IRJET - Introduction of STATCOM in PV Grid System

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 07 Issue: 03 | Mar 2020 www.irjet.net p-ISSN: 2395-0072
© 2020, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 1749
Introduction of STATCOM in PV grid system
Arti Pandey1, Bhupendra singh Niranjan2, Chandra Shekhar Azad3, Umesh Maurya4
1Assistant Professor, Dept. of EEE, MGIMT, Lucknow, UP, India
2 Assistant Professor, Dept. of EEE, MGIMT, Lucknow, UP, India
3Associate Professor, Dept. of EEE, MGIMT, Lucknow, UP, India
4UG Scholar, Dept. of EEE, MGIMT, Lucknow, UP, India
---------------------------------------------------------------------***------------------------------------------------------------------------
Abstract – Due to fast reduction of conventional energy, the
power demand escalating every passing day. This paper
focuses on the photo voltaic (PV) system integrated to a three
phase four wire system at the distribution level with power
quality improvement features. The power quality
measurements and the norms followed according to the
guiding principle specified in the International Electro
technical Commission standard, IEC61400 are the active and
reactive power variations, variation of voltages, flicker,
harmonics and electrical behavior of switching operations.
The paper describes overall good functional characteristics,
better performance and faster response than existingsystems.
The proposed system of having STATCOMissmallerinsize and
less costly when compared to the existing system.
Key Words: PV Grid, STATCOM, Power Quality
Measurement, power quality etc.
1. INTRODUCTION
Power is the very essential input for the growth of
any economy. Therefore, it is considered as a core industry
as it facilitates development across a variety of sectors, such
as agriculture, manufacturing, railways, education,
commercial etc. to expel economic development.Tomeet the
high GDP rates the energy needs of the country are
unavoidable. To have sustainable growth and social
evolution, it is necessary to meet the energy demand by
utilizing the non-conventional energy resources like wind,
biomass, hydro, co-generation, etc. The need to incorporate
the renewable energy like wind energy into power system is
to make it possible to reduce the environmental impact on
conventional plants [1].
The integration of wind energy into on hand
electrical power systeminducespower qualityproblemslike
voltage regulation, stability, harmonic distortion, voltage
sag/swell and poor power factor. The power quality is
primarily customer-focused measure and is significantly
affected by the operation of a distribution and transmission
network. In this proposed scheme one of the Flexible AC
transmission system (FACTS) device i.e., STATCOM is
connected at point of common coupling (PCC) witha battery
energy storage system (BESS) to mitigate power quality
problems. Since, STATCOM connected to the grid provides
reactive power support to windgeneratoraswell astoloads.
The BESS is integrated to sustain real power source under
changeable wind or solar power.
In the event of sudden load change or change in voltage
profile during short circuit at point of common coupling
STATCOM responds fast and stabilises the voltage and also
helps to maintain power quality norms during such sudden
and unexpected challenges.
This proposed PV cell STATCOM control scheme for grid
connected wind energy generation for power quality
improvement has following objectives.
• Unity power factor at the source side.
• Reactive power support only from STATCOM to wind
Generator and Load.
• Simple bang-bang controller for STATCOM to achieve fast
dynamic response.
1.1 Problems related to power quality:
Utility should make sure that the power matches the
customer requirements and shouldnotviolatethelimitsthat
are specified for the parameters which define the power
quality. From the customer point of view the voltage
variations and large amount of harmonics in the grid power
are extremely undesired as they affect the performance of
the end equipments. For the IIP’s who have planned the
wind power project, the voltage profile of evacuating
substation and nearby substations is of prime concern.
1.1.1 Voltage variation:
Discontinuous nature of wind power causes numerous
problems and one is variation of voltage of buses in the
region of high RE penetration. Wind generators generally
employedinductiongeneratorsandpowerelectroniccircuits
which requires reactive power for operation. Voltage
sag/swell is observed where unproductive methods of
reactive power management are employed. If voltage
increases beyond the controllable limit, forced tripping of
lines carried out, cascaded tripping may strike at the
foundations of a weak power system. Generally the power
factor of evacuating substation is maintained near to unity
preferably slightly lagging.

1.1.2 Voltage Transient:
Fault in the power system network, capacitor switching and
HVDC systems are the main cause of voltage transients.
Voltage transients are responded well by STATCOM.
1.2 Power quality issues:
In wind energy generating system the power quality
primarily concerned with the quality of current waveform
which is being drawn or generated bythe windturbine.Poor
power quality affects the performance of the loads
connected to the grid.
1.2.1 Reactive Power Consumption:
Induction generators draw reactive power to produce its
working flux while generate active power at the same time.
As induction generators are most widely preferred in wind
turbine generators, collectively a wind farm demand huge
amount of reactive power.
As the wind speed is not constant, the use of electronic
power conversion devices in wind turbine generators
becomes inevitable to achieve a rotor speed for maximum
extraction of energy from wind. The operation of power
electronic devices also requires reactive power. To avoid
voltage stability problem either STATCOM or capacitor
arrangement is used to supply this demand of reactive
power.
1.2.2 Current Harmonics Generation:
Capacitors are used as an essential part of the wind
turbine generators for supplying reactive power demand.
Capacitor switching may cause large voltage transient. The
frequency and amplitude of such transient are enormous,
particularly when back to back switching is involved, for
instance capacitor bank switching. The over voltages may
damage the insulation, Moreover, electronic equipments
such as controllers are very sensitive to these transients,
may produce incorrect commands. In addition, lightning
strikes will cause an over voltage in the electrical system of
wind turbine.
2. TOPOLOGY FOR POWER QUALITY IMPROVEMENT:
The PV cell STATCOM based current control voltage
source inverter injects the currentintothegridinsucha way
that the source current are harmonic free and their phase-
angle with respect to source voltage has a desired value.The
injected current will cancel out the reactive part and
harmonic part of the load and induction generator current,
thus it improves the power factor and the power quality. To
accomplish these goals, the grid voltages are sensed and are
synchronized in generating the current command for the
inverter. The proposed grid connected system is
implemented for power quality improvement at point of
common coupling (PCC), as shown in Figure 1. The grid
connected system in Fig. 1, consists of wind energy
generation system and battery energy storage system with
PV cell and Statcom.
Figure 1: Grid Connected system for Power Quality
improvement
2.1 Static Synchronous Compensator (STATCOM):
A Static Synchronous Compensator (STATCOM) also
known as Static Synchronous Condenser. STATCOM is a
regulating device used onalternatingcurrent(AC)electricity
transmission network. It is based on power electronic
voltage source or sink of reactive AC power to an electricity
network. STATCOM is shuntconnectedcompensationdevice
having the ability of injecting or absorbing the reactive
power.
Figure 2: Circuit Diagram of STATCOM
2.2 BESS-STATCOM:
The battery energy storage system (BESS) is used as an
energy storage element to support the wind farm during
intermittencies it also support grid during any disturbance
and loss of generation. The BESS will naturally maintain dc
capacitor voltage constant and is best suited in STATCOM
since it readily manages demand and supply of real power
and also injects or absorbed reactive power to stabilize the
grid system. It also controls the distribution and
transmission system at a very fast rate. When power
fluctuations occur in the system, the BESS can be used to

level the power fluctuations by charging and discharging
operation. The BESS system is connected in parallel tothe dc
capacitor of STATCOM [2]–[6].
The applications of the BESS-STATCOM are as following,
 Power quality improvement
 Load shifting
 Peak power shaving
 Uninterrupted power supply
 Intermittency mitigation
 Frequency regulation
Figure 3: Battery Energy Storage System
STATCOM comes fromthefamilyofFACTSdevices.These
are basically solid-state devices which are having the
capability to respond to the reactive power demand.
STATCOM have the edge over the SVC’s as the former have
constant current characteristics while in the SVC's the
capacitive current drops linearly withthevoltage. STATCOM
can easily be interfaced with real power sources like the
battery systems, fuel cells etc. STATCOM effectively control
the system voltage and avoid voltage collapse. [8]
STATCOM are solid state shunt connected devices.
STATCOM’s strategicallyplacedinthepowersystemto make
the grid robust to the disturbances. STATCOM are finding
applications in the renewable energy integration.
2.3 System operation:
In the system under study STATCOM is interfaced with
the BESS system. The STATCOM-BESS system is then
connected to the PCC in the grid where non-linear loads and
induction generator based wind turbine are also interfaced.
Current control strategy is adopted to control the STATCOM
–BESS system. The control strategy controls the output of
STATCOM in such a manner so as to achieve power quality
norms in the electrical grid. The STATCOM is intended here
to support both reactive as well as real power demandofthe
other sub-systems. [7]
Figure 4: System Operation
3. Control scheme:
Figure 5: Control System Scheme
Figure 6: Statcom Operation in Power System
The charged capacitor C dc provides a DC voltage, Udc to
the converter, which produces a set of controllable three-
phase output voltages, Uin synchronism with the AC system.
The synchronism of the three-phase output voltage with the
transmission line voltage has to be performedby anexternal
controller. The amount of desired voltage across STATCOM,
which is the voltage reference, UREF, is set manually to the
controller. The voltage control is thereby to match UT with
UREF which has been elaborated. This matching of voltages is
done by varying the amplitudeoftheoutputvoltageU,which
is done by the firing angle set by the controller. The
controller thus sets UT equivalent to the UREF.

The control scheme approach is based on injecting the
currents into the grid using “bang-bang controller.” The
controller uses a hysteresis current controlled technique.
Using such technique, the controller keeps the control
system variable between boundaries of hysteresis area and
gives correct switching signals for STATCOM operation.
3.1 Bang-Bang Current Controller:
In control theory, a bang–bang controller (on–off
controller), also known as a hysteresis controller, is a
feedback controller that switches quickly between two
states. These controllers may be realized in terms of any
element that provides hysteresis. They are often used to
control a plant that accepts a binary input, for example a
furnace that is either completely on or completely off. Most
common residential thermostats are bang–bangcontrollers.
The Heaviside step function in its discrete form is an
example of a bang–bang control signal. Due to the
discontinuous control signal, systems that include bang–
bang controllers are variable structure systems, and bang–
bang controllers are thus variable structure controllers.
Thus the ON/OFF switching signals for IGBT of
STATCOM are derived from hysteresis controller.
3.2 Voltage Source Current Control:
The three phase injected current into the grid from
STATCOM will cancel out the distortion caused by the
nonlinear load and wind generator. The IGBT based three-
phase inverter is connected to grid through the transformer.
The generation of switching signalsfrom referencecurrentis
simulated within hysteresis band of 0.08. The choice of
narrow hysteresis band switching in the system improves
the current quality.
The choice of the currentbanddependsontheoperating
voltage and the interfacing transformer impedance. The
compensated current for the nonlinear load and demanded
reactive power is provided by the inverter.
4. CONCLUSION
The paper presentstheSTATCOM-basedcontrol scheme
for power quality improvement in grid connected system
and with non linear load. The power quality disturbances
and its consequences on the consumerandelectric utility are
presented. It has a capability to cancel out the harmonics
parts of the load current. It maintains the source voltageand
current in phase and support the reactive power demand,
thus it gives an opportunity to enhance the utilization factor
of a transmission line. Thus the proposed scheme in the grid
connected system fulfills the power quality normsasperthe
IEC standard 61400-21.
5. REFERENCES
[1] A. Sannino, “Global power systems for sustainable
development”, in IEEE General Meeting,Denver,CO,Jun.
2004.
[2] Z. M. Salamah, M. A. Casacca, and W. A. Lynch, “A
mathematical model forlead-acidbatteries,”IEEETrans.
Energy Conversion, vol. 7, no. 1, pp. 93–97, Mar. 1992.
[3] Z. Yang, C. Shen, L. Zhang, M. L. Crow, and S. Atcitty,
“Integration of a STATCOM and battery energystorage,”
IEEE Trans. Power Syst., vol. 16, no. 2, pp. 254–260,May
2001.
[4] M. Black and G. Strbac, “Value of bulk energy storage for
managing wind power fluctuations,”IEEE Trans. Energy
Conversion, vol. 22, no. 1, pp. 197–205, Mar. 2007.
[5] E. Spahic, G. Balzer, and A. D. Shakib, “The impact of the
‘wind farm battery’ unit on the power system stability
and control,” in Proc. IEEE Power Tech., Lausanne, Jul.
2007, pp. 485–490.
[6] S. W. Mohod and M. V. Aware, “Grid power quality with
variable speed wind energy conversion,” in Proc. IEEE
Int. Conf. Power Electronic Drives and Energy System
(PEDES), Delhi, Dec. 2006.
[7] C. Han, A. Q. Huang, M. Baran, S. Bhattacharya, and W.
Litzenberger, “STATCOM impact study on the
integration of a large wind farm into a weak loop power
system,” IEEE Trans. Energy Conv., vol. 23, no. 1, pp.
226–232, Mar. 2008.
[8] R. S. Bhatia, S. P. Jain, D. K. Jain, and B. Singh, “Battery
energy storage system for power conditioning of
renewable energy sources,” in Proc. Int. Conf. Power
Electron Drives System, Jan. 2006, vol. 1, pp. 501–506.
[9] Ganesh.Harimanikyam1, S.V.R. Lakshmi Kumari2
“Power Quality Improvement of Grid Connected Wind
Energy System by Statcom forBalancedand Unbalanced
Linear and Nonlinear LoadsGa” International Journal of
Engineering Research and Development, Volume 3,
Issue 1 (August 2012), PP. 09-17.
[10] K. Sheshu Kumar, K. Suresh Kumar, SkBaji “A New
Control Scheme for Power Quality Improvement with
STATCOM” IJERA Vol. 3, Issue 4, Jul-Aug 2013, pp.2555-
2561.
[11] P. Ramanathan “A Statcom-Control Scheme for Grid
ConnectedWind Energy System for Power Quality
Improvement”Middle-East Journal of Scientific
Research, 57-61, 2014.
[12] Yuvaraj,Dr.S.N.Deepa N.D. (2011), “Improving grid
power quality with FACTS device on integrationofwind
energy system”, student pulse, april 2011, vol.3, issue 4,
www.studentpulse.com

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