
Nodes connected with PV are shown in Table I.
Feeder1-bus17,18,19,20,21,22,23,24,25,
26,27
Feeder2-bus11,21,24,25,34,36,46,47,48,49,
50,51,52,53,54,55,69,70,71,72,85,89,90,91,92,93,9
4,95,96,97,98,99,100,101,102,103,104,
105,106,107,108,109,110,111,112,113,119
D. Simulated Scenarios
Scenario 1: It assumes that the distribution system is
balanced and without harmonics in the grid.
Scenario 2: It assumes that the grid (without PV
installation) has some harmonics making the Total
Harmonic Distortion voltage (THDv) is nearly 2%.
Case study are 4 cases as:
Case 1. PV1 is installed in scenario 1 with 10% to 80%
PV penetration
Case 2. PV1 is installed in scenario 2 with 10% to 80%
PV penetration
Feeder1-bus17,18,19,20,21,22,23,24,25,
26,27
Feeder2-bus11,21,24, 25,34,36,46,47,48,49,
50,51,52,53,54,55,69,70,71,72,73,74,75,76,77,78,8
5,89,90,91,92,93,94,95,96,97,98,99,100,101,102,1
03,104,105,106,107,108,109,110,
111,112,113,119
Feeder3-bus21,51,88
©2016 Int. J. Electron. Electr. Eng.
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International Journal of Electronics and Electrical Engineering Vol. 4, No. 3, June 2016
limitation of THDi at PCC are shown in Table III and
Table IV.
Case 3. PV2 is installed in scenario 1 with 10% to 80%
PV penetration
Case 4. PV2 is installed in scenario 2 with 10% to 80%
PV penetration
All cases are considered at loading level, 25%, 50%
and 80% of rated power transformer.
I 2  I3  I4    
2
THDi (%) 
2
2
 100
(1)
 100
(2)
I1
V2  V3  V4    
2
THDv (%) 
E. Standard Harmonics Limitation
Total Harmonic Distortion (THD): The ratio of RootSum-Square (RMS) of the harmonic component and
RMS of the fundamental component in the percentage as
the total harmonic distortion current (THDi) and the total
harmonic distortion voltage (THDv) in (1) and (2)
respectively. Ref. [4], [5] the limitation of THDv at Point
of common coupling (PCC) are shown in Table II and the
2
2
V1
TABLE II. HARMONICS VOLTAGE LIMITATION
PEA recommendation (PRC-PQG-01/1998) IEEE Std. 519-1992
THDv less than 5%
Odd less than 4%
Even less than 2%
THDv less than 5%
Individual THD less
than 3%
TABLE III. PEA RECOMMENDATION HARMONIC CURRENT LIMITS FOR CUSTOMERS AT POINT OF COMMON COUPLING (PRC-PQG-01/1998)
Harmonic
order
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
0.4kV
48
34
22
56
11
40
9
8
7
19
6
16
5
5
5
6
4
6
Current limitation (A, rms) at PCC
11 and 22kV 22, 24 and 33kV 69kV 115kV and more
13
11
8.5
5
8
7
5.9
4
6
5
4.3
3
10
9
7.3
4
4
4
3.3
2
8
6
4.9
3
3
3
2.3
1
3
2
1.6
1
3
2
1.6
1
7
6
4.9
3
2
2
1.6
1
6
5
4.3
3
2
2
1.6
1
2
1
1
1
2
1
1
1
2
2
1.6
1
1
1
1
1
1
1
1
1
TABLE IV. IEEE STD. 519-1992 HARMONIC CURRENT LIMITS
Current Distortion Limits for General Distribution Systems
(120V Through 69000V)
Maximum Harmonic Current Distortion in Percent of IL
Individual Harmonic Order (Odd Harmonics)
ISC/IL
<11
11≤h<17
17≤h<23
23≤h<35
35≤h
TDD
<20*
4.0
2.0
1.5
0.6
0.3
5.0
20<50
7.0
3.5
2.5
1.0
0.5
8.0
50<100
10.0
4.5
4.0
1.5
0.7
12.0
100<1000
12.0
5.5
5.0
2.0
1.0
15.0
>1000
15.0
7.0
6.0
2.5
1.4
20.0
Even harmonics are limited to 25% of the odd harmonic limits above.
Current distortions that result in a dc offset, e.g. half-wave converters, are not allowed.
*All power generation equipment is limited to these values of current distortion, regardless of actual ISC/IL.
where
ISC = maximum short-circuit current at PCC.
IL
= maximum demand load current (fundamental frequency component) at PCC.
TDD = Total demand distortion (RSS), harmonic current distortion in % of maximum demand load current (15 or 30 min demand).
PCC = Point of common coupling.
III.
loading is changed to 80%, the trend of THDv in system
is the same.
When PV penetration integrated to the network is more,
the total harmonic distortion voltage of buses on the
network is higher as Fig. 5(a) and Fig. 5(b).
When the large number of PVs are connected to the
polluted grid (with total harmonic distortion voltage
about 2%), harmonics background in system and
TEST RESULT
When PV1 (THDi<2%) were connected to system
more than with 60% PV Penetration in Case 1 and 2, the
THDv of buses exceed the limitation (must less than 5%).
For PV2 (THDi>5%) were installed less than 40% PV
Penetration, THDv of buses still be in standard.
Comparing Fig. 4(a) and Fig. 4(b) when the network
©2016 Int. J. Electron. Electr. Eng.
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International Journal of Electronics and Electrical Engineering Vol. 4, No. 3, June 2016
harmonics from PV inverters are making THD of the
network higher as Fig. 6(a), Fig. 6(b). As Fig. 6(c), none
of PVs were connected on feeder 3 while PV penetration
installed on feeder 1 and 2 is from 10% to 70%. It causes
to increase THDv of buses on feeder 3.
(a)
(a)
(b)
(b)
Figure 4. (a) %THDv in system when PVs were connected to grid with
10-80% PV penetration in case 1-4 and network loading is 50%,
(b) %THDv in system when PVs were connected to grid with 10-80%
PV penetration in case 1-4 and network loading is 80%.
(c)
Figure 6. (a) %THDv at buses on feeder 1 when PVs were connected
to grid with 50% PV penetration and network loading 50% in case 1-4 ,
(b) %THDv at buses on feeder 2 when PVs were connected to grid with
50% PV penetration and network loading 50% in case 1-4, (c) %THDv
on feeder 3 when PVs were connected to grid with 10-80% PV
penetration in case 1-4.
IV.
CONCLUSION
This paper studies harmonics impact of rooftop PV
with inverter 2 type (which has THDi<2% and >5% in
PV1 and PV2 respectively). Although THDi of PV
inverter is less than 2%, it is possible to face the THDv of
buses in system exceed the limitation if PVs were
connected to grid with higher 60% to 80% penetration of
the rated power of the distribution transformer.
Considering system loading level at 25%, 50%, and 80%,
it has an effect on to THD of system slightly. Besides,
harmonics background in network should be measured
and taken into account before high penetration PV will be
integrated to LV network. When PVs were connected to
the polluted grid, both THDi of PV inverter and
harmonics background may affect THD of network to
increase or higher the standard.
(a)
ACKNOWLEDGMENT
This study was supported by the Provincial Electricity
Authority (PEA), Thailand under the Smart Grid
Scholarship Program at SIIT, Thammasat University,
Thailand.
(b)
Figure 5. (a) %THDv at buses on feeder 2 when PVs were connected
to grid with 10-80% PV penetration, (b) %THDv at buses on feeder 3
when PVs were connected to grid with 10-80% PV penetration.
©2016 Int. J. Electron. Electr. Eng.
224
International Journal of Electronics and Electrical Engineering Vol. 4, No. 3, June 2016
Sirindhorn International Institute of Technology Thammasat University
(SIIT) Master Degree Scholarship. She is currently a student of Master
degree in engineering technology field of Sirindhorn International
Institute of Technology (SIIT), Thammasat University.
REFERENCES
[1]
[2]
[3]
[4]
[5]
R. Torquato, F. C. L. Trindade, and W. Freitas, “Analysis of the
harmonic distortion impact of photovoltaic generation in Brazilian
residential networks,” presented at the 16th IEEE International
Conference on Harmonics and Quality of Power, Bucharest,
Romania, May 25-28, 2014.
K. Dartawan, R. Austria, H. Le, and M. Suehiro, “Harmonic issues
that limit solar photovoltaic generation on distribution circuits,”
presented at World Renewable Energy Forum, Denver, Colorado,
May 13-17, 2012.
X. Y. Zhao and S. Y. Liu, “A research of harmonics for multiple
PV inverters in grid-connected,” presented at Asia-Pacific Power
and Energy Engineering Conference, Shanghai, China, March 2729, 2012.
Harmonic Regulations for the Commercial and Industrial
(Thailand), PRC-PQG-01/1998.
IEEE Recommended Practices and Requirements for Harmonic
Control in Electric Power Systems, IEEE Std. 519-1992.
Chalie
Charoenlarpnopparut obtained
B.ENG. (1st Class Honor) in Electrical
Engineering,
Chulalongkorn
University,
Bangkok, Thailand and M.S. and Ph.D. in
Electrical Engineering, The Pennsylvania
State University, University Park, PA, USA.
He is currently an Associate Professor and
Assistant Director for General Administration,
Bangkadi Campus in Sirindhorn International
Institute
of
Technology
Thammasat
University (SIIT). He has received many Teaching Award and
Outstanding Teacher both at SIIT and Thammasat University. His
research interest include Multidimensional systems and signal
processing, Robust control, Image processing, Wavelet and filter bank,
Signal processing for communication, Convolutional code design.
Orawan Poosri obtained B.ENG degree in
Electrical Engineering and M.SC degree in
Information
Technology
from
King
Mongkut's
University
of
Technology
Thonburi, Bangkok, Thailand in 2006 and
2012. Since 2008 to 2013, she has worked as
an engineer at Provincial Electricity Authority
Central Area 3 (Nakhon Pathom Province),
Thailand. Since 2013, she has received
Provincial Electricity Authority (PEA)
©2016 Int. J. Electron. Electr. Eng.
225
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