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International Journal of Innovative Research in Advanced
Engineering (IJIRAE) ISSN: 2349-2163 Issue 2, Volume 2 (February
2015) www.ijirae.com
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2015, IJIRAE- All Rights Reserved Page -170
Parallel Active Filter Modelling and control strategy for
harmonic elimination
Hamza Nawar Abdulateef Alobidi * Marouani Ismail Electrical
department, College Of Technology. Electrical department, College
Of Technology. Jeddah. KINDGOM OF SAUDI ARABIA Jeddah. KINDGOM OF
SAUDI ARABIA AbstractIn an electrical network, unbalanced and
harmonic currents generated by nonlinear and unbalanced loads can
cause harmonics and unbalanced voltage. These voltage perturbations
along with voltage sag can strongly degrade customer power quality.
Nowadays, the active filters such as shunt, is studied as a
flexible solution to compensate all current and voltage
perturbations. Therefore, in order to improve power system quality,
eliminate the harmonics and improve the power factor, we have also
brought to address the different structures of the parallel active
filter (PAF) with a detailed study which affects both its modeling,
its size and its control strategy. The FAP is simulated on
Matlab-Simulink software. A low voltage network supplying
non-linear loads, is considered as an application in this paper.
The simulation results show the effectiveness, robustness and good
adaptability to network disruption forthis PAF. The results of
simulation study presented in this paper are found quite
satisfactory to eliminate harmonics components from utility
current. The shunt active filter is found effective to meet IEEE
519 standard recommendations on harmonics levels.
Keywords parallel active filter , power supply, , total harmonic
distorsion, reactive power , power factor ,Pulse Width
Modulation.
I. INTRODUCTION
The increased severity of the harmonic pollution in power
systems over the last couple of decades has lead the power
electronics engineers to develop high performance solutions to
power quality problems created by power electronic circuits. This
technological development for power quality problems involves
parallel active filters. With various successful some circuit
topologies and control strategy, parallel active filters are
capable of not only harmonic current compensation, but also
negative sequence current, reactive power, and neutral wire current
(zero sequence current) compensation[1]. Parallel Active filters
are also utilized to suppress voltage harmonics and voltage
flickering, regulate load terminal voltages, balance voltages in a
power system, and damp resonances. The active filters can be
parallel (shunt) type, series type, and combination of both
depending on the type of nonlinear loads and the required
functionality [2], [3].
The Parallel Active Filter (PAF), shown in Figure 1[4], is the
earliest and most recognized active filter configuration in the
technical literature and it has been utilized in practical
applications. Due to the parallel connection to the load, it is
also termed as parallel filter. Parallel active filter is
controlled as a current source and it is utilized to inject a
compensating current into the system (to the load), so that its
current cancels the harmonic current, the reactive power current
and the unbalanced current components on the AC side of a nonlinear
load. When it is employed to three-phase four-wire systems, The
Parallel Active Filter also has the capability of compensating the
neutral current (zero sequence current) component.
Fig 1. PAF implemented as a harmonic compensating current
source.
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International Journal of Innovative Research in Advanced
Engineering (IJIRAE) ISSN: 2349-2163 Issue 2, Volume 2 (February
2015) www.ijirae.com
_________________________________________________________________________________________________
2015, IJIRAE- All Rights Reserved Page -171
Therefore, with the application of Parallel Active Filter, the
current drawn form utility grid becomes harmonic free,
balanced, and in phase with utility voltage, and zero-sequence
free in three-phase four-wire systems. The nonlinear load in the
Parallel Active Filter application shown in Figure 1 is presented
as a general purpose thyristor rectifier with DC link inductor for
illustration. In fact, PAF is suitable and generally employed for
diode/thyristor rectifiers with AC and/or DC side inductors. Such
rectifier loads generally constitute the front-end circuits of
systems such as ASDs and UPSs, which behave as harmonic current
generator/source nonlinear loads (inductive loads) [5], [6]. PAF
also has the capacity of damping harmonic resonance between an
existing passive filter and the supply impedance[7]. The parallel
active filtering technology is well matured and the Parallel Active
Filter performance attributes are attractive such that many leading
power electronic companies manufacture Parallel Active Filters. ABB
[8], manufacture PAFs complying with the harmonic standards of IEEE
519 and EN61000-3-4 for the industrial and domestic
applications.
II. PARALLEL ACTIVE FILTER A. Parallel active filter
connection
The active filter can be connected in parallel or in series with
the network, we are interested in what follows the
parallel active filter (shunt). In the general case, the current
absorbed by the load has an active component ( Lai ), a reactive
component ( Lri ), and a harmonic component ( Lhi ) as:
L La Lr Lhi i i i (1) With : s Lai i .
The Parallel active filter provides reactive and distorting
power:
f Lr Lhi i i (2) To define the harmonic content of a waveform
(or distortion level of a waveform), the term Total Harmonic
Distortion (THD) is used and can be applied to either voltage or
current. The THD of current is defined as:
THDi= (3)
where the Ih is the rms value of the current harmonic components
and I1 is the rms value of the fundamental current component.
The phasor diagram illustrated by the Figure 2 shown the
Distorting power D and the power factor PF, that are respectively
given by the equation x and y:
(4)
(5)
Fig 2. Phasor diagram of powers
B. three-phase voltage inverter An inverter is a converter for
supplying an AC load from a DC source. If the source is a
continuous voltage source
inverter is called voltage inverter. Fig 3. illustrate the
topology of a three-phase voltage inverter.
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International Journal of Innovative Research in Advanced
Engineering (IJIRAE) ISSN: 2349-2163 Issue 2, Volume 2 (February
2015) www.ijirae.com
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2015, IJIRAE- All Rights Reserved Page -172
Fig 3.Three-phase voltage inverter The commutation of the power
switches (IGBT:S1,S2, S3) is reflected by the following
equations:
dc
Mc
Mc
Mc
VSSS
VVV
.
3
2
1
3
2
1
(6)
(7)
III. INSTANTANEOUS REACTIVE POWER THEORY
To generate the Harmonic Current Reference, the harmonic current
extraction methods utilized in the PAF application
is the Instantaneous Reactive Power Theory. Instantaneous
reactive power theory (IRPT) known as Akagi-Nabae Theory defines
the instantaneous real power and instantaneous reactive power in a
3-phase 3-wire system where no zero-sequence voltage is included.
IRPT is utilized to derive the fundamental and harmonic components
of load current via measured line voltages and currents.
This method exploits the transformation ( , ) to get the real
and imaginary powers. Denote by ( sVsV , ) and
orthogonal components of the landmark ()( , ss II ) associated
respectively with voltages (Vs123) for connecting the
parallel active filter and current absorbed by the pollutant
loads. The transformation ( , ) can be write the following
relationship of voltage and current:
1 11 11
2 2 232 2 23 3 303 32 2
V Vs sVs V VT s sVs V Vs s
(8)
Z Z
ic1 ic2 ic3
M
Vc3
VcVc1
i
ik1 ik2 ik3
ik2
ik3
k1 k2 k3
k2 k3
Vd
k1
N
1 2
3
ik1
Load
Z
dc
c
c
c
VSSS
VVV
.211121112
3/1
3
2
1
3
2
1
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International Journal of Innovative Research in Advanced
Engineering (IJIRAE) ISSN: 2349-2163 Issue 2, Volume 2 (February
2015) www.ijirae.com
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2015, IJIRAE- All Rights Reserved Page -173
1 1
2 2
33
1 112 2 2
32 3 3 302 2
L L
L L
LL
i iI si iTIs ii
( 9)
Where (iL1 , iL2, iL3 ) are the current load and T32 is the
transformation 3 phase-2 phase [9]. The instantaneous active power
P and imaginary Q are defined by the following relationships
Fig 4. Transformation Model (T32 :3phase to 2 phase) Current
voltage for parallel active filter.
1 2 31 2 3s s sL L LV V Vi i iP (10)
2 33 2 11
1 2 3 13 S SL L LV V V V V VQ i i is s s s
(11)
In the landmark ( , ) we can build the following matrix
equation:
32
V IV sP ssIQ V sV ss
(12)
The active power P and reactive power Q respectively consist of
active and reactive fundamental component p , q of most these
powers respectively include an active harmonic component p
~ and a reactive harmonic component q
~:
qqQppP~~
(13)
The current harmonics are calculated in the landmark ( , ) by
the following matrix:
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International Journal of Innovative Research in Advanced
Engineering (IJIRAE) ISSN: 2349-2163 Issue 2, Volume 2 (February
2015) www.ijirae.com
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2015, IJIRAE- All Rights Reserved Page -174
(14)
22 SS VV (15)
We can separate the current in the ( , ) we get:
03 1 3 1 3 1
2 2 20s S S S S S S
s S S S S s S
I V V V V V V ppI V V V V V V qq
(16)
The transition to the phase marker is carried out by the
following matrix:
1
2
3
1 0
2 1 33 2 2
1 32 2
re fre f
re fr e f
re f
ii
ii
i
(17)
With iref and iref perturbation currents calculated in the ()
from reactive currents and harmonic currents of the relation
(14)
IV. SIMULATION RESULTS
The active power filter was implemented with matlab simulink .
the supply grid line-to-neutral voltage VS was 230 V (RMS) and the
filter capacitor voltage VC was controlled to 980v V, tested on a
non linear load model. the inverter output filter Lf= 2mH and CF =
10 F. the pulse width modulation technique (PWM) used with
switching frequency fd = 12 KHz and coefficient setting rmax =
0.8.
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-6
-4
-2
0
2
4
6
Time (s)
Load
cur
rent
(iL1
, iL2
, iL3
) [A
]
Fig 5. Non linear Load current
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-40
-30
-20
-10
0
10
20
30
40
50
Time (s)
Sou
rce
curre
nt (i
s1, i
s2, i
s3) [
A]
is1is2is3
Fig 6. Source current
3 12
S Sh
h s s
V pVqV V
ii
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International Journal of Innovative Research in Advanced
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2015) www.ijirae.com
_________________________________________________________________________________________________
2015, IJIRAE- All Rights Reserved Page -175
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-40
-30
-20
-10
0
10
20
30
40
Times (s)
Filte
r cur
rent
(iF1
,iF2,
iF3)
[A]
iF1iF2iF3
Fig 7. Current generated by the parallel active filter
Fig 8, Fig 9 and Fig 10 chown that the parallel active filter
with inverter three phase gave results within acceptable limits
standards the harmonic distortion that does not exceed 5% and
reactive power is almost nil after compensation, three network
current are sinusoidal and balanced.the power factor is improved
.
0 2 4 6 8 10 12 14 16 180
1
2
3
4
5
Order of Harmonic
Mag
nitu
de h
arm
onic
Peak Magnitude Spectrum of load current
Fig 8. Peak magnitude spectrum of the load current with Total
harmonic distortion THDi=16.42%
0 2 4 6 8 10 12 14 16 180
1
2
3
4
5
Order of Harmonic
Mag
nitu
de h
arm
onic
Peak Magnitude Spectrum of source current
Fig 9. Peak magnitude spectrum of the source current with Total
harmonic distortion THDi=1.38%
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International Journal of Innovative Research in Advanced
Engineering (IJIRAE) ISSN: 2349-2163 Issue 2, Volume 2 (February
2015) www.ijirae.com
_________________________________________________________________________________________________
2015, IJIRAE- All Rights Reserved Page -176
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2-400
-300
-200
-100
0
100
200
300
400
Time (s)
is1(
A),v
s1 (V
)
vs1is1
Fig 10. Current and source voltage
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-400
-200
0
200
400
600
800
1000
1200
Time (s)
DC
bus
vol
tage
Fig 11. Voltage across capacitor
The fig 11 shows the robustness of the control loop of the
regulation system included in this parallel active filter.
V. CONCLUSIONS In this paper, the connection of a parallel
active filter, its modeling and its control strategy and the
harmonic
identification portion are well developed. the characteristics
of the harmonics producing nonlinear loads and the application
consideration of the PAF to these loads are analyzed . Actually,
Parallel active filters are presented as a modern solution; they
provide the answer to all the disadvantages of passive filters and
have the advantage of being in combination with other active filter
and / or hybrid passive again with a more efficient manner. The
different simulation results also show that the parallel active
filter is able to decrease the harmonic levels within acceptable
limits for a non-linear load and therefore improving the power
factor and compensation of reactive power which allows clean up the
grid by improving the quality of electrical energy which is always
requested.
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