Filtros armonicos

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IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES-2016)
Removal of Source Current Harmonics under
Harmonically Balanced Condition using Shunt
Hybrid Active Filters
Dhiraj Bharatl, Priti Srivastava2
1,
2
Electrical Engineering Department, PEC University of Technology, Chandigarh, India
E-mail: Idhirajbharat@pec.ac.in. 2pritisrivastava.meeleI4@pec.edu.in
Abstract-Paper is produced to grant a concept
regarding the use of shunt hybrid active power filter to
counteract the deteriorating effect of harmonies in electrical
power utility system. 3-phase uncontrolled bridge rectifier
has been used as a source of current harmonies of order 6n±1
where n is an integer, producing Harmonically Balanced
Condition by drawing equal magnitude of (6n±1)
th
current
harmonie in each phase. Two shunt hybrid active filters
connected at point of common coupling are used to reduce
current harmonics through insertion of "Positive
Inductance" to tune the passive filter. "PLL Free" approach
of harmonies detection is used which reduces the additional
hardware cost. Implementation of proposed method is
carried out in MATLAB/SlMULINK environment. The
description starts with a brief outline of harmonic distortion
problems and their effects on electrical system under power
quality issues.
Keywords-Active Power Line Conditioner (APLC);
Active Power Filter (APF); Pure Active Filter (PAF); PLL
(Phase Locked Loop); Modijied Synchronous Rejerence
Frame (MSRF); Shunt Hybrid Active Filter (SHAF); Pulse
Width Modulation (PWM)
I. I NTRODUCTION
Power quality concept is gaining more and more
importance day-by-day in electrical engineering domain.
The word itself explains the meaning as the standard of
quality of power that we are using. Poor power quality is a
result of various factors which can be broadly c1assified
into two main categories:
l. Problems in quality of supply.
2. Installation and load related problems.
Supply quality problems refer to voltage sag, voltage
swell, total loss of supply, under/over voltage, harmonie
distortion etc. Installation and load related problems
include harmonie current, earth leakage current, voltage
dips and transients. So, power quality is a big domain.
Harmonie distortion caused by current harmonics is one of
its subset. The foremost sources of current harmonics
includes nonlinear loads such as power electronic
converters (mostly used now-a-days), printers, computers,
adjustable speed drives etc. Thus, with the increasing
penetration of power electronics, level of harmonie
978-1-4673-8587-9/16/$31.00 ©2016 IEEE [1)
pollution also increases in power utility systems and need
to be addressed. It requires the engineers to develop a
perennial solution to address power quality problems [1].
The first and basic solution includes the passive filter
tuned for specific harmonie frequency at point of common
coupling (PCC) [2]. But owing to its various drawbacks
such as detuning from tuned frequency due to ageing of
filter components, dependence on source impedance,
parallel resonance (which causes amplification of
harmonie current) etc. has made its use obsolete. With the
technological advancement in the field of power
electronics various high speed devices such as IGBTs,
MOSFETs etc. are evolved and put into practical use in an
active filters. APFs are of two kinds viz. pure and hybrid
active power filter [3]. These filters are configured as
Voltagel Current source (PWM) inverters and are able to
unravel various power quality issues such as harmonie
distortion, reactive power compensation etc. [4]-[6].
PAF also have some drawbacks of high preliminary
cost and high KVA rating of inverter. Thus, thorough
study and research are carried out to evolve hybrid active
filters which combine the advantage of both passive and
active filter. It reduces the KVA requirement of the PWM
inverter acting as an APF as compared to PAF. Hybrid
active filter are of two kinds viz. shunt active shunt
passive and series active shunt passive filter. The former is
more suitable to use as compared to later for high power
applications [7]-[9].
Present work airns to design SHAF based strategy to
eliminate current harmonics in harmonically balanced
condition caused by 3-cp diode rectifier. It works on the
concept of tuning of passive filter by inserting a
dynamically variable "positive inductance" in the form of
output voltage of voltage source PWM inverter [lO]-[l1].
MSRF method is used for harmonie detection because of
its better dynamic response [12].
11. SYSTEM LAYOUT
Fig. 1 represents the system layout and table. I
represent the parameters of the system.

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IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES-2016)
yoltage
SHAF2 SHAF1
I: Block Oiagram Representation of Proposed System Layout
TABLE I: PARAMETERS OF SYSTEM
Phase voltage (RMS) 240V
Line frequency (f) SO Hz
System source inductance (Ls) ImH
Fig.
System Parameters for SHAFI System Parameters for SHAF2
Passive filter components Passive filter components
Inductance(L7) 14.83mH Inductance (Lr) 10.sl mH
Capacitance (C7) 142/-1F Capacitance (Cr) 13O.2/-1F
Inverter (Active Power Filter) Parameters
OC link voltage (Vdc) 18sV OC link voltage (Vdc) Isov
Switching frequency 137S0 Hz Switching frequency 137s0 Hz
System eonsists of two SHAFs eonneeted in shunt at
PCC, one is SHAF1 (reduees 5th and 7th eurrent
harmonies) and seeond is SHAF2 (reduees all hannonies
exeept 5th and 7th). SHAF1and SHAF2 eonsists of a
passive filter eonneeted in series with PWM inverter
through a eoupling transformer to aet as positive
induetanee insertion deviee.
SHAF1 works by tuning the passive filter for 5th
harmonie frequeney. The Passive filter is tuned at 7th
harmonie frequeney and then additional induetanee to tune
the filter for 5th frequeney is aetively introdueed through
VSI based STATCOM operating at 5th harmonie
frequeney. The induetanee required at 5th harmonie (L5) is
more than that required at 7th harmonie (L7) so the
differenee (Lind5= L5 - L7) is always positive for all
parametrie (± 10%) and frequeney (± 2%) variations.
Thus, only positive induetanee is required to be inserted
by APF to tune the passive filter for 5th harmonie [10],
[13], [14]. In SHAF2, passive filter eomponents value is
set as given in table. I sueh that only positive induetanee is
inserted by PWM inverter to tune the filter up to 29th
eurrent harmonies as after 29th harmonie frequeney THD
eontent of individual hannonie is less than 2%.
I I I. POSlTlVE I NOUCTANCE I NSERTION TECHNIQUE
This teehnique is used in SHAF1 and SHAF2 for
inserting variable induetanee at speeifie harmonie
frequeney and is explained below.
[21
A. SHAFl
The operation of this filter for aetive filtering ean be
understood by operation of STATCOM [14] operating at
harmonie frequeney. In this, passive filter is tuned to
provide low impedanee path to 7th harmonie frequeney
and an aetive power filter is eonneeted in series to injeet
required induetanee to tune passive filter for 5th harmonie
frequeney. Fig.2 shows single phase equivalent eireuit
diagram for SHAFl. The value of induetanee to be
inserted is given as,
Lind5 = _I [�c -OJ50 ] (1)
OJ5 OJ5 7
Voltage eorresponding to (1) is given as,
VindS =
jOJsljSLindS (2)
where, 1jS is the 5th harmonie eomponent of filter
eurrent.
Fig. 2: Per Phase Equivalent Circuit of SHAFI for
Positive Inductance Insertion
The output voltage required to be generated by
voltage souree PWM inverter to tune the filter for 5th
frequeney is given as,
� � �
Vpwm5 = Vind5 + j1j5Xc5 (3)
where, XeS is the eoupling transformer leakage
reaetanee at 5th harmonie frequeney.
VpwmS =
jOJsljSLindS + jljSXeS
jOJsljSLindS =
VpwmS - jljSXeS
1
where, a,
=
� and a2
jOJ 5Ij5 OJ5
(4)
(5)
(6)
(7)
Aetive induetanee Lind5 = 4.67mH inserted by APF is
direetly proportional to output voltage of PWM inverter as
given by (7).
B. SHAF2
In SHAF2, a passive filter of an induetor (Lf) =
O.51mH and eapaeitor (Cs) = 30.2J.1F is eonneeted in series
with aetive power filter. Induetanee required for tuning
SHAF2 at hth harmonie frequeney is given as,

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IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES-2016)
Ltndh =
_I [_I- - WhL! ] (8)
Wh Whe!
where, h eorresponds to higher order harmonies (upto
29th harmonie) exeept Sth and 7th. Fig.3 shows per phase
equivalent of SHAF2.Voltage eorresponding to (8) is
given as,
� �
Vindh =
jWhijhLindh (9)
where, Ijh is hth harmonie eomponent of filter
eurrent. The required output voltage to be generated by
voltage souree PWM inverter is given as,
� � �
Vpwmh =
Tfndh + jIjhXch (10)
where, Xch is the eoupling transformer leakage
reaetanee at hth harmonie frequeney.
Fig. 3: Per Phase Equivalent Cireuit of SHAF2 for Positive Induetanee
Insertion
� � �
Vpwmh =
jWhijhLindh + jijhXch
� � �
jwhljhLindh =
Vpwmh - jijhXeh
L dh =
Vpwmh _ Xch
In �
jWhijh Wh
(11)
(12)
(13)
Lmdh =ajVpwmh - a2 (14)
where, al
= 1 � and a2 = X e
h
jW h1jh Wh
Equation (14) shows the direet relation between
inverter output voltage and induetanee required to
eliminate partieular harmonies in SHAF2.
IV. SINGLE PHASE EQUIVALENT CIRCUlTS
Fig. 4 (a) represents single phase equivalent eireuit at
7th frequeney. Nonlinear load eurrent is modeled as a
eurrent souree at eharaeteristie harmonies (Sth, 7th, h:;:: 11).
Fig. 4 (b) represents tuning of passive filter for Sth
harmonie frequeney by inserting Tjnd5 in SHAFl. This
voltage is inserted in phase quadrature so as to lead the Sth
harmonie eurrent by 90 degree. Fig. 4 (e) shows insertion
of Vindh by SHAF2 to tune for higher order harmonies
exeept Sth and 7th.
[31
(a) (b)
Cv.4�· 1'·(e)
Fig. 4: Single Phase Equivalent (a) for 7th Harmonie Frequeney (b) for 5'"
Harmonie Frequeney (e) for Higher Order Harmonies (:;:: II)
V. HARMONICS REDUCTION UNDER HARMONICALLY
BALANCED CONDITION
Under this eondition, a non-linear load of 3-cfJ diode
reetifier is eonneeted to supply. It eauses the amplitude
speetrum of all harmonies to be same in all 3-phases.
Control strategy and simulation results are explained in
this seetion.
A. Contral Strategy of SHAFI
Control strategy basieally refers to the teehnique of
generating referenee signal eorresponding to whieh gate
pulses for inverter gate drive eireuit is obtained. MSRF
method is used to obtain referenee signal in SHAFl. It
generates sin OJt and eos OJt for 3-cfJ diode bridge reetifier
type of non-linear load. This is aehieved by transforming
phase souree voltages Va, Vb, Vc into stationary referenee
frameaß whieh operate at SOHz frequeney. The matrix
involved is given as,
[Va] = Jfv ß
0 j
.,f2
Vsin OJI =
ß
�V2 + v2a
ß
(lS)
(16)
v
cos wt =
a
(17)
'v2 + v2V a
ß
Passive filter is tuned to 7th harmonie frequeney with
C7 = 42.Sf.!F and L7 = 4.86S4mH and is tuned aetively for
Sth harmonie frequeney. This requires referenee signal
eorresponding to Sth harmonie frequeney by MSRF
method. Sinee, Sth harmonie is a negative sequenee eurrent
so we need to generate sin (-Swt) and eos(-Swt) from (16)
and (17).
sin20Jt = 2sinwtcoswt = KI
cos2wt=2cos2 wt-l=K2
sin3wt=3sinwt-4sin
3
wt=K3
(18)
(19)
(20)

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IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES-2016)
cos3at=4coJ at-3CO'Blr/=K4 (21)
From (18) to (21), we can generate,
sin( - 5wt) = - (K2 K3 + K) K4) = K5 (22)
cos( - 5wt) = cos(5wt) = (K2 K4 - K) K3) = � (23)
Fig.5 shows block diagram to generate reference
waveform for 5th harmonie frequency using MSRF. Fig.6
shows MATLAB/SIMULINK waveform for the same.
Equations involved for generating reference waveform are
given as,
[�
d
l=
[c�s K'pwt
lq smK'pwt
-sinK'pwt][�a
lcosK'pwt lß
[�a 1=
[co
.
sK'pwt sinK'pwt][i
.
d 1
lß -smK'pwt cosK'pwt lq
where, K'= 1, p =6n+1 (for positive sequence)
(24)
(25)
K'= -1,p =6n-l (for negative sequence), n = 1,2,3......
"Sin(-m (osm "Sin(-50i) (os5:!J:
Fig. 5: Block Oiagram to Generate Reference Waveform for SHAFI
.::
0_8 0_82 0_84 0_86 0_88 0_9 0_92 0_94 0_96
(a)
"'IpI1!'! bela
, , I , I I I, "
.:g±ITcYIT0_8 0_82 0_84 0_86 0_88 0_9 0.92 0_94 0_96
(b)
05Q5
�
, , , , ,
w�o - - - - - - - - -
-10 - :- - -
:
- - -
:
- - :
- - - :
- - -
0.8 0.81 0.82 0.83 0.84 0.85
(c)
D505
4 , , , ,
:1::::::::::::t:::::::::::j·::::::::::::1:::::::::::::[::::::::::::11 -------------
:
--- --- --- --- -i - --- --- --- --- i-- --- --- --- --� ------------
0
0 0
'
2 0
'
4 0
'
6 0
'
6 1
(d)
'
:::�iRlmtlf���
b
&
5
fß!PJ&fJ1f&fAd
.;:::
_I8J
0.8 0.81 0.82 0.83 0.84 0.85
(e)
a5b5c5
'�
0.5
: :
0 : : ' :
-0.5 : , : - :
:
-b.a O.�1 Q�2 Q�3 Q� O.�
(f)
Fig. 6: (a) abc Rectifier Current (b) Corresponding Currents in aß
Stationary Frame (c) Currents in Synchronously Rotating Reference
Frame (d) Extraction of 5'" Harmonie as a OC Component (e) Inverse
Transform to Stationary Frame Named as a5ß5(f) Inverse Transform of
a5ß5Stationary Frame To Va5,Vb5,Vc5
[41
abc load currents (50Hz) are transformed to
synchronously rotating frame (250Hz) as shown in
Fig.6(c). Then, the DC value corresponding to 5th
harmonie frequency is obtained by FFT block present in
MATLAB SIMULINK Library. This DC value is
compared with zero (desired value) to generate error and
is send to PI controller to minimize error through
feedback. The output of PI controller is interchanged and
inverse transformed using (25) and (15) to generate abc
reference voItages of 3-phase inverter.
B. Contral Strategy of SHAF2
Fast Fourier Transform (FFT) based control technique
is used to generate reference waveform and is explained in
Fig.7. Fig.8 represents reference waveform obtained for
SHAF2 in SIMULINK model.
FFTto extract
fundamental
Magnitude(M)
phaseN) Msin«2'"pl"rt)+(pr<W180))
Magnitude(M)
phase(q,J
Magnitude(M)
phase(<jl)
Fig. 7: Block Oiagram to Generate Reference Waveform for SHAF2
abc
.::-0.8 0.82 0.84 0.86 0.88 0.9 0.92 0.94 0.96
(a)
a1b1c1
10 _. .
....
....
.
.
....
..
..
....
.... .
..
.
....
.. .
.;.... .
o .
...c . . .. . c ..
.., . . . . c .... •...
.,..
...,.
...
-10 �
0.8 0.82 0.84 0.86 0.88 0.9 0.92 0.94 0.96
(b)
Varef Vbref Vcref
0.4 , , , , ,
0.2 - --- ---- -r- --- --- +- --- ---- -i- ---- --- +- --- ---- -i-- ---- --- -
:.:�o .
.
08 O� �a �a �M ��
(c)
Fig. 8: (a) ILa, ILb, ILcCurrent (b) Fundamental Current Waveform
(c) Reference Waveform
ha, hb, hc as shown in Fig.l obtained after removal of
5th and 7th harmonics (by SHAFl) are sensed and FFT
analysis is done to obtain magnitude and phase
corresponding to fundamental frequency. Fundamental
waveform is obtained and is subtracted from total abc
current to obtain reference corresponding to higher order
harmonie frequencies (2:11) in such a way so that APF
inserted voItage will lead the current by 90 degree.

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IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES-2016)
C. Simulation Results 2) Result of SHAF2
To implement and validate the processing of above
mentioned technique, MATLAB/SlMULINK model has
been developed. For simulation studies, sampIe time taken
is Sf.!sec and solver used is ode23tb (stiftlTR-BDF2). Fig.l
and table. I show the SIMULINK model specification.
Non-linear load used here is 3- ifJ uncontrolled bridge
rectifier to which an R-L load is connected on its DC side
with R= 400hms, L= ImH drawing a non-linear load
current of peak value ISA on AC side. IGBT based VSI is
used as APF for introducing active inductance at specific
harmonie frequency. Sinusoidal PWM technique is used to
generate gating signal with triangular carrier wave
J) Results of SHAFJ
SHAFI is connected in shunt at PCC along with
SHAF2. Passive filter is tuned at 7th harmonie frequency
and the value of Lind5 required to tune the passive filter for
Sth harmonie frequency is given by equation (1).
Corresponding voltage need to be inserted by APF is
obtained by equation (2). This voltage is generated by
proper gating pulses given to the APF by SPWM in which
reference wave signal is obtained for Sth harmonie
frequency as explained in previous section and carrier
wave is triangular in nature. Fig.9(a) represents L-L
voltage injected by SHAF and Fig.9(b) shows its RMS
value equals to 46V and Vdc � 8SV. Thus, modulation
index (m) is 0.S4. Fig.lO shows filter performance in
terms of its spectrum.
Vpwmh
=-o
-00 ' : :
-100
0.8 0.82 0.84 0.86 0.88 0.9 0.92 0.94 0.96
(a)
Vons
�ffimmtmml··mmmjo 0.2 DA 0.6 0.8
(b)
Fig. 9: (a) PWM Voltage Injected by SHAFI (b)
RMS Value of the Same
iS"oo' " '00""
:�08 082 084
T
�86s 088 09
FFTanalysis
10 15
Harmonie order
Fig. 10: Filter Current Waveform and its Spectrum for SHAFI
[51
SHAF2 is configured to reduce higher order
harmonics (h 2:: 11) and is connected at PCc. The voltage
required to be generated is obtained by (9) taking Lindh as
given by (8) and Vdc = SOV. Fig.ll shows L-L voltage
injected by SHAF2. Different voltages are required to be
inserted for different values of Lindh at different higher
order (hth) frequency. The voltage is injected by proper
gating signal obtained by sinusoidal PWM in which
reference wave corresponds to reference signal obtained as
shown in fig.8(c). Fig.12 shows filter performance in
terms of its spectrum.
Fig. II: PWM Voltage Injected by SHAF2
Signal to analyze---------_
FFT window: 6 of 50 cycles of selected signal
:�0.8 0.82 0.84 0.86 0.88 0.9
Time (5)
;-FFT analysis
THO= 52.52%
60
l
� 40
,j'
I
� 20
�
�
I I 1
10 15 20 25 30
Harmonie order
Fig. 12: Filter Current Waveform and its Spectrum for SHAF2
3) THD result for complete system
Fig.13 represents THD percent of source current
without filter. Fig.14 represents total THD percent of the
system with SHAFI and SHAF2.
FFT window: 6 cf 50 cycles cf selected signal
Time s
FFT analysis-------------�
Fig. 13: Source Current Waveform and its Harmonics
Spectrum without Filter

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IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES-2016)
FFT window: 6 of 50 cycles of selected signal
0.8 0.82 0.84 0.86 0.88 0.9
lime s
ri"I -'=, , ,Io 10 15 20 25 30
Hanmonic order
Fig. 14: Souree Current Waveform and its Harmonie
Speetrum with Filters
The combination of SHAFI and SHAF2 results in
total THD reduction of the system from 28.56% to 4.28%
with all individual harmonics less than 3 percent. Table 11
gives a comparative study of THD content (in percent) to
have a c1ear understanding of resuIts of
MATLAB/SIMULINK model.
TABLE 2: COMPARISION OF THD CONTENT OF SOURCE CURRENT
WITHOUT AND WITH FILTER
Harmonics Without filter With SHAFI and
order (THD in percent) SHAF2
(THD in percent)
5" 22.58 0.52
7" 10.96 0.42
11" 8.68 0.40
13" 5.94 0.27
17" 5.13 2.54
19" 3.74 1.36
23'" 3.35 1.78
25" 2.55 1.13
29" 2.28 1.24
Total THD 28.56 4.28
VI. CONCLUSION
This paper proposes methods of elimination of
dominant & higher order current harmonics produced by
uncontrolled diode rectifier using cost effective
combination of SHAFI and SHAF2. ResuIts obtained
shows that THD of individual harmonie currents are less
than 3 percent with total THD of source current equal to
4.28 percent which comply with the IEEE 519 standard
for current harmonics. The proposed system is highly
economical owing to less KVA rating of the inverter &
PLL free harmonie detection. The feasibility of this
method for harmonically unbalanced condition (multiple
non linear loads of different types connected to the PCC)
is under study which represents more realistic scenario in
power system.
[6)
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