journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals, yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal

1. International Journal of Engineering Research and Development
e-ISSN: 2278-067X, p-ISSN: 2278-800X, www.ijerd.com
Volume 9, Issue 4 (December 2013), PP. 25-29
Development of a MPPT-based Single Phase PWM Solar
String Inverter for AC output for off grid applications
Manisha R. Kandgaonkar1, N.N.Shinde2, P.S.Patil3
1
Department of Energy Technology, Shivaji University, Kolhapur,.Maharashtra, India.
Department of Energy Technology, Shivaji University, Kolhapur, Maharashtra, India.
2,3
Abstract: A microcontroller based technique of generating a sine wave from the solar panel output is designed
and implemented in this paper using a two-stage topology for a solar string inverter. This paper presents the
development of a maximum power point tracking (MPPT) and control circuit for a single phase inverter using a
pulse width modulation (PWM) IC. The attractiveness of this configuration is the elimination of a complex
circuitry to generate oscillation pulses for transistor switches. The controller IC TL494 is able to generate the
necessary waveforms to control the frequency of inverter through proper use of switching pulse. The DC to AC
inversion is successfully achieved alongside the switching signals; the circuit produced inverter output of
frequency nearly 50 Hz. The main objective of the proposed technique is to design a low cost, low harmonics
voltage source inverter essentially focused upon low power electronic appliances using variable solar power as
inputs.
Keywords: AC solar panels, DC-AC converters, MPPT charge controllers, PWM inverters, solar string
inverters.
I.
INTRODUCTION
a) Maximum Power Point Tracking (MPPT)
When a solar PV module is used in a system, its operating point is decided by the load to which it is
connected. Also, since solar radiation falling on a PV module varies throughout the day, the operating point of
the module also changes throughout the day. Ideally under all operating conditions, one would like to transfer
maximum power from a PV module to the load. In order to ensure the operation of PV modules for maximum
power transfer, a special method called Maximum Power Point Tracking (MPPT) is employed in PV systems
where, electronic circuitry is used to ensure that maximum amount of generated power is transferred to the load.
The maximum power point tracking mechanism makes use of an algorithm and an electronic circuitry. The
mechanism is based on the principle of impedance matching between load and PV module which is necessary
for maximum power transfer. This impedance matching is done by using a DC to DC converter by changing the
duty cycle (d) of the switch.
Fig.1 Block diagram of the MPPT algorithm along with the circuit.
25

2. Development of a MPPT-based Single Phase PWM Solar String Inverter…
Fig.2 (a) Flow chart of hill climbing method and (b) schematic diagram demonstrating how the operating point
moves towards the maximum power point(MPP)
The power from the solar module is calculated by measuring the voltage and the current. This power is
an input to the algorithm, which then adjusts the duty cycle of the switch, resulting in the adjustment of reflected
load impedance according to the power output of PV module. For instance, the relation between the input
voltage (Vi) and the output voltage (Vo) and impedance of load (RL) reflected at the input side (Ri) of a buck type
DC to DC converter can be given as:
Vo = Vi x d
𝑅𝐿
Ri =
𝑑2
Where d is the duty cycle. By adjusting the duty cycle, Ri can be varied which should be same as the
impedance of solar PV module (RPV) in a given operating condition for maximum power transfer [15,16].
b) Inverter: A power inverter, is an electrical power converter that changes direct current (DC) to
alternating current (AC); the converted AC can be at any required voltage and frequency with the use of
appropriate transformers, switching and control circuits. In an inverter, dc power from the PV array is
inverted to ac power via a set of solid state switches—MOSFETs or IGBTs—that essentially flip the dc
power back and forth, creating ac power. Fig.3 shows basic H-bridge operation in a single-phase inverter.
This solid state switching process is known as inversion [6].
Fig.3 An H-bridge circuit performs the basic conversion from dc to ac power.
The inverter will receive input of 12 V dc from the controller circuit and it will convert this to 230 V
ac. The inverter circuit designed as an H bridge inverter with an IC which incorporates PWM technique and
converts, with the help of a 12V/230 V transformer, the obtained 12V dc from MPPT circuit, to the output 230V
ac for use.
26

3. Development of a MPPT-based Single Phase PWM Solar String Inverter…
Fig. 4 Full bridge single phase inverter
The full bridge (single phase) inverter is built from two half bridges connected to form what is known
as a full bridge or H-bridge inverter. Its arrangement is shown in figure 4. It comprises of DC voltage
source, 4 power switches (usually bipolar junction transistors-BJTs, metal-oxide semiconductor field effect
transistors-MOSFETs, insulated gate bipolar transistors- IGBTs or gate turned on transistors-GTOs) and the
load.
To create a square-wave output voltage, the device pairs Q1Q3 and Q2Q4 are switched
alternatively at a delay of 180 degrees. When Q1 and Q3 are ON with Q2Q4 OFF for a duration t, also
with Q2Q4 ON and Q1Q3 OFF at t. Assuming there is a sinusoidal load current, the load will absorb
power when Q1Q3 and Q2Q4 pairs are conducting alternatively whereas feed backing occurs when the
diode pairs are conducting[22].
II.
APPROACH AND METHOD
The block diagram for the circuit is as shown.
Fig.5 Block diagram for a solar power system
MPPT Circuit: The next step is to design and test the MPPT circuit. The voltage and the current
output from the panel array have to be measured and the maximum power has to be supplied to the battery.
+5V
BAT_V
U4
+5V
LCD1 LCD 16x2
2
R12
3
C4
100uF/25V
C22
0.1uF
R1
100K
R14
C5
0.1uF
LCD_RS
BATV
1k
R13
1K
22K
LCD_EN
C9
0.1uF
LCD_D4
LCD_D5
LCD_D6
LCD_D7
+5V
C10
3
C13
0.1uF 2
R25
+5V
0.1uF
8
R24 1K
+
R42 33E
B_C
1
-
1
2
3
4
5
4
R26
+5V
J10
CON1
J12
CON1
J13
CON1
J14
CON1
RESET
+5V
PGD
PGC
PROG
J39
CON2
100K
R3
10K
D1
1N4148
1
2
R4
Solar_V
1K
R9
RESET
SW1
SW PUSHBUTTON
GND
Vcc
CNT
RS
RW
EN
D0
D1
D2
D3
D4
D5
D6
D7
A
C
J11
U3A
LM358
1K
+5V
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
VOUT
C2
0.1uF
1
VIN
LM7805/TO
C1
100uF/25V
1
1
10A FUSE
1
2
BAT
1
BAT_V
F1
GND
BAT+
J4
100K
R11
C25
0.1uF
Solar_ADC
R10
1K
Y1
8MHz
XTAL2
22K
XTAL1
C23
33PF
C8
C24
33PF
0.1uF
LOAD+
R43
100K
R45
BAT_V
Load_ADC
U7
Q2
D3
IRF9530
R44
1K
1N5822
D4
RESET
BATV
B_C
Solar_ADC
C30
22K
D6
0.1uF
1N5408
Solar_V
1N5822
J2
+5V
2
1
SOLAR
R19
C12
D5 1000uF/25V
47K
R20
10E
Q4
R21
BC547
1N5408
R22
R23
XTAL1
XTAL2
PIN8
C_CNTRL
LOAD_CNTRL
R8
4K7
C_CNTRL
1K
3K3
J6
BAT_V
LOAD+
IRF9530
R31
PGD
PGC
LCD_RS
LCD_EN
LCD_D4
LCD_D5
LCD_D6
LCD_D7
+5V
J9
RX
TX
C17
0.1uF
1
2
3
4
+5V
RX
TX
CON4
R28
1K
CON2
J5
2
1
LED
1
2
J3
1N4148
47K
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
1K
D7
R15
MCLR/VPP/RE3
RB7/KB13/PGD
RA0/ANO
RB6/KB12/PGC
RA1/AN1
RB5/KB11/PGM
RA2/AN2/VREF-/CVREF
RB4/KB10/AN11
RA3/AN3/VREF+
RB3/AN9/CCP2
RA4/TOCKI/C1OUT
RB2/INT2/AN8
RA5/AN4SS/HLVDIN/C2OUT
RB1/INT1/AN10
RE0/RD/AN5
RB0/INT0/FLT0/AN12
RE1/WR/AN6
VDD
RE2/CS/AN7
VSS
VDD
RD7/PSP7/P1D
VSS
RD6/PSP6/P16
OSC1/CLKI/RA7
RD5/PSP5/P1B
OSC2/CLKO/RA6
RD4/PSP4
RCO/T1OSO/T13CKI
RC7/RX/DT
RC1/T1OSI/CCP2
RC6/TX/CK
RC2/CCP1/P1A
RC5/SDO
RC3/SCK/SCL
RC4/SDI/SDA
RD0/PSP0
RD3/PSP3
RD1/PSP1
RD2/PSP2
1
2
Q1
0.1E/1W
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
C7
1uF
CON2
R16
LOAD
R30
PIN11
PIN11
1
2
Q3
R17
BC547
R32
1K
J7
10E
1K
Load_CNTRL
CON2
1K
R18
3K3
Fig.6 Schematic diagram for MPPT circuit
Fig.7 MPPT circuit.
Inverter Circuit: Next is the circuit for the inverter part. For the inverter the IC TL494 is used. The
four MOSFETs IR740 are arranged in a bridge network and will be switched on two at a time alternately by the
two switching MOSFETs IRF50N06 so that two will conduct at a time. The timing is set by using RC network
and IC TL494 controls the waveform. The transformer will convert the output to 230 V a.c.
27

4. Development of a MPPT-based Single Phase PWM Solar String Inverter…
Fig.8 Schematic diagram for inverter circuit
III.
Fig.9 Inverter circuit.
TESTING
The MPPT and Inverter circuit:
The circuit of the MPPT is first tested with the help of a D.C. power supply. It is checked whether the
voltage is passed to the battery to charge it. Finding it to work as required, it is then tested with solar panels. The
regulator is also checked by varying the d.c. voltage. It shows the expected readings on the display.
Fig.10 a. Waveform of inverter output.
b .Observation of Output on Hyper terminal.
The efficiency of the MPPT circuit is tested and found to be around 80%. It increases with the increase
in intensity. The efficiency of the inverter is tested and found to be as much as 90%. It increases with increase in
load.
IV.
RESULTS AND ANALYSIS
The time required to charge the battery is tested. This is done first using an SMPS and then with the
two solar panels. The efficiencies of the MPPT and inverter circuits are found to be around 90% and 79.9%
respectively.
V.
CONCLUSION
The experiments and observations shows that MPPT based charge controllers are best suitable for solar
systems as they track the maximum power in case of power fluctuations at the input side due to environmental
condition variation. Hence it is recommended to use the MPPT based charge controllers. Use of microcontroller
28

5. Development of a MPPT-based Single Phase PWM Solar String Inverter…
based systems provide huge computational capability and reduction in the hardware. Microcontroller is a mini
computer and brings much more accuracy in the control of MOSFET and IGBT.
It is recommended to use a single phase PWM inverter with H bridge using IRF740B N-channel
MOSFETs and the TL494 power supply controller. The TL494 incorporates all the functions required in the
construction of a pulse-width-modulation (PWM) control circuit on a single chip. Designed primarily for powersupply control, this device offers the flexibility to tailor the power-supply control circuitry to a specific
application. Several outstanding features of the developed Sinusoidal PWM inverter are: fewer harmonic, low
cost, simple and compact.
REFERENCES
[1].
[2].
[3].
[4].
[5].
[6].
[7].
[8].
[9].
[10].
[11].
[12].
[13].
[14].
[15].
[16].
[17].
[18].
[19].
[20].
[21].
[22].
Ministry of New & Renewable Energy, Government of India, Solar Lighting Systems Module,
Trainers Textbook.
Dr. B.D.Sharma, Performance Of Solar Power Plants In India- Submitted To Central Electricity
Regulatory Commission New Delhi-February, 2011.
Deepak Kumar, Solar India and JNNSM, 1st November 2010.
International Finance Corporation, World Bank Group, ‘Utility Scale Solar Power Plants’, New Delhi
(India), February 2012.
Fritz Schimpf, Lars E. Norum- Grid connected Converters for Photovoltaic, State of the Art, Ideas for
Improvement of Transformerless Inverters- Norwegian University of Science and Technology, NTNU
Department of Electrical Power Engineering.
James Worden and Michael Zuercher-Martinson, How Inverters Work, SOLARPRO, April/May, 2009.
AN2794 Application note Cd00201961.pdf
http://en.wikipedia.org/wiki/Wikipedia: CleanupTaskforce/String Inverter.
http://www.greenworldinvester.com / /topics/solar-renewable-energy-greeninvest/solar inverters/ (6th
July 2011).
Avinash H.N. and Palak Timbadiya, Global Energy National Institute,
Overview of sustainable
renewable energy potential of India, 2010.
Dr. B.R. Gupta, Generation of Electrical Energy, S. Chand & Co. Ltd. New Delhi, Reprint 2010.
Prof H.P. Garg and Dr. J Prakash, Solar Energy-Fundamentals and applications, Tata McGraw-Hill
Publishing Company Limited, New Delhi, Eleventh Reprint, 2009.
Prof. Dr. Andrea Vezzini, BFH Bern, Switzerland, Institute for Energy and Mobility Research.
Angelina Tomova, TU Sofia, Grid Connected Pv Inverter Topologies An Overview, 07 April 2011,
Glasgow, UK
Chetan Singh Solanki, Solar Photo voltaics, PHI Learning Private Limited, July 2011.
Sachin Jain and Vivek Agarwal, A Single-Stage Grid Connected Inverter Topology Solar PV
Systems With Maximum Power Point Tracking, IEEE Transactions On Power Electronics, Vol. 22,
No. 5, September 2007.
Søren Bækhøj Kjær, Design and Control of an Inverter for Photovoltaic Applications, Aalborg
University, DENMARK Institute of Energy Technology, January 2005.
A. A. Mamun, 1, M. F. Elahi M. Quamruzzaman, M. U. Tomal Design and Implementation of Single
Phase Inverter International Journal of Science and Research (IJSR), India Online ISSN: 2319-7064
Muhammad H. Rashid, Power Electronics, Circuits Devices and Applications, Third Edition, Published
by Dorling Kindersley (India) Pvt. Ltd., licensees of Pearson Education in South Asia.
Muhammad Ali Mazidi, Janice Gillispie Mazidi, Rolin D. McKinlay, The 8051 Microcontroller and
Embedded Systems, Second Edition, Published by Dorling Kindersley (India) Pvt. Ltd., licensees of
Pearson Education in South Asia.
Dr. Amiya Kumar Rath, Alok Kumar Jagadev and Santosh Kumar Swain, Computer Fundamentals and
C programming, Scitech Publications, (India) Pvt. Ltd.
Omokere, E. S and Nwokoye, Evaluating the Performance of a Single Phase PWM Inverter Using
3525A
PWM IC, International Journal of Engineering Research & Technology (IJERT), Vol. 1
Issue 4, June – 2012
Author profile: Manisha R. Kandgaonkar
29