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Novel FUZZY and Series Transformer based
Fault Current Limiter
R.jeyapandiprathap,M.E.,AP/EEE ,M.Siva Kumar, K.K.Venkatsabari,K.SeemanKlnce, Madurai
Abstract: Developing power system networks and
their interconnections may increase the short-circuit
levels beyond the capacity of circuit breakers (CBs).
Short-circuit fault can cause overvoltage transients,
loss of synchronization. This paperproposes a novel
transformer-based solid state fault current limiter
(TBSSFCL) for radial distribution network
applications. The proposed TBSSFCL is capable of
controlling the magnitude of fault current. In order to
control the fault current, primary winding of an
isolating transformer is connected in series with the
line and the secondary side is connected to a reactor,
paralleled with a bypass switch which is made of
anti-parallel insulated gate bipolar transistors. By
controlling the magnitude of ac reactor current, the
fault current is reduced and voltage of the point of
common coupling is kept at an acceptable level.
Also, by this TBSSFCL, switching overvoltage is
reduced significantly.
I INTRODUCTION
Inpowersystemdesignview,limitingthefaultcurrentto
alowlevelcan
reducethedesigncapacityofsomeelectricalequipment
inthepowersystem.Thiswillleadtothereductiontothei
nvestmentcostforhighcapacitycircuitbreakers
andconstructionofnewtransmissionline.Consequentl
y,frombothtechnicalandeconomicalpointsofview,fa
ultcurrentlimitingtechnologyforreducingshortcircuitc
urrentisneeded.
FCLisavariable-
impedancedeviceconnectedinserieswithacircuittolim
itthecurrentunderfaultconditions.TheFCLshouldhav
everylowimpedanceduringnormalconditionandhighi
mpedanceunderfaultcondition.Onthebasisof
theabovecharacteristic,varioustypesofFCLhavebeen
developed.Someofthese
FCLarebasedonsuperconductor,powerelectronic
switchesandtunedcircuitimpedance.
Thefaultcurrentlimitingtechnologyhasbeco
mehotspotinpowersystem
protectionresearch.However,theresearchareconcentr
atedonthesuperconducting
andpowerelectronicswitchestypesofF
Overthelastfourdecades,differenttypesofFCLshavebe
enunderthe
spotlightinpowerprotectionresearch.Inrecentyears,va
rioustypesofFCLhave
beenproposedanddevelopedinmanycountries.Mainlytw
otypesofthemare
discussedmost.Oneissuperconductorfaultcurrentlimit
er(SFCL),theotherone
issolidstatefaultcurrentlimiter(SSFCL).Thisinterestc
omesnotjustduetotheir
excellentcurrentlimitingcharacteristicsbutalsoduetot
heirpositivecontribution
tothequalityofsupply.FCLscanbeeffectiveinreducing
supplyoutageandmitigatevoltagesagonpowernetwork
.
FaultCurrentLimiter FCLsisadevicethathaspotentialtoreducefaultlevelont
heelectricitypowernetworksandmayultimatelyleadtol
owerratedcomponentsbeingusedortoincreasedcapaci
tyonexistingsystems.Electricityindustryisveryattract
edinsuchdevices,providingthatFCLofferthemsatisfa
ctionineconomicsaspectaswell
astechnicalconstraints.
II PROPOSED WORK
Developing power system networks and their
interconnections may increase the short-circuit levels
beyond the capacity of circuit breakers (CBs). Short-
circuit fault can cause overvoltage transients, loss of
synchronization. This paperpropose a novel
transformer-based solid state fault current limiter
(TBSSFCL) for radial distribution network
applications. The proposed TBSSFCL is capable of
controlling the magnitude of fault current. In order to
control the fault current, primary winding of an
isolating transformer is connected in series with the
line and the secondary side is connected to a reactor,
paralleled with a bypass switch which is made of
anti-parallel insulated gate bipolar transistors.
• fuzzy control logic used to control active
devices switching activities
• By controlling the magnitude of ac reactor
current, the fault current is reduced and
voltage of the point of common coupling is
kept at an acceptable level. Also, by this
TBSSFCL, switching overvoltage is reduced
significantly.
Block Diagram
Source Load
Gate DriverCurrent Measurement
Micro controller
LCD
Power
Supply
+5V
-5V
GND
Series Transformer
•M1- MOSFET 1
•M2- MOSFET 2
The basic configuration of the SSFCL
consisting of two connected solid state
switches with Series Transformer.
The M1 & M2 act as the Series transformer
switches.
Switches are connected in inversely serial
manner for both branches.
The corresponding firing pulse is generated
from the controller whenever the faulty
current flows through the load.
CIRCUIT DESCRIPTION
The proposed circuit diagram consists of our project
the power supply circuit the circuit is a dual power
supply (+5V,-5V). The output voltage goes to all IC‟s
operating voltage. The line current measuring devices
CT, the current transformer connect to the series of
the load. Current transformer output connects to the
Shunt resistor to drop the current and allow the
voltage.
The voltage signals goes to IC 741 pin 2. This
attenuator circuit increases the voltage. The output
signals go to microcontroller. Phase current signal go
to controller .The microcontroller is PIC 16f877A is
using of our project. The controller input analog
signals convert into digital signal.
The controller compares the input value and set
value. To increase the input signal the controller
output is high. As a same time the LCD display is
displaying the current. The controller output signal is
go to buffer. The buffer amplifies the signals. This
outputis connected to the opto coupler.
The optocoupler electrically isolate the devices.
Optocoupler output is connected to the Mosfetgate.
The gate pulse is high, Mosfet is switched ON. Also
if, SFCL switch is in ON condition means, if any
fault current flows the SFCL Mosfet will be ON. And
corresponding fault current will be limited through
the inductive load.
IV RESULT AND DISCUSSION
The proposed system was implemented with the help
of Simulink and simulted power system tool boxes in
the MATLAB R2013a software. The following figure
represents the following figure depicts the power
system network considered in this work.
Figure Simulink model of three phase power
system network with 3L-L fault
The aforementioned Simulink model is designed for
11kV distribution grid and the 11kV/415V three
phase transformer and it is connected with the 415V
bus and followed by the linear load. The three phase
L-L fault is added with the model ta the load side.
The Simulink model after adding the TBSSFCL in
series with the feeder line is shown in the following
figure 4.2
FigSimulink model of the power system with
TBSSFCL
The TBSSFCL is serially added with respect to the
feeder line from the main grid. The TBSSFCL is
responsible for limiting the over current from due to
presence of Fault on the load side. The Simulink
model for the TBSSFCL block is represented in the
following figure.
Fig Simulink model for TBSSFCL for single
phase line
The IGBTs present inside the TBSSFCL has to be
controlled very precisely in order to limit the fault
current as dictated at Chapter 3. The main control
block for controlling the IGBT is shoen in the figure
4.4. The circuit contains comparator cirucits and that
comparing the actual value of line current with the
referenece current and turning off the IGBT by
controlling its Gate pulse and parallelly limitinf the
high rate of fault current on the system .
Fig Simulink model for IGBT control block
The Gate pulse generated for the IGBTs in the
TBSSFCL is shown in the following figure. The Plot
represents that the L-G fault is injected between the
time intervals 0.002 to 0.004s. The control block
shown on the above figure produces the logic „0‟ at
the fault occurrence time. Hence by the IGBTs are in
the OFF state.
Fig generated gate Pulse for IGBT
The injected 3L-L fault current and voltage are
measured with the help V-I measurement block and
the corresponding waveforms are shown in the
following figure 4.6
Figure L-L fault voltage and current
The fault current limitation is analyzed on both load
side and source side and with and without TBSSFCL
block. The current waveforms on the source side with
fault on two cases ie.with and without TBSSFCL is
represents in the following figures 4.7 and 4.8
respectively.
FigSource side current with Fault & without
TBSSFCL
FigSource side voltage & current with Fault
&TBSSFCL block
The above waveforms demonstrates the importance
of TBSSFCL on the power system very clearly. The
source current and voltage are still stable during the
fault occurrence time period [0.002 to 0.004s]. By
this way the TBSSFCL supports the source side
stability at critical scenarios.
The voltage and current waveforms on the load side
with fault on two cases ie.with and without
TBSSFCL is represents in the following figures 4.9
and 4.10 respectively.
FigLoad Voltage & current with Fault & without
TBSSFCL
FigLoad voltage & current with Fault
&TBSSFCL block
The above waveformsdemonstrates the importance of
TBSSFCL on the power system very clearly. The
source current and voltage are still stable during the
fault occurrence time period [0.002 to 0.004s]. By
this way the TBSSFCL supports the source side
stability at critical scenarios.
V CONCLUSION
The project work has been completed
successfully. The project work works satisfactorily.
From the beginning we conducted many block wise
experiments and verified operation of all the blocks
individually and as a result we did not face much
difficulty in the final integration of the project. In an
attempt develop the project by the way we had the
opportunity to learn PC the concepts of PC based
system design and we also learned the basic concepts
of designing and fabricating SOLID STATE FAULT
CURRENT LIMITER. We also had an opportunity to
work in microcontrollers. This work helped us to
think constructively and led to inculcating a habit of
learning and hard working. We also realized the need
for innovative thinking. Finally we can say that the
entire venture into the development of the project
work was educative and interesting and we could see
many theories that we have learned through class
room lectures now work perfectly in a real world
application.
REFERENCES
[1] Umer.A.khan.”Feasibility Analysis of the positioning of super
conduction fault current limiter for the smart grid Application
Using Simulink and simpower systems ,”IEEE transaction on
applied superconductivity Aug2010.
[2] Min Cheol Ahn and Tac Kuk Ko, “Proof of concept of a smart
fault current controller with a super conducting coil for the
smart Grid “IEEE Transaction on applied super
conducting”,Aug2010.
[3] Woo-Jae Park, Byung chul sung, “The Effect of SFCL on
Electric power grid with wind-turbine generation system
“IEEE Transaction on applied super conductivity,
Vol.20,No.3,June 2010.
[4] Mark Stemmle “Analysis of unsymmetrical faults in high
voltage power systems with super conducting fault current
limiter, ”IEEE Transaction on applied super conductivity,
Vol.17,No.2, June 2007.