International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 10, October 2012)
Performance Investigation of Active Power Line Conditioner
using Simulink
Ankita Singh1, Sanjiv kumar2
1
Research Scholar, Department of Electrical Engineering, H.B.T.I. Kanpur, India.
2
Asst. Professor, Department of Electrical Engineering, H.B.T.I. Kanpur, India.
Abstract— Active power conditioners have been developed
over the years to solve the problems to improve power quality.
Among which shunt active power conditioners is used to
eliminate load current harmonics and reactive power
compensation. The controller ensures that the dc-side
capacitor voltage is nearly constant with small ripple besides
extracting fundamental reference currents. The PLL block
assists the active filter to function even under distorted voltage
or current conditions. The shunt APLC system is
implemented with voltage source inverter and is connected at
PCC for compensating the reactive power. The shunt APLC
system is modeled and investigated under unbalanced nonlinear load conditions using MATLAB simulation. The
simulation results reveal that the active power filter line
conditioner is effectively compensating the reactive power and
improves power factor at point of common coupling.
II. BASIC COMPENSATION PRINCIPLE
Figure 1 shows the basic compensation principle of a
shunt active power filter.
It is controlled a compensating current ic from the utility,
so that it cancels current harmonics on the Ac side, and
makes the source current in phase with the source
voltage[7,8].
Keywords— Active power line conditioners (APLC), PWM
inverter, PLL, PI, PID, Fuzzy logic controller and Hysteresis
current controller (HCC).
I. INTRODUCTION
To cancel the compensate the reactive power APLC is
the suitable solution. The APLC concept is to use an
inverter to inject currents or voltages harmonic
components to cancel the load harmonic components. The
more usual configuration is a shunt APLC to inject
current harmonics into the point of common coupling
(PCC). The APLC can be installed in a low voltage power
system to compensate one or more loads; thus, it avoids the
propagation of current harmonics in the system. The
developments of different control strategies give APLC to
a new location. As APLC compensate the reactive power
and cancel the harmonics, it is also called as active
power line conditioners (APLC). The concept of shunt
APLC was first introduced by Gyugyi and strycula in
1976 .
Figure 1 Basic Compensation Principle
The load current waveform, the desired mains current
and compensating current injected by the active filter
containing all the harmonics, to make mains current
sinusoidal [6]. From Figure.1, the instantaneous currents
can be written as
Is(t) = il(t) - ic(t)
( 1)
Source voltage is given by
Vs (t) = Vm sin wt
(2)
If a non-linear load is applied, then the load current
will have a fundamental component and harmonic
components which can be represented as
Il(t)= ∑ (ln sin (nwt+Φn) =I1(x) sin (nwt+ Φn) +∑n
= 2 sin (nwt+ Φn)
(3)
The instantaneous load power can be given as
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 10, October 2012)
Pl(t) = Vs(t) * Il(t)
(4)
Pl(t) =VmI1 sin2wt *cosΦ1+VmI1 sinwt*coswt*
sinΦ1+ Vm sinwt*∑In sin (nwt+Φn)
Pl(t) = P f (t) + Pr (t) + Ph (t)
(5)
P f (t) =Vm I1 sin2wt*cosΦ1 =Vs (t) * is (t)
(6)
From equation (6), the source current supplied by the
source, after compensation is
Is (t) =Pf (t)/Vs (t) = I1 cosΦ1 sinwt=Im sinwt
(7)
Where Ism =I1 cosΦ1
There are also some switching losses in the PWM
converter, and hence the utility must supply a small
overhead for the capacitor leakage and converter switching
losses in addition to the real power of the load. The total
peak current supplied by the source is therefore [12]
Isp =Ism + Is1
(8)
If the active filter provides the total reactive and
harmonic power, then is(t) will be in phase with the utility
voltage and purely sinusoidal. At this time, the active filter
must provide the following compensation current:
Ic(t)=Il(t)-Is(t)
(9)
Hence, for accurate and instantaneous compensation of
reactive and harmonic power it is necessary to estimate, i.e.
the fundamental component of the load current as the
reference current [12,13].
Figure 2. Simulink Model of Shunt APLC System with PWM VSI
The model of APLC system contained three subsystems,
PLL based reference current generator, PI or PID or Fuzzy
logic controller and Hysteresis current controller as shown
in Simulation model in fig 3.
III. MODELING OF ACTIVE POWER LINE CONDITIONER
The proposed shunt Active Power line conditioning
diagram shown in figure-2.It has PWM voltage source
inverter connected to a Dc capacitor reduction in current
harmonics is achieved by injecting equal but opposite
current harmonics at the PCC (point of common
coupling).This process will cancel the original distortion
and improving the power quality of the connected power
system. The active filter is based on a PWM voltage source
inverter is connected to the PCC through interface filter;
the active filter is connected in parallel with the AC/DC
converter. This inverter uses dc capacitor as supply and can
switch at high frequency to generate the current that will
cancel the harmonics from AC/DC converter. The current
waveform for canceling harmonics is achieved by using
VSI in the current controlled mode and the interface
filter[12,13].
Figure 3 Simulink model of Active power line conditioning block
A
92
Modeling of PLL Based Reference Current Generator
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 10, October 2012)
Figure 4 Simulink Model of PLL based Reference Current Generator
The PLL block tracks continuously the fundamental
frequency of the system voltages (Vsc,Vsb,Vsa).The PLL
based subsystem shown in Fig. 4 determines
automatically the system frequency and the outputs of the
PLL synchronizing block are Iar, Ibr and Icr the three
phase currents.
B
Figure 3 Simulink Model of Hysteresis Current Controller
Modeling of PI, PID and Fuzzy Logic Controller
This subsystem contained PI or PID or Fuzzy logic
controller which on the difference of Vref and Vdc .The PI
controller estimates the magnitude of peak reference
current Imax and control the dc-side capacitor voltage of
voltage source inverter.
IV. RESULT ANALYSIS
A. Performance of Proportional Integral controller based
APLC system
The simulation of APLC system is done with PI
controller. The three phase unbalanced RL load is
connected in parallel with diode rectifier load to the three
phase ac mains and active power filter is connected in
parallel at the PCC for suppressing the harmonics and
reactive power.
The Source voltage, source current and load current
under unbalanced RL with non linear load without
compensation block are shown in Fig 8 (a), (b) and (c)
respectively.
Figure 1 Simulink Model of PID controller
Figure 2 Simulink Model of Fuzzy Logic controller
C
Modeling of Hysteresis Current Controller
This subsystem Hysteresis Current Controller has been
developed for switching of converters by comparing the
actual current to the reference current. In the case of
positive input current, if the error current e(t) between the
desired reference current iref(t) and the actual source
current iactual(t) exceeds the upper hysteresis band limit
(+h), the upper switch of the inverter arm is become OFF
and the lower switch is become ON as shown in the Fig.7.
Here the hysteresis band limit h=0.5. The range of the error
signal e(t) directly controls the amount of ripple voltage in
the output current from the PWM-VSI.
Figure 8 Simulation results before compensation under unbalanced
RL with non linear load (a) Source voltage (b) source current and
(c) load current
The Simulation results for PI controller based APLC
system under unbalanced RL with non linear load with
compensation are shown in Fig 9.
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 10, October 2012)
The active power and reactive power are calculated by
averaging the voltage-current product at the fundamental
frequency 50 Hz, shown in Figure 11.
Figure.11 Active Power and Reactive Power without Active Power
Line Conditioner
Figure 9 Simulation results after compensation under unbalanced RL
with non linear load (a) Source voltage (b) Dc capacitor side output
voltage (c) Source current and (d) load current (e) Compensation
current and (f) Reference current
The dc side capacitance voltage (Vdc) and its settling
time are controlled by PI-controller; this controller reduces
the ripple and makes settling time less; this is plotted in
Fig 9 (b) for non-linear with unbalanced load (t=0.055s).
Figure .12 Active Power and Reactive Power with Active Power
Line Conditioner
B. Performance of Proportional Integral derivative
controller based APLC system
The Simulation results for PID controller based APLC
system under unbalanced RL with non linear load with
compensation are shown in Fig 13.
Figure.10 Power factor after compensation under unbalanced RL
with non linear load using PI controller
The power factor is improve after compensation over
nonlinear and unbalanced load and reach to unity (0.9998)
when simulation of APLC System is done with PI
controller.
94
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 10, October 2012)
Figure. 15 Active Power and Reactive Power with Active Power Line
Conditioner
C. Performance of Fuzzy Logic controller based APLC
system
The Simulation results for Fuzzy logic controller based
APLC system under unbalanced RL with non linear load
with compensation are shown in Fig 16.
Figure .13 Simulation results after compensation under
unbalanced RL with non linear load” (a) Source voltage, (b) Source
current, (c) load current, (d) Dc capacitor side output voltage, (e)
Compensation current and (f) Reference current
The dc side capacitance voltage (Vdc) and its settling
time are controlled by PID-controller; this controller
reduces the ripple and makes settling time less; this is
plotted in Fig 13 (d) for non-linear with unbalanced load
(t=0.053s)
Figure .14Power factor after compensation under unbalanced RL
with non linear load
The power factor is improve after compensation over
nonlinear and unbalanced load and reach to unity (0.9999)
when simulation of APLC System is done with PI
controller. The active power and reactive power of PID
based APLC system are calculated by averaging the
voltage-current product at the fundamental frequency 50
Hz, shown in Figure 15.
Figure.16 Simulation results after compensation under unbalanced
RL with non linear load” (a) Source voltage, (b) Dc capacitor side
output voltage, (c) Source current, (d) load current, (e)
Compensation current and (f) Reference current
The dc side capacitance voltage (Cdc) and its settling
time are controlled by Fuzzy logic-controller; this
controller reduces the ripple and makes settling time less;
this is plotted in Fig16 (b) for non-linear with unbalanced
load (t=0.050s).
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 10, October 2012)
The simulation is done for various non-linear
unbalanced load conditions. PI, PID and fuzzy logic
controller with PLL synchronizing control based
compensator filter makes the source current balanced and
sinusoidal after compensation. . The PI or PID or FLC
ensures that the dc-side capacitor voltage is nearly constant
with small ripple besides extracting fundamental reference
currents. The performance of a PI, PID and fuzzy logic
controlled APLC system is verified and compared under
non-linear and unbalanced loads with various parameters
that are presented graphically.
Figure. 17 Power factor after compensation under unbalanced RL
with non linear load
The power factor is reach to unity when fuzzy logic
controller is used in the place of PI and PID controller. This
is the best power factor for APLC system.
This simulation model of APLC system improves power
factor on non-linear unbalanced load conditions.
Real power in watts (W) and reactive power in voltamperes (VAR) are measured under non-linear with
unbalanced load condition and are presented in table 2.
Table 2
Comparison of PI, PID and FLC for real Power and reactive Power
Compe
nsation
conditio
ns
Without
APLC
Figure.18 Active Power and Reactive Power with Active Power Line
Conditioner
The active power and reactive power of FLC based
active power line Conditioning are calculated by averaging
the voltage-current product at the fundamental frequency
50 Hz, shown in Figure 18.
With
APLC
Power
Factor
PI
0.55
0.9998
PID
0.53
0.9999
FLC
0.50
1
PID
FLC
P=14.68KW
P=14.68KW
P=14.68KW
Q=0.85VAR
Q=0.85VAR
Q=0.85VAR
P = 34.50KW
P=34.80KW
P= 19.1KW
Q = 0.68VAR
Q=0.45VAR
Q= 0.21VAR
V. CONCLUSIONS
In this dissertation work the performance of the shunt
active power line conditioner is analyzed using HCC with
PI, PID and Fuzzy logic controllers for improving the
power factor in the power system. The PI or PID or FLC
ensures that the dc-side capacitor voltage is nearly constant
with small ripple besides extracting fundamental reference
currents. The PLL synchronizing circuit assists the active
filter to function even under distorted voltage or current
conditions. The shunt APLC system is implemented with
voltage source inverter and is connected at PCC for
compensating the reactive power. The inverter gate control
signals are derived from hysteresis band current controller.
The performance of a PI, PID and fuzzy logic controlled
Table 1 :Comparison of PI, PID and FLC for DC voltage settling time
and power factor
VDC settling
time in
seconds
PI
The phase locked loop with Fuzzy logic controller based
APLC system effectively compensates the reactive power
and improves power factor.
D. Comparison of Performance of PI, PID And Fuzzy
Logic Controllers
The settling time of the DC-side capacitor voltage of the
inverter using PI, PID and fuzzy logic controller for non
linear and unbalance load conditions; these are presented in
Table 1.
Types of
Controller
Types of Controller
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 10, October 2012)
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APLC system is verified and compared under non-linear
and unbalanced loads with various parameters that are
presented graphically. This active power line conditioner
system is tested and verified using MATLAB. The
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reactive power and power factor due to nonlinear load. The
obtained results indicate that DC-capacitor voltage and the
reactive power control can be adapted easily under nonlinear load conditions.
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