Download FULL TEXT - rs publication house of research and scientific journals

International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
Improving The Performance of PV System Using STATCOM
A Review and Working Approach
Vikarn sharma
Department of Electrical Engineering
Lovely Professional University, Punjab
Punjab, India
Kulraj kaur
Department of Electrical Engineering
Lovely Professional University, Punjab
Punjab, India
Abstract—SOLAR energy is considered to be future source of energy. As with the passage
of time most of our non-renewable energy sources are going to be exhausted, so photovoltaic
technology has found immense applications to utilize the vast amount of solar energy. In
power system our main concern is to enhance the performance parameters of the system,
similar is the case with the PV system. So for that purpose we have decided to insert a
STATCOM in the PV system. STATCOM serves the multiple purposes in the system. Firstly
as we know the PV system remains almost idle during the night and does not serve any
purpose but due to STATCOM it will operate during the night as well for the compensation
purposes .Moreover the STATCOM has the capability of voltage regulation which is very
much needed in the PV system as it is always subjected to the voltage fluctuations due to
change in the intensity of light. In addition to this STATCOM can also cope up the other
parameters of the system such as power factor. Thus inserting a STATCOM in the PV system
can enhance its capability many times. During the present time when the demand of
STATCOM is increasing day by day then this combination of STATCOM along PV system
can be proved vital.
Keywords—PV system, STATCOM , V.S.I , C.S.P, MPPT
I.
INTRODUCTION
Photo voltaic system is used to convert solar energy into the electricity and this is achieved
by using one or more solar panels. The basic component of a PV system includes PV
modules, electrical and mechanical connections, mountings and provisions for output
regulations. The PV systems when connected with grid works on the principle of the
exchange of energy between grid and the PV system. During the day time the consumer uses
the electrical energy produced by his or her own local installation. However during the night
or when the light is not sufficient or when there is a situation that consumer requires more
energy than installation then the electrical energy is provided by the grid to the consumer. So
this integration of PV system with grid guarantees the necessary supply of electricity demand.
This is called nighttime applications of PV system as STATCOM to regulate Grid voltage[1].
R S. Publication (rspublication.com), [email protected]
Page 824
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
Also with the addition of STATCOM in the PV system the performance parameters of the
system are also improved. Moreover by the applications of STATCOM it is also possible to
resolve power quality issues of grid connected 3 phase system [2].
II.
STAPLE OF PV SYSTEM
Basic Scenario of solar energy
Solar energy is abundantly available renewable energy. It is cheap and easily available.
Solar energy is received on Earth in intermittent, cyclic and dilute form with very low power
density 0 to 1.1 kW/m2.Solar energy which is received on the ground level is affected by
atmospheric clarity, degree of latitude, etc. For design purposes, the variation in available solar
power, the optimum tilt angle of the solar flat plate collectors, location and orientation of the
heliostats should be calculated. Grid-relevant solar energy technologies can be broadly divided
into two types: PV and concentrated solar power (CSP). PV generates electricity directly,
converting sunlight to electricity through a semiconductor such as silicon. CSP technologies
produce electricity by reflecting and concentrating sunlight onto a fluid, which then heats and
boils water, the steam from which then drives a turbine that produces electricity. Presently,
CSP has a lower contribution to RE production than solar”.
A.
Basics of PV system
A photovoltaic system (or PV system) is a system which uses one or more solar panels to
convert sunlight into the electricity. It consists of different type of components, which
includes photovoltaic modules, electrical and mechanical connections and mountings and
means of regulating and/or modifying the electrical output. Grid-connected photovoltaic solar
installations work n the basis of energy exchange with the local grid. In practice ,however in
daylight hours the consumer uses the electrical energy produced by his/her own installed
capacity, however when there is no light or it is not sufficient or the consumer requires
more energy than his installation is capable of providing the supply from , the electrical grid.
Thus it guarantees the supply of necessary electrical energy. On the other hand, it can occur
that the solar installation produces more energy than required by consumer, and so the energy
may be absorbed by the grid. In this case there is a possibility of transfer of "surplus" to the
local electrical grid.
.
B.
C.
COMPONENTS OF GRID CONNECTED PV SYSTEM



Photovoltaic modules: They produce electrical energy whenever exposed to the sun.
The energy produced is in the form of direct current and voltage. Their number and
the relative connections depends on installation size
Batteries: Batteries are used for storing the charge or energy. The best batteries used
are those with positive tubular plates. It is very important to select the type and choice
of the battery.
Regulator: Regulator is used to regulate the batteries by controlling the charge and
discharge in the system. It is essentially called the brains of the installations, which
regulates consumer end output. if the battery voltage goes below a certain minimum
level beneath which the accumulator would become damaged).
R S. Publication (rspublication.com), [email protected]
Page 825
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm

Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
Inverter: It is used to convert the direct voltage and current to the alternating current
in the system. As it is cleared that the produced voltage is D.C one in case of the PV
system so it should be converted into A.C voltage.
Due to the low voltage of an individual solar cell (typically ca 0.5V), several number of
cells are wired in series in the manufacture of a laminate. Solar panels are obtained by
assembling these laminate into weather proof coverings. The electricity which is then
generated can be either stored, used directly (island/standalone plant) or fed into a large
electricity grid powered by central generation plants (grid-connected or grid tied)
combined with one or many domestic electricity generators to supply into a small grid
(hybrid type plant). The rest of the system consists of different components depending on
type of application. The BOS depends on load profile and the system type. Systems are
usually designed in order to ensure the highest energy yield for a given investment.The
grid connected systems are designed mostly with battery. These systems are basically
consists of charge controllers which are used to prevent overcharging of the battery.
. The diagrammatic representations of the various components of the grid connected
PV system are shown in fig. (a)
Fig (a) Components of grid connected PV system
R S. Publication (rspublication.com), [email protected]
Page 826
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
III .Modeling of PV System a Review
(a) Review of electrical equivalent of PV system
A simple PV cell can be represented in electrical terms with a simple circuit shown below in
fig 5. It consists basically of a diode, a series resistance, a current source. The output current
can be obtained from the equation below
I = I PH – ID =IPH - IO [exp {V + IRS}-1]
Vt
This current depends on the temperature, voltage, solar radiations as well as cell’s
characteristics. In the above equation various parameters are
Io = dark saturation current
VT = Thermal temperature
ID = Diode current
IRS= Current in the series resistance
Fig (b) Electrical model of PV cell
The effect of solar radiation on the PV characteristics is shown in fig 6 below. It is clearly that
with the increase the radiation leads to obtaining the maximum operating point at higher
operating voltages
Fig. (c). Solar radiation effect on the P–V characteristic in constant temperature
R S. Publication (rspublication.com), [email protected]
Page 827
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
In an attempt to improve the accuracy a two diode modal is proposed by Zainal Salam,
KashifIshaque and HamedTaheri. Here PV cell is represented by two equivalent diodes. This
model is known to have better accuracy at irradiance level which results into more accurate
predictions of PV system performance. In this method values of Rpand Rs are estimated
through iteration method. Simulators are further interfaced with power electronic converters
and MPPT algorithms. It is cleared from the observations that this two diode model is much
superior to RP and RS model. Results found using this model are much close to theoretical
prediction.[3]
(b) Review of MPPT techniques used in PV system
MPPT is a control algorithm used in PV systems to take full advantage of available solar
energy. The effectiveness of MPPT can be theoretically defined as the ratio of practical output
power to the true maximum power value. There is lot of work going to compare various
MPPT techniques and improving the performance of MPPT [4]-[9]. But the main hindrance in
comparison studies is the non ideal factors which generally lead to inaccurate results. However
in the latest developments a dual channel bench system has been proposed. It proposes t-test
formulas which are able to filter out the effect of difference in PV panel outputs and able to
accurately quantify the statistical significance between two MPPT methods[10].
IV. Inserting STATCOM in PV system a Review
(A) Basics of STATCOM
Static Synchronous compensator (STATCOM) was developed as an advanced Static VAR
compensator in which a voltage source convertor (VSC) is used in-stead of the controllable
reactors and switched capacitors. Although VSCs require self-commutated power
semiconductor devices such as IGBT, GTO, IGCT, MCT, etc (with higher costs and losses)
unlike in the case of variable Impedance type SVC which use thyristor devices, there are
many technical advantages of a STATCOM over a SVC. It is a device connected in the
derivation, basically composed of a coupling transformer, which serves as a link between the
electrical power systems (EPS) and the voltage synchronous controller (VSC) that generates
the voltage wave comparing it to the one of the electric system to realize the exchange of
reactive component of power. Thecontrol system of STATCOMadjusts at each moment the
inverse voltage so that the current injected .In the network is in quadrature to the system
voltage, in these conditions Q=0 and P=0. In its most general way, STATCOMcan be
modelled as a regulated voltage source VI connected to a voltage bar Vs through a
transformer. The diagrammatic representation is given below.
(B) Various Applications of STATCOM in PV SYSTEM
(i) Resolving the Power Quality Issues
Junbia Han1, Jignesh Solanki2, SarikaKhushalani and Jens Schoene2in 2011 have explained
the unified control of STATCOM to resolve power quality issues of a grid connected three
phase PV system. Some of the general power quality issues related to three phase PV system
are continuity of supply, transient voltage, harmonics, voltage flicker. There are mainly two
types of challenges involved in solar generation i.e system stability and power quality. Solar
R S. Publication (rspublication.com), [email protected]
Page 828
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
stability depends on the solar penetration level, reactive power support and fault ride through
ability. Power quality is more about consumer driven issues and dynamic performance. In
this paper control strategies are proposed for STATCOM to address these issues and
moreover tested in a grid connected PV system. The simulation results confirm the same [11].
(ii) Optimal utilization of PV system
Rajiv. K. Varma, IEEE, Byomakesh Das, Member IEEE, IurieAxente and Tim Vanderheide,
Member IEEE “Optimal 24-hr Utilization of a PV Solar System STATCOM (PVSTATCOM) in a Distribution Network” in year 2012 have explained about optimal 24 hour
use of PVsystem as STATCOM. Their paper presents a novel optimal utilization of
photovoltaic solar system as STATCOM for voltage regulation and power factor correction
during both night-time and daytime. The PV solar system conventionally generates real
power during the day but the entire asset remains idle during the night .When this novel PV
solar system operated as STATCOM it is termed PV-STATCOM which utilizes the entire
inverter capacity in the night and that remaining after real power generation during the day
for accomplishing various STATCOM functions[12]
(iii) PV STATCOM for Voltage Regulation and P.F Improvement
Rajiv. K. Verma, Member IEEE, Ehsan M. Siavashi, Byomakesh Das, and Vinay Sharma,
Member IEEE. have explained about STATCOM applications in the PV system This paper
presents a real-time digital simulation study of a PV solar system as a STATCOM (PVSTATCOM) on RTDS (Real Time Digital Simulator) in a unique state-of-the-art research
laboratory in a utility premise. This PV-STATCOM technology is utilized in the night for
power factor correction and voltage regulation at the terminals of an induction motor
operating at the poor power factor. During the daytime, the same objectives will be
accomplished together with production of real power from solar insolation, by utilizing the
inverter capacity remaining after real power generation. The local distribution company
London Hydro is implementing this latest technology, for first time in Canada, on a 10 kW
solar system to be installed on the rooftop of their headquarters building in fall 2012. The
proposed new control on PV solar system will help increase the utilization of the PV system,
improve the overall electrical system performance and also provide a potential of additional
revenue earning for solar farms for providing the above mentioned services, both during day
and night [13]
(iii) Nighttime applications of PV systems
Rajiv K. Varma, Shah Arifur Rahman, Mahendra, A.C., Ravi Seethapathy and Tim
Vanderheide)”. In year 2012 have explained about the usage of PV system during the night
as STATCOM.Photovoltaic solar farms generate power only during daytime and remain
completely idle during the nights. This paper presents a novel technology of utilizing
Photovoltaic (PV) Solar Farms in the night-time. New controls are developed for the solar
farm inverters to operate as STATCOM – a Flexible AC Transmission System (FACTS)
Controller, using the entire inverter capacity in the night for accomplishing various power
system objectives, such as voltage regulation, improvement of power transfer capacity, load
compensation, etc. During the daytime, the same objectives can be achieved to a substantial
degree with the inverter capacity remaining after real power generation. This technology is
termed PV-STATCOM. Two novel applications of solar farms operating as PVSTATCOM in
realistic transmission and distribution systems are presented in this paper. These are: i)
R S. Publication (rspublication.com), [email protected]
Page 829
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
Improving power transfer capacity of transmission lines; and ii) Increasing the connectivity
of neighbouring wind farms[14]. Research are going on to utilise the P.V farms as
STATCOM and also increase the connectivity with the grid.[15-20]
(iv)Absorbing maximum solar power
N. Farokhnia H. N. Farokhnia G.H. Raihy Department of Electrical Engineering Tehran, Iran
have explained about the integration of PV system with STATCOM in order to extract
maximum output from the PV system. AS Photovoltaic (PV) module produces DC output, so
it should be connected to the network through inverter. Considering the PV characteristics it
is clear that maximum power is obtained in some specific operating regions or points. These
optimal points depend on the solar radiation as well as ambient temperature and vary with
their corresponding changes. Therefore, DC-DC converter is normally used between PV
module and inverter to keep PV module at its optimal operating points[21-23]. STATCOM,
considered as an advanced compensator, consists mainly of VSI (Voltage Source Inverter)
which is connected through shunt transformer to network[24-26]. One of the common
tasks is regulating DC voltage of VSI at desired voltage like the optimal voltage. By
connecting the PV module directly to STATCOM, PV module can always work in its optimal
operating point without DC-DC converter because STATCOM regulates DC voltage at the
optimal point. Also, in our proposed integrated system, STATCOM still perform its
compensating tasks such as fixing load voltage at the nominal value or compensating reactive
power in a proper way. In this very paper, integration of PV module and STATCOM is
studied and also, a sample system is simulated in the MATALB software to verify the
advantages of proposed integrated system.[27]
V Research Methodology
(a) Observations from Different Literature Survey
After studying the various papers related to the PV system it is clear that for getting the
maximum advantage from the PV system some of the key points which should be kept in
mind are as
 It should operate at maximum operating point

System should also be utilized during the night

Power factor correction and voltage regulation mechanism should be there
To match these criteria there is a need of installing some of the FACTS devices which should
enhance the power carrying capability of the system. But after studying the various FACTS
devices we have chosen to go with STATCOM
(b) Reasons For Choosing STATCOM

STATCOM is the most commonly used FACTS device. So it is very much reliable
and moreover cost is also reasonable

As in the PV system D.C voltage is produced so inverter should be present in the
circuit to convert D.C in to the A.C as most of the systems today are A.C operated.
Moreover a STATCOM consists of V.S.I(VOLTAGE SOURCE INVERTER) thus a
V.S.I can replace simple inverter in the PV system thereby compensating the cost
R S. Publication (rspublication.com), [email protected]
Page 830
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149

Also a DC - DC converter is required in the PV system to operate the system at
maximum operating. However a STATCOM also have a DC side which when
integrated with PV system will operate the system at maximum operating point
The simple circuit involving the integration of the STATCOM with PV system is shown in
figure below
Fig(d) Integration of the STATCOM with PV system
(c) Approach to be used
We are using MATLAB/ SIMULINK programming techniques for this purpose. Firstly the
STATCOM applications are justified through a simple circuit and simulation results and then
the PV output obtained will be given as input to the STATCOM Theoverall work can be
shown in the form of block diagram
Fig (e) Overall work done shown in block diagram
R S. Publication (rspublication.com), [email protected]
Page 831
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
CONCLUSION
As we know that most of our existing energy sources are going to be exhausted in near future
so we have to step towards the renewable energy sources. SOLAR energy can be used to a
great extent in producing electricity and photovoltaic’s technology can be proved very helpful
in this direction. By introducing the STATCOM in the PV system we can enhance the
capability of the system and also make the system much more dependable. In future when the
PV system will find a major place in the power generation then this work of inserting the
STATCOM in the PV system can find new dimensions. By integrating the PV system with
STATCOM we can control the reactive power flow in the system i.e. both the systems (PV
system as well as existing system) .SO this work has significant role in future keeping the
present energy scenario in the view.
REFERENCES
[1] Rajiv K. Varma, Senior Member IEEE, Shah Arifur Rahman, Mahendra, A.C., Ravi
Seethapathy, Senior Member IEEE, and Tim Vanderheide Novel Nighttime Application of
PV Solar Farms as STATCOM (PV-STATCOM).
[2] Junbiao Han1, SarikaKhushalani- Solanki1, Jignesh Solanki1and Jens Schoene2 Study of
unified control of STATCOM to resolve the Power quality issues of a grid connected three
phase PV system
[3] Zainal Salam, KashifIshaque, and HamedTaheriAn Improved Two-Diode Photovoltaic
(PV) Model for PV System
[4] M.Miyatake, M. Veerachary, F. Toriumi, N. Fujii, and H. Ko, “Maximum power point
tracking of multiple photovoltaic arrays: A PSO approach,” IEEE Trans. Aerosp. Electron.
Syst., vol. 47, no. 1, pp. 367–380, Jan. 2011.
[5] N. Tat Luat and L. Kay-Soon, “A global maximum power point tracking scheme
employing DIRECT search algorithm for photovoltaic systems,” IEEE Trans. Ind. Electron.,
vol. 57, no. 10, pp. 3456–3467, Oct. 2010.
[6] T. Suntio, Leppa, X. J. Aho, J. Huusari, and L. Nousiainen, “Issues on solar-generator
interfacing with current-fed MPP-tracking converters,”
IEEE Trans. Power Electron. vol. 25, no. 9, pp. 2409–2419, Sep. 2010.
[7] M. Sabahi, S. H. Hosseini, M. B. Sharifian, A. Y. Goharrizi, and
G. B. Gharehpetian, “Bi-directional power electronic transformer with maximum power-point
tracking capability for induction heating applications,” IET Power Electron., vol. 3, no. 5, pp.
724–731, Sep. 2010.
[8] A. N. Ridge and G. A. J. Amaratunga, “Photovoltaic maximum power point tracking for
mobile applications,” Electron. Lett., vol. 46, no. 22,pp. 1520–1521, Oct. 2010.
[9] L. Piegari and R. Rizzo, “Adaptive perturb and observe algorithm for
photovoltaicmaximum power point tracking,” IET Renewable Power Generation,vol. 4, no.
4, pp. 317–328, Jul. 2010
[10] Weidong Xiao, Member, IEEE, H. H. Zeineldin, Member, IEEE, and Peng Zhang,
Senior Member, IEEE Statistic and Parallel Testing Procedure for Evaluating Maximum
Power PointTrackingAlgorithms of Photovoltaic Power Systems July 2013
[11] Junbiao Han1, SarikaKhushalani- Solanki1, Jignesh Solanki1and Jens Schoene2 Study
of unified control of STATCOM to resolve the Power quality issues of a grid connected three
phase PV system
[12] Rajiv. K. Varma, Senior Member IEEE, Byomakesh Das, Student Member IEEE,
IurieAxente and Tim Vanderheide, Member IEEE Optimal 24-hr Utilization of a PV Solar
Systemas STATCOM (PV-STATCOM) in a Distribution Network
R S. Publication (rspublication.com), [email protected]
Page 832
International Journal of Emerging Trends in Engineering and Development
Available online on http://www.rspublication.com/ijeted/ijeted_index.htm
Issue 4, Vol.2 (March 2014)
ISSN 2249-6149
[13] Rajiv. K. Varma, Senior Member IEEE, Ehsan M. Siavashi,Byomakesh Das, and Vinay
Sharma, Member IEEE. Real-Time Digital Simulation of a PV Solar System as STATCOM
(PV-STATCOM) for Voltage Regulation and Power Factor Correction
[14] Rajiv K. Varma, Senior Member IEEE, Shah Arifur Rahman, Mahendra, A.C., Ravi
Seethapathy, Senior Member IEEE, and Tim Vanderheide Novel Nighttime Application of
PV Solar Farms as STATCOM (PV-STATCOM).
[15] Rajiv K. Varma, Vinod Khadkikar, and Ravi Seethapathy, "Nighttimeapplication of PV
solar farm as STATCOM to regulate grid voltage,"IEEE Trans. on Energy Conversion
(Letters), vol. 24, no. 4. Dec. 2009.
[16] Rajiv K. Varma and Vinod Khadkikar, “Utilization of Solar FarmInverter As
STATCOM” US Provisional Patent application filed 15 Sept.2009.
[17] R.K. Varma, S A Rahman, and R. Seethapathy, “Novel Control of GridConnected
Photovoltaic (PV) Solar Farm for Improving TransientStability and Transmission Limits
Both During Night and Day,” in Proc.2010 World Energy Conference, Montreal, Canada,
pp. 1-6.
[18] R.A. Walling and K. Clark, "Grid Support Functions implemented inUtility-Scale PV
Systems,” in Proc. IEEE PES 2010, T&D Conferenceand Exposition, pp. 1-5.
[19] G. C. Pyo, H. W. Kang and S. I. Moon, “A New Operation Method forGrid-Connected
PV System Considering Voltage Regulation inDistribution System,” in Proc. IEEE 2008,
Power and Energy SocietyGeneral Meeting - Conversion and Delivery of Electrical Energy
in the21st Century, pp. 1-7.
[20] F.L. Albuquerque, A.J. Moraes, G.C. Guimaraes, S.M.R. Sanhueza andA.R. Vaz,
“Photovoltaic solar system connected to the electric powergrid operating as active power
generator and reactive powercompensator,”Solar Energy, vol. 84, no. 7, pp. 1310-1317, July
2010.
[21] J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz and et al, “Powerelectronic systems
for the grid integration of renewable energy sources:a survey”, IEEE Trans. Industrial
Electronics, vol. 53, no. 4, august2006
[22] S. Jain, V. Agarwal, “New current control based MPPT technique forsingle stage grid
connected PV systems”, Elsevier Trans. EnergyConversion and Management, vol. 48, 2007,
pp. 625–644
[23] V. Salas, E. Olias, A. Barrado, A. La´zaro, “Review of the maximumpower point
tracking algorithms for stand-alone photovoltaic systems”,Solar Energy Materials & Solar
Cells, vol. 90, 2006, pp. 1555–1578
[24] K. K. Sen, “STATCOM-STATic synchronous compensator: Theory,modeling, and
applications,” in Proc. IEEE-PES, 1999, pp. 1177–1183.
[25] P. G. Gonzalez and G. Cerrada, “Control system for a PWM-basedSTATCOM,” IEEE
Trans. Power Delivery, vol. 15, no. 4, Oct. 2000, pp.1252–1257.
[26] Q. Yu, P. Li, W. Liu, X. Xie, “Overview of STATCOM technologies”, inProc. IEEE
Electric Utility Deregulation, Restructuring and Power
Technologies, vol. 2, 5-8 April 2004, pp. 647 – 652
[27] H. Toodeji, N. Farokhnia and G.H. Riahy Department of Electrical Engineering,
Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran Integration of PV
Module and STATCOM to Extract Maximum Power from PV.
R S. Publication (rspublication.com), [email protected]
Page 833