Download International Electrical Engineering Journal (IEEJ) Vol. 6 (2015) No.8, pp. 1994-1998

International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.8, pp. 1994-1998
ISSN 2078-2365
http://www.ieejournal.com/
Harmonic Reduction and Power Transmission
Enhancement in a Grid Interface of Wind Power
Using Shunt-Connected FACTS Device
R.Siva Subramanyam Reddy, Asst.professor, Dept of EEE,
Srikalahasteeswara Institute of Technology(SKIT), Srikalahasti, A.P, India.
[email protected]
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Abstract—The demand for electricity is increased day to day
now a day’s. With this increase in demand, the renewable
energy sources like wind energy are one of the best alternatives
for power generation because of its tremendous environmental
social and economical benefits. However, the effect of a wind
turbine in the grid system affects the performance of the power
system and also it introduces more harmonic distortion in the
electric grid system. In this paper STATCOM connected
FACTS controller is used to overcome the various power quality
problems in a wind connected electric grid system. The
STATCOM control scheme for the grid connected wind energy
generation system for power quality improvement is simulated
using MATLAB/SIMULINK in the power system.
both inductive and capacitive regions and hence it supplies
capacitive and inductive reactive reactance’s to the
transmission line so as to transmit optimal power. However
with the recent innovations in high power semiconductor
switch (IGBT), converter topology and digital control
technology, faster STACTCOM with low cost is emerging,
which is promising to help integrate wind energy, into the grid
to archive a more cost-effective and reliable renewable wind
energy [4],[5].
Index Terms— Power quality, STATCOM, THD
I. INTRODUCTION
Energy is the primary and most universal measures
of all kinds of work by human beings and nature. Everything
that happens in the world is the expression of the flow of
energy in one of its forms; energy is an important input in all
sectors of a country's economy.
From the past decades due to globalization,
industrialization, and civilization there is great demand for
electrical energy. to satisfy these things we have different
sources of energy are available, these are thermal, nuclear,
hydro, diesel, solar, wind and fuel cells. The need to integrate
the renewable energy like wind energy into power system is to
make it possible to minimize the environmental impact on
conventional plants [1].
The integration of wind energy into existing power
system presents a technical challenge and that requires
consideration of voltage realization, stability, power quality
problems. The power quality is an essential customer focused
measure and is greatly affected by the operation of a
distribution and transmission network. The issue of power
quality is of great important to the wind turbine [2], [3].
In this paper the STATCOM FACTS device with
PWM techniques is used to solve the above said problem,
because the STATCOM provide many advantages such as
fast response time and better voltage support capability in
Fig. 1 Block diagram of the control scheme
Power quality can affect machine or equipment
reliability and reduce the life of components. However,
voltage transients and voltage system sags and swells are all
power quality problems and are all interdependent.
Conventionally the low cast mechanical switched devices
and transformer taps changes are used to address these
issues related to stability and power quality. Moreover the
fastest switching of MSD and TC to deal with power quality
issues may even cause resonance and transient over voltage,
add additional stress on wind turbine gearbox and shaft,
make themselves and turbines wear out quickly and hence
increase the maintenance and replacement cost. Therefore a
fast shunt VAR compensator is needed to address these
issues more effectively. The STATCOM is considered for
these applications because it provides many advantages, in
particular, the fast response time and superior voltage
support capability with its nature of voltage source. [6], [7].
1994
Reddy
Harmonic Reduction and Power Transmission Enhancement in a Grid Interface of Wind Power Using Shunt-Connected FACTS Device
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.8, pp. 1994-1998
ISSN 2078-2365
http://www.ieejournal.com/
The grid connected system shown in above fig 1.
Consist of wind energy generation system and shunt
connected STACTCOM FACTS device in the grid system.
The STATCOM output is varied according to the controlled
strategy so as to maintain the power quality norms in the grid
system.
In this proposed system wind generations are based
on constant speed topologies with pitch control turbine and
the induction generator is used in the proposed scheme
because of its simplicity it does not require a separate field
circuit, it can accept constant and variable loads and has
natural protection against shunt circuit.
The STATCOM come in a 3-phase voltage source
inverter having the capacitance on its Dc link and connected
at the point of common coupling. The STATCOM injects a
compensating current of variable magnitude and frequency
component at the bus of common coupling.
II. ENERGY RESOURCES
Energy is used for heating, cooking, transportation and
manufacturing. Energy can be generally classified as
 Non-renewable energy resources
 Renewable energy resources
A. Non-renewable energy resources
Over 85% of the energy used in the world is from
non-renewable supplies. Most developed nations are
dependent on non-renewable energy sources such as fossil
fuels (coal and oil) and nuclear power.
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B. Disadvantages of non-renewable energy
sources
They are not- renewable and fast depleting.
They leave behind harmful by-products upon
combustion, thereby causing a lot of pollution.
Mining of such fuels leads to irreversible damage to
the adjoining environment.
Fossil fuel pollution the environment.
It will eventually run out.
It cannot be recycled.
C. Renewable energy resources
Renewable energy is generally defined as an energy
that comes from resources which are naturally replenished on
a human timescale such as sunlight, the wind, rain, tides,
waves and geothermal heat. Renewable energy replaces
conventional fuels in four distinct areas: electricity
generation, hot water/space heating, motor fuels, and rural
(off-grid) energy services.
About 16% of global final energy consumption
presently comes from renewable resources, with 10% of all
energy from traditional biomass, mainly used for heating, and
3.4% from hydroelectricity. New renewable (small hydro,
modern biomass, wind, solar, geothermal, and biofuels)
Reddy
account for another 3% and are growing rapidly. At the
national level, at least 30 nations around the world already
have renewable energy contributing more than 20% of energy
supply. National renewable energy markets are projected to
continue to grow strongly in the coming decade and beyond.
Wind power, for example, is growing at the rate of 30%
annually [8].
D. Wind turbine
These are clean and green (pollution free) and
non-conventional sources are up to end of the living beings.
Airflows can be used to run wind turbines. Modern
utility-scale wind turbines range from around 600 kW to 5
MW of rated power, although turbines with rated output of
1.5–3 MW have become the most common for commercial
use; the power available from the wind is a function of the
cube of the wind speed, so as wind speed increases, power
output increases dramatically up to the maximum output for
the particular turbine [9].
III. POWER QUALITY AND ITS IMPORTANCE
Power quality is defined as the fitness of electrical
power supplied to the consumers.
A. Cost of poor power quality
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Unexpected power supply failures
Equipment overheating
Damage to sensitive equipment
Electronic communication interferences.
The Increase of system losses.
Penalties imposed by utilities because the site pollutes
the supply network too much.
 Connection refusal of new sites because the site would
B. Effect of Low Voltage poor Power
Quality
 Reactive power, as it loads up the supply system
unnecessary,
 Harmonic pollution, as it causes extra stress on the
networks and makes installations run less efficiently,
 Load imbalance, especially in office
 Fast voltage variations leading to the flicker.
All this phenomena potentially lead to the inefficient running
of installations, system downtime and reduced equipment life
and consequently high installation running costs. If due to
poor Power Quality the production is stopped, major costs are
incurred [10].
C. POWER QUALITY IMPROVEMENT METHODS
 Power factor correction(Active and Reactive power
management through FACTS)
 Harmonic filtering (reduction of THD)
1995
Harmonic Reduction and Power Transmission Enhancement in a Grid Interface of Wind Power Using Shunt-Connected FACTS Device
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.8, pp. 1994-1998
ISSN 2078-2365
http://www.ieejournal.com/
 Transient voltage surge suppression.
 Proper earthling systems.
IV. PRINCIPLE OPERATION OF STATCOM FACTS
DEVICE
Flexible AC Transmission Systems, called FACTS,
got in the recent years a well-known term for higher
controllability in power systems by means of power electronic
devices. Several FACTS devices have been introduced for
various applications worldwide. The most used
FACTS-device is the SVC or the version with Voltage Source
Converter called STATCOM. Almost half of the SVC and
more than half of the STATCOMs are used for industrial
applications. STATCOM has a characteristic similar to the
synchronous condenser, but as an electronic device it has no
inertia and is superior to the synchronous condenser in several
ways, such as better dynamics, a lower investment cost and
lower operating and maintenance costs. An STATCOM is
built with Thyristors with turn-off capability like GTO or
today IGBT or with more and more IGBTs. The advantage of
an STATCOM is that the reactive power provision is
independent of the actual voltage on the connection point.
This can be seen in the Fig.2 for the maximum currents being
independent of the voltage in comparison to the SVC. This
means, that even during most severe contingencies, the
STATCOM keeps its full capability. Several different control
techniques can be used for the firing control of the
STATCOM, Pulse Width Modulated (PWM) techniques,
which turn on and off the GTO or IGBT switch more than
once per cycle, can be used. STATCOM can also behave as a
shunt active filter, to eliminate unbalance or distortions in the
source current or the supply voltage. Theoretically, the power
converter employed in the STATCOM can be either a VSC or
a current-source converter (CSC).In practice; however, the
VSC is preferred because of the bi-directional
voltage-blocking
capability.
Fig. 2 STATCOM structure and voltage / current characteristics
STATCOM block diagram
An STATCOM is a controlled reactive source,
which includes a Voltage Source Converter (VSC) and a DC
link capacitor connected in shunt, capable of generating
A.
and/or absorbing reactive power. The AC terminals of the
VSC are connected to the Point of Common Coupling (PCC)
through an inductance, which could be a filter inductance or
the leakage inductance of the coupling transformer,
as shown in Fig. 3.
Fig.3 Block diagram of STATCOM
The DC side of the converter is connected to a DC
capacitor, which carries the input ripple current of the
converter and is the main reactive energy storage element.
This capacitor could be charged by a battery source, or could
be recharged by the converter itself. In this proposed scheme,
A STATCOM is built with Thyristors with turn-off capability
device called IGBT used.[4]
B. Features of IGBT
Today IGBT or with more used because of high
voltage, high current, and low switching frequencies favor
IGBTs.An IGBT features a significantly lower forward
voltage drop compared to a conventional MOSFET in higher
blocking voltage rated devices. As the blocking voltage rating
of both MOSFET and IGBT devices increases, the depth of
the drift region must increase and the doping must decrease,
resulting in roughly square relationship decrease in forward
conduction vs. blocking voltage capability of the device.
V. SIMULATION RESULTS
In this paper the proposed system is simulated in the
MATLAB/SIMULINK in power system environment and it is
observed that the source current on the grid is affected due to
the effects of wind generator, the purity of waveforms may be
lost in respect of active power, reactive power, voltage, and
current. The harmonic pollution is often characterized by the
Total Harmonic Distortion or THD which is by definition
equal to the ratio of the RMS harmonic content to the
fundamental. Also, it is found that the total harmonic
distortion (THD) without STATCOM is 0.1015. And with the
introduction of STATCOM the performance of the system is
improved also the THD level has been reduced to 0.04919.
1996
Reddy
Harmonic Reduction and Power Transmission Enhancement in a Grid Interface of Wind Power Using Shunt-Connected FACTS Device
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.8, pp. 1994-1998
ISSN 2078-2365
http://www.ieejournal.com/
Fig. 4 Simulation block diagram
Fig.6 Active and Reactive power waveforms for without STATCOM
model
Fig.5 Voltage and Current waveforms for without STATCOM model
1997
Reddy
Harmonic Reduction and Power Transmission Enhancement in a Grid Interface of Wind Power Using Shunt-Connected FACTS Device
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.8, pp. 1994-1998
ISSN 2078-2365
http://www.ieejournal.com/
Instrum. Meas., vol. 58, no. 2, pp. 375–382, Feb. 2009.
N.Nirmala and V.suresh kumar, “A STATCOM-Control Scheme for
Wind Energy System to Improve Power Quality,”IETCG-2013.
[5] M. N. Eskander, M.A.Saleh, Maged N.F.Nashed and S. Amer,
“Superiority of LVRT of Grid Connected Wind Energy Conversion
System Using Unified Power Quality Controller,” International
Electrical Engineering Journal (IEEJ) Vol. 6 (2015) No.6, pp.
1925-1930,Jun.2015.
[6] K. S. Hook, Y. Liu, and S.Atcitty,“Mitigation of the wind generation
integration related power quality issues by energy storage,” EPQU
J.vol. XII, no. 2, 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] J.Manel, “Power electronic system for grid integration of renewable
energy source: A survey,” IEEE Trans. Ind. Electron., vol. 53, no. 4,
pp. 1002–1014, 2006.
[9] M. Tsili and S. Papathanassiou, “A review of grid code technology
requirements for wind turbine,” Proc. IET Renew. Power gen., vol.3,
pp. 308–332, 2009.
[10] Narain G. Hingoranl, Laszlo Gyugyi, ”Understanding FACTS
Concepts and Technology of Flexible AC Transmission Systems”
IEEE Power Engineering Society.
[4]
Fig.7 Voltage and Current waveforms for with STATCOM model
Fig.8 Active and reactive power waveforms for with STATCOM model
I. CONCLUSION AND FUTURE SCOPE
This paper mainly focused on power quality
improvement in a grid connected wind energy system by
using shunt connected FACTS devices such as STACTCOM
using MATLAB/SIMULINK environment and also absorbed
that THD level after STATCOM is very much reduced, which
intern enhance the power transmission in the line using
STACTCOM FACTS device. In future with the use of
combined FACTS devices the performance of the grid is more
enhanced by connecting more and more renewable energy
system sources.
REFERENCES
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[3]
R.Billinton and Y.Gao, “Energy conversion system models for
adequacy assessment of generating systems incorporating wind
energy,” IEEE Trans. on E. Conv., vol. 23, no. 1, pp. 163–169, 2008.
D. L. Yao, S. S. Choi, K. J. Tseng, and T. T. Lie, “A statistical
approach to the design of a dispatchable wind power—Battery energy
storage system,” IEEE Trans. Energy Conv., vol. 24, no. 4, Dec. 2009.
J. J. Gutierrez, J. Ruiz, L. Leturiondo, and A. Lazkano , “Flicker
Measurement system for wind turbine Certification,” IEEE Trans.
1998
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Harmonic Reduction and Power Transmission Enhancement in a Grid Interface of Wind Power Using Shunt-Connected FACTS Device