International Journal of Recent Advances in Engineering & Technology (IJRAET)
MITIGATION OF POWER QUALITY PROBLEMS BY USING
D-STATCOM
1
Shaik Khaja Gareeb Nawaz, 2Shaik Hameed
1
(PG Scholor), Department of EEE, QCET
Associate Professor, Department of EEE, QCET
E-mail: 1nawaz.261@gmail.com, 2hameedqcet@gmail.com
2
different bases. One of those power electronic solutions
to the voltage regulation is the use of a Distribution ST
A TCOM (DSTA TCOM). D-ST A TCOM is a class of
custom power devices for providing reliable distribution
power quality. They employ a shunt of voltage boost
technology using solid state switches for compensating
voltage sags and swells. The DST A TCOM applications
are mainly for sensitive loads that may be drastically
affected by fluctuations in the system voltage
Abstract - This paper presents the systematic procedure of
the modeling and simulation of a Distribution STATCOM
(DSTATCOM) for power quality problems, voltage sag
and swell based on Sinusoidal Pulse Width Modulation
(SPWM) technique. Power quality is an occurrence
manifested as a nonstandard voltage, current or frequency
that results in a failure of end use equipments. The major
problems dealt here is the voltage sag and swell. To solve
this problem, custom power devices are used. One of those
devices is the Distribution STATCOM (D-STATCOM),
which is the most efficient and effective modern custom
power device used in power distribution networks. DSTATCOM injects a current in to the system to correct the
voltage sag and swell. The control of the Voltage Source
Converter (VSC) is done with the help of SPWM. The
proposed D-STATCOM is modeled and simulated using
MATLAB/SIMULINK software.
II. POWER QUALITY PROBLEMS
The power disturbances occur on all electrical systems,
the sensitivity of today's sophisticated electronic devices
make them more susceptible to the quality of power
supply. For some sensitive devices, a momentary
disturbance can cause scrambled data, interrupted
communications, a frozen mouse, system crashes and
equipment failure etc [5]. A power voltage spike can
damage valuable components. Power quality problems
encompass a wide range of disturbances such as voltage
sags, swells, flickers, harmonic distortion, impulse
transients, and interruptions.
Index Terms- Distribution STATCOM (D-STATCOM),
MATLAB/ SIMULINK, Power quality problems,
Sinusoidal Pulse Width Modulation (SPWM), Voltage sag
and swell, Voltage Source Converter(VSC)
I. INTRODUCTION
Now a days, modern industrial devices are mostly based
on the electronic devices such as programmable logic
controllers and electronic drives. The electronic devices
are very sensitive to disturbances and become less
tolerant to power quality problems such as voltage sags,
swells and harmonics. Voltage dips are considered to be
one of the most severe disturbances to the industrial
equipments . Voltage support at a load can be achieved
by reactive power injection at the load point of common
coupling. D-ST A TCOM injects a current into the
system to correct the voltage sag and swell.
III. DISTRIBUTION STATIC
COMPENSATOR (D-STATCOM)
A D-STATCOM (Distribution Static Compensator),
which is schematically depicted in Fig. 5.1, consists of a
two-level Voltage Source Converter (VSC), a dc energy
storage device, a coupling transformer connected in
shunt to the distribution network through a coupling
transformer. Suitable adjustment of the phase and
magnitude of the D-STATCOM output voltages allows
effective control of active and reactive power exchanges
between the D-STATCOM and the ac system.
These power quality devices are power electronic
converters connected in parallel or series with the lines
and the operation is controlled by a digital controllers.
The modeling of these complex systems that contains
both power circuits and control systems can be done
Such configuration allows the device to absorb or
generate controllable active and reactive power.
The D-STATCOM has been utilized mainly for
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International Journal of Recent Advances in Engineering & Technology (IJRAET)
regulation of voltage, correction of power factor and
elimination of current harmonics. Such a device is
employed to provide continuous voltage regulation
using an indirectly controlled converter. In this paper,
the D-STATCOM is used to regulate the voltage at the
point of connection.
It may be mentioned that the effectiveness of the DSTATCOM in correcting voltage sag depends on the
value of ZTH or fault level of the load bus. When the
shunt injected current ISH is kept in quadrature with V L,
the desired voltage correction can be achieved without
injecting any active power into the system. On the other
hand, when the value of ISH is minimized, the same
voltage correction can be achieved with minimum
apparent power injection into the system.
The control is based on sinusoidal PWM and only
requires the measurement of the rms voltage at the load
point.
IV. METHODOLOGY
To enhance the performance of distribution system, DSTATCOM was connected to the distribution system.
D-STATCOM was designed using MATLAB simulink
version R2009a. Fig. 5.6 below shows the flowchart for
the methodology:
Fig. Schematic diagram of a D-STATCOM
From the Fig. 5.1, the shunt injected current I SH corrects
the voltage sag by adjusting the voltage drop across the
system impedance ZTH. The value of ISH can be
controlled by adjusting the output voltage of the
converter.
The shunt injected current ISH can be written as,
ISH = IL ─ IS
Where IS =
V TH − V L
Z TH
Therefore
ISH = IL ─ IS = IL ─
V TH − V L
Z TH
Or
ISH∠η = IL∠−θ −
V TH
Z TH
∠ (δ−β) +
VL
Z TH
∠−β
Fig. Flowchart for the Methodology
D-STATCOM Simulations and Results for Voltage
Sags
The complex power injection of the D-STATCOM can
be expressed as,
Fig. 6.1 shows the test system used to carry out the
various D-STATCOM simulations presented in this
SSH = VL ISH
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International Journal of Recent Advances in Engineering & Technology (IJRAET)
section. The test system composes a 230 kV, 50 Hz
generation system, represented by a Thevenin
equivalent, feeding into the primary side of a 3-winding
transformer. A varying load is connected to the 11 kV,
secondary side of the transformer. A two-level DSTATCOM is connected to the 11 kV tertiary winding
to provide instantaneous voltage support at the load
point.
THD =
Sum of square of amplitudes of all harmonics
Fundamental
component
Power factor(PF) is defind as the ratio between the
average power and the product of the rms values of the
input voltage and cureent; that is,
Power factor =
average power
apparent power
=
KW
KVA
The relationship between PF and THD for non- linear
loads can be determinied by,
D-STATCOM Simulations and Results for THD
Total harmonic distortion, or THD, is the summation of
all harmonic components of the Voltage or current
waveform compared against the fundamental component
of the voltage or current wave:
power factor =
1
1+(THD )2
Fig. Simulink model for the test system for Voltage Sags
D-STATCOM without LCL Passive Filter
Table Results of THD and PF for different types of
fault without LCL passive filter
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International Journal of Recent Advances in Engineering & Technology (IJRAET)
Table shows the percentage of THD shows that it is
not within the IEEE STD 519-1992. The percentage
of power factor is low in the range of 74.82 to 91.35
lagging.
Fig. shows the waveform of distortion output current
and spectrum of distortion output current.
D-STATCOM with LCL Passive Filter
Table Results of THD and PF for different types of
fault with LCL passive filter.
THD
(%)
Power
Factor
(%)
SLG
fault
LL
fault
DLG
fault
TP
fault
TPG
fault
1.15
0.66
1.11
1.11
1.10
99.99
99.99
99.99
99.99
99.99
Table shows that with LCL Passive filter, the
percentage of THD has reduced. Now the THD is
within the IEEE STD 519-1992. The power factor
increases close to unity.
Fig. Distortion output current without LCL
Passive Filter
Fig. Output current with LCL Passive Filter
V. CONCLUSION
Fig. shows the waveforms of output current and
spectrum of output current. It is sinusoidal with LCL
Passive filter was connected to the D-STATCOM.
This paper has presented the power quality problems
such as voltage sags, swells and total harmonic
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International Journal of Recent Advances in Engineering & Technology (IJRAET)
distortion in the distribution system and simulation
techniques of a D-STATCOM. The simulation results
show that the voltage sags and swells (such as LG, LL,
DLG and TPG) can be mitigate by inserting DSTATCOM to the distribution system. By adding LCL
Passive filter to D-STATCOM, the THD reduced within
the IEEE STD 519-1992. The power factors also
increase close to unity. Thus, it can be concluded that by
adding D-STATCOM with LCL filter the power quality
is improved.
[4] G. Venkataramana, and BJohnson, "A pulse width
modulated power line conditioner for sensitive load
centers," IEEE Trans. Power Delivery,vol. 12, pp.
844-849, Apr. 1997.
[5] Rosli omar, Nasrudin abd rahim and Mazizan
sulaiman "Modeling and simulation for voltage
sags/swells mitigation using dynamic voltage
restorer (DVR), " journal of theoretical and applied
information technology, pp 464-470.
[6] Bhattacharya
Sourabh,
"Applications
of
DSTATCOM Using MATLAB/Simulation in
Power System," Research Journal of Recent
Sciences, Vol. 1(ISC-2011), pp 430-433 (2012).
VI. SCOPE OF FUTURE WORK
Further investigation of the D-STATCOM applications
the newly development of the semiconductor devices
and the rising demands inutility application provide a lot
of opportunities of power flow control. With the
promotion and development of smart grid and renewable
energy application in the power system, the DSTATCOM applications will extend to different areas,
from the high voltage transmission system to the
residential distribution system. Further improvement of
D-STATCOM power stage design Modular converter
topology, ETO semiconductor device enable the low
cost, high reliability and transformer less connection of
D-STATCOM in transmission system application. With
the new proposal of the D-STATCOM applications, the
power stage design with different voltage/current rating
in different application areas should be paid more
attentions.
[7] Rodda Shobha Rani, B. Jyothi, "VSC Based
DSTATCOM & Pulse-width modulation for Power
Quality Improvement," International Journal of
Engineering Trends and Technology- Vol. 2, pp
38-41, 2011.
[8] M. Mohammadi, M. Akbari Nasab, "Voltage Sag
Mitigation with D-STATCOM In Distribution
Systems," Australian Journal of Basic and Applied
Sciences, 5(5), pp 201-207, 2011.
[9] Walmir Freitas, "Impacts of AC Generators and
DSTATCOM
Devices
on
the
Dynamic
Performance of Distribution Systems," IEEE
Trans. Power Delivery, vol. 20, no. 2, pp 14931501, April 2005.
Further D-STATCOM control development the
controller response to the disturbance and parameter
variation also need to be considered in the future study
of D-STATCOM applications. The D-STATCOM fault
detection and protection although the fault tolerant
design has been proposed, the D-STATCOM converter
protection scheme is still one open research topic for
real applications.
[10] Alpesh Mahyavanshi, M. A. Mulla, R. Chudamani,
"Reactive Power Compensation by Controlling the
DSTATCOM," International Journal of Emerging
Technology and Advanced Engineering, Volume 2,
Issue 11, pp 212-218, November 2012.
[11] W. Mack Grady, Robert J. Gilleskie, "Harmonics
and how they related to power factor," Proc. of the
EPRI Power Quality Issues & Opportunities
Conference (PQA’93), San Diego, CA, pp 1-8,
November 1993.
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[12] Mohit Bajaj, Vinay Kumar Dwivedi, Ankit
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[13]
[3] Noramin Ismail, Wan Norainin Wan Abdullah,
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