chapter 4 mitigation of voltage sag / swell using fuel...
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54
CHAPTER 4
MITIGATION OF VOLTAGE SAG / SWELL USING FUEL
CELL BASED DYNAMIC VOLTAGE RESTORER
4.1 INTRODUCTION
The widely used energy storage systems are capacitors and
batteries. But capacitors have limitations of low storage and charging and
discharging speeds. Battery backup systems operate similarly to adding
capacitive energy storage, with the advantage that their energy per volume
ratio is much higher than standard capacitors. The batteries are easily
available with low cost; provide ride through for deep sags and full outages.
These have low life and require additional space and maintenance. A super
capacitor can overcome these limitations and provide an efficient working but
super capacitors do not have a conventional solid dielectric.
Fuel cell is used to charge the supercapacitor to restore the voltage
during distortions. Systems for electro chemical energy storage and
conversion include batteries, fuel cells and electro chemical capacitors.
Although the energy storage and conversion mechanisms are different, there
are electro chemical similarities of these three systems. In batteries and fuel
cell, electrical energy is generated by conversion of chemical energy via red-
ox reactions at anode and cathode. The negative electrode is denoted as anode
Alkaline Fuel C
ell(A
FC)
H2
Potassium
Hydroxide
(40-200) °C
60%
Molten C
arbonate Fuel C
ell (M
CFC
)C
H4, H
2, CO
Molten
Carbonate
(650) °C
45-50%
The following are the advantages of using fuel cell:
The unit is lighter and smaller and require little m
aintenance
They cause little pollution and little noise
Very efficient
They are a renewable source of energy.
4.3FU
EL
CE
LL
BA
SED
DV
R
The majority of pow
er quality problems are due to different fault
conditions. These
conditions cause
voltage sag,
swell
and distortions.
Dynam
ic voltage restorer (DV
R) can provide the cost effective solution to
mitigate pow
er quality problem by establishing the appropriate voltage
quality level. This mitigation of voltage is provided w
ith the help of a fuel
cell. Fuel cell coupled with the supercapacitor is used as the energy storage
device for the DV
R in this research w
ork as shown in the Figure 4.2. The D
C
57
voltage from the fuel cell is stored in a super capacitor. Super capacitors are
new generation energy storage devices which store energy via charge
separation at the electrode-electrolyte interface, and they can withstand a
large number of charge/discharge cycles without degradation.
Figure 4.2 Block diagram of Fuel cell based DVR
The major advantages of super capacitors include higher
capacitance density, higher charge-discharge cycles, reliable, long life, and
maintenance-free operation, environmentally safe, wide range of operating
temperature, high power density and good energy density, so they are a good
alternative. The dc voltage is converted using a impedance source inverter.
The proposed Z-source inverter has the unique feature that it can boost/buck
the output voltage by introducing shoot through operation mode, which
is forbidden in traditional voltage source inverters. With this unique feature,
the Z-source inverter provides a cheaper, simpler, buck-boost inversion by
single power conversion stage, strong EMI immunity and low harmonic
distortion.
58
4.4 MATHEMATICAL FORMULATIONS
4.4.1 PI Controller
Sag occurs when there is increase in load or during the occurrence
of load while a swell occurs when there is a sudden removal of load or due to
addition of capacitor banks. This sag or swell in load voltage is sensed and its
magnitude is compared with a reference voltage and the error signal is given
to the PI controller. The output of error detector is
–ref inV V (4.1)
where Vref is the reference voltage
Vin is the load voltage
The difference between load voltage Vin and reference voltage Vref
is supplied to the PI controller. The PI controller voltage is taken as feedback.
The IGBT inverter is triggered from the pulse generated by the PWM
generator. The IGBTs are triggered depending upon the firing angle which
introduces additional lag or lead in the voltage.
= ( + + ) (4.2)
= (4.3)
The supply side voltages Va, Vb and Vc are transformed into d–q
values of positive sequence.
C=1
21
2
0 32
32
(4.4)
( ) = cos sinsin cos (4.5)
59
4.4.2 Synchronous Frame Theory
Adda et al (2013) discussed the synchronous reference frame
theory for nanogrid applications. Whenever the system detects a voltage
sag/swell, the DVR should react as fast as possible and inject an ac voltage
into the grid. It can be implemented using the synchronous reference frame
(SRF) technique based on the instantaneous values of the supply voltage. The
control algorithm produces a three phase reference voltage to the PWM
inverter to maintain the load voltage at its reference value. The voltage
sag/swell is detected by measuring the error between the supply voltage and
the reference value. The reference component is set to a rated voltage. The
SRF method can be used to compensate all type of voltage disturbances,
voltage sag/swell, voltage unbalance and harmonic voltage. The difference
between the reference voltage and the supply voltage is applied to the ZSI to
produce the load rated voltage, with the help of pulse width modulation
(PWM) through the PI controller.
d a b cV = 2 3[V sin( t)+ V sin( t-2 / 3) V sin( t+2 / 3)] (4.6)
q a b cV = 2 3[V cos ( t)+ V cos( t-2 / 3) V cos ( t+2 / 3)] (4.7)
0 a b cV =1 3[V + V V ] (4.8)
where w= rotation speed (rad/s) of the rotating frame.
a d q 0V =[ V sin ( t) V cos( t) V ] (4.9)
b d q 0V =[ V sin ( t-2 / 3) V cos( t-2 / 3) V ] (4.10)
c d q 0V =[ V sin ( t+2 / 3) V cos( t+2 / 3) V ] (4.11)
60
4.4.3 Fuzzy Logic Controller
The PI controller is the most frequently used controller in the
DVRs. The disadvantage of the PI Controller is its inability to work well
under a wider range of operating conditions. Hence fuzzy controller is
proposed. In this control method, PLL for each phase tracks the phase of
network voltage phasor and generates a reference signal with magnitude of
unit to supply frequency for each phase. The supply voltage for each phase is
converted to p.u. and error is obtained from the difference of reference PLL
generated signal and actual supply voltage converted to p.u. Error and error
rate are the inputs for the Fuzzy Logic Controller (FLC). The output of the
FLC is fed to the PWM generator to produce switching pulses for ZSI. Jurado
et al (2003) described the voltage sag correction by DVR using FLC.
Ashari et al (2007) discussed the fuzzy controller for DVR. The
desired response from DVR-PLL system is quite different from other
applications. It is because, the phase of the supply voltage prior to the sag is
generally preferred and if the PLL reacts quickly to changes in the phase
during sag, the post-sag phase may be used. Therefore the DVR would not be
able to compensate for the phase jump. Conventionally, once sag is detected,
the target phase of the voltage reference is fixed to the pre-sag phase to ensure
that if the reference is correctly tracked, then the load voltage phase will
remain unaffected. Through a suitable choice of the time constant of the PLL,
the DVR restores the instantaneous voltage waveform in the sensitive load
side to the same phase and magnitude as the initial pre-sag voltage. The fuzzy
member function is shown in the Figure 4.3 and the fuzzy matrix is shown in
the Table 4.2.
61
Figure 4.3 Fuzzy Member Functions
Table 4.2 Fuzzy Matrix
4.5 SIMULATION STUDIES
The Fuel cell based DVR is simulated with three controllers for sag
and swell compensation using matlab/simulink platform.
62
4.5.1 Sag Compensation Using PI, SRF and Fuzzy Controller
The Simulink model for sag compensation is shown in the
Figure 4.4. The Fuel cell, Fuzzy controller and SRF subsystems are shown in
the Figure 4.5 to Figure 4.7.
Figure 4.4 Simulink model for sag compensation
Figure 4.5 Fuel cell subsystem
63
Figure 4.6 Fuzzy Controller Subsystem
Figure 4.7 SRF Subsystem
PI Controller
The sag compensation using PI controller is shown in the
Figure 4.8. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz. The linear load considered is an R-L load (R=250 ,
L=31e-5 H). Additional load is added during the period of 0.05 sec to 0.2 sec,
64
so sag occurs and the voltage in all the 3 phases drops to 249V. DVR is
activated at 0.05 sec and it provides the compensating voltage of 141V to
phase A, 137V to phase B and 120V to phase C. The load voltage is not
compensated to 415V.
Figure 4.8 Sag compensation using PI Controller
SRF Controller
The sag compensation using SRF controller is shown in the
Figure 4.9. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz. The linear load considered is an R-L load (R=250 ,
L=31e-5 H). Additional load is added during the period of 0.05 sec to 0.2 sec,
so sag occurs and the voltage in all the 3 phases drops to 249V. DVR is
activated at 0.05 sec and it provides the compensating voltage of 146V to
phase A, 143V to phase B and 126V to phase C. The load voltage is not
compensated to 415V.
65
Figure 4.9 Sag compensation using SRF controller
Fuzzy Logic Controller
The sag compensation using Fuzzy Logic controller is shown in the
Figure 4.10. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz. The linear load considered is an R-L load (R=250 ,
L=31e-5 H). Additional load is added during the period of 0.05 sec to 0.2 sec,
so sag occurs and the voltage drops to 249V. DVR is activated at 0.05 sec and
it provides the compensating voltage of 166V. The load voltage is
compensated to 415V.
66
Figure 4.10 Sag Compensation using Fuzzy Logic Controller
Table 4.3 Comparison of Distorted voltage, Injected voltage and Load
voltage for different controllers (Sag compensation)
Controllers
Distorted voltage (volts)
Injected voltage (volts)
Load voltage (volts)
Phase A
Phase B
Phase C
Phase A
Phase B
Phase C
Phase A
Phase B
Phase C
PI 249 249 249 141 137 120 390 386 369
SRF 249 249 249 146 143 126 395 392 375
Fuzzy 249 249 249 166 166 166 415 415 415
4.5.2 Swell Compensation using PI, SRF and Fuzzy Controller
(Sudden Removal of Load)
The simulink model for swell compensation (sudden removal of
load) is shown in the Figure 4.11.
67
Figure 4.11 Simulink model for swell compensation (sudden removal of
load)
PI Controller
The swell compensation using PI controller is shown in the
Figure 4.12. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz.The linear load considered is an R-L load (R=250 ,
L=31e-5 H). A sudden removal of load at 0.05 sec causes voltage swell to
456.5V(10% Swell).DVR is activated at 0.05 sec and injects negative voltage
of 64.5V to phase A, 86.5V to phase B and 74.5V to phase C. The Load
voltage is not compensated to 415V.
Figure 4.12 Swell compensation using PI Controller
68
SRF Controller
The swell compensation using SRF controller is shown in the
Figure 4.13. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz. The linear load considered is an R-L load (R=250 ,
L=31e-5 H). A sudden removal of load at 0.05 sec causes voltage swell to
456.5V (10% Swell). DVR is activated at 0.05 sec and injects negative
voltage of 53.5V to Phase A, 81.5V to phase B and 66.5V to phase C. The
Load voltage is not compensated to 415V.
Figure 4.13 Swell compensation using SRF controller
Fuzzy Logic Controller
The swell compensation using FLC controller is shown in the
Figure 4.14. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz. The linear load considered is an R-L load (R=250 ,
L=31e-5 H). A sudden removal of load at 0.05 sec causes voltage swell
to 456.5V (10% Swell). DVR is activated at 0.05 sec and injects
69
negative voltage of 41.5V up to 0.2 second. The Load voltage is compensated
to 415V.
Figure 4.14 Swell compensation using Fuzzy Logic Controller
Table 4.4 Comparison of Distorted voltage, Injected voltage and Load
voltage for different controllers (Swell compensation)
Controllers
Distorted voltage (volts)
Injected voltage (volts)
Load voltage (volts)
Phase A
Phase B
Phase C
Phase A
Phase B
Phase C
Phase A
Phase B
Phase C
PI 456.5 456.5 456.5 64.5 86.5 74.5 392 370 382
SRF 456.5 456.5 456.5 53.5 81.5 66.5 403 385 390
Fuzzy 456.5 456.5 456.5 41.5 41.5 41.5 415 415 415
70
4.5.3 Sag Compensation for LG, LL, LLG and Three Phase Fault
using PI, SRF and Fuzzy Controller
The simulink model for sag compensation (Fault) is shown in the
Figure 4.15.
Figure 4.15 Simulink model for Fault Compensation
PI Controller
Line to Ground fault (LG)
The sag compensation for LG fault using PI controller is shown in
the Figure 4.16. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz. The linear load considered is an R-L load (R=250 ,
L=31e-5 H). Single line to ground fault occurs during the period of 0.05 sec to
0.2 sc, so sag occurs and the voltage drops to 225V in phase A and 390V in
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phase C. DVR is activated at 0.05 sec and it provides the compensating
voltage of 85V to phase A and 23V to phase C. The load voltage is not
compensated to 415V.
Figure 4.16 Sag compensation for LG fault using PI Controller
Line to Line fault (LL)
The sag compensation for LL fault using PI controller is shown in
the Figure 4.17. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz. The linear load considered is an R-L load (R=250 ,
L=31e-5 H). A line to line fault occurs during the period of 0.05 sec to 0.2
sec, so sag occurs and the voltage drops to 413V in phase A and 340V in
phase B and 330V in Phase C. DVR is activated at 0.05 sec and it provides
the compensating voltage of 2V to phase A and 63V to phase B and 72V to
phase C. The load voltage is not compensated to 415V.
72
Figure 4.17 Sag compensation for LL fault using PI Controller
Double Line to Ground fault (LLG)
The sag compensation for LLG fault using PI controller is shown in
the Figure 4.18. The source supplies a nominal voltage of 415 V and nominal
frequency of 50Hz. The linear load considered is an R-L load (R=250 ,
L=31e-5 H). A double line to ground fault occurs during the period of 0.05
sec to 0.2 sec, so sag occurs and the voltage drops to 410V in phase A and
310V in phase B and 320V in Phase C. DVR is activated at 0.05 sec and it
provides the compensating voltage of 5V to phase A and 90V to phase B and
70V to phase C. The load voltage is not compensated to 415V.
73
Figure 4.18 Sag compensation for LLG fault using PI Controller
Three Phase Fault
The sag compensation for three phase fault using PI controller is
shown in the Figure 4.19. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz.The linear load considered is an R-L load (R=250
, L=31e-5 H). A Three phase fault occurs during the period of 0.05 sec to
0.2 sec, so sag occurs and the voltage drops to 210V in all the phases. DVR is
activated at 0.05 sec and it provides the compensating voltage of 215V to
phase A and 205V to phase B and 170V to phase C. The load voltage is not
compensated to 415V.
74
Figure 4.19 Sag compensation for Three Phase fault using PI Controller
Synchronous Reference Frame Controller
Line to Ground fault (LG)
The sag compensation for LG fault using SRF controller is shown
in the Figure 4.20. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz. The linear load considered is an R-L load
(R=250 , L=31e-5 H). Single line to ground fault occurs during the period
of 0.05 sec to 0.2 sec, so sag occurs and the voltage drops to 225V in phase A
and 390V in phase C. DVR is activated at 0.05 sec and it provides the
compensating voltage of 188V to phase A and 20V to phase C. The load
voltage is not compensated to 415V.
75
Figure 4.20 Sag compensation for LG fault using SRF controller
Line to Line fault (LL)
The sag compensation for LL fault using SRF controller is shown
in the Figure 4.21. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz. The linear load considered is an R-L load
(R=250 , L=31e-5 H). A line to line fault occurs during the period of 0.05
sec to 0.2 sec so sag occurs and the voltage drops to 413V in phase A and
340V in phase B and 330V in Phase C. DVR is activated at 0.05 sec and it
provides the compensating voltage of 2V to phase A and 72V to phase B and
80V to phase C. The load voltage is not compensated to 415V.
76
Figure 4.21 Sag compensation for LL fault using SRF controller
Double Line to fault (LLG)
The sag compensation for LLG fault using SRF controller is shown
in the Figure 4.22. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz. The linear load considered is an R-L load
(R=250 , L=31e-5 H). A Double line to ground fault occurs during the
period of 0.05 sec to 0.2 sec so sag occurs and the voltage drops to 410V
in phase A and 310V in phase B and 320V in Phase C. DVR is activated
at 0.05 sec and it provides the compensating voltage of 5V to phase A and
101V to phase B and 93V to phase C. The load voltage is not compensated
to 415V.
77
Figure 4.22 Sag compensation for LLG fault using SRF controller
Three Phase Fault
The sag compensation for three phase fault using SRF controller is
shown in the Figure 4.23. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz.The linear load considered is an R-L load (R=250
, L=31e-5 H).A Three phase fault occurs during the period of 0.05 sec to 0.2
sec so sag occurs and the voltage drops to 210V in all the phases. DVR is
activated at 0.05 sec and it provides the compensating voltage of 215V to
phase A and 210V to phase B and 170V to phase C. The load voltage is not
compensated to 415V.
78
Figure 4.23 Sag compensation for Three Phase fault using SRF controller
Fuzzy Logic Controller (FLC)
Line to Ground fault (LG)
The sag compensation for LG fault using FLC controller is shown
in the Figure 4.24. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz. The linear load considered is an R-L load
(R=250 , L=31e-5 H). Single line to ground fault occurs during the period
of 0.05 sec to 0.2 sec, so sag occurs and the voltage drops to 225V in phase A
and 390V in phase C. DVR is activated at 0.05 sec and it provides the
compensating voltage of 190V to phase A and 25V to phase C. Thus the load
voltage is compensated to 415V.
79
Figure 4.24 Sag compensation for LG fault using Fuzzy logic controller
Line to Line fault (LL)
The sag compensation for LL fault using FLC controller is shown
in the Figure 4.25. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz. The linear load considered is an R-L load
(R=250 , L=31e-5 H). A line to line fault occurs during the period of 0.05
sec to 0.2 sec, so sag occurs and the voltage drops to 413V in phase A and
340V in phase B and 330V in Phase C. DVR is activated at 0.05 sec and it
provides the compensating voltage of 2V to phase A and 75V to phase B and
85V to phase C. The load voltage is compensated to 415V.
80
Figure 4.25 Sag compensation for LL fault using Fuzzy logic controller
Double Line to Ground fault (LLG)
The sag compensation for LLG fault using FLC controller is shown
in the Figure 4.26. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz. The linear load considered is an R-L load
(R=250 , L=31e-5 H).A Double line to ground fault occurs during the
period of 0.05 sec to 0.2 sec, so sag occurs and the voltage drops to 410V in
phase A and 310V in phase B and 320V in Phase C. DVR is activated at 0.05
sec and it provides the compensating voltage of 5V to phase A and 105V to
phase B and 95V to phase C. The load voltage is compensated to 415V.
81
Figure 4.26 Sag compensation for LLG fault using Fuzzy logic controller
Three Phase Fault
The sag compensation for three phase fault using FLC controller is
shown in the Figure 4.27. The source supplies a nominal voltage of 415 V and
nominal frequency of 50Hz. The linear load considered is an R-L load
(R=250 , L=31e-5 H). A Three phase fault occurs during the period of 0.05
sec to 0.2 sec, so sag occurs and the voltage drops to 210V in all the phases.
DVR is activated at 0.05 sec and it provides the compensating voltage of
215V to phase A and 215V to phase B and 215V to phase C. The load voltage
is compensated to 415V
82
Figure 4.27 Sag compensation for Three Phase fault using Fuzzy logic controller
Table 4.5 Comparison of Distorted voltage, Injected voltage and Load voltage for different controllers (Fault compensation)
Controllers Faults
Distorted voltage (volts)
Injected voltage (volts)
Load voltage (volts)
PhaseA
PhaseB
PhaseC
PhaseA
PhaseB
PhaseC
PhaseA
PhaseB
PhaseC
PI
LG 225 415 390 85 0 23 310 415 413
LL 413 340 330 2 63 72 415 403 402
LLG 410 310 320 5 90 70 415 400 390
3 phase 210 210 210 215 205 170 425 405 380
SRF
LG 225 415 390 188 0 20 413 415 410
LL 413 340 330 2 72 80 415 412 410
LLG 410 310 320 5 101 93 415 411 413
3 phase 210 210 210 215 210 170 425 420 380
Fuzzy
LG 225 415 390 190 0 25 415 415 415
LL 413 340 330 2 75 85 415 415 415
LLG 410 310 320 5 105 95 415 415 415
3 phase 210 210 210 215 215 215 415 415 415
83
4.5.4 Comparative Analysis of Various Controllers for Sag and Swell
Compensation
The comparative analysis of various control methods for sag
compensation is shown in the Figure 4.28.
Figure 4.28 Comparative analysis for sag compensation
Additional load is added during the period of 0.05 sec to 0.2
sec, so sag occurs and the voltage drops.
DVR is activated at 0.05 sec and it provides the compensating
voltage.
From the three control methods, it is evident that the Fuzzy is
superior than the other methods.
With the Fuzzy controller, voltage restoration is maximum.
Phase A Phase B Phase C
Conventional 390 386 370SRF 395 392 375Fuzzy 415 415 415
340
350
360
370
380
390
400
410
420
VOLT
AG
EV
84
The comparative analysis of various control methods for swell
compensation is shown in the Figure 4.29.
Figure 4.29 Comparative analysis for swell compensation (sudden
removal of load)
A sudden removal of load at 0.05 sec causes voltage swell.
(10% Swell).
DVR is activated at 0.05 sec and injects negative voltage up to
0.2 sec.
From the three control methods, it is evident that the Fuzzy is
superior than the other methods.
With the Fuzzy controller, voltage restoration is maximum.
Phase A Phase B Phase C
Conventional 390 370 380SRF 400 380 390Fuzzy 415 415 415
340
350
360
370
380
390
400
410
420VO
LTA
GE
V
85
The comparative analysis of various control methods for sag
compensation (LG fault) is shown in the Figure 4.30.
Figure 4.30 Comparative analysis for LG fault sag compensation
Single line to ground fault occurs during the period of 0.05 sec
to 0.2 sec, so sag occurs and the voltage drops in phase A and
phase C.
DVR is activated at 0.05 sec and it provides the compensating
voltage.
From the three control methods, it is evident that the Fuzzy is
superior than the other methods.
With the Fuzzy controller, voltage restoration is maximum.
Phase A Phase B Phase C
Conventional 310 415 413SRF 413 415 410Fuzzy 415 415 415
300
320
340
360
380
400
420
440
VOLT
AGE
V
86
The comparative analysis of various control methods for sag
compensation (LL fault)is shown in the Figure 4.31.
Figure 4.31 Comparative analysis for LL fault sag compensation
A line to line fault occurs during the period of 0.05 sec to 0.2
sec, so sag occurs and the voltage drops in phase A, phase B
and phase C.
DVR is activated at 0.05 sec and it provides the compensating
voltage.
From the three control methods, it is evident that the Fuzzy is
superior than the other methods.
With the Fuzzy controller, voltage restoration is maximum.
Phase A Phase B Phase C
Conventional 415 403 402SRF 415 412 410Fuzzy 415 415 415
395
400
405
410
415
420VO
LTAG
EV
87
The comparative analysis of various control methods for sag
compensation (LLG fault)is shown in the Figure 4.32.
Figure 4.32 Comparative analysis for LLG fault sag compensation
A Double line to ground fault occurs during the period of 0.05
sec to 0.2 sec, so sag occurs and the voltage drops in phase A,
phase B and phase C.
DVR is activated at 0.05 sec and it provides the compensating
voltage.
From the three control methods, it is evident that the Fuzzy is
superior than the other methods.
With the Fuzzy controller, voltage restoration is maximum.
Phase A Phase B Phase C
Conventional 415 400 390SRF 415 411 413Fuzzy 415 415 415
375
380
385
390
395
400
405
410
415
420VO
LTAG
EV
88
The comparative analysis of various control methods for sag
compensation (Three phase fault)is shown in the Figure 4.33.
Figure 4.33 Comparative analysis for three phase fault sag compensation
A Three phase fault occurs during the period of 0.05 sec to 0.2
sec, so sag occurs and the voltage drops in all the phases.
DVR is activated at 0.05 sec and it provides the compensating
voltage.
From the three control methods, it is evident that the Fuzzy is
superior than the other methods.
With the Fuzzy controller, voltage restoration is maximum.
Phase A Phase B Phase C
Conventional 415 405 380SRF 415 410 380Fuzzy 415 415 415
360
370
380
390
400
410
420VO
LTAG
EV
89
Simulation parameters
Nominal Frequency : 50Hz
Three phase Peak Amplitude : 415V
Line Resistance : 0.1
Line Inductance : 10e-3
Active power : 10e3 W
Resistance : 250
Inductance : 31e-5
4.6 CONCLUSION
This chapter explained the fuel cell based dynamic voltage restorer
for voltage sag and swell compensation. The DVR is based on a shunt
capacitor fed series Z source inverter through dc-to-dc step up converter. The
three different voltage controllers were designed for DVR voltage regulation
such as PI Controller, SRF controller and Fuzzy logic controller. The
comparative analysis for three controllers has been done. The detailed
simulation analysis found that fuzzy logic controller is the best method. Fuel
cell coupled with the supercapacitor is used as the energy storage device for
the DVR. Band controlled DVR is designed and further validated by
simulation results.