Modeling and Simulation of Grid Connected PV Generation System Using Matlab/Simulink

International Journal of Power Electronics and Drive System (IJPEDS)
Vol. 8, No. 1, March 2017, pp. 392~401
ISSN: 2088-8694, DOI: 10.11591/ijpeds.v8i1.pp392-401  392
Journal homepage: http://iaesjournal.com/online/index.php/IJPEDS
Modeling and Simulation of Grid Connected PV Generation
System Using Matlab/Simulink
Omar Mohammed Benaissa1
, Samir Hadjeri2
, Sid Ahmed Zidi3
1,2,3
Laboratory of Intelligent Control and Electrical Power System, DjillaliLiabes University, Sidi Bel Abbes, Algeria
Article Info ABSTRACT
Article history:
Received Oct 28, 2016
Revised Jan 03, 2016
Accepted Jan 13, 2017
This paper describes the Grid connected solar photovoltaique system using
DC-DC boost converter and the DC/AC inverter (VSC) to supplies electric
power to the utility grid. The model contains a representation of the main
components of the system that are two solar arrays of 100 kW, boost
converter and the grid side inverter. The paper starts with a system
description, in this part we have given a definition and a short overview of
every component used in this system and they are taken separately. The PV
cell model is easy, accurate, and takes external temperature and solar
radiation into consideration. It also proposes a maximum power point
tracking (MPPT) algorithm. The algorithm incorporated in a DC/DC
converter is used to track the maximum power of PV cell. Finally, the
DC/AC inverter (VSC) of three- level is used to regulate the ouput voltage of
DC/DC converter and connects the PV array to the grid. Simulation results
show how a solar radiation’s change can affect the power output of any PV
system, also they show the control performance and dynamic behavior of the
grid connected photovoltaic system.
Keyword:
Boost converter
Grid-connected
Matlab/Simulink
MPPT
Photovoltaic system
VSC inverter
Copyright © 2017 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Omar Mohammed Benaissa,
Laboratory of Intelligent Control and Electrical Power System,
Djilali liabes University,
SidiBel Abbes, Algeria.
Email: omarioriquelme10@yahoo.fr
1. INTRODUCTION
Because energy resources and their utilization will be a prominent issue of this century, the
problems of natural resource depletion, environmental impacts, and the rising demand for new energy
resources have been discussed fervently in recent years [1].Grid-connected photovoltaic (PV) power systems
have been sustaining an exponential growth rate during the past decade. This steep growth is driven by a
growing concern about climate change, rebates and tax incentives, and reduction in PV system cost. The
main disadvantage of solar energy based electrical power supply is that power generation is not constant
throughout the day, as it always changes with atmospheric conditions [2]. Further, the efficiency of solar
energy conversion to electrical energy is very low, only in the range of 9-17%. Therefore, maximum power
point tracking (MPPT) is an essential part of a grid-tied solar PV system to ensurethat maximum available
power is always extracted out of the PV panel at all conditions and steered to the AC grid, considered as an
infinite sink of power ideally [3].This feature has an essential role in dynamic response andefficiency of the
photovoltaic system, in literature, different MPPT algorithms are introduced and among them the “Perturb
and Observe (P&O)” and “Incremental Conductance” are mostly used [4],[5], on the other hand, some
MPPTs are more rapid and accurate and thus more impressive, which need special design and familiarity
with specific subjects such as fuzzy logic [6], or neural network [7] methods.
Grid connected PV systems feed electricity directly to the electrical network, operating parallel to
the conventional electric source. The simplest grid-connected PV system contains a PV array and an inverter

IJPEDS ISSN: 2088-8694 
Modeling and Simulation of Grid Connected PV Generation System Using .... (Omar Mohammed Benaissa)
393
unit used for residential purpose to generate clean electricity near the point of use [8]. One of the main
technical barriers that can ultimately limit further PV penetration is the fast variations in the PV system’s
output power induced by cloud transients. Such events are known to cause voltage fluctuations which may
lead to excessive operations of voltage regulation equipment and light flickering [9].
Solar irradiance variability, which can be easily recorded using a pyranometer and a data logger, is
used in numerous studies to assess the AC power injected into the grid by PV systems. But in reality, the two
variables are not perfectly proportional with one another, nor synchronized in time due to delays within the
inverter circuit elements and controls.
As a consequence, computer models that accurately simulate the dynamic behavior of PV systems
under moving clouds would thus be of high value. In this paper, a dynamic MATLAB/Simulink model of a
three phase grid-connected PV system that can be used to predict the deviations in AC power output under
variable solar irradiance is presented. The commonly used perturb-and-observe technique for Maximum
Power Point Tracking (MPPT) is used in the present model. Figure 1 shows a typical utility interactive PV
system, it is found that the deviation between solar radiation and output power variability that may be caused
by the MPPT and buffer capacitor is minimal and can often be neglected. As a result, the variations in solar
irradiance can be considered as a good indication of power fluctuations.
Figure 1. Utility interactive pv system
2. SYSTEM DESCRIPTION
Figure 2 shows two PV arrays of 100kW connected to a 25kV grid via two DC-DC boost converters
and a three-phase three-level Voltage Source Converter (VSC). Maximum Power Point Tracking (MPPT) is
implemented in the boost converter by means of a Simulink model using the 'Perturb & Observe' technique.
The proposed model contains the following components:
a. Two PV arrays delivering a maximum of 200 kW at 1000 W/m² sun irradiance.
b. Two DC-DC boost converters (orange block) that are used to increase the voltage output of PV1 and
PV2 to 500 V DC.
c. Three-level three-phase VSC inverter (blue blocks) that is used to convert the DC voltage delivered by
the arrays of (500 V) to an AC voltage of 260 V and also to keep a unity power factor.
d. Capacitor Banks of 20 kVar used to filter the harmonics produced by the VSC.
e. A three-phase coupling transformer of 200 kVA. And 260/25kV.
f. Utility grid.

 ISSN: 2088-8694
IJPEDS Vol. 8, No. 1, March 2017 : 392 – 401
394
Figure 2. Whole PV grid-connected system
2.1. The photovoltaic generator
The PV system represented in this paper consists of two photovoltaic arrays work in parallel that are
PV1 array and PV2 array. The 100-kW PV1 array « SunPower (SPR-305) », consists of 66 strings of 5
series-connected 305.2W modules connected in parallel (66*5*305.2 W= 100.7 kW).
Manufacturer specifications for the module « SPR-305 » are listed in Table 1. The PV array block
has one input that allow you varying sun irradiance (input 1 in W/m²). The irradiance profile is defined by a
Signal Builder block which is connected to the PV array inputs. The characteristics I-V and P-V of one
module SunPowerSPR-305-WHT type are represented in Figure 3.
Table 1. Specifications of « SunPower (SPR-305) » PV-array
Model name SunPower SPR-305-WHT
No. of cells 96 in series
Open circuit voltage (Voc) 64.2 V
Short circuit current (Isc) 5.96 A
Maximum Power Voltage(Vmp) 54.7 V
Maximum Power Current (Imp) 5.58 A
Figure 3. The characteristics I-V and P-V of one module SunPower SPR-305-WHT type

395
The characteristics of PV1 array are shown below:
Figure 4. The Characteristics I-V and P-V of the PV1 array
However the PV2 array of 100 kW, uses 488 panels « Kyocera KD205GX-LP », consists of 61
strings of 8 series-connected 205 W modules connected in parallel (61*8*205 W= 100.04 kW).
Manufacturer specifications for the module « Kyocera KD205GX-LP »are listed in the Table 2:
Table 2. Specifications of « Kyocera KD205GX-LP » PV-array
Model name Kyocera KD205GX-LP
No. of cells 54 in series
Open circuit voltage (Voc) 33.2 V
Short circuit current (Isc) 8.359 A
Maximum Power Voltage(Vmp) 26.6 V
Maximum Power Current (Imp) 7.7 A
The characteristics I-V and P-V of one module Kyocera KD205GX-LP type are represented in
Figure 5.
Figure 5.The characteristics I-V and P-V of one module Kyocera KD205GX-LP type
The characteristics of PV2 array are shown below:

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396
Figure 6. The Characteristics I-V and P-V of the PV2 array
2.2. Boost converter
It is implemented in this proposed system by using a diode and a MOSFET. In the boost converter
the average output current is less then the average inductor current. and a much higher rms current would
flow through the filter capacitor dueto this reason a large value of the inductor and filter capacitor is required
than those of buck converter [10].When the MOSFET switch is ON, the current through the inductor
increases and the inductor starts to store energy. When the MOSFET switch is closed, the energy stored in
the inductor starts dissipating. The current from the voltage source and the inductor flows through the fly
back Diode D to the load. Thus the average voltage across the load is greater than the input voltage and is
determined with help of the duty cycle of the gate pulse to the MOSFET switch [12].
Figure 7 shows the schematic diagram for the boost converter used in this research work to step up
the PV output voltage to a higher level suitable for the DC/AC inverter operation that connected to the utility
grid [11].
Figure 7. Boost converter
0
1
S
V
V
D


(1)
on
SW
T
D
T
 (2)
SW on off
T T T
  (3)
Where:
a. S
V Is source voltage
b. 0
V Is the output voltage of the converter
c. DIs the duty cycle

397
d.
1
SW
SW
F
T
 Is switching frequency of the converter
e. on
T Is on time period of the semiconductor switch
f. off
T Is off time period of the semiconductor switch
In our model, we have two boost converters used to increase the DC voltage delivered by the two
PV1 and PV2 arrays to 500V. The two boost converters use the MPPT controller that automatically varies the
duty cycle to generate the voltage required to extract the maximum power.
2.3. Maximumpower utilization of photovoltaic (PV) power sources
At any given time, to extract the maximum power generated by a solar cell, the solar System has to
be equipped with a maximum power point tracker (MPPT). It helps to operate the PV system at the
maximum output power point for a given set of conditions, thereby maximizing the array efficiency. The
MPPT does this by constantly controlling the PV voltage or current independently regardless of the load
connected. The MPPT technology is commonly implemented in the DC-DC converters, but due to
technological advancements in recent times, now it can also be implemented in the DC-AC inverters.
Although, several MPPT methods are available, the most commonly practiced is Perturb and Observe so it
will be used in our present study [13]-[14].
2.3.1. Perturb-and-observe (P&O) method
The perturb-and-observe (P&O) algorithm is the most commonly used in practice for MPP tracking.
It is based on the fact that as the voltage is perturbed and the rate of change of power is observed. Based on
the sign (positive or negative) of the derivative , the voltage value is increased or decreased to reach MPP,
thereby yielding a zero, derivative. As the nature of this algorithm is absolutely based on perturbation, one
can notice some oscillations even after the MPP is reached [13],[15].
Figure 8. Power vs voltage curve showing MPP
2.4. VSC Inverter
PV modules generate direct current (DC) and voltage. However, to feed the electricity to the grid,
alternating current (AC) current and (AC) voltage are needed. Inverters are the equipment used to convert
DC to AC. In addition, they can be in charge of keeping the operating point of the PV array at the MPP. This
is usually done with computational MPP tracking algorithms. There are different inverter configurations
depending on how the PV modules are connected to the inverter.
The VSC converts the 500 V DC link voltages to 260 V AC and keeps power factor at unity. The
VSC control system consists of two control loops:
a. An external control loop which regulates DC link voltage to +/- 250 V.
b. An internal control loop which regulates grid currents (active and reactive) current components.
c. The control system uses a sample time of 100 microseconds for voltage and current controllers.
Boost and VSC converters with pulse generators use a fast sample time of 1 microsecond in order to
get an appropriate resolution of PWM waveforms [16].

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3. SIMULATION RESULTS AND DISCUSSION
Simulation starts with standard test conditions (25 °C, 1000 W/m²). From t=0 sec to t=0.05 sec, the
pulses for boost converters and VSC inverter are blocked. The voltage of PV1 array correspond to the open
circuit voltage (5 panels in Series * Voc = 5 * 64.2 = 321 V), and for PV2 array (8 panels in Séries *Voc =8
* 33.2 = 265.6 V) (see Figure 9). At this time the VSC inverter of three-level functions as an uncontrolled
rectifier (diode) and the DC capacitors are charged over 500 V (Figure 11).
At t = 0.05 s, boost converter and VSC inverter are unlocked. The DC voltage is set at Vd = 500V
(see Figure 11). The duty cycles of the two boost converter equal to 0.5 and 0.6 respectively (see Figure 10)
irradiance is set at 1000 W/m2 as shown in Figure 12. The nominal speed is reached at t = 0.25s, the voltage
generated by the array PV1 is VPV1 = (1-D1) * Vd= (1-0.5) * 500 = 250 V, while the voltage generated by the
array PV2 is VPV2 = (1-D2)*Vd = (1-0.6) * 500 = 200 V.
Figure 9. Voltage generated by PV1 and PV2 arrays Figure 10. Duty cycles of PV1 and PV2 arrays
Figure 11. DC link voltage Vd Figure 12. Irradiance of the PV1 and PV2 arrays
The power generated by arrays PV1 and PV2 are on the order of 97 kilowatts and 98 kilowatts
respectively, while the maximum powers with irradiance of 1000W/ m² are estimated at 100.7 kilowatts to
100.04 kilowatts (see Figure 13). It is important to note that the voltage and current of phase A at 25 kV
busbar are in phase (power factor equals to 1) as shown in Figure 14.

399
Figure 13. The powers generated by the PV1 and
PV2 arrays
Figure 14. Current and voltage injected into the grid
At t = 0.4 s both MPPT controls are enabled. MPPT1 controller starts controlling the voltage
generated by PV1 by acting on the duty cycle of the first boost converter in order to extract the maximum
power. The maximum power of the first PV array (100.7 kilowatts) is obtained when the duty cycle D1
equals to 0.453. At t = 0.6 s, the voltage of the array PV1=274 V as expected from the specifications of the
PV array (N_série*Vmp = 5 * 54.7 = 273.5 V).
From t = 0.7 s to t = 1.2 s, the irradiance Ir1 decreases linearly from 1000 W/m² to 250 W/m². From
time t=1.1, the irradiance Ir2 also decreases linearly from 1000 W/m² to 250 W/m² (Figure 16). Both MPPT
controllers continue tracking the maximum power delivered by each PV array. At t = 1.2 s when the
irradiance Ir1 reaches the value of 250 W/m², the duty cycle D1 is around 0.485. The corresponding voltage
and power are 255 V and 22.6 kilowatts respectively. For the second PV array, the irradiance Ir2 reaches the
value of 250 W/m² at t = 1.65 s, where the duty cycle D2=0.6.
Note that tracking the maximum power point by the MMPT controller is ensured even when the
irradiance changes rapidly. From t = 1.5 s to t = 3 s various changes of the irradiance Ir1 and Ir2 are applied to
illustrate the good performance of the MPPT controller.
Figure 15. Power generated by the PV1 and PV2
arrays
Figure 16. Irradiance of the two arrays

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Figure 17. Duty cycles of the PV1 and PV2 arrays Figure 18. Voltage generated by the PV1 and PV2
arrays
Figure 19 shows the power injected into the grid. From t = 0 s to t = 0.05 s the power injected into
the grid is growing because the pulses of boost converter and VSC inverter are blocked. At t = 0.05s the
pulses are enabled, the power injected into the grid is 195 kW.
From t = 0.2 s to t = 0.75 s the irradiance is 1000W / m², while the injected power reaches its
maximum value. From t = 0.75 s to t = 2.75 s several variations in the irradiance lead to change the power
injected into the grid to stabilize at 2.75 s and takes the value of 200 kilowatts.
Figure 19. Power injected into the grid
4. CONCLUSION
This paper presents the modeling and simulation of grid connected PV system with Perturb and
Observe MPPT Algorithm to inject the power extracted from a photovoltaic array and obtain unitary power
factor in varying weather conditions. According to the results obtained from the simulation, we can say that it
is essential to operate the system at the MPP (Maximum Power Point) of a PV array, in other words we
should always extract the maximum power from the PV module by modulating the duty cycle of the boost
converter in order to enhance the power injected into the grid, otherwise the PV array is not fully exploited
which consecontly is reflected by a higher losses in the energy transferred from the PV array to the utility
grid. Also the Pulse width modulation (PWM) technique has been developed beside inverters. So that we can
obtain a sinusoidal waveform at the output of the inverter and the total harmonic distortion (THD) of the
output voltage can be reduced.The results confirm the adequate performance of whole designed control.
REFERENCES
[1] K. S. Srikanth, “A Three Phase Multi Level Converter for Grid Connected PV System,” International Journal of
Power Electronics and Drive System (IJPEDS), vol/issue: 5(1), pp. 71-75, 2014.
[2] M. C. Mira, et al., “Boost Converter With Combined Control Loop for a Stand-Alone Photovolainc Battery Charge
System,” IEEE 14th Workshop On Control and Modeling Power electronics, 2013.
[3] “Photovoltaic Cell Conversion Efficiency,” U.S. Department of Energy, Retrieved, 19 May 2012.
[4] D. Sera, et al., “On the Perturb-and-Observe and Incremental Conductance MPPT Methods for PV Systems,” IEEE
Journal of Photovoltaics, vol/issue: 3(3), pp. 1070-1078, 2013.

401
[5] F. Liu, et al., “Variable Step Size INC MPPT Method for PV Sytems,” IEEE Transactions on Industrial
Electronics, vol/issue: 55(7), 2008.
[6] T. F. Wu, et al., “A Fuzzy Logic-Controlled Single Stage Converter for PV-Powred Lighting System
Applications,” IEEE Transactions on Industrial Electronics, vol/issue: 47(2), pp. 287–296, 2000.
[7] M. Veerachary, et al., “Neural-Network Based Maximum Power Point Tracking of Coupled-Iductor Interleaved-
Boot Converter Supplied PV System Using Fuzzy Controller,” IEEE Transactions on Industrial Electronics,
vol/issue: 50(4), pp. 749-758, 2003.
[8] P. H. Zope, et al, “Performance and Simulation Analysis of Single-Phase Grid Connected PV System Based on Z-
Source Inverter,” in International conference on Power Electronics, Drives and Energy System, 2010.
[9] S. Li, et al, “A Novel Maximum Power Point Tracking Control Method With Variable Weather Parameters for
Photovoltaic Systems,” (ELSEVIER), Solar Energy, vol. 97, pp. 529-536, 2013.
[10] A. A. Siddik and M. Shangeetha, “Implimentation of Fuzzy Logic Controller in photovoltaic Power generation
using Boost converter and Boost Inverter,”International Journal of Power Electronics and Drive System (IJPEDS),
vol/issue: 2(3), pp. 249-256, 2012.
[11] G. E. Saady, et al., “Performance of Photovoltaic Water Pumping System under Different MPPT Algorithms,” in
17th International Middle –East power system Conference, 2015.
[12] R. Teodorescu and M. Liserre, “Power Electronics for Renewable Energy,” Slides presented at the course PERES,
2006.
[13] J. J. Nedumgatt, et al., “Perturb and Observe MPPT Algorithm for Solar PVSystems-Modeling and Simulation,” in
Annual IEEE India Conference, pp. 1-6, 2011.
[14] K. Manohar and P. S. Rani, “MPPT and Simulation for a Grid-Connected Photovoltaic System and Fault Analysis,”
International Journal of Engineering And Science (IJES), pp. 158-166, 2013.
[15] M. D Singh and K. B Khanchandani, “Power Electronics,” Tata Mcgraw Hill publishers, 2nd edition, pp. 135-670,
2011.
[16] J. Kasera, et al, “Design of grid connected Photovoltaic System Employing Incrimental Conductance MPPT
Algorithm,” Journal of Electrical Engeneering.

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