International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 1 – Jul 2014
Design and Fabrication of Improved Power Quality
Converter for Photovoltaic based UPS System
S.Selvakumar
A.Vinothkumar
M.Vigneshkumar
PG Schloar/PGES
PA College of Engg & Technology
Pollachi -642002
Assistant Professor
PA College of Engg & Technology
Pollachi-642002
Assistant Professor
PA College of Engg & Technology
Pollachi-642002
Abstract— Uninterruptible power supply acts of heart of
providing supply to electronic devices in home in case of power
failure. The output of UPS contains harmonics and it is reduced
by using proposed modified rectifier utilizing solar energy as a
source. This paper deals with design and fabricate improved
power quality converter for Uninterruptible Power Supply
system and analyze the total harmonic distortion at input supply
as well as charging the battery with the help of photovoltaic
system.
Keywords- Pulse Width Modulation (PWM), Uninterrupatable
Power Supply (UPS), Total Harmonic Distortion (THD),
Photovoltaic (PV).
I.
INTRODUCTION
An uninterruptible power supply, sometimes also called an
uninterruptible power source is a form of power supply that
utilize the main power source such as the supply voltage, and
also able to provide power to the equipment being powered
when the main source fails or is interrupted. An uninterruptible
power supply differs from auxiliary power supply in that the
UPS provides instantaneous protection from interruption of
power. An supporting power supply may be needed some
time to replace the power. The aim of an uninterruptible power
supply is to provide AC power from the normal line or mains
connection when it is available, but in the situation of failure
of power, the UPS will make use of back-up batteries. Using
inverters , get fixed constant AC supply to maintain the power
to the equipment. UPS are used in applications where there is
a need to maintaining power sufficient.
A wide range of applications like hospital, data and computer
center, cellular or landline communication where continuity of
service is essential .The recent times of extensive power cuts,
have made UPS an integral part of our life in the modern
world which is exclusively technology driven, loss of data
cannot be afforded UPS has come as a life saver in this issue.
In industries three phase diode rectifier is used in UPS system
in order to rectify three phase AC supply. These rectifiers are
non linear loads which draw the current that is not necessarily
sinusoidal. The proposed system not only reduces the total
harmonic distortion but also uses photovoltaic (PV) to charge
the battery during day time. Power quality is improved when
harmonics at the AC mains is considerably reduced and also
ISSN: 2231-5381
the output voltage is regulated even under the fluctuations of
source voltage.
II.
PV BASED UPS
Adequate availability of inexpensive energy is the
most important need today. Economic development dependent
on the availability of energy, but present situation problem is
energy sources are fast depleting and this fast depleting energy
resources have put the world in a grip of energy crisis so this is
the time to take steps to conserve the non-renewable sources
energy and also find the alternative sources of energy or
another way is to tap or harness the solar energy. The
photovoltaic solar cells are increasingly used to supply power
to houses for increse of the knowledge of the solar renewable
technology with the ongoing legal benefits. Achieving
continuity of service for some predefined loads and providing
the ability to define, among them, a priority list for the
continuous supply of energy in order to ensure a longer and
more effective period of operation according to the estimated
charge of the battery pack. It will Increase the energy saving
through the planned use of the UPS system for specifically
selected power loads in stand-alone operation. PV based UPS
allows: (i) The minimization of the consequences of blackouts
through the intervention of a sine wave inverter connected
between the battery and load outgoing default.(ii) the
possibility of an automatic switching between grid network
and the standalone photovoltaic UPS system.(iii) The
possibility to supply selected electrical load by a
programmable action plan by the standalone photovoltaic UPS
resulting in energy saving and discharge through the
standalone photovoltaic cycles with battery pack to ensure the
best use.(iv) the optimization of the charge profile of the
battery pack which can be obtained with the help of combined
management of grid network supply with regulation of the
current charge by the DC-DC converter connected between the
photovoltaic modules and the accumulators.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 1 – Jul 2014
III. OPERATION OF PROPOSED SYSTEM
IV. CHARACTERISTICS OF PV CELLS
a.
Characteristics of PV cell at Constant
Temperature
160
140
T c=25
d e gre e
ce ntigra de
OUTPUT POWER
120
1000 W /m 2
800 W /m 2
600 W /m 2
400 W /m 2
200 W /m 2
100
80
60
40
20
0
0
10
Fig.2.
20
30
40
50
OUTPUT V OLTAGE
60
70
80
Power and voltage waveform at constant temperature
for PV cells
3
T C= 25 DEG CENT IGRADE
1000 W /m 2
2.5
800 W /m 2
2
The output of the battery is given to the single phase
inverter through opto coupler. The switches (Q1, Q2, Q3, Q4)
of the inverter are triggered with the help of control circuit i.e.
processor. The AC output from the inverter is stepped upto 12
V by 12 V step up transformer and then given to load. In order
to measure the total harmonic distortion at the input side of the
proposed rectifier, the 10 A current transformer and 5 V
potential transformer is connected to the input side. The output
of the transformers is connected to analog to digital converter
pin of the processor. Accordingly THD is calculated by using
the formula which is fed to the processor. The following next
section we are going to see about variation of voltage and
current waveform at different temperatures and irradiance. The
switches used in the inverter were IGBT switches because it
gives low switching losses ,low snubber circuit requirement
and gate triggering losses.
ISSN: 2231-5381
600 W /m 2
1.5
400 W /m 2
1
200 W /m 2
0.5
0
0
10
Fig.3.
20
30
40
50
OUTP UT V O LTA GE
60
70
80
Power and Voltage Waveform at Constant
Irradiance for PV cell
b. Characteristics of PV cell at constant irradiance
180
160
IR RA DIAN CE = 1000 W /m 2
25 D EG. CEN TIGR AD E
140
0 D EG C ENT IG RA DE
120
POWER OUTPUT
Block diagram of the proposed system is shown
below in the Figure 1. The 440V three phase AC supply is
stepped down to 12V through a 12V step down transformer. It
is converted into DC using the proposed rectifier. During night
time and cloudy days when the supply is present, the battery is
charged by the supply from the rectifier. During day time
when the light intensity is high, the battery is charged with the
help of Photovoltaic panel. When both the sources are absent
the battery will act as a source. By using the change over
relay, switching from main supply to photovoltaic panel or
vice versa can be achieved for charging the battery.
OUTPUT CURRENT
Fig.1. Block Diagram of the Proposed System
100
50 D EG C ENT IG RA DE
80
75 D EG C ENT IG RA DE
60
40
20
0
0
10
Fig.4.
20
30
40
50
O UTP UT VO LTAG E
60
70
80
90
Power and Voltage waveforms at Constant
Irradiance for PV cell
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 1 – Jul 2014
3
0 ce ntig ra de
2.5
25 ce n ti gr a d e
OUTPUT CURRENT
2
50 c e n tig r a d e
1000 W /m 2
1.5
75 ce n ti gr a d e
1
0.5
0
0
10
20
30
40
50
O U TP U T V O LTA G E
60
70
80
90
Fig.5. Current and voltage waveform at constant irradiance
For PV Cells
From the above characteristics (Fig.2, Fig.3, Fig.4,
Fig.5) curves the power generation continuously varies along
with two main factors, which are known as cell temperature
and irradiance. In this work MPPT technique is used for
finding the maximum output at various instant of time.
V. HARDWARE IMPLEMENTATION
Fig 7. Overall Hardware Setup
The modified rectifier is typically the association of three
circuits: a classical diode bridge that is responsible for the
energy rectifying operation, a modulation circuit that has the
major role in the current shaping process, and a distribution
circuit which has the property of injecting a zero sequence
current into the source phases, avoiding thus the current be
either passive or active. By the make use of passive
modulation circuit yields a high power factor at the expense of
a low efficiency shows a different topology of three phase
rectifier with active current injection proposed. This circuit
consists of an inductor that operates at high frequency. This
proposed converter offers high efficiency, high power factor
and also total harmonic distortion will be reduced.
Table 1. Specifications of the Proposed Circuit
S.NO
COMPONENTS
SPECIFICATIONS
Potential Transformer
440 to ( 12-0-12)V, 230 to 5V, (012)V
2
Current Transformer
(0-10)A
3
Diode
IN4001, IN5408
4
Inductor
600mH
1.
Fig 6. Overall Hardware Circuit
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 1 – Jul 2014
5
Capacitor
1000µF, 2200µF
6
Lead Acid Battery
12V
7
PV panel
3W
8
MOSFET
IRF840
9
Resistor
33KΩ, 100Ω
10
AtMega 32
-
11
Opto coupler
MOC3021
12
LCD
-
13
CFL
5W
Fig 10. Voltage, Current and Frequency Values of Modified
Rectifier
VI. RESULT ANALYSIS AND DISCUSSION
Fig 11. Voltage Waveform of Modified Rectifier
Fig 8. Voltage, Current and Frequency Values of Three Phase Diode
Rectifier
Figure 12. Harmonic Analysis of Modified Rectifier
The output results shown in the fig 8, fig 9, fig 10, fig 11, fig
12 are measured using power quality analyzer (FLUKE 435
Meter). When three phase supply is given to the modified
rectifier, the total harmonic distortion obtained in it is 4.6% of
fundamental frequency.
Fig 9. Voltage Waveform of Three Phase Diode Rectifier
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International Journal of Engineering Trends and Technology (IJETT) – Volume 13 Number 1 – Jul 2014
VII. TESTING USING DIGITAL STORAGE OSCILLOSCOPE
The proposed photovoltaic based UPS system is tested
for instantaneous voltage and the results are obtained by
Digital Storage Oscilloscope. The tested results obtained are
following as
Power Quality Analyzer. The proposed photovoltaic based
UPS system has also been tested using Digital Storage
Oscilloscope. Thus, the harmonic analysis has been made and
compared between the conventional three phase diode rectifier
and proposed modified rectifier and harmonics has been
reduced upto 5%.
VIII. CONCLUSION
Improved power quality UPS system has been
designed and implemented. Harmonic analysis was performed
at input side of the three phase diode rectifier and Modified
rectifier using power quality analyzer. The result shows that,
Total Harmonic Distortion in three phase diode rectifier was
reduced to 4.6% by using Modified rectifier. The proposed
system ensures reduction in harmonics at the input side and
offers continuous power supply with the help of photovoltaic
panel. The recent times of extensive power cuts, have made
UPS an integral part of our life in the modern world which is
exclusively technology driven, loss of data cannot be afforded
UPS has come as a life saver in this issue. More overdue to the
problems persisting in the quality of power, UPS is needed to
increase the life time of the appliances.
Fig 13.Output Voltage Waveform of Inverter Unit
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Fig14. Waveform of the Triggering Pulse
Fig15. Output voltage Waveform of the Solar Panel
The conventional three phase diode rectifier and proposed
modified rectifier system has been tested using FLUKE 435
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