International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.5, pp. 1898-1904
ISSN 2078-2365
http://www.ieejournal.com/
Grid Connected Single-Phase
Bidirectional Inverter with MPPT
Tracker
1
M.Srikanth1, S. Tarakalyani2 and Poonam Upadhyay 3
Assistant Professor in EEE Department, KL University, Vaddeswaram, Guntur, India.
2
Professor & Head in EEE Department, JNTUH, Hyderabad.
3
Professor in EEE Department, VNRVJIET, Bachupally, Hyderabad
sikanth_ee250@kluniversity.in, tarasunder98@yahoo.co.in, poonampu@yahoo.com,

Abstract— This study is focused on Grid Connected SinglePhase Bidirectional Inverter with Boost Maximum Power Point
Tracker (MPPT). By using PV system and a DC-DC boost
converter with MPPT generate power that power utilized by
the dc applications .Whenever surplus power is available that
power sell to grid, When sun intensity is in bad condition we
can buy the power from a grid, a bidirectional inverter is
required to control the power flow between dc bus and ac grid.
It also proposes (MPPT) algorithm is used to track the
maximum power of PV cell. In this grid connected inverter,
inverter can be operated with pulse switching and unipolar
PWM switching and a suitable LC filters. Simulation results
show that the model can effectively realize the actual physical
characteristics of a Grid Connected Single-Phase Bidirectional
Inverter with Boost Maximum Power Point Tracker (MPPT).
Index Terms— Photovoltaic system, MPPT, boost converter,
bidirectional inverter, grid-connection and unipolar PWM
switching.
I. INTRODUCTION
On account of continually expanding energy requirement,
grid linked Photovoltaic or PV systems tend to be becoming a
lot more well-known, and several nations around the world
possess granted, motivated, and in many cases financed
distributed-power-generation systems. The technology
nevertheless offers faults for instance large original
installation expense in addition to lower energy-conversion
performance hence requiring steady upgrades regarding both
equally PV cell in addition to electrical power converter
technologies. Various types of environmentally friendly
energy, for example photovoltaic or PV, the wind, tidal, as
well as geothermal energy, possess captivated a lot of
awareness within the last few decade [1]–[3]. Amongst these
kind of natural means, the SUN energy is often a major as well
as suitable environmentally friendly energy regarding
low-voltage dc-distribution techniques, owing to the is worth
connected with thoroughly clean, quiet, air pollution free of
charge, as well as abundant. In the Grid Connected
Single-Phase Bidirectional Inverter is shown in Fig. 1, in
which one PV array with one maximum power point tracker
(MPPT) is implemented. However, the i–v characteristics of
the PV arrays are nonlinear, and they require MPPTs to draw
the maximum power from PV array. Moreover, the
bidirectional inverter has to fulfil grid connection (GC) (sell
power) and rectification (buy power) with power-factor
Correction (PFC) to control the power flow between dc bus
and ac grid.
PV array
Boost with
MPPT
Technique
Bi-directional
Inverter
Filter
Grid
Fig: 1 Configuration of a Grid connected PV system.
In this paper, operational basic principle along with control
laws and regulations of the PV system will be 1st identified,
along with the MPPT control formula, Boost converter
manner connected with functioning, bidirectional inverter
along with filtering design and style are usually next tackled.
Simulation benefits from the single-phase bidirectional
inverter using enhance MPPT will be displayed to help
examine the particular investigation along with conversation.
II. OPERATIONAL PRINCIPLE AND CONTROL
LAWS FOR THE PV SYSTEM
A simple solar cell consist of solid state p-n junction
fabricated from a semiconductor material (usually silicon).In
dark, the IV characteristic of a solar cell has an exponential
characteristic similar to that of a diode[4]. However when the
1898
Srikanth et. al.,
Grid Connected Single-Phase Bidirectional Inverter with MPPT Tracker
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.5, pp. 1898-1904
ISSN 2078-2365
http://www.ieejournal.com/
solar energy (photons) hits on the solar cell, energy greater
than the band gap energy of the semiconductor, and release
electrons from the atoms in the semiconductor material,
creating electron-hole pairs [5].The charged carrier are
moved apart under the influence of internal electric fields of
the p-n junction and hence a current proportional to the
incident photon radiation is developed. This phenomenon is
called photovoltaic effect, first observed by A.E Becquerel in
1839[6]. The easiest comparable enterprise of a photovoltaic
cell is often a current source within parallel with a diode. The
output of the current source will be directly proportional for
the solar panel technology (photons) in which strikes about
the photo voltaic cell (photocurrent Iph). In the course of
night, the particular photovoltaic mobile seriously isn't a
dynamic product; that works as a diode, i.e. a p-n junction. It
produces neither a current nor a voltage. However, if it is
allowed to connect to an external source (large voltage) it
generates a current Id, called diode (D) current or dark
current. The diode determines the IV characteristics of the
cell [11].
Fig: 4 Current-Voltage (IV) curve for a PV cell
A general I-V characteristic of the solar cell for a given
ambient insolation ‘G’ and fixed cell temperature ‘T’ is shown
in Fig 4.For a certain resistive load, the load characteristic is a
straight line with slope . Power delivered to the load depends
on the value of the resistance only. In some cases if the R Load
is very small; the PV cell operates in the M-N region of the IV
curve (Fig4), the PV cell act as a constant current source,
which is almost equivalent to a short circuit current. However,
if the R load is large, the PV cell operates in the P-S region of
the IV curve, the PV cell act as a constant voltage source
almost equivalent to the open circuit voltage [8].
III. MAXIMUM POWER POINT TRACKING (MPPT)
Fig: 2 Equivalent circuit of a solar cell
MPPT algorithms are necessary throughout PV programs
considering that the MPP of a solar power varies with the
insulation and heat, so the use of MPPT algorithms is required
in order to obtain the maximum power from a solar array.
Having Perturb and observe method discover the Maximum
Power Point for any insulation corresponding flowchart
offeredunder.
The circuit diagram of a PV cell is shown above in Fig2.The
PV cell produces output current I is given by
Where Iph is the Photon current, Id is the diode current and Ish
is the shunt current. Fig 3 shows the characteristic of IV curve.
The net current I is obtained from the photo current Iph and
the diode current Id [7].
Fig: 3 i-v characteristic of solar cell
Fig 5: Flowchart of Perturb and observe method
1899
Srikanth et. al.,
Grid Connected Single-Phase Bidirectional Inverter with MPPT Tracker
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.5, pp. 1898-1904
ISSN 2078-2365
http://www.ieejournal.com/
IV. THE BOOST CONVERTER
The boost converter is shown in Fig. 6. In boost converter
the output voltage is higher than the input voltage hence the
name “boost” converter. When the Switch is closed inductor
stores energy in the form of magnetic field like VL =VS during
DT period. When the Switch is open the voltage across the
inductor is VL =VS-VO .during T period shown in fig. 7
Expressing capacitance in terms of output voltage ripple
yields
Boost converter design completed from the above three
Equations 4,5,& 6 .
V. BIDIRECTIONAL INVERTER
The proposed bidirectional inverter is a full-bridge
configuration, as shown in Fig. 8,
Fig: 6 The Boost converter
Fig: 8 Bidirectional inverter with LC filter.
Fig: 7 Voltage across the inductor during ON and OFF time
The average inductor voltage must be zero for periodic
operation. Expressing the average inductor voltage over one
switching period.
From this
A single-phase full-bridge bidirectional inverter is modeled
in this study. The power electronic switch used is IGBT as it
can handle very large power, which is suitable for this solar
system. In the developed grid connected (GC) inverter model
unipolar switching scheme has two switching states as
outlined in Table 1. The PWM inverter output waveform is
then filtered to produce a sinusoidal AC waveform.
Table 1. Switching States of 1-Ø Full-Bridge Inverter
The minimum inductance and switching frequency for
continuous current in the boost converter is therefore
From a design perspective, it is useful to express L in terms of
a desired ∆iL
Switching
State
1
2
ON switch
OFF Switch
O/p Voltage
SA+,SBSA-,SB+
SA-,SB+
SA+,SB-
+Vdc
-Vdc
The inverter switching is controlled by the sinusoidal
PWM (SPWM) gating signals which drive the gate of the
IGBTs. In order to generate the gating signal (Vg) for the
IGBTs by implementing the unipolar polar switching scheme,
there are two inputs for the comparator which are a sinusoidal
modulating signal (Vm) and a triangular carrier signal (Vcr).
1900
Srikanth et. al.,
Grid Connected Single-Phase Bidirectional Inverter with MPPT Tracker
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.5, pp. 1898-1904
ISSN 2078-2365
http://www.ieejournal.com/
When Vm has higher magnitude than Vcr, the comparator
output is high (ON), otherwise it is low (OFF).
The output voltage of the inverter is controlled by the
amplitude, phase and frequency of Vm. The amplitude of Vm
(Am) controls the modulation index, “m” as in Eq. (7), thus
controls the amplitude of inverter output voltage.
m = 𝐴𝑚 /𝐴𝑐𝑟
(Vgrid) to enable the inverter current (Iinv) to be supplied to the
grid. Fig. 9 shows the Vgrid, Vinv, Iinv and voltage across
decoupling inductor (VXL) in the equivalent circuit at the AC
side of the inverter. The decoupling inductor, XL is needed to
control the power flow from the inverter to the grid.
(7)
Where,
m = modulation index (decimal)
Am = amplitude of modulating signal (V)
Acr = amplitude of carrier signal (V)
In this developed model, the modulating signal frequency
(fm) is set to 50 Hz to match the frequency of the utility grid,
while switching frequency (fs) is set to 20 kHz. In reality,
switching frequency of 20 kHz or above is commonly used to
operate outside the audible noise. Generally, the level of
audible noise decreases with the increase of switching
frequency [9]. However in simulation, a very high switching
frequency (20 kHz or above) will require a very small value of
simulation step size (μs or less) for accurate switching
simulation studies which will result in very long simulation
time [10]. The simulation step size used in this simulation
studies is 1 μs.
Fig: 9 Inverter connected to Grid
In order to achieve the unity power factor, the waveform of
Iinv must be in phase with the waveform of Vgrid as illustrated
in Fig. 10. In the phasor diagram, it is represented as in Fig.
11. As in Fig. 11, Vinv has to lead Vgrid with the angle α in
order to get the Iinv in phase with the Vgrid. This is achieved
by adjusting the phase angle of the modulating signal (Vm).
VI. VI LOW-PASS LC FILTER DESIGN
The SPWM waveform of the inverter output voltage
contains harmonics. According to the IEC 61727 standard
(PV System, characteristics of the utility interface), the
maximum allowed THD for the output current is 5 %.
Therefore an LC filter is a crucial part in designing the grid
inverter. The low-pass LC filter is designed accordingly so
that the cut-off frequency, fc is higher than the grid frequency
and lower than the inverter switching frequency, based on Eq.
(8).
Fig:10 Inverter & Grid Waveforms
Where,
fc = cut-off frequency (Hz)
Lf = filter inductor (H)
Cf = filter capacitor (F)
Fig: 11 Vector Diagram of Grid fed to Inverter
A. Grid Synchronization
Grid inverter needs a pure sinusoidal reference voltage to
ensure that the sinusoidal output of the inverter is
synchronized to the grid frequency. The voltage magnitude of
the inverter output (Vinv) needs to exceed the grid voltage,
The phase angle of modulating signal (Vm) is varied with
solar irradiance and temperature level in order to get the I inv
synchronized with the Vgrid. The appropriate phase angle for a
certain range of temperature and irradiance level has to be set.
1901
Srikanth et. al.,
Grid Connected Single-Phase Bidirectional Inverter with MPPT Tracker
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.5, pp. 1898-1904
ISSN 2078-2365
http://www.ieejournal.com/
VII. MATLAB SIMULATION & RESULTS
Fig: 12 Simulation Circuit for Grid connected inverter with pulse switching
Fig: 13 Simulation Circuit for Grid connected inverter with SPWM switching
1902
Srikanth et. al.,
Grid Connected Single-Phase Bidirectional Inverter with MPPT Tracker
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.5, pp. 1898-1904
ISSN 2078-2365
http://www.ieejournal.com/
output voltage
The
simulation
is
implemented
using
MATLAB/SIMULINK that is simplified diagram for
simulation shown in fig 12 &13. In Grid connected Inverter,
Grid can be operated at 230V rms value based on that
calculated
inverter
input
voltage
by
using
230*1.414*1.1=360V DC, but for loading
reasons
considering DC Bus voltage 400V then chosen PV Cell
output voltage is 132V and duty cycle is 0.675. Based on this
data simulation of grid connected inverter with pulse
generation switching shown in fig 12 gives the output voltage
is 230V. Considering another grid connected inverter with
SPWM switching shown in fig 13 gives the output voltage is
230V with reduced THD. By the simulation obtain the
DC-DC converter output voltage is 400V shown in fig 14 that
converter output voltage is connected to inverter with pulse
generation switching gives 230V shown in fig 15 with THD is
6.10% shown in fig 17.The DC bus voltage connected to
inverter with SPWM switching gives 230V AC shown in fig
18 with reduced THD 1.27% is shown in fig 20.
400
300
Voltage (V)
200
100
0
-100
-200
-300
-400
4.5
4.55
4.6
4.65
4.7
4.75
4.8
4.85
4.9
4.95
5
Time (sec)
Fig:16 Output Voltage of Inverter with Puse switching(4.5-5 sec)
Selected signal: 250 cycles. FFT window (in red): 20 cycles
200
0
-200
DC Bus Voltage
0
500
0.5
1
Voltage (v)
400
1.5
2
2.5
Time (s)
3
3.5
4
4.5
5
800
900
1000
Fundamental (50Hz) = 334.9 , THD= 6.10%
6
300
Mag (% of Fundamental)
5
200
100
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
4
3
2
5
Time (sec)
1
0
0
100
200
300
400
500
600
Frequency (Hz)
Fig: 14 DC Bus Output Voltage
700
Output Voltage
400
Fig:17 THD of Output Voltage of Inverter with Puse switching
300
200
300
0
200
-100
Voltage (v)
Voltage (V)
SPWM Output Voltage
400
100
-200
-300
100
0
-100
-400
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
-200
Time (sec)
-300
-400
Fig:15 Output Voltage of Inverter with Puse switching(0-5 sec)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Time (sec)
Fig:18:OutputVoltage of Inverter with SPWM switching
(0-5sec)
1903
Srikanth et. al.,
Grid Connected Single-Phase Bidirectional Inverter with MPPT Tracker
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.5, pp. 1898-1904
ISSN 2078-2365
http://www.ieejournal.com/
[2] L. N. Khanh, J.-J. Seo, T.-S. Kim, and D.-J. Won, “Power-management
strategies for a grid-connected PV-FC hybrid system,” IEEE Trans. Power
Deliv., vol. 25, no. 3, pp. 1874–1882, Jul. 2010.
SPWM Output Voltage
400
300
Voltage (v)
200
100
[3] Y. K. Tan and S. K. Panda, “Optimized wind energy harvesting system
using resistance emulator and active rectifier for wireless sensor nodes,”
IEEE Trans. Power Electron., vol. 26, no. 1, pp. 38–50, Jan. 2011.
0
-100
-200
-300
-400
4.5
4.55
4.6
4.65
4.7
4.75
4.8
4.85
4.9
4.95
5
Time (sec)
Fig:19:OutputVoltage of Inverter with SPWM switching (4.5-5sec)
Selected signal: 250 cycles. FFT window (in red): 20 cycles
[5] Lorenzo, E. (1994).Solar Electricity Engineering of Photovoltaic
Systems. Artes Graficas Gala, S.L., Spain.
[6] https://en.wikipedia.org/wiki/A._E._Becquerel
200
[7] Marcelo Gradella Villalva, Jonas Rafael Gazoli, and Ernesto Ruppert
Filho. “Comprehensive Approach to Modeling and Simulation of
Photovoltaic Arrays” -IEEE Transactions on power electronics, vol. 24, no.
5, May 2009 .
0
-200
0
0.5
1
1.5
2
2.5
Time (s)
3
3.5
4
4.5
[8] Francisco M. González-Longat - 2do congreso iberoamericano de
estudiantes de ingeniería eléctrica, electrónica y computación, “Model of
Photovoltaic Module in Matlab” (II CIBELEC 2005).
5
[9] A. Malfait, R. Reekmans, and R. Belmans, "Audible noise and losses in
variable speed induction motor drives with IGBT inverters-influence of the
squirrel cage design and the switching frequency," in Industry Applications
Society Annual Meeting, 1994., Conference Record of the 1994 IEEE, 1994,
pp. 693-700 vol.1.
Fundamental (50Hz) = 324.4 , THD= 1.27%
1
0.9
Mag (% of Fundamental)
[4] G. Walker, "Evaluating MPPT converter topologies using a MATLAB
PV model,” Journal of Electrical & Electronics Engineering,
Australia,IEAust, vol.21, No. 1, 2001, pp.49-56.
0.8
0.7
[10] M. H. Nehrir and C. Wang, Modeling and control of fuel cells:
distributed generated applications: John Wiley & Sons, 2009.
0.6
0.5
[11] Ashish Kumar Singhal , Neha Yadav ,N.S. Beniwal, “Global Solar
Energy: A Review”, International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.3 , pp. 1828-1833,ISSN 2078-2365.
0.4
0.3
0.2
systems from NIT Nagpur, and Ph.D in Electrical Engineering
from JNTU College of Engineering, Hyderabad. She is currently
working as Professor in VNR VJIET Bachupally, Hyderabad, in
Electrical and Electronics Engineering Department.
0.1
0
0
100
200
300
400 500 600
Frequency (Hz)
700
800
900
1000
Fig: 20 THD of Output Voltage of Inverter with PWM switching
VIII. CONCLUSION
This single-phase full-bridge inverter for grid-connected
PV power system has been designed along with demonstrated.
This THD with the inverter together with pulse switching
output voltage is more when compared to inverter with
SPWM switching. This bidirectional inverter has got to
satisfied grid link (sell power) along with rectification (buy
power) together with power-factor Correction (PFC) to
control the power circulation in between dc bus along with air
conditioning unit grid.
REFERENCES
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Guisado, Ma. A. M. Prats, J. I. Leon, and N. Moreno-Alfonso,
“Power-electronic systems for the grid integration of renewable energy
sources: a survey,” IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1002–
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1904
Srikanth et. al.,
Grid Connected Single-Phase Bidirectional Inverter with MPPT Tracker