Mitigation of Power Quality Issues by Utilizing
Shunt Hybrid Active Power Filter Strategy on
the Power Distribution System
Senthilkumar.A1
S.Srinivasan2
Dr .P.Ajay-D-VimalRaj3
Research Scholar,
EEE Dept.,
Pondicherry Engineering College,
Pondicherry-14,
Senthil.pec14@pec.edu
M.tech,
EEE Dept.,
Pondicherry Engineering College,
Pondicherry-14,
srinivasanpec23@gmail.com
Assistant professor,
EEE Dept.,
Pondicherry Engineering College,
Pondicherry-14,
Abstract— This paper investigates compensation of power
quality problems generated in industrial and domestic
applications using three phase shunt hybrid active power
filter strategy. The current harmonic distortion and
reactive power demand were serious power quality
problems occurred to distort the performance of the power
system load. Traditionally, VSI based shunt active power
filter is used to address the power quality problems. The
conventional shunt active power filter required high DC
link voltage to compensate power quality problems. To
overcome this problem, neutral point clamped inverter
based shunt active power filter strategy is proposed in this
paper. The simulation investigations were carried out
using matlab/simulink and results are verified to validate
the proposed system and compared to conventional
technique.
Keywords–NPC;
dc
link
capacitor;
harmonic
compensation; power factor correction; reactive power
compensation; hybrid filter.
I. INTRODUCTION
N recent days, most of the industrial and house hold
equipments adopts nonlinear load such as computer,
inverter, fan, elevator, washing machine, fax machine,
UPS etc. This class of nonlinear loads wide used to
spread power pollution in transmission and distribution
system. In modern era, the power quality is not only
defined by the continuity of electricity but also
characterized by its supply voltage and current. Power
pollution causes disturbances in source voltage and
current like harmonic content, power factor correction,
unbalancing of current and reactive power
compensation [1-3]. Therefore power quality has
become an important issue in regard to the power
supply system. A shunt hybrid active power filter
strategy is one of a better device proposed to
compensate for power disturbances in distribution
system [4-8].
I
In this paper, two broad types of inverter topology
used as active filter are discussed. Primarily strategy
ajayvimal@pec.edu
namely voltage source inverter based shunt hybrid
active power filter strategy [9-10] and later is neutral
point clamped voltage source inverter based shunt
hybrid active power filter strategy. These two topologies
are used to compensate the power quality issues such as
harmonic mitigation, unbalancing of current, reactive
power compensation, power factor correction. The
hybrid filter strategy is the combination of RL tuned
passive filter and a small rated active filter connected in
series. These filters were connected in parallel to the
transmission line at the point of common coupling
(PCC).In these strategies the dc link capacitor voltage is
used in the pi controller are applied to the feedback gain
of the extinction synchronous reference frame
technique, producing the switching sequence to the
active power filter strategies.
The basic introduction for power quality issues and
active power filter topology based shunt hybrid active
power filter strategy is discussed in section I. Two types
of inverter topologies are expressed in section II. The
system configuration of the shunt hybrid active power
filter strategy is modeled in section III. The extension
synchronous reference techniques based dc-link voltage
regulation for shunt hybrid active power filter strategy is
designed and explained in Section IV. The simulation
results of the strategy analyzed in Section V. The
conclusion of the paper finds a place in Section VI.
II. SYSTEM CONFIGRUATION
The configuration of three phase, three wire shunt
hybrid active power filter strategy for compensating the
power quality problems in a distribution system is
illustrated in Fig. 1. The diode bridge rectifier RL load
and RL load are used as non linear load causes
unwanted power quality issues in the grid system. The
power quality issues such as current harmonic,
unbalancing of current, reactive power and power factor
correction were compensated by using shunt hybrid
active power filter strategy. The active power filter
strategy consist of two types are conventional topology
and proposed topology. The hybrid filter is a
1
combination of three phase RL tuned passive filter and a
small rated conventional or proposed topology based
voltage source inverter act as an active filter which is
connected in series without transformer.
A.
Conventional topology
Conventional topology consists of three phase
voltage source inverter by which it acts as an active
power filter shown in Fig.2. It has six active switches
and six
In order to overcome the above drawbacks, the
proposed topology based shunt hybrid active power
filter strategy is utilized.
B.
Proposed topology
In this proposed topology consist of the three-level
neutral-point-clamped voltage source inverter (NPC
VSI) was introduced by Nabae in 1981 [10] and is
regarding as the most popular among the multilevel
converter topologies for high voltage, high power
applications. The neutral point clamped voltage source
inverter shown in Fig.3. it has twelve active switches
and eighteen diodes. It consists of twelve power diode
and six freewheeling diode. The inverter circuit of three
leg, each leg have four active switches and four power
diode. The power diode coupled parallel with each
active switches and two freewheeling diode were
connected in parallel to the each active switching leg to
freewheeling the extra circulating power in the inverter.
At the end of inverter, two dc link capacitor are
connected parallel to the active switching inverter legs.
The midpoints of two dc link capacitor are connected to
the midpoint of the freewheeling diode leg. In this
midpoint connection is express the neutral point
clamped voltage source inverter. The two dc link
capacitor act has energy storing device. It requires low
voltage to save more power from the system.
Fig. 1 Three Phase Shunt Hybrid Active Power Filter Strategy
freewheeling diode. In these three phase voltage source
inverter has three legs, each leg has two active switches
and each active switches are coupled with a
freewheeling diode. A dc link capacitor is an energy
storing device connected in parallel to the voltage
source inverter. This inverter topology acts as an active
power filter of shunt hybrid active power filter strategy.
S1
S5
R Y B
S1
S5
S9
S4
S8
S12
S2
S6
S10
S3
S7
S11
Vdc
S3
R
Y
B
Vdc
Fig.3 Proposed Topology
TABLE ISPECIFICATIONS OF THE SYSTEM PARAMETERS
S4
S2
S6
Fig. 2 Conventional Topology
In this traditional topology have large number of
drawbacks to controlling the power quality problems.
The conventional topology based shunt hybrid active
power filter strategy requires high dc link voltage
compensating the power quality problems. The
requirement of dc link voltage makes the control
technique very complex and also it increases the rating
of the system.
Supply Voltages VS
230V
Supply Frequency FS
50Hz
R,L tuned passive filter RF,LF
1Ω, 20mH
DC-Link capacitor CF
1600µF
DC-Link voltage Vdc
500V
Rectifier based R,L Load
7Ω, 20mH
2
Feed back block
isu
isv
id1
d1-q1
id1
transform
HPF
isw
iq1
iq1
ω1
d5-q5
d1-q1
Δid1
iLw
K
IAF
Ishv
Inverse
Ishw
+
*
+ i Afv
+
+
+
i*Afu
i*Afw
+
Vdc +
ω1
PI
Vdc*
iLd5
iLd5
id5
iLv
transform
Ishu
transform
Feed forward block
iLu
+
iLq5
LPF
iLq5
d5-q5
Inverse
ZF
iq5
transform
ω5= -5ω1
ω5
Fig. 4 Extension synchronous reference frame control technique
III.
CONTROL STRATEGY
The control circuit of the three phase three wire shunt
hybrid active power filter strategy is shown in Fig. 4.
The extension synchronous reference frame current
control technique consist of three sections, they are
feedback block, feedforward block and dc link capacitor
voltage block. This three blocks are expressed has
follows [11] and [13].
A. FEEDBACK BLOCK
In this feedback block consist of three phase source
current isu, isvand isw are taken has inputs applied to d-q
transformation. The d1-q1 transformation converts three
phase supply current into two phase synchronous direct
and quadrate axis current id1-iq1.

2π 
2π  


sin ωt  sin  ωt   sin  ωt     is u 
id1 2 
3
3     (1)


 is v 
  
iq1 3 cos ωt  cos  ωt  2π  cos  ωt  2π   
is

3
3   w 



Then, the inverse transformation of d1-q1 produces their
supply harmonic currents.

sinωt 

 ishu  
2π 


 
 ish v    sin ωt  3 
ish w  
 sin ωt  2π 

3 



 ~
2π  i d1 (2)

cos  ωt 
  ~ 
3  i q1


2π 

cos  ωt 

3 

cos ωt 
Iafb  k  ish
(3)
The Each harmonic current ishu, ishv, ishwwere
amplified by the feedback gain k will produced three
phase feedback path current reference namely I *AFb. The
harmonic content of the source current can be calculated
in equation (4)
Ish 
Zf
 Ilh
K  Zf  Zs
(4)
B. FEEDFORWARD BLOCK
The feedforward control for the most dominant fifth
order harmonic current converters three phase load
currents i Lu , i Lv , and iLW to two-phase currents i Ld5 and
i Lq5
on the reference frame rotating at the fifth-harmonic
frequency ω5. The fifth order harmonic current is not a
positive sequence but negative sequence current. The dc
components of fifth order harmonic currents presented
in the load current i Ld 5 and i Lq5 were extracted by the
two first order low pass filters (LPF) with the same
cutoff frequency as 16Hz. Then the feedforward fifth
order harmonic direct and quadrature axis current in the
steady state can be calculated by equation (5).

RF
id5 
   
iq5  ω5 LF  1

ω5 CF
1 

ω5 CF  iLd5 (5)


 iLq5
RF

 ω5 LF 
3
The fifth order harmonic direct and quadrature current
i*d5 and i*q5 are transformed to three phase currents
I*Aff , I*Bff , I*Cff using inverse d-q transformation are
mention in equation (6)

 sin ωt 

IAff  
2π 
   
 IBff    sin  ωt  3 

 ICff   


2π 

 sin  ωt 

3 
 



2π   id5

cos ωt 
  
3   iq5

2π 

cos ωt 

3 

(6)
cos ωt 
C. DC LINK VOLTAGE BLOCK
The DC link voltage is regulated at rated value by
the support of a proportional and integral (PI) controller
is discussed in this section. The shunt active power filter
requires an amount of active power for minimizing
switching losses and to generate the compensation
current. As a result, the current reference (∆Id1) obtained
in this control loop is added to the direct axis current
component Idh.
PI Controller =
Fig. 5 Waveform of source voltage, current, power and power factor
for before compensation of rectifier RL load
Case B. Performance analysis between conventional
and proposed VSI based SHAPFS
A. Dc link voltage

ki 
Verror   k p   (7)
s 

where
*
V error  Vdc  Vdc ,
kp– proportional gain,
ki – integral gain.
IV. SIMULATION RESULTS
The analysis of power quality issues compensation
by using proposed shunt hybrid active power filter
strategy is simulated in Matlab/Simulink environment.
The effectiveness of the proposed voltage source
inverter topology based shunt hybrid active power filter
strategy for compensation capability is realized for three
phase rectifier RL load and compared with conventional
technique. The system parameters were shown in Table
1.
Fig. 6 Waveform of dc link voltage for conventional and proposed
VSI based SHAPFS of rectifier RL load
B.
IsTHD Vs Vdc
Case A. Analysis of before compensation for three
phase rectifier RL load
The simulation results of rectifier RL load for before
compensation of normal load condition is shown in
Figs. 5. From the obtained results, it is observed that the
non linear load created harmonic content to the source
voltage and current of 8% and 30% respectively, and
also power factor is observed to be lagging from the
grid.
Fig. 7 Waveform of source current THD verses dc link voltage for
conventional and proposed VSI based SHAPFS of rectifier RL load
The performance analysis of dc link voltage, source
current THD and reactive power compensation were
analyzed between conventional and proposed voltage
source inverter based shunt hybrid active power filter
4
i)
Reactive power Vs Vdc
Fig. 8 Waveform of reactive power verses dc link voltage for
conventional and proposed VSI based SHAPFS of rectifier RL load
strategies are highlighted in Figs. 6 - 17. The dc link
voltage for conventional topology is observed to be
500V where as the dc link voltage for proposed
topology is 250V. This analysis demonstrates, the
proposed topology reduce to half off the dc link voltage
when compared to conventional topology. The analysis
of source current THD verses Vdc for conventional
topology is obtained 4.65% at 500V Vdc in proposed
topology is much reduction of THD 2.89% at 250V Vdc
when compared to conventional topology. The
performance analysis of reactive power compensation of
proposed topology is found to be better compensation.
Case C. Performance investigation on proposed
SHAPFS based rectifier RL load
Prior to compensate, the source voltage and current
is observed to be distorted. After connecting the
proposed shunt hybrid active power filter strategy, the
simulation analysis of voltage and current are illustrated
in Figs. 9. Initially, the shunt hybrid active power filter
strategy detects harmonics produced by the load and
injects the compensation current. After injecting
compensation current, the source current harmonics is
found to be minimized to 3.4%. The harmonic content
in the source voltage is also compensated with the aid of
proposed shunt active power filter strategy. It also
observed that power factor is unity.
The waveform for power consumed at grid is
represented in Fig. 10. The active power supplied by the
grid during load change condition is found to be
6.2KW. Before compensation, the reactive power
demand of load is observe to be 1.1KW. after
connecting filter strategy, The reactive power demand
of load is supplied by the proposed shunt active power
filter strategy thereby reactive power is compensated at
grid.
The peak overshoot and settling time of DC link
voltage is comparatively analyzed for conventional and
proposed shunt hybrid active power filter strategy with
respect to three operating conditions is represented in
Fig. 9 Waveforms of voltage and current analysis for proposed VSI
based SHAPFS of rectifier RL load with load change condition
Fig. 10 Waveform of source power for proposed VSI based SHAPFS
of rectifier RL load with load change condition
table II. From the table II, the peak overshoot and
settling time is observed to be minimum in proposed
technique with respect to all operating conditions.
Table III shows that comparison of mitigation of
source current harmonic distortion using conventional
and proposed shunt hybrid active power filter with
respect to three different operating conditions. From the
table III, compensation of source current harmonic
distortion is found to be better in proposed technique
compared to conventional shunt hybrid active power
filter strategy. The overall investigations demonstrated
that the proposed shunt hybrid active power filter
strategy required minimum DC link voltage and it has
better compensation capability on mitigating power
quality problems compared to conventional shunt hybrid
active power filter strategy.
5
TABLE II
Analysis of dc link voltage for different operating condition of conventional and proposed VSI based uncontrolled rectifier RL load
Normal Operating
Condition
Condition
CVSI
Unbalance Load
Condition
Load Change Condition
PVSI
CVSI
PVSI
CVSI
PVSI
Dc link voltage
500V
250V
500V
250V
500V
250V
Peak overshoot
46.08%
42.605%
12.08%
9.55%
61.32%
56.45%
Settling
320ms
280ms
90ms
45ms
100ms
68ms
TABLE III
THD analysis for source current for different operating condition of conventional and proposed VSI based uncontrolled rectifier RL load
3Φ
A
B
C
Normal Operating Condition
With filter
With Out
Filter
(%)
CVSI
(%)
PVSI
(%)
Load Change Condition
With
With filter
Out
CVSI
PVSI
Filter
(%)
(%)
(%)
34.6
32.8
29.5
4.58
5.03
4.96
3.40
3.23
3.35
34.48
30.54
33.13
4.03
3.86
3.95
[5]
V. Conclusion
A neutral point clamped voltage source inverter
based shunt hybrid active power filter strategy for the
compensation of power quality issues is proposed in this
paper. The performance of the proposed shunt hybrid [6]
active power filter strategy is better with the
conventional shunt hybrid active power filter strategy
for mitigation of current harmonics generated by
nonlinear load. The proposed shunt hybrid active power [7]
filter strategy helps to maintain the power factor of the
system to unity. The better computational efficiency of
the proposed approach has shown that it can be a wide [8]
range of power quality problems. The dynamic
simulation results have brought out the advantage of the
proposed shunt hybrid active power filter strategy for [9]
power quality enhancement of domestic and industrial
[10]
applications.
[11]
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