Development and Implementation of Novel
Techniques for the Control of Shunt Active
Filter
By
P.Rathika,
Asso.Prof, Cape Institute of Technology
Levengipuram, Kanyakumari.
Guided By
Dr.D.Devaraj,
Professor/EEE,
Arulmigu Kalasalingam College of Engineering,
Krishnankoil
Plan of Presentation
I
Introduction
•
•
•
•
II
III
Shunt Active Filter
•
•
•
Principle of operation
Reference Current Extraction
Voltage and Current control method
Proposed Control Strategies
•
•
•
•
•
•
IV
Power Quality
Harmonics – an overview
Sources of harmonics
Mitigation Techniques for Harmonics
Hysteresis Current Control Techniques
Fuzzy Logic based Current control strategies
Voltage Control Techniques
Time and Frequency domain based current extraction
Simulation Results
Hardware Implementation with Results
Conclusions
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Power Quality
Any deviation from a perfect sinusoidal waveform that
can results in failure or mis-operation of customer
equipment
Quality of the current and voltage provided to the
customers
 Providing customers with a pure sinusoidal waveforms
at 50 Hz without any deviations.
 Providing power to allow sensitive electronic
equipment operate reliably.
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What are Harmonics
Harmonics
A sinusoidal voltage or current having frequencies that are
integral multiples of the power frequency.
In the resultant
wave the
sinusoidal
character is lost
f(x) = sin(x)
+
=
f(x) = sin(x) + sin(5x)
5
f(x) =
sin(5x)
5
4
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Sources of Harmonics
Non-linear loads: draw current only a part of the
voltage cycle
Non-linear load devices create harmonics when they convert ac to dc,
dc to dc, dc to ac, and ac to ac






Modern electronic equipments such as
personal or notebook computers
laser printers
fax machines
telephone systems, stereos, radios, TVs
adjustable speed drives and variable frequency drives
battery chargers, UPS, and any other equipment powered
by switched-mode power supply (SMPS) equipment
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Harmonics
Total Harmonic Distortion (THD)
It is the ratio between the RMS value of the
harmonic currents to the fundamental current.
THD 


2
 In
n2
I
1
 100
(%)
I 22  I 32 ...............
 100
I
1
(%)
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Harmonics Sources
Examples
Computer
THD = 80 to 140%
Rectifiers
THD = 20 to 60%
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Effects of Harmonics

Over heating of Transformer

Excessive neutral current

Damage of sensitive electronic equipments

Tripping of Circuit Breakers

Low system efficiency

Poor power factor

Skin Effect

Interference in the nearby communication
systems
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Recommended limits - IEEE 519
The Institute of Electrical and Electronics Engineers (IEEE)
has set recommended limits on both current and voltage
distortion in IEEE 519-1992.
Voltage Harmonic Distortion Limits
Bus Voltage at PCC
Individual Voltage
Distortion (%)
Total Voltage
Distortion THD (%)
69 kV and below
3.0
5.0
69.001 kV through
161kV
1.5
2.5
161.001 kV and above
1.0
1.5
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Harmonic Current Limits
Isc/IL
h<11 11≤h<17 17≤h<23 23≤h<35
35≤h
THD
(%)
<20
4.0
2.0
1.5
0.6
0.3
5.0
20-50
7.0
3.5
2.5
1.0
0.5
8.0
50-100
10.0
4.5
4.0
1.5
0.7
12.0
100-1000
12.0
5.5
5.0
2.0
1.0
15.0
>1000
15.0
7.0
6.0
2.5
1.4
20.0
Isc:
IL:
Maximum short-circuit current at the Point of Common
Coupling (PCC).
Maximum demand load current (fundamental) at
the PCC.
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Harmonics Solution Techniques
Filters: The harmonics filters are the solution to
eliminate the harmonics.
1
2
3
Active Filter
 shunt active filter
Passive Filter
 series active filter
Hybrid Filter
 hybrid shunt –
series active filter
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Basic Operation of Shunt Active Filter
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Heart of Shunt Active Filter
Reference Current Generator
1
Heart of
SAF
3
DC Voltage Control
2
Gating Signal Generator
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Block Diagram of SAF
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Research Objectives
This research work focuses on developing suitable control
techniques and reference current extraction method for the
shunt active filter for three phase 3-wire and three phase 4-wire
system.
The objectives are
 To develop an effective and reliable control strategy for three
phase shunt active filter to suppress harmonic currents and
compensate reactive power under ideal, non-ideal source
voltage condition and also it should maintain a constant
switching frequency.
 To develop an effective reference current calculation method to
extract the harmonics content present in the load current under
ideal, non-ideal and noisy voltage source condition.
 To develop a suitable voltage controller to maintain constant
voltage across the DC bus capacitor.
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Shunt Active Filter with Fixed
Hysteresis Band
Technique
Hysteresis current controller
When the current through the inductor exceeds the upper hysteresis limit
a negative voltage is applied by the inverter to the inductor. This causes
the current in the inductor to decrease. Once the current reaches the
lower hysteresis limit a positive voltage is applied by the inverter to the
inductor and this causes the current to increase and the cycle repeats.
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Current Extraction Techniques
Methods
 Time domain Techniques
 Frequency Domain Techniques
- Large number of calculation is involved hence it is less
practical.
Time Domain Technique
 Harmonics extraction methods in the time domain are
based on instantaneous derivation of compensating
signals in the form of either voltage or current signals
from distorted and harmonic polluted voltage or
current signals.
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Reference Current Extraction
Clarke Transformation
Voltage
1  V
 1
 a
1




V 
2
2
2

 Vb 

V 
3  3 3 
 
0 2 2  Vc 
Current
1  I
 1
 a
1




 I 
2
2
2
I 



I 
 b
3
3
3



 
0 2 2   I c 
…..Contd
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Contd…..
Instantaneous Real and Reactive Power
 p   V V   I  
q    V V   I 
   
    
Reference compensation currents in α-β coordinates
ic *  V  V   ~ 
p
 *  
 
ic  V V  q 
Reference compensation currents in a-b-c coordinates


ica *   1
 * 
1
icb    
2
 * 
icc  
1
 
2

05/07/11


0

3 

2 

3 


2 
ic * 
 *
ic 
20
PI – DC Bus Voltage Control
Vc ref – Reference DC Voltage
Vc - Actual DC Voltage
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Simulation Results
Test System
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Circuit Diagram of Shunt Active Filter
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Without Filter
Distorted three phase line current
Harmonic Spectrum of the distorted line current
THD=26.34%
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Results with AF
Three phase line current with filter
Harmonic Spectrum of the line current with filter
THD=4.1%
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Switching Frequency
•The switching frequency is varying between 19kHz to 20kHz
• The switching loss gets increases
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Constant Frequency Hysteresis
Band Control
Constant Frequency Hysteresis Current Control
generates switching pulses based on the prediction of current error and its slope and the
past switching ON/OFF time of the switches in the inverter. In this technique, the
hysteresis bandwidth need not be specified in the entire control algorithm.
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Calculation of Switching Time
The switching time is calculated from the system parameters


2
V
1
dc

t ,OFF  

*
 [ L (i (t )  i (t )] t 
 ,ON 
 f fa 1 fa 1
t  ,OFF  t  ,ON 
1
T
2


2
V
1
dc

t,ON  

*
 [ L (i (t )  i (t )] t

 ,OFF 
 f fa 3 fa 3
t ,OFF  t ,ON
1
T

2
30
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Without Filter
Distorted three phase line current
Harmonic Spectrum of the distorted line current
THD=26.34%
31
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Results with Filter
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Harmonic Contents -supply current and voltage
Harmonic
Order
Individual Harmonic Content (% of fundamental)
Without Filter
Filter with FHBCC
Filter with CFHCC
Current
Voltage
Current
Voltage
Current
3
0
0.01
0.5
0
0.03
5
23
0.12
1.5
0.11
1.27
7
12
0.12
1.52
0.13
1.03
9
0
0.01
0.12
0.01
0.07
11
9
0.3
1.61
0.28
1.34
13
7
0.23
1.45
0.23
1.1
15
0
0.02
0.26
0.01
0.15
17
5
0.39
1.33
0.39
1.0
19
4
0.25
0.9
0.25
0.2
THD(%)
26.34
3.3
4.1
2.91
3.89
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Source voltage and Current
Real and Reactive power supplied by the source to the Load
34
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Average Switching Frequency of the Inverters
05/07/11
35
DRAWBACKS
The performance is poor under non-ideal source
voltage condition- Not suitable for unbalance
system
The switching frequency is high
Switching loss is high
36
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Fuzzy Adaptive Hysteresis Band
Current Control
Adaptive Hysteresis Current Control
Band width
di * fa
HB j  f (vs (t ),
)
dt
vs (t )  Supply Voltage
i * fa  Filter Re ference Current
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Fuzzy Membership function
39
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Fuzzy Rule Base
di * fa
dt
NL
NM
EZ
PM
PL
NL
PS
PM
PM
PM
PS
NM
PS
PM
PL
PM
PS
EZ
PVS
PM
PVL
PM
PVL
PM
PS
PM
PL
PM
PS
PL
PS
PM
PM
PM
PS
vs (t )
05/07/11
40
Simulation Results
Test System
42
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Four wire System with APF
43
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Distorted Phase and Neutral current
44
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Ideal supply voltage conditions
45
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Ideal supply voltage conditions (Contd..)
46
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Unbalanced and Distorted Condition
47
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Result-After filtering
48
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Results Summary
THD (%)
Voltage
Current Control
Control
Without Filter
PI
Fixed Hysteresis
Phase A
Phase B
Phase C
18.74
25.74
50.42
3.4
4.3
4.5
2.72
3.6
3.6
Fuzzy-Adaptive
PI
Hysteresis
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Average Switching Frequency
Average Switching
Real Power Supplied from
Frequency (KHz)
Source (Kw)
Fixed HBCC
19
4500
2
CFHCC
16
4000
3
Fuzzy-Adaptive HBCC
10
3400
S.No
Control Technique
1
50
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Average Switching loss
51
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Fuzzy Logic based PWM Current
Control
Block Diagram of SAF
53
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Fuzzy Logic Controller
54
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Membership Function
55
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Rule Base
e
NL
NM
EZ
PM
PL
NL
PB
PM
PM
PM
PB
NM
PB
PM
PL
PM
PB
EZ
PVB
PM
PVL
PM
PVL
PM
PB
PM
PL
PM
PB
PL
PB
PM
PM
PM
PB
de
56
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Fuzzy Based DC bus Voltage Control
The input to the fuzzy logic controller are
I.
II.
DC voltage error e (t)
Rate of Change in error de(t)/dt
Block diagram of the DC voltage control
using a Fuzzy controller
57
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Membership Function
58
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Fuzzy Rule Base
e
NL
NM
NS
ZE
PS
PM
PL
NL
NL
NL
NL
NL
NM
NS
ZE
NM
NL
NL
NL
NM
NS
ZE
PS
NS
NL
NL
NM
NS
ZE
PS
PM
ZE
NL
NM
NS
ZE
PS
PM
PL
PS
NM
NS
ZE
PS
PM
PL
PL
PM
NS
ZE
PS
PM
PL
PL
PL
PL
NL
NM
NS
ZE
PS
PM
PL
de
59
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Simulation Results
Test System
61
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Without Filter
Distorted three phase line current
Harmonic Spectrum of the distorted line current
THD=26.34%
62
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Harmonic compensation with Fuzzy-Controller
63
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Result – Unbalanced Condition
64
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Result with Filter
65
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Under Varying load condition
66
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Performance comparison of PI and Fuzzy
controller
67
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Wavelet Transform based Current
Extraction
Block Diagram of SAF
69
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Wavelet Decomposition
70
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Wavelet Reconstruction
71
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Fundamental Current Extraction
Fundamental current Extraction using Wavelet Transform Technique
Estimated phase A harmonic current using db8
72
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Simulation Results
Test System
74
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Source Current and Spectrum-Before Filtering
75
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Fundamental Current Extraction
76
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Result –After Filtering
77
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Source current –After Filtering with p-q theory
78
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Result-Summary
THD (%)
Phase
With Filter
Without
Filter
p-q method
Wavelet Method
Phase A
30.66
16.0
10.0
Phase B
29.58
16.3
10.34
Phase C
30.02
16.7
10.34
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Performance Summary
Detection Parameter
Performance Comparison
Source Voltage Condition
Ideal
Noisy
THD of Source voltage
(%)
0
16
Current Detection
Method
p-q
WT
p-q
WT
Transient time (cycle)
1
<1/4
1
<1/4
Fundamental Extraction
good
good
bad
good
Response Time
high
low
high
low
Selective harmonic
Elimination
Not suitable
suitable
Not suitable
Suitable
80
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Hardware Implementation
Overall Block Diagram
82
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Power circuit
83
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Distorted Source Current
84
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Source Current and Frequency Spectrum
85
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Source Current after Filtering
Source Current
FFT Spectrum
THD = 4.5 %
86
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Hardware setup
87
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Conclusion
This research work has focused on the development and
implementation of novel techniques for the control of Shunt Active
Filter to suppress harmonics and compensate reactive power. A
suitable reference current extraction method is also developed
which performs well under noisy condition.
 The constant frequency hysteresis current controller proposed to overcome the
drawback of the conventional hysteresis control, namely variable switching
frequency.
 The fuzzy logic based adaptive hysteresis current control technique proposed for
the three phase four-wire system can effectively cancel the neutral current produced
due to the unbalanced load. Also, the proposed controller maintains constant
switching frequency with reduced switching loss.
 The fuzzy logic based PWM current control technique proposed to eliminate
harmonics under varying load conditions. the proposed fuzzy-logic based DC
voltage control keeps constant voltage across the capacitor. The proposed controller
maintains the reference voltage without any deviations.
 The wavelet transform based approach proposed for current extraction method can
effectively calculate the reference compensation current under noisy source voltage
condition compared with the conventional p-q theory.
 The simulation results obtained using fuzzy logic based hysteresis current control
techniques are validated by implementing the proposed technique using DSP
processor.
88
Journal Publications
1.
2.
3.
4.
5.
6.
7.
P.Rathika, D. Devaraj, “Fuzzy Logic – Based Approach
for
Adaptive
Hysteresis Band and DC Voltage Control in Shunt Active Filter” International Journal of
Computer and Electrical Engineering, vol.2, No.3, June 2010, pp 1793-8163.
P.Rathika, D. Devaraj, “Fuzzy Logic Based Three-Phase Four-Wire and Four-Leg Shunt
Active Power Filter for Harmonics, Reactive and Neutral Current Compensation”,
International journal of Electrical Engineering, 2011.
P.Rathika, D. Devaraj, “Fuzzy Logic Based D.C Voltage and Current Control Technique for
Shunt Active Filter Design”, Asian journal of Power electronics Applications (Accepted for
Publication)
P.Rathika, D. Devaraj, “Fuzzy-Adaptive Hysteresis Based Current Control based VSI for
Active Power Filter to Reduce Switching Frequency” International journal of Electronics,
Taylor and Francis publications (Revised and submitted)
P.Rathika, D. Devaraj,” Artificial Intelligent Controller Based Three- Phase Shunt Active
Filter for Harmonic Reduction and Reactive Power Compensation” International
journal of Lecture notes in Engineering and Computer Science, 2010.
P.Rathika, D. Devaraj, “Wavelet Transform Based Reference Current Computation and
Fuzzy adaptive Hysteresis Band Current Control for Shunt Active Power Filter”,
International journal on Electrical Engineering, Springer Publication. (Under Review)
P.Rathika, D. Devaraj, “Fuzzy Logic-Based Adaptive Hysteresis Current Control Technique
for Shunt Active Filter”, International Journal on Adaptive and Innovative Systems,
Inderscience Publication. (Under Review)
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International Conference Publications
1. P.Rathika, D. Devaraj, ” Artificial Intelligent Controller Based
Three- Phase Shunt Active Filter For Harmonic Reduction And
Reactive Power Compensation” International Multi Conference of
Engineers and Computer Scientists 2010 Hotel Royal Garden, Hong
Kong , March 2010, pp 1170-1175 .
2. P.Rathika, D. Devaraj, “Discrimination of Power Quality
Disturbances using Combined Mathematical Transforms and
Artificial Neural Network”, IEEE International Conference on
Sustainable Energy Technologies (IEEE-ICSET’08), SMU
Conference Centre, Singapore, Nov 2008, pp 1265-1270.
3. P.Rathika, D. Devaraj, “Power Quality Monitoring using wavelet
transform and Artificial Neural Networks”, India International
Conference on Power Electronics (IICPE ’06), Hotel Le Royal
Meridien, Chennai, Dec 2006, pp 425-430.
90
05/07/11
National Conference Publication
1. P.Rathika, D. Devaraj,” Implementation of Shunt Active Filter using DSP”,
INCOS’10 Kalasalingam University, Krishnanakoil, Apr 2010, pp 63-68.
2. P.Rathika, D. Devaraj,” Design of D-STATCOM using DSP Controller for
Voltage
sag/swell
Mitigation”,
INCOS’10
Kalasalingam University, Krishnanakoil, Apr 2010, pp 52-56.
3. P.Rathika, D. Devaraj,” Shunt Active Filter with Fuzzy Logic Control of
DC Bus Voltage”, Power and Energy Systems (NPES’09) Kalasalingam
University, Krishnanakoil, March 2009, pp 183-186.
4. P.Rathika, D. Devaraj,” Power Quality Monitoring by evaluation of Energy
curves using wavelet Transform”, Recent Trends and Emerging technologies
in Electrical Systems (ELCON’06), National Engineering College,
Kovilpatti, Nov 2006, pp 198-207.
5. P.Rathika, D.Devaraj, ”Shunt Active Power Filter for Power Quality
Improvement”, Recent Trends and Emerging technologies in Electrical
Systems (ELCON’06), National Engineering College,
Kovilpatti,
Nov 2006, pp 81-88.
91
05/07/11
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
Akagi, H., Kanazawa, Y. and Nabae, A. “Generalized theory of the Instantaneous Reactive
power in Three-phase circuits”, International Power Electronics Conference Tokyo, Japan, pp.
1375-1386, 1983.
Anshuman shukla, Arindam Ghosh and Avinash Joshi. “Hysteresis current control operation of
flying capacitor Multilevel inverter and its Application in shunt Compensation of Distribution
Systems”, IEEE Transactions on Power Delivery, Vol. 22, No.1, pp.396-405, 2007.
Aredes, M. and Watanabe, E.H. “Three-phase four-wire shunt active filter control strategies”,
IEEE
Transactions
on
Power
Electronics,
Vol. 12, No.2, pp.311-318, 1997.
Bhim Singh, Kamal Al Haddad and Ambrish Chandra, “A Review of Active Filters for Power
Quality Improvement”, IEEE Transactions on Industrial Electronics, Vol. 46, No. 5, pp. 960970, 1999.
Carl Ngai-Man Ho, Victor, S.P., Chung and Henry Shu-Hung Chung, “Constant-Frequency
Hysteresis Current Control of Grid Connectec VSI without Bandwidth Control”, IEEE
Transactions Power Electronics, Vol. 24, No. 11, 2009.
Chelladurai, J., Saravana Ilango, G., Nagamani, C. and Senthil Kumar, S. “Investigation of
various PWM techniques for Shunt Active Filter”, proceedings of World Academy of Sciences,
Engineering and Technology, Vol. 29, pp.192-197, 2008.
Cupertino, F. and Marinelli, M. “EKF and Wavelet-based Algorithms Applied to Harmonic
Detection for Active Shunt Filters”, 11th International Conference on Harmonics and Quality of
Power, pp.721-727, 2004.
Dwivedi, U.D, and Singh, S.N. “A Wavelet-based Denoising Technique for Improved
Monitoring and Characterization of Power Quality Disturbances”, Electric Power Components
and Systems, Vol. 37, pp. 753-769, 2009.
92
REFERENCES
9.
10.
11.
12.
13.
14.
15.
16.
Edson, H. Watanabe, Mauriclo Aredes and Hirofumi Akagi, “The p-q theory for Active filter
control: some problems and solutions”, Revista Control & Automacao, Vol. 15, pp.78-84,
2001.
Firouzjah, K.G., Sheikholeslami, A., Karami-Mollaei, M.R. and Khateghi, M. “A new
Harmonic Detection Method for Shunt Active Filter Based on Wavelet Transform”, Journal
of Applied Science Research, Vol. 4, No. 11, pp.1561-1568, 2008.
Herrera, R.S., Salmeron, P. and Hyosung Kim, “Insantaneous Reactive Power Theory
Applied to Active Power Filter Compensation: Different Approaches, Assessment and
Experimental Results”, IEEE Transactions Industrial Electronics, Vol. 55, No. 1, pp.184196, 2008.
Hui Liu, Guohai Liu and Yue Shen, “A Novel Harmonics Detection Method based on
Wavelet Algorithm for Active Power Filter”, Proceedings of the 6th World Congress on
Intelligent Control and Automation, pp. 21-23, 2006.
Joao Afonso, Carlos Couto and Julio Martins, “Active Filters with Control Based on the p-q
Theory”, IEEE Industrial Electronics Society Newsletter, Vol. 47, No.3, pp.5-10, 2000.
Lucian Asiminoaei, Frede Blaabjerg and Steffan Hansen, “Evaluation of Harmonic
Detection Methods for Active Power Filter Applications”, Applied Power Electronics
Conference, Vol. 1, pp. 635-641, 2005.
Mehmet Ucar, Engin Ozdemir, “Control of a 3-phase 4-leg Active Power Filter under nonideal mains voltage condition”, Electric Power System Research, Vol. 78, pp. 58-73, 2008.
Vardar, K., Akpinar, E. and Surgevil, T. “Evaluation of reference current extraction methods
for DSP implementation in Active Power Filters”, Electric Power Systems Research, Vol.
79, pp. 1342-1352, 2009.
93
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