a new hybrid series active filter configuration to compensate voltage sag, swell, voltage and...
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7/23/2019 A New Hybrid Series Active Filter Configuration to Compensate Voltage Sag, Swell, Voltage and Current Harmonics…
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IEEE International Symposium on Industrial Electronics (ISlE 2009)
Seoul Olympic Parktel, Seoul, Korea July 5-8, 2009
New Hybrid Series ctive Filter Configuration to Compensate Voltage Sag
Swell Voltage and Current Harmonics and Reactive Power
Ab. Hamadi, Student Member, IEEE, S. Rahmani and K. AI-Haddad, Fellow, IEEE
Canada Research Chair in Energy Conversion and Power Electronics CRC-ECPE
Ecole de Technologie Superieure, 1100 Notre-Dame West, Montreal, Quebec H3C 1K3, Canada.
Email: [email protected]@[email protected]
Abstract- This paper proposes a new system configuration
for a series hybrid power filter (SHPF) realized for all
harmonic types
of
loads. The series hybrid filter consists
of
a small rated series active power filter (SAPF) and a shunt
passive filter with variable inductance using a thyristor
control reactor (TCR). The DC voltage available at the load
side of a typical voltage harmonics source, such as a diode
bridge rectifier followed by a capacitor, is utilized as a
source
of
DC power for the SAPF. To increase the filtering
performance of the shunt passive filter, SAPF is control in
such a way that it increases the network impedance at the
harmonic frequency. This also helps to avoid any series or
parallel resonance that may occur. The shunt passive filter
together with a TCR is used to support the variable load
reactive power demand as well to tackle the current
harmonics generated by non-linear load. The performance
of proposed series hybrid power filter is validated through
MATLAB/Simulink simulation study and successfully
utilized to compensate the voltage sag, voltage swell,
voltage harmonics, current harmonics and load reactive
power demand.
Index Terms- Hybrid active filter, series active filter,
thyristor control reactor, voltage sag and swell, harmonics,
reactive power support.
I. INTRODUCTION
The rapid increase in the technology, especially in electric
power sector, the use of non-linear loads on a typical
distribution system has been increased significantly in
recent years. These non-linear loads are the major source of
harmonics in modem distribution system which is making
the distribution system polluted. On the other side, the
modem equipments are becoming increasingly sophisticated
and require clean power for their proper operation. Any
variation in supply voltage, such as voltage sag and swell or
even harmonics in voltage causes the sensitive equipment to
malfunction.
To improve the quality of power, several solutions have
been proposed by several authors. Among them the shunt
and series active power filters have proven as an important
and flexible alternative to compensate most important
voltage and current related power quality problems in the
978-1-4244-4349-9/09/ 25.00 ©2009 IEEE
286
distribution system [1-8]. The other alternative is the use
of
a unified power quality conditioner (UPQC) to compensate
voltage and current problem simultaneously. However, the
use of UPQC is an expensive solution [9]. A SAPF
essentially requires a source of energy, such as a DC
battery, in order to compensate for voltage sag and swell.
Generally, a separate rectifier is used to provide the
necessary DC power for the
SAPF.
A full bridge diode
rectified followed by a capacitor is extensively used in
modern plants, for example, as in adjustable speed drive.
However, such a topology is often considered as a source
of
voltage harmonics as it generates harmonics in supply
voltage. This paper proposes a new topology for a SHPF
which utilizes an existing front end diode bridge rectifier as
a source
of
DC power for the SAPF. This arrangement thus
helps to eliminate the use
of
additional rectifier require
of
the SAPF. A shunt passive filter together with a thyristor
control reactor (TCR) is used to tackle the harmonics
generated by non-linear load as well as to support the load
reactive power demand. The TCR in passive filter is used to
support the variable load reactive power demand [10-12].
Moreover, the TCR considerably reduces the size
of
overall
shunt passive filter. A hybrid detection method is added to
increase the impedance
of
the series transformer at the
harmonic frequency, which force the current harmonic to
flow in the shunt passive filter. The DC bus voltage of SAPF
is maintained at a constant level by regulating the voltage at
load bus at desired constant level.
II .
PROPOSED HYBRID SERIES ACTIVE POWER FILTER
TOPOLOGY
The system configuration
of
proposed SHPF is shown in
Fig. 1. It consists
of
- (i) small rated series active power
filter, (ii) shunt passive filter and (iii) a typical voltage and
current harmonics type
of
source. The SAPF protects the
sensitive load from variation in the supply voltage. It injects
a voltage component in series with the supply voltage and
thus considered as a controlled voltage source. The required
DC bus voltage for SAPF is provided from the load side.
The output of DC voltage of front end diode bridge rectifier,
as shown in Fig.1, is shared with the
SAPF. This
arrangement thus eliminates the need
of
additional separate
rectifier for the SAPF. The regulation
of
necessary active
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power during the voltage sag and swell condition is done by
maintaining the load voltage at constant level. Thus in the
proposed configuration the need
of SAPF
DC bus voltage
regulation is also eliminated.
In the proposed topology a reduced size passive LC filter
alone with a TCR is connected in parallel with the load. The
SAPF controlled as a harmonic isolator, forcing the load
current harmonics to circulate mainly through the passive
filter rather than the power distribution system. The main
advantage of this scheme is that it reduces the required
power rating
of SAPF.
Where icd » ieq denote the currents in the SAPF inductors,
expressed in synchronous
(d-q)
frame. v
sd
' v
sq
represent
the voltages at the primary side of the transformer,
i
sd
'
i
Sq
are the d-q components
of
the line currents at the primary
side
of
the SAPF.
d
a»
d
q
represent the duty cycles
of
the
upper switches in the inverter topology, Vde is the DC
voltage
of
the inverter and aJ
o
is the mains angular
frequency.
III. SERIES ACTIVE POWER FILTER MODELING
IV .
REFERENCE CURRENT GENERATION
(1)
The
SAPF
is connected in series with the AC source. The
system can mathematically be represented as: [13,14]
L
diea
e -=vea - v
an
dt
L
dieb
e
veb
-v
bndt
The necessary equations to generate the reference signals
are given below:
C
d VCd C
= =
VSq-Zcd+zsd-» ; (6)
dV
cq
-ClOOV
sd
- lcq
+
lsq
u
q
dt
Applying the Park transformer to the Eqn. (1) and to the
Eqn. (2), yield to:
Using PI controller to regulate the voltage of the SAPF.
»:
=
k
p
v
cd
+k, JVeddt (7)
u
q
=k
p
v
eq
+ k
i
JV
eq
(8)
From Eqn. (4), the control law is given by
U
id
- v
ed
- Lemoi
eq
dd =
(13)
v
de
V. IMPROVING FILTER PERFORMANCE
Using PI controller to regulate the current of the
SAPF.
U
id
=kpi
cd
+k, Jieddt (11)
u
iq
=
kpi
eq
+k, Jieqdt (12)
The reference current controller is then given by
i
ed
*
=
-u
d
+
Cm
o
v
eq
+ t; (9)
i
eq
*
=
-u
q
-Cmov
ed
+i
Sq
(10)
(2)
(3)
dv;
. .
=
sc
-lee
dt
1
[
Sin(
lO
ot) -COS lOot
]
P = cos(mot) sin(mot) 0 0
3 0 0 1 3
2
L
dice
e
ee
-V
en
dt
dv
ea
. .
=
sa -lea
dt
dv
eb
. .
=
sb
-leb
dt
Where ie,a,b,e are the currents flowing through the SAPF
inductors and the
is,a,b,e
are the line currents at the primary
side
of
the
SAPF.
To reduce the system order and optimize
the mathematical representation the Park transformation is
considered. The transformation matrix P can be defined as:
1 1
~ - ~
J3 J3
2 2
3 3
2 2
(4)
(5)
The SHPF control scheme is shown in Fig. 4. The approach
uses a hybrid control; detect simultaneously the source
current
is (abc)
and the load voltage
V
L
(abc)
to get their
harmonic components. The main idea is to increase the
impedance of the series transformer at the harmonics
frequency. The reference compensation voltage of the SAPF
adopting hybrid control approach is: [15]
v
=
ki
sh
V
Lh
(15)
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(16)
C
pF
:i CPFa
i a
iLp a
: C
pF
= .
, LpFCa):
Fig. 3. TCR equivalent circuit
The main concept behind controlling TCR is the control of
the firing instant of the thyristor to control the current in the
reactor, thus controlling the reactive power absorbed by the
TCR. Kirchoff's laws of voltages and currents neglecting
the resistor of the inductance applied to this system provide
three differential equations in the
a-b- c
frame. The TCR
control scheme is shown in Fig. 5.
Applying these transformations in dq frame to the shunt
passive filter:
d
2
i
1
J Fd J . dipFq i CI Fd
Ll lJa -- -Lp
F a
)aT UFd
=
2L
p
p(
a )(J)---- - -
dt dt
C
w
d
2
iU>q .
d i
l J' Fd i Cl' Fq
LPF a - - -LpF a)al lu FQ= 2L
PF
(a ) (JJ----= - -+ -
dt dt C
PF
FldarwiI f ttl):t2MID l14443'
-
II.
o
o 5 10 15 20 25
,...,
o
5 10 15 20
25
..
10 15
-,..
.1.1.
~ l I { I :
S 1 1 .
The compensation effects are, to a great extent, dependent
on the control gain k, which is the ratio of the compensating
harmonic voltage generated by the SAPF to the harmonic
current flowing through it. Fig. 2 shows the series voltage
harmonic versus gain k.
One can observe that by deceasing
k, from 5 to 2, reduce the amplitude of the series
transformer voltage harmonics which affects negatively the
filtering performance. For k =
5
the reflected impedance
of
SAPF becomes high and therefore load current harmonic
flows through the shunt passive branches.
k =5(THD
1S
=3%) k=3(THD
1S
=10%) k=2 (THD
1S
=30%)
Fig. 2 voltage harmonic of series active filter versus gain
k
One knows that:
Only the reactive part is chosen:
(17)
(19)
(18)
The following relation is obtained
A.
Sag and
swell compensation
The extractions of three phases voltage references signals
are based on Unit Vector Template Generation. A Phase
Locked Loop (PLL) is used to extract the sinusoidal signal
at fundamental frequency. The PLL gives signal in terms
of
sine and cosine functions. The obtained v Ca ,b,c) are
compared with the measured
VLCa ,b,
c ) As shown in Fig. 4,
the error signal is feed forwarded to the V
hd
and the
v
hq
signal and compared to the compensator voltages
v
cd
and v
cq
' The feedforward signal enhances the filtering
performance by compensating sag, swell and voltage
harmonics.
To regulate the current i
PFq
a model reference adaptive
control is used. The reactance of the inductance can be
modeled as: [10,11]
Jr
L
Pl
.. {
a ) =
L
pF
,
(20)
2J r
- 2a +
sm(2a)
VI.
SHUNT PASSIVE FILTERMODELING
Thyristor controlled reactor for continuously variable
reactive power can be obtained across the entire control
range, with full control
of
both inductive and capacitive
of
the compensator. The principal benefit is its optimum
performance during major disturbances in the system such
as sudden load change and load rejections. This type of
TCR is characterized by continuous control, low losses,
redundancy, and flexibility. Fig. 3 shows the TCR
equivalent circuit. [16,17].
i
CPFq •
u
j
=
B a - -+
oll
Ll
Fq
C
pF
(
2, C
pF
U 1 -OJ
I
LPFq
-
= B
a
I
CPFq
(21)
(22)
The shunt passive filter presents great impedance at the
fundamental frequency and very low impedance at the
harmonics frequency. This filter combined with the series
active filter is able to absorb practically all the current
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harmonics generated by the nonlinear load. The passive
filter is reduced in term of components and is very robust
when its parameters change.
VII. SIMULATION RESULTS
The proposed series hybrid power filter configuration is
simulated under MATLAB-PSB environment to estimate
its' performance. The set of loads consists
of
current-source
type
of
nonlinear load and voltage-source type
of
nonlinear
load to study of the effectiveness of the proposed scheme.
The SHPF system was tested for several different operating
conditions such as - steady-state, transient condition,
voltage sag, voltage swell, and under balanced
nonsinusoidal utility voltages, intending to validate the
SHPF system performance. The simulation results are
shown in Figs. 6 - 8 and discussed in the following
subsections.
A. Dynamic performance under load change condition
In order to verify the performance of the SHPF during
transient response, two types of three phase nonlinear loads
are used simultaneously (diode bridge rectifier followed by
R-L load and diode bridge rectifier followed by R-C load).
Fig.6 shows the transient response of SHPF system. The
load current is abruptly increased and decrease. As viewed
from the simulation results, the changeover from one
operating condition to the other is quite smooth,
maintaining the perfect compensation. The sudden increase
(decrease) in the load though causes a small decrease
(increase) in the DC link voltage.
It was observed that this
decrease (increase) in DC link voltage was around 10V for
nov DC link. Consequently as the load on the system
changes, the control algorithm takes minimum two cycles to
compute the new steady-state load active power demand.
This proves that the SHPF system compensates the
harmonics and reactive power of the load during steady
state as well as transient operating conditions without losing
its performance.
The harmonics spectrums befor and after compensation are
shown in the Fig.7. The compensated source current and
load voltage profile show that the SHAF system was
working effectively, reducing the source current THD from
22.34 % to 1.94 % and the load voltage THD from 18.03 %
to 3.31 %, respectively.
B. Voltage sag, swell
and
harmonics compensation
The performance
of
SHPF system is also tested under
voltage swell, voltage sag and balanced non-sinusoidal
utility voltages. The simulation results are shown in Fig.8.
The source voltage has a voltage THD of 18.03% with
dominant 5
th
and 7th harmonics of 15 % and 10 %,
respectively. In consecutive cycles, the voltage swell is
introduced voluntarily in the utility voltage (20%). And
after that, the voltage sag is also introduced in the utility
voltage (-40%). The SHPF system does not show any
significant effect
of
distortion present in the utility voltages
on its compensation capability and, the source current and
the load voltage THD under this condition, are found pure
sinusoidal. Since the load voltage is maintained constant.
VIII.
CO
NCLUSION
To improve the power quality and to reduce the overall cost
of compensator, in this paper a new hybrid series active
power filter configuration has been proposed. The most
important power quality problems, such as, voltage sag,
voltage swell, voltage harmonics, current harmonics and
load reactive power are compensates effectively utilizing
the proposed system configuration. Thus it could be an
economical solution over a UPQC to tackle similar power
quality problems. Moreover, this configuration requires
reduced size of series active power filter. The
MATLAB/Simulink results show that the voltage sag and
swell are compensates effectively providing a regulated
voltage at load terminal. Additionally , the harmonics
present in the load current (load current THD= 22.34%) and
source voltage (source voltage THD= 18.03%) are
significantly reduced to 1.94% in source current and 3.31%
in load voltage. This proposed system configuration thus
eliminates the need of additional energy source required for
the series active power filter.
11
v / .
VLb
VL c
i l , a :
u l h l C s u u r ce typ e HO
li n
e r
lo t
~
u n t
p s si v e filter
Fig. I Proposed series hybrid power filter configuration
289
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P
V
s(abc) { re f )
vc(abc)
e
+
U
iq
i
cq
ti l
VI
c:
tlZ
:U 0>
0>
:= .S
(l 3
LL
.i;
C
Fig. 4 SHPF control scheme
V
sa
_
i u
. • u q t j3
I
q 0 - .1 H
H
r
__y cont rol ler Eq.22 oo k up
table
c=7..r
PF q
0. 4
.3 5
.3
.1 5
0 .2 0 .2 5
Fig.6 Sudden load variation
0. 1
.0 5
Fig. 5 TCR control scheme
~
f \ . J C A
A 7 \
n
A 7 \
n
f \ . J C A __
\ J C A ~
- A
A A ~
-200
.
__ 0 .1 0 .1 5 __ 0 .2
__
__ 0 .4
~ -20g
o 0 .0 5 0 .1 0 .1 5 0 .2 0 .2 5 0 .3 0 .3 5 0 .4
o
0
.0 5
0 .1 0
.1 5
0
.2
0
.2 5
0
.3
0
.3 5
0
.4
~ ~
o
0
.0 5
0 . 1 0
.1 5
0
.2
0
.2 5
0 .3 0 .35 0. 4
:g
o 0 .0 5 0 .1 0 .1 5 0 .2 0 .2 5 0 .3 0 .35 0 .4
2 0
.
~ g ~
o 0 .0 5 0 .1 0 .1 5 0 .2 0 .2 5 0 .3 0 .3 5 0 .4
~ ~
o 0
.0 5
0 .1 0
.1 5
0
.2
0
.2 5
0 .3 0 .35 0. 4
~ ~ ~ ~ ? = S F ±
: : :
3
o
THD=1 8.03%
SourceVoltage HarmonicSpectrum
i
80
-36 0
'0 40
to
1
20
o
_ L ~ _
5 10 15
Harmonicorder
THO
=
3.31%
10 15
HarmonICO.de.
Load
Voltag
e Har mon ic Spectrum
THO 22.34%
Load Current Harmonic Spectrum
THO;;1.94%
10 15
Harmonlco rtler
Source Current HarmonicSp
ectrum
a) Source current b) Load current d) Load voltage c) Source voltage
Fig.? Harmonics spectrum a) source current b) load current c) load voltage d) source voltafe
290
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0 .4 5.4.3 5.3.2 5.2.1 5.1
~
2000
0.05 0. 1 0.15
0. 2_ _
0.25 0.3 0 .35
0. 4
0 .45
~ ~ 0 ? L n ~ n ~ f ~
200
0.05
0 .1
0.15
0. 2
0 .25 0.3 0 .35
0. 4
0 .45
,_20
•
. e s -2g ~
o 0 .0 5 0 .1 0 .1 5 0 .2 0 .2 5 0 .3 0 .35 0 .4 0 .45
~
1000 0.05 0. 1 0.15 0.2 0 .25 0.3 0 .3 5
0. 4
0 .45
~ ~ _ 1 0 ~ ~
200 0 .0 5
0. 1
0.15 0.2 0 .25 0 .3 0 .3 5 0. 4 0 .4 5
~
_ 5
: : ~ - 2 0
0.05
0. 1
0 .1 5 0 .2 0 .2 5 0. 3 0 .3 5 0. 4 0 .4 5
g
~
E
l i
. . ; ; : ;; ;; 1 : j @
o
0.05
Fig. 8 Voltage sag, voltage swell and voltage harmonics compensation
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