International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
Mitigation of Single Line to Ground Fault using Dynamic
Voltage Restorer
Ms Astha Bhargav1, Mr. S.S.Thakur2, Mr. S.P.Phulambrikar3
1. PG Student at Department of Electrical Engineering in SATI VIDISHA(M.P.)
2. Assistant Professor at Department of Electrical Engineering in SATI VIDISHA(M.P)
3. Associated professor & HOD at Department of Electrical Engineering in SATI VIDISHA(M.P.)
Abstract: -Power quality is one of major concerns
in the present era. It has become important,
especially with the introduction of sophisticated
devices, whose performance is very sensitive to the
quality of power supply. Power quality problem is
an occurrence manifested as a nonstandard
voltage, current or frequency that result in failure
of end utility distribution networks all suffer from
various types of outages and service interruptions
which may result in a significant financial loss. To
improve the power quality, custom power devices
are used the device considered in this work is DVR
this paper presents modelling, analysis and
simulation of a dynamic Voltage Restorers (DVR)
test system using MATLAB in This paper dqo
controller and Discrete PWM pulse generator are
used for the controlling purpose .In this paper
single line to ground fault is mitigate using DVR.
Key words:- Power Quality, Voltage Sag, DVR,
Series Compensation .,VSC
Introduction
The electrical power system is considered to be
composed of three blocks-generation, transmission,
distribution. For a reliable power system, the
generation unit must produce adequate power to
meet customer‟s demand, transmission system must
transport bulk power over long distance without
overloading or jeopardizing system stability and
distribution system stability and distribution system
must deliver electric power to each customer‟s
premises from bulk power system. Distribution
system locates the end of power system and is
connected to base the customer directly, so the
power quality mainly depends on distribution
system. The reason behind this is that the electrical
distribution network failures account for about 90%
of the average customer interruptions. In the earlier
days, the major focus for power system reliability
was on generation and transmission only, as more
capital cost is involved in these. In addition their
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insufficiency can cause widespread catastrophic
consequences for both society and its environment.
But now a day‟s distribution systems have begun to
receive more attention for reliability assessment.
initially for the improvement of power quality or
reliability of the system FACTS devices like static
synchronous compensator (STATCOM), static
synchronous series compensator (SSSC), interline
power flow controller(IPFC), and unified power
flow controller(UPFC) etc are introduced. These
FACTS devices are designed for the transmission
system. But now a days more attention is on the
distribution system for the improvement of power
quality, these devices which are used in distribution
system for power quality improvement are
distribution static synchronous compensator
(DSTATCOM), dynamic voltage restorer (DVR),
active
filter(AF),
unified
power
quality
conditioner(UPQC) etc.
In this paper work form the above custom power
devices, DVR is used with zero order hold for the
power quality improvement in the distribution
system. Here two different load are considered, one
is linear load and the other is sensitive load. Line to
ground fault condition are considered with these
loads to analyze the operation of DVR to improve
the power quality in distribution system.
Dynamic voltage Restorer
Among the power quality problems like sag, swell
harmonic etc, voltage sag is the most severe
distribution system. To overcome these problems
the concept of custom power devices is introduced
lately. One of those devices is dynamic voltage
restorer (DVR), which is most efficient modern
custom power device used in power distribution
networks.
DVR is a recently proposed series connected solid
state device that injects voltage into the system in
order to regulate the load side voltage . it is
generally installed in a distribution system between
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
the supply and the critical load feeder at the point
of common coupling (PCC). Other than voltage
sags and swells compensation DVR can also added
other features like line voltage harmonics
compensation reduction of transients in voltage and
fault current limitations.
Figur1:- Location of DVR
Figure2:- Basic arrangement of DVR
Basic Arrangement of DVR
The DVR mainly consists of the following
components:
1.
2.
3.
4.
5.
6.
An injection transformer
DC charging unit
Storage devices
A voltage source converter (VSC)
Harmonic filter
A control and protection system
The dc charging circuit is used after sag
compensation event the energy source is charged
again through dc charging unit. It is also used to
maintain dc link voltage at nominal dc link voltage.
3 Voltage Source Converter
1. Injection Transformer
Three single phase transformers are connected in
series with the distribution feeder to couple the
VSC (at the lower voltage level )to the higher
distribution level. It links the DVR system to the
distribution network via the HV- windings and
transforms and couples the injected compensating
voltages generated by the voltage source converters
to the incoming supply voltage. In addition the
injection transformer also serves the purpose of
isolating the load from the DVR system.
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2 DC Charging Unit
A VSC is a power electronic system consists of
storage device and switching devices, which can
generate a sinusoidal voltage at any required
frequency, magnitude, and phase angle. It could be
a 3 phase- 3wire VSC or 3 phase 4 wire VSC.
Either a conventional two level converter or a three
level converter is used. For DVR application the
VSC is used to momentarily replace the supply
voltage or to generate the part of the supply voltage
which is absent .there are four main types of
switching devices; metal oxide semiconductor field
effect transistors (MOSFET), gate turn off
thyristors (GTO) , insulated gate bipolar transistors
(IGBT) ,and integrated gate commutated thyristors
(IGCT). Each type has its own benefits and
drawbacks. the function of storage devices is to
supply the required energy to the VSC via a dc link
for generation of injected voltages. The different
kinds
of
energy
storage
devices
are
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
superconductive energy storage (SMES) , batteries
and capacitance.
4. Harmonic Filter
As DVR consist of power electronic devices, the
possibility of generation self harmonics is three so
harmonic filter is also become a part of DVR. The
main task of harmonic filter is to keep the harmonic
voltage content generated by the VSC to the
acceptable level.
5. Control and Protection
The control mechanism of the general
configuration typically consists of hardware with
programmable logic. All protective functions of the
DVR should be implemented in the software.
Differential current protection of the transformer,
or short circuit current on the customer load side
are only two examples of many protection
functions possibility.
Simulation modal
In this simulink model we have a system in which
two parallel feeders are shown in both the feeders
further loads are also connected in parallel in one
feeder DVR is connected in series with line and the
other feeder is kept as it is. dqo controller is used
for the control purpose. Here DVR system is
connected to the distribution system using a booster
transformer.
Figure3:- simulation modal
As discussed, firstly supply voltage (including
voltage sag) is convert from abc to dq0 with the
help abc to dq0 transformation. Here reference sine
wave, which is vectorized inputs in terms sine
wave is provided for abc to dq0 transformation.
After this transformation zero order hold is used to
hold at Voltage Sag in the waveform of one axis
either it is direct axis or quadrature axis.
The test system employed to take out the
simulations regarding The DVR actuation this
system is composed by a 13KV ,50 Hz generation
system, represented by a Thevenin‟s equivalent
feeding two transmission lines through a three
winding transformer connected in Υ/Δ/Δ 13/7/7
KV. such transmission lines feed two distribution
network‟s through two transformers connected Δ/
Υ , 7/2 KV.
Figure4 :- control circuit for DVR
After the zero order hold reference, voltage signal
will multiply and divided by itself due to that 1p.u.
signal will be generated in direct axis or quadrature
axis. That 1p.u. signal will compare with the
constant 1 with the help of product block to
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
generate 1p.u. either direct or quadrature axis. To
generate 1p.u. in AC system dq0 to abc
transformation is performed. In this transformation
two inputs are taken from zero i.e. terminator signal
and remaining one input is taken from above
generated 1p.u. Here dq0 to abc transformation is
done with the help of dq0 to abc transformation in
which stationary frame is converted into rotator
frame.
This magnitude of error signal is injected
to the PWM generator coupled with voltage source
inverter is arrangement will give the required
amount of missing voltage of load side.
Figure7 :- Low pass filter
Because of these conversion‟s the output voltage
of VSI have number of harmonic to eliminate these
harmonic the output of VSI connected to the low
pass filter. This output is provide to injecting
transformer.
Figure5:- PWM Generator
Due to that sine wave with the magnitude 1p.u. is
generated is three phase system. This 1p.u.
reference sine wave is compared with the supply
voltage due to that error is generated, which is
required to be injected in the system .
Figure8 :- voltage of source side at the time of Line to
Ground fault
Figure:- source voltage at the time of line to
ground fault
Figure6:- Voltage Source Inverter
Figure9 :-voltage at the time of fault
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
4.
5.
6.
7.
8.
Figure10 :- voltage at load 1 side
(without compensation)
9.
The wave form present in fig 10 shown the sag
during the line to ground fault ,because at load 1
side compensation device is not connected. But at
load 2 side compensation device is connected so
the voltage sag is reduced as shown in fig 11.
Mahesh singh “modelling analysis and solution of power
quality problems
“SSCET Bhilai india.
Vetrivel, A., „A NOVEL METHOD OF VOLTAGE SAG
AND SWELL ESTIMATION FOR POWER SYSTEM
APPLICATIONS‟ American Journal of Engineering and
Applied Sciences 6 (2): 233-240, 2013
Ms.Santoshi Gupta Simulation of PQ Disturbances by
MATLAB International Journal of Emerging Trends in
Electrical and Electronics (IJETEE).
ROSLI OMAR, MODELING AND SIMULATION FOR
VOLTAGE SAGS/SWELLS MITIGATION USING
DYNAMIC VOLTAGE RESTORER (DVR) Journal of
Theoretical and Applied Information Technology
Sanjay A Deokar DVR Control Strategy for Dynamic
Power Quality Disturbance MitigationInternational Journal
of Scientific and Research Publications, Volume 2, Issue
11, November 2011
Shazly A. Mohammed1Analysis, Modeling and
Simulation of Dynamic Voltage Restorer (DVR) for
Compensation
of
Voltage‐Quality
Disturbances
INTERNATIONAL
JOURNAL
OF
CONTROL,
AUTOMATION AND SYSTEMS.
10. DOMINIK VIGLAŠ, Implementation of Dynamic voltage
restorer for mitigation of voltage sags in the distribution
system Advances in Computer Science
Figure11 :-voltage at lode 2 side
(with compensation)
Conclusion
The modelling and simulation of DVR using
MATLAB/SIMULINK has been presented. A
control system based on dqo technique which is
detect error between source side of the DVR and its
reference for voltage sags correction. The
simulation result shows that the DVR performance
is satisfactory for removal of voltage sags.
References
1.
2.
3.
N.G.Hingorani , Flexible AC Transmission “IEEE
Spectrum vol 30 pp.40-44 1993
Bhim singh kamal “A Review of Active Filters for Power
Quality Improvement “senior member IEEE .
D Mohan Reddy “cascaded multilevel inverter Based DVR
for Restructured power system ” international journal of
Advanced Research in electrical and electronic and
instrumentation engineering vol2 issue 1.
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