Comparison of PI and ANN Control Techniques for Nine Switches UPQC to Improve Power Quality

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Vol.03,Issue.33
October-2014,
Pages:6565-6581
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Comparison of PI and ANN Control Techniques for Nine Switches
UPQC to Improve Power Quality
SHAIK.MABUSUBANI
1
, SURESH KORNEPATI
2
1
PG Scholar, Dept of EEE, Sri Mittapalli College of Engineering, Guntur, AP, India, E-mail: subanimseee@gmail.com.
2
Associate Professor, Dept of EEE, Sri Mittapalli College of Engineering, Guntur, AP, India, E-mail: kornesuresh@gmail.com.
Abstract: This paper presents a comprehensive review on the UPQC to reinforce power quality. Typically this can be often
speculated to gift a broad outline on the varied possible intelligent controls used with UPQC. The most purpose of a UPQC is to
control on voltage flicker/unbalance, reactive power and harmonics. In different words, the UPQC has the potential of up power
quality at the purpose of installation on power industrial power systems. The appliance of computing is growing quick within the
space of power electronics and drives. From olden days to now days we are using twelve switches used in back to back
configuration. But now we are using nine switches instead of 12 switches. In 9 switch UPQC converters given the most useful
benefits compared to 12 switches power converter. The nine switches UPQC converter gets the best results by using of two
methods. They are one is PI controller technique and other one is ANN controller technique. By contrast PI and ANN, ANN is
better than PI for power quality enhancement and voltage sag and voltage swell mitigations. The factitious neural network
(ANN) is taken into account as a replacement tool to style management electronic equipment for power-quality (PQ) devices. A
whole simulation study is administrated to analysis the performance of the ANN controller and compares its performance with
the quality PI controller results. The nine-switch convertor has already been proved to possess sure benefits, additionally to its
part saving topological feature. Despite these benefits, the nine-switch convertor has thus far found restricted applications
because of its several perceived performance tradeoffs like requiring associate degree outsized dc-link capacitance, restricted
amplitude sharing, and unnatural part shift between its 2 sets of output terminals. Rather than acceptive these tradeoffs as
limitations, a nine-switch power conditioner is projected here that nearly ―converts‖ most of those topological short comings into
fascinating performance benefits. Aiming more to cut back its switch losses, Harmonics, Voltage Sag & Swell associate degree
acceptable discontinuous modulation theme is projected and studied here thoroughly to doubly make sure that top reduction of
commutations is achieved. With associate degree suitably designed management theme with PI and ANN with physical
phenomenon controller then incorporated, the nine-switch convertor is shown to favorably raise the general power quality in
Simulation, thus justifying its role as an influence conditioner at a reduced value.
Keywords: ANN, Active Power Filters, PI Controller, Nine Switch Converter, Power Quality, UPQC.
I. INTRODUCTION
The use of electronic controllers within the electrical power-
supply system has become quite common. These electronic
controllers behave as nonlinear load and cause serious
distortion within the distribution system and introduce
unwanted harmonics within the supply system, resulting in
slashed potency of the facility system network and
instrumentality connected within the network [1]. To satisfy
the wants of harmonic regulation, passive and active power
filters area unit being employed together with the standard
converters [2]. Presently, active power filters (APFs) have
become value-effective attributable to cost reductions in
power semiconductor devices, their auxiliary components, and
integrated digital management circuits. Additionally, the APF
conjointly acts as a power-conditioning device that provides a
cluster of multiple functions, like harmonic filtering, damping,
isolation and termination, load equalization, reactive-power
management for power-factor correction and voltage
regulation, voltage-flicker reduction, and/or their mixtures.
Resent analysis focuses on use of the universal power quality
conditioner (UPQC) to catch up on power-quality issues [3],
[4].
The performance of UPQC principally depends upon
however accurately and quickly reference signals area unit
derived. Once economical extraction of the distorted signal, an
acceptable dc-link current regulator is used to derive the
particular reference signals. numerous management
approaches, like the PI, PID, fuzzy-logic, sliding-mode,
predictive, unified constant frequency (UCF) controllers, etc.,
area unit in use [5]–[7]. kind of like the PI standard controller,
the PID controller needs precise linear mathematical models,
that area unit tough to get, and fails to perform satisfactorily
beneath parameter variation nonlinearity load disturbance, etc.
fashionable management theoretic controllers area unit state
feedback controllers, self-tuning controllers, and model
reference adjustive controllers, etc. These controllers
conjointly would like mathematical models and area unit so

SHAIK MABUSUBANI, SURESH KORNEPATI
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.33, October-2014, Pages: 6565-6581
sensitive to parameter variations [8]. In recent years, a serious
effort has been afoot to develop new and unconventional
management techniques that may typically augment or replace
standard management techniques. Variety of unconventional
management techniques have evolved, providing solutions to
several tough management issues in trade and producing
sectors. not like their standard counterparts, these
unconventional controllers (intelligent controllers) will learn,
remember, and create choices. Artificial intelligence (AI)
techniques, notably the NNs, area unit having a major impact
on power-electronics applications.
Neural-network-based managementlers give quick dynamic
response whereas maintaining the soundness of the device
system over a good in operation vary and area unit thought of
as a brand new tool to style control circuits for PQ devices
[9]–[12]. Over the previous couple of years, major analysis
works are disbursed on feedback circuit style for UPQCs with
the target of getting reliable management algorithms and quick
response procedures to get the switch management signals
[13]–[15]. During this paper, for raising the performance of a
UPQC, a multilayer feed forward-type ANN-based
managementler is meant for the present control of the shunt
active filter rather than the standard PI controller. Associate
rule for coaching the ANN controller is developed and trained
offline. Numerous simulation results area unit given and
verified through an experiment, and compare the performance
of the ANN controller with standard PI controller results. A
DSP-based microcontroller is employed for the period of time
simulation and implementation of the management rule. Since
its initial introduction, static power convertor development has
full-grown quickly with several convertor topologies currently
pronto found within the open literature. Incidental this
development is that the equally speedy identification of
application areas, wherever power converters will contribute
absolutely toward raising the general system quality [1], [2].
In most cases, the known applications would need the
ability converters to be connected nonparallel [3] or shunt [4],
looking on the operational situations into consideration.
Additionally, they have to be programmed with voltage,
current, and/or power regulation schemes in order that they'll
swimmingly make amends for harmonics, reactive power
flow, unbalance, and voltage variations. For even additional
tight regulation of provide quality, each a shunt and a series
convertor square measure more with one amongst them tasked
to perform voltage regulation, whereas the opposite performs
current regulation. nearly always, these 2 converters square
measure connected in an exceedingly back to-back
configuration [5], victimization twelve switches in total and
sharing a typical dc-link capacitance, as mirrored by the
configuration drawn in Fig. 1(a). Wherever obtainable, a small
supply may be inserted to the common dc link, if the intention
is to supply for distributed generation in an exceedingly small
grid [6], while not considerably impacting on the long proved
correct functioning of the succeeding configuration.
Even though facing no major operative issues at the present,
enhancements through topological modification or replacem-
ent of the consecutive configuration to scale back its losses,
part count, and quality would still be favored, if there's no or
solely slight expected trade-off in performance. A classical
different that may straight off be brought out for thought is
that the direct or indirect matrix device, wherever eighteen
switches area unit employed in total. That represents six
switches quite the consecutive configuration, however has the
advantage of removing the intermediate electrical condenser
for compactness and period of time extension. If the
significant switch count remains of concern, those indirect thin
matrix converters planned in [7], [8] is thought-about,
wherever the minimum switch count getable is 9, however at
the expense of supporting solely one-way power flow. Neither
storage electrical condenser nor dc micro source is once more
required, that therefore renders the traditional and thin matrix
converters as not the well-liked selection, if ride-through could
be a demand. Matrix converters also are not most popular, if
voltage buck and boost operations area unit each required for a
specified direction of power flow.
Yet another reduced semiconductor topology is found in
[9], wherever the B4 device is introduced for dc–ac or ac dc
energy conversion. The B4 device uses four switches to create
2 section legs with its third section drawn from the centre of a
split dc electrical phenomenon link. For fastening 2 ac systems
along, 2 B4 converters area unit required with their split dc
link shared [10]. The full variety of switches required is
therefore eight, that most likely is that the minimum possible
for interfacing 2 ac systems. The ensuing ac–dc–ac device
ought to then be a lot of truly cited because the B8 device. The
B8 device is, however, known to suffer from massive dc-link
voltage variation, unless each systems area unit of constant
frequency and synchronized in order that no basic current
flows through the dc link. That actually could be a constraint,
additionally to the lower ac voltage that may be made by every
B4 device from its given dc-link voltage.
Overcoming some limitations of the B8 device is that the 5
leg device introduced in [11], that conceptually is viewed as
adding a fifth section leg to the B8 device. The other section
leg is shared by the 2 interfaced ac systems with currently no
massive basic voltage variation ascertained across its dc link.
The sole constraint here is that the imposition of common
frequency operation on the 2 interfaced ac systems that then
makes it unsuitable for applications like utility steam-powered
adjustable speed drives and series-shunt power conditioners.
Presenting a much better reduced semiconductor different for
top quality series–shunt compensation, this paper proposes
one stage integrated nine-switch power conditioner, whose
circuit association is shown in Fig.1(b). As its name roughly
inferred, the planned conditioner uses a nine-switch convertor
with 2 sets of output terminals, rather than the same old twelve
switch back-to back convertor. The nine-switch convertor was
earlier planned in [12] and [13] at regarding a similar time,
and was counseled for twin motor drives [14], rectifier–
inverter systems, and uninterruptible power provides [15].
Despite functioning as supposed, these applications are
burdened by the restricted part shift and strict amplitude
sharing enforced between the 2 terminal sets of the nine-

Comparison of PI and ANN Control Techniques for Nine Switches UPQC to Improve Power Quality
switch convertor. More significantly, a far larger dc-link
capacitance and voltage ought to be maintained, so as to
supply similar ac voltage amplitudes as for the consecutive
convertor.
Uncalled-for to mention, the larger dc-link voltage would
amplify the semiconductor switches unnecessarily, and would
possibly to some extent overshadow the saving of 3
semiconductor switches created potential by the nine-switch
topology. The attractiveness of the nine-switch convertor, if so
any, is thus not nonetheless absolutely brought out by those
existing applications mentioned in [13]–[15]. Though follow-
up topological extensions will later be found in [16], wherever
a Z-source network and different modulation schemes are
introduced, they didn’t absolutely address those crucial
limitations sweet-faced by the nine-switch convertor, and not
its ancient consecutive counterpart. Investigating more by
taking a more in-depth read at those existing applications
delineate earlier, a general note discovered is that they
normally use the nine-switch convertor to exchange 2 shunt
converters connected consecutive. Such replacement can limit
the total functionalities of the nine-switch convertor, as
explained in Section II. Within the same section, an alternate
conception is mentioned, wherever the nine-switch convertor
is chosen to exchange a shunt associate degreed a series
convertor found in an integrated power conditioner, rather
than 2 shunt converters.
Fig.1. (a) back-to-back and (b) nine-switch power
conditioners.
Underlying operational principles are mentioned
comprehensively to demonstrate however such ―series–shunt‖
replacement will induce the total blessings of the nine-switch
convertor, whereas nonetheless avoiding those limitations
sweet-faced by existing applications. Details explaining sleek
transitions between traditional and sag operational modes are
provided to clarify that the lot of restricted nine-switch
convertor won't underperform the lot of freelance back-to
back convertor even for sag mitigation. During voltage sags,
the second set of management schemes conjointly has the
flexibility to endlessly keep the load voltages inside tolerable
vary. This sag mitigation ability, along with different abstract
findings mentioned during this paper however not within the
open literature, has already been verified in experiment with
favorable results discovered.
II. POWER QUALITY
Power Quality (PQ) connected problems area unit of most
concern today. The widespread use of equipment, like info
technology instrumentality, power physical science like
adjustable speed drives (ASD), programmable logic
controllers (PLC), energy-efficient lighting, diode to a whole
modification of electrical hundreds nature. These hundreds
area unit at the same time the key causers and also the major
victims of power quality issues [8]. Because of their non-
linearity, of these hundreds cause disturbances within the
voltage undulation. alongside technology advance, the
organization of the worldwide economy has evolved towards
globalisation and also the profit margins of the many activities
tend to decrease [11]. The magnified sensitivity of the
overwhelming majority of processes (industrial, services and
even residential) to PQ issues turns the provision of electrical
power with quality an important issue for fight in each activity
sector. The foremost crucial area unit as are the continual
method trade and also the info technology services [15]. Once
a disturbance happens, immense money losses could happen,
with the ensuing loss of productivity and fight. Though several
efforts are taken by utilities, some shoppers need tier of PQ
beyond the extent provided by fashionable electrical networks
[12]. this means that some measures should be taken so as to
attain higher levels of Power Quality.
III. UNIFIED POWER QUALITY CONDITIONER
The Unified Power Quality Conditioner may be a custom
power device that's used within the distribution system to
mitigate the disturbances that have an effect on the
performance of sensitive and/or essential load [19]. it's a kind
of hybrid APF and is that the solely versatile device which
might mitigate many power quality issues connected with
voltage and current at the same time thus is multi functioning
devices that compensate numerous voltage disturbances of the
ability offer, to correct voltage fluctuations and to stop
harmonic load current from getting into the ability system.
The system configuration of a single-phase UPQC is shown in
Fig.2. Unified Power Quality Conditioner (UPQC) consists of
2 IGBT primarily based Voltage supply converters (VSC), one
shunt and one series cascaded by a typical DC bus. The shunt
convertor is connected in parallel to the load. It provides
power unit support to the load and provides harmonic currents.
Whenever {the offer the availability the provision} voltage
undergoes sag then series convertor injects appropriate voltage
with supply [2]. Therefore UPQC improves the ability quality
by preventing load current harmonics and by correcting the
input power issue.

The most elements of a UPQC square measure series and
shunt power converters, DC capacitors, low-pass and high-
pass passive filters, and series and shunt transformers the most
purpose of a UPQC is to catch up on offer voltage power
quality problems, such as, sags, swells, unbalance, flicker,
harmonics, and for load current power quality issues, such as,
harmonics, unbalance, reactive current, and neutral current.
The key elements of this technique square measure as follows.
 2 inverters —one connected across the load that acts as a
shunt APF and different connected nonparallel with the
road as that of series APF.
 Shunt coupling inductance Lsh is employed to interface
the shunt electrical converter to the network. It
conjointly helps in smoothing this wave. Generally
associate isolation electrical device is employed to
electrically isolate the electrical converter from the
network.
 a typical dc link that may be fashioned by employing a
condenser or associate inductance. In Fig.2, the dc link is
accomplished employing a condenser that interconnects
the 2 inverters and conjointly maintains a continuing
independent dc bus voltage across it.
 Associate LC filter that is a passive low-pass filter (LPF)
and helps to eliminate high-frequency switch ripples on
generated electrical converter output voltage.
 Series injection electrical device that's accustomed
connect the series electrical converter within the
network. an acceptable flip magnitude relation is
commonly thought-about to scale back the voltage and
current rating of series electrical converter.
In principle, UPQC is associate integration of shunt and
series APFs with a typical independent dc bus. The shunt
electrical converter in UPQC is managementled in current
management mode such it delivers a current that is adequate to
the set price of the reference current as ruled by the UPQC
control algorithmic program [20]. To boot, the shunt electrical
converter plays a vital role in achieving needed performance
from a UPQC system by maintaining the dc bus voltage at a
group reference price. so as to cancel the harmonics generated
by a nonlinear load, the shunt electrical converter ought to
inject a current. Similarly, the series electrical converter of
UPQC is managementled in voltage control mode such it
generates a voltage and injects nonparallel with line to realize
a curved, free from distortion and at the required magnitude
voltage at the load terminal. Within the case of a voltage sag
condition, actual supply voltage can represent the distinction
between the reference load voltage and reduced offer voltage,
i.e., the injected voltage by the series electrical converter to
take care of voltage at the load terminal at reference price.
Altogether the reference papers on UPQC, the shunt electrical
converter is operated as controlled current supply and also the
series electrical converter as controlled voltage supply except
during which the operation of series and shunt inverters is
interchanged.
A unified power quality conditioner (UPQC) may be a
device .The UPQC, sort of a UPFC, employs 2 voltage supply
inverters (VSIs) that area unit connected to a standard dc
energy storage condenser. One among these 2 VSIs is
connected serial with the AC line whereas the opposite is
connected in shunt with an equivalent line. A UPFC is used in
an exceedingly power gear mechanism to perform shunt and
series compensation at an equivalent time. Equally a UPQC
may perform each the tasks in an exceedingly power
distribution system. However, at now similarities within the
operational principles of those 2 devices finish. Since an
influence cable typically operates in an exceedingly balanced,
distortion (harmonic) free surroundings, a UPFC should solely
give balanced shunt or series compensation. An influence
distribution system, on the other hand, could contain
unbalance, distortion and even dc elements. Thus a UPQC
should operate below these surroundings whereas providing
shunt or series compensation.
The UPQC may be a comparatively new device and not a
lot of work has been reported thereon however. It has been
viewed as an integration of series and shunt active filters. It
has been shown that it may be accustomed attenuate current
harmonics by inserting a series voltage proportional to the
road current. Instead, the inserted series voltage is
supplemental to the voltage at the purpose of common
coupling specified the device will give a buffer to eliminate
any voltage dip or flicker. It is additionally potential to control
it as a mixture of those 2 modes. In either case, the shunt
device is employed for providing a path for the important
power to flow to assist the operation of the series connected
VSI. Additionally enclosed during this structure may be a
shunt passive filter to that the entire comparatively low
frequency harmonics area unit directed.
Fig.2. UPQC general block diagram.
IV.OVERALL CONTROL CIRCUIT CONFIGURATION
OF NINE SWITCH UPQC
REFERENCE GENERATION (PHASE LOCKED LOOP)
Reference currents and voltages square measure generated
victimization part secured Loop (PLL). The management
strategy is predicated on the extraction of Unit Vector
Templates from the distorted input provide. These templates
are going to be then a dore pure curving signal with unity
(p.u.) amplitude. The 3-ph distorted input supply voltage at
PCC contains basic element and distorted element. To induce
unit input voltage vectors Uabc, the input voltage is perceived
and increased by gain adequate to 1/Vm, wherever Vm is
adequate to peak amplitude of basic input voltage. These unit

input voltage vectors square measure taken to part secured
loop (PLL). With correct part delay, the unit vector templates
square measure generated. The management strategy is
predicated on the extraction of Unit Vector Templates from
the distorted input provide. These templates are going to be
then a dore pure curving signal with unity (p.u.) amplitude.
The extraction of unit vector templates is
(1)
Multiplying the height amplitude of basic input voltage
with unit vector templates of equation (1) offers the reference
load voltage signals,
*
.abc m abcV V U (2)
The error generated is then taken to a physical phenomenon
controller to get the desired gate signals for series APF. The
unit vector template are often applied for shunt Fig.3
Extraction of Unit Vector Templates and three-Φ Reference
Voltages shown within the Fig.3.The unit vector templates
square measure generated APF to compensate the harmonic
current generated by non-linear load. The shunt APF is
employed to catch up on current harmonics likewise on
maintains the dc link voltage at constant level [13-14]. To
realize the higher than mentioned task. The dc link voltage is
perceived and compared with the reference dc link voltage. A
PI controller then processes the error. The signal from PI
controller is increased with unit vector templates of equation
(1) giving reference supply current signals. The supply current
should be adequate to this reference signal. So as to follow
this reference current signal, the 3-phase supply currents
square measure perceived and compared with reference
current signals. The error generated is then processed by a
physical phenomenon current controller with appropriate
band, generating gating signals for shunt APF. The 9 Switch
UPQC uses 2 consecutive connected 3 part VSI‟s sharing a
standard dc bus. The physical phenomenon controller is
employed here to manage the switch of the each VSI’s.
Fig.3. Extraction of 3-Φ Reference Voltages Unit Vector
Templates.
In order to own distortion less load voltage, the load
voltage should be adequate to these reference signals. The
measured load voltages square measure compared with
reference load voltage signals. The error generated is then
taken to a physical phenomenon controller to get the desired
gate signals for series APF. The unit vector templates are often
applied for shunt APF to compensate the harmonic current
generated by non-linear load. The shunt APF is employed to
catch up on current harmonics likewise on maintains the dc
link voltage at constant level. to realize the higher than
mentioned task the dc link voltage is perceived and compared
with the reference dc link voltage. A PI controller then
processes the error. The signal from PI controller is increased
with unit vector templates of equation (1) giving reference
supply current signals. The supply current should be adequate
to this reference signal. So as to follow this reference current
signal, the 3-ph supply currents square measure perceived and
compared with reference current signals. The error generated
is then processed by a physical phenomenon current controller
with appropriate band, generating gating signals for shunt
APF.
V. CONTROL STRATEGY OF NINE SWITCH UPQC
A. Static Shunt Compensator using PI
Nine Switch UPQC consists of series compensator and
shunt compensator. The shunt compensator is managementled
by a PWM current control formula, whereas the series
convertor is managementled by a PWM voltage control
formula. In step with the adopted management theme, these 2
components of 9 Switch UPQC have totally different
functions as follows:
Static Shunt Compensator: Shunt electrical converter
control: during this study, shunt electrical converter
undertakes 2 main duties. initial is compensating each current
harmonics generated by nonlinear load and reactive power,
second is injecting active power generated by PV system. The
Fig.4.Control block diagram of shunt inverter using PI.
shunt electrical converter dominant system ought to be
designed during a manner that it'd give the power of

enterprise 2 higher than duties. Shunt electrical converter
management calculates the compensation current for current
harmonics and reactive power once PV is out of the grid. the
facility loss caused by electrical converter operation ought to
be thought-about during this calculation. Also, shunt electrical
converter management undertakes the duty of (stabilizing) DC
link voltage throughout series electrical converter operation to
compensate voltage distortions. DC link electrical condenser
voltage dominant loop is employed here by applying PI
controller. Fig.4 shows the circuit diagram of shunt electrical
converter dominant.
Shunt electrical converter management in interconnected
mode: Mode one of shows UPQC shunt voltage supply
electrical converter dominant diagram applying synchronous
coordinate system theory technique wherever sensitive load
currents area unit Ia, Ib and Ic. Measured load currents applying
synchronous coordinate system conversion technique (dq0),
area unit transferred to dq0 frame victimization curved
functions. Sinusoidal functions are obtained by PLL using grid
voltage. Currents during this synchronous reference area unit
rotten to 2 DC and AC (50 Hz) quantities (using ~ sign higher
than the parameter).
0
0
dq
ldq abc abcI T I
(3)
0
2 2
cos cos cos
3 3
2 2 2
sin sin sin
3 3 3
1 1 1
2 2 2
dq
abcT
 
  
 
    
    
     
    
    
      
    
 
 
   (4)
,ld ld ld lq lq lqI I I I I I    
(5)
where, Id is active and IQ is reactive a part of power. AC and
DC components is extracted by an occasional pass filter. In
this case:
l s cI I I  (6)
In Eq. 4, Is is that the supply current, Il is that the load current
and Ic is that the compensating current injected by shunt
electrical converter. If compensation reference currents area
unit thought-about as follow:
* *
,fd ld fq lqI I I I  
(7)
In this case, the system`s currents are:
,sd ld sq lqI I I I 
(8)
In the Eq. 6, simply the load current harmonics area unit
remunerated. If power issue is taken into account too, the
reference currents would be as follow:
* *
,fd ld fq lqI I I I 
(9)
then system currents are:
, 0sd lq sqI I I 
(10)
So, no harmonic and reactive power are provided by the
supply. Switching losses and therefore the power that the
series electrical converter receives from electrical condenser,
will scale back the voltage average worth of DC bus.
alternative distortions like unbalanced and unexpected load
current variations will cause oscillation in DC bus voltage. so
as to trace the error exists between the measured and desired
worth of electrical condenser voltage, a PI controller is
applied. This dominant signal is applied to current system in
shunt voltage supply during a manner that it management DC
electrical condenser voltage by getting needed active power
(Id) from the grid. The output a part of PI controller (Δidc), is
additional to the letter of the alphabet a part of reference
current, where, the reference current would modification as
follow:
* *
,cd ld dc cq lqI I i I I   
(11)
As it is shown in Fig.4, the reference currents can transfer to
fundamentals frame by reverse changing the synchronous
coordinate system, as Eq. 1. Resulted reference currents are
compared with shunt electrical converter output currents (Ifa,
Ifb, Ifc) during a PWM current controller (hysteresist type) and
needed dominant pulses area unit generated. Applying these
signals to shunt electrical converter power switches gate,
needed compensation current is generated by electrical
converter.
In addition to earlier duties, shunt electrical converter
management ought to inject active power of PV system to the
grid once PV is working. Active power is injected to grid by
electrical condenser voltage dominant loop. In alternative
words, once voltage will increase and reaches to {the
worth|the worth} that is quite the reference voltage value,
shunt electrical converter injects active power to grid and once
it decreases to worth that is a smaller amount than the
reference voltage value; shunt electrical converter receives
active power from the grid.
B. Static Shunt Compensator using ANN
In Fig.5 the fast current of the nonlinear load is expanded
into three terms. the primary term is that the load functions
sent from PLL (Phase latched Loop) in accordance with
equation.(3)
0
0
dq
Ldq abc LabcI T i (12)
Fig.5. Control of the shunt Converter of the Nine Switch
UPQC using ANN.

By this remodel, the basic positive sequence parts area unit
remodeled into dc Quantities in d and letter of the alphabet
axes, which may simply be extracted by low-pass, filter (LPF).
All harmonic parts area unit remodeled into ac quantities
with a harmonic shift
Lq LqLqI i i  (13)
Since
L s ci i i  (14)
This means there's no harmonics and reactive parts within
the system currents. The change loss will cause the dc link
electrical condenser voltage to decrease. alternative
disturbances, like unbalances and unexpected variations of
masses can even cause this voltage to fluctuate. so as to avoid
this, in Figure four. a PI controller is employed. The input of
the PI controller is that the error between the particular
electrical condenser voltage and therefore the desired worth,
its output then additional to the reference current part within
the d-axis to create a replacement.
C. Series Inverter Control using PI
The duty of series electrical converter is compensating
voltage distortions that are caused by fault in distribution grid.
Series electrical converter management calculates the voltage
reference values, that are injected to grid by series electrical
converter.
Fig.6. Control block diagram of series inverter using PI.
In order to regulate series electrical converter of UPQC, load
curving voltage dominant strategy is projected. during this
condition, UPQC series electrical converter would be
controlled during a approach that it compensates the total
distortions and helps the voltage of load voltage keep
(balanced curving 3-phase). so as to succeed in this aim,
synchronous frame of reference theory is applied (11). In this
methodology the specified worth of load section voltage is
replaced in d and q-axises rather than high pass and low pass
filters. Load voltage ought to be utterly a curving perform and
has constant frequency and amplitude. Desired voltage of load
is as combining weight. 14:
* 0 *
0 . 0
0
m
dq
ldq abc labc
V
V T V
 
    
   (15)
 
 
 
*
cos
cos 120
cos 120
m
labc m
m
V t
V V t
V t
 
 
 
 
 
    
     (16)
where, Vm is desired peak worth of load voltage and (θ) is
voltage point that is calculated by section latched loop (PLL).
By subtracting the specified worth of d-axis section voltage
from Vsd, all distortions in d-axis are obtained. Also, the
specified worth of load section voltage in q-axis is zero. In
alternative words, Vsq represents total q-axis distortions. So,
series compensation reference voltage is resulted by
combining weight. 16:
* *
0 0 0fdq ldq sdqV V V 
(17)
These voltages are compared with associate angular wave
form in PWM controller and needed dominant pulses (g1,...,
g6) are generated to be applied to series voltage supply
electrical converter switches. This corrected methodology is
programmable with an occasional price. the opposite
advantage is that the dominant system`s calculation time is
shortened and then dominant system`s response is quicker.
Fig.6 shows the diagram of series compensator`s dominant
circuit applying synchronous frame of reference methodology.
so as to enhance series electrical converter operation, SPWM
methodology is employed wherever, the resulted worth of
subtracting from Vfabc is increased to a continuing constant
and also the obtained worth is superimposed to . Applying
this methodology distinctively improves operation of series
electrical converter.
Fig.7. Control block diagram of the series converter of the
UPQC using ANN.
D. Series Inverter Control Using ANN
The system aspect voltage might contain negative-zero-
sequence still as harmonics parts which require to be
eliminated by the series compensator [15-16]. The
management of the series compensator is shown in Fig.7. The

system voltages are detected then reworked into synchronous
dq-0 frame of reference exploitation equation (6).
VI. ARTIFICIAL NEURAL NETWORK
The ANN controller used is a feed forward one, comprising
three neuron layers, the input layer, the hidden layer and the
output layer shown in the Fig.8. The input layer offers
connection points to transmit the input signal to the hidden
layer. The latter begins the learning process and the output
layer continues the learning process and provides outputs. The
hidden layer neurons have a tan-seg-moid transfer function,
and the output layer neurons have a linear transfer function.
The control objective of the NN is to provide the wanted
proper gating patterns of the PWM inverter, leading to
adequate tracking of the APF reference phase currents and
constant DC voltage. Neurons in the hidden layer is specified
as the minimum number that produces the permitted training
criterion. The training criterion is taken as the mean square
error of the NN outputs with a value of 0.0001. Sufficient
input-output training examples are obtained by using the
triangular carrier modulation technique.
Fig.8. The basic architecture of the feed forward neural
network with accompanying equations that describe the
transfer functions between layers.
An ANN is basically a cluster of fittingly interconnected
non-linear components of terribly easy kind that possess the
flexibility of learning and adaptation. These networks square
measure characterized by their topology, the means during
which they convey with their atmosphere, the style during
which they're trained and their ability to method data [18].
Their easy use, inherent reliableness and fault tolerance has
created ANNs a viable medium for management. An alternate
to fuzzy controllers in several cases, neural managementlers
share the requirement to switch laborious controllers with
intelligent controllers so as to extend control quality. A feed
forward neural network works as compensation signal
generator. This network is meant with 3 layers. The input
layer with 7 neurons, the hidden layer with 21 and therefore
the output layer with 3 neurons. Activation functions chosen
square measure tan sigmoid and pure linear within the hidden
and output layers severally.
The speedy detection of the disturbance signal with high
accuracy, quick process of the reference signal, and high
dynamic response of the controller square measure the prime
needs for desired compensation just in case of UPQC. the
traditional controller fails to perform satisfactorily below
parameter variations nonlinearity load disturbance, etc. now
shows that NN-based controllers offer quick dynamic response
whereas maintaining stability of the device system over wide
operational vary. Shows The Fig.9 ANN is created of
interconnecting artificial neurons. It is basically a cluster of
befittingly interconnected nonlinear components of terribly
straightforward kind that possess the power to find out and
adapt. It resembles the brain in 2 aspects: 1) the data is
nonheritable by the network through the educational method
and 2) interneuron association strengths square measure wont
to store the data. These networks square measure characterized
by their topology, the means during which they convey with
their atmosphere, the style during which they are trained, and
their ability to method info.
ANN has gained plenty of interest over the previous few
years as a robust technique to solve several world issues.
Compared to standard programming, they own the aptitude of
finding issues that don't have recursive answer and square
measure thus found appropriate to tackle issues that folks
square measure sensible to unravel like pattern recognition.
ANNs square measure getting used to solve AI issues while
not essentially making a model of a true dynamic system. For
up the performance of a UPQC, a multilayer feed forward-
kind ANN-based controller is intended. This network is
intended with 3 layers, the input layer with two, the hidden
layer with twenty one, and also the output layer with one
somatic cell, severally.
Fig.9. The basic architecture of ANN.

This network is meant with 3 layers, the input layer with a
pair of, the hidden layer with twenty one, and therefore the
output layer with one vegetative cell, severally. The big
information of the dc-link current for n and (n-1) intervals
from the traditional methodology area unit collected and area
unit hold on within the Mat lab space. These information area
unit used for coaching the NN. The activation functions
chosen area unit tan colon for hidden and input layers and pure
linear within the output layer, severally. This multilayer feed
forward-type NN works as a compensation signal generator.
The topology of the ANN is as shown in Fig.10. The
compensator output depends on the evolution and its input.
The NN is trained for output basic reference currents. The
signals so obtained area unit compared during a physical
phenomenon band current controller to produce change
signals.
Fig.10 Block diagram of the ANN-based compensator for
offline training.
VII. SIMULATION CIRCUITS
Simulation circuits of this paper is as shown in bellow
Figs.11 to 17.
Fig.11. Block diagram of without UPQC.
Fig.12. Block diagram of Nine Switch UPQC.
Fig.13. Block diagram of Nine Switch UPQC with PI
controller.
Fig.14 Block diagram of Nine Switch UPQC with ANN
controller.

Fig.15. Neural network sub circuit.
Fig.16. Neural network layer 1.
Fig.17. Neural network layer 2.
VIII. SIMULATION RESULTS
The harmonic content of input and output of the
Bridge convertor are shown in Fig.18. (three phase
voltages) and Figure nine. (three phase currents). because
of non-linear masses, like massive thyristor power
converters, rectifiers, voltage and current unsteady
because of arc in arc furnaces, sag and swell because of
the shift of the loads etc. one in every of the numerous
solutions is that the use of a combined system of shunt
and active series filters like 9 Switch Unified power
quality conditioner (UPQC) . This device combines a
shunt active filter beside a series active filter in an
exceedingly consecutive configuration, to at the same
time compensate the provision voltage and also the load
current or to mitigate any kind of voltage and current
fluctuations and power issue correction in an exceedingly
power distribution network. The management methods
used here are supported PI & ANN controller of the 9
Switch UPQC well.
The management methods are sculptured victimization
MATLAB/SIMULINK. The simulation results are listed
compared of various management methods are shown in
figures. To verify the operational performance of the
projected 9 Switch UPQC, a 3-Φ electrical system, a PLL
extraction circuit with physical phenomenon controlled 9
Switch UPQC is simulated victimization MATLAB
software system. Figure22. Shows the unit vector
templates generated by victimization projected
management technique.
Fig.18. without UPQC at Load Voltage, input Voltage,
and Injected Voltage.
Fig.19. PI without UPQC at Load Current, input
Current, and Injected Current.

Fig.20. PI controller with SAG condition at Load
Voltage, input Voltage, and Injected Voltage.
Fig.21.PI controller with SAG condition at Load
Current, input Current, and Injected Current.
Fig.22.Dc voltage, without compensation and Neutral
compensation current.
Fig.23.PI controller with SWELL condition at Load
Fig.24.PI controller with SWELL condition at Load
Fig.25.PI controller with SAG & SWELL condition at
Load Voltage, input Voltage, and Injected Voltage.

Fig.26.PI controller with SAG & SWELL condition at
Load Current, input Current, and Injected Current.
Fig.27.ANN controller with SAG condition at Load
Fig.28.ANN controller with SAG condition at Load
Fig.29.ANN controller with SWELL condition at Load
Fig.30.ANN controller with SWELL condition at Load
Fig.31.ANN controller with SAG & SWELL condition
at Load Voltage, input Voltage, and Injected Voltage.

Fig.32.ANN controller with SAG & SWELL condition
at Load Current, input Current, and Injected
Current.
Without UPQC Utility side voltage THD is 4.15% at 3rd
harmonic order.
Fig.33. without UPQC Utility side voltage at 3rd
harmonic.
Without UPQC utility side Current THD is 12.11% at
3rd
harmonic order.
Fig.34. without UPQC utility side current at 3rd
harmonic.
Without UPQC utility side voltage THD is 4.15% at 5th
harmonic order.
Fig.35. without UPQC Utility side voltage at 5th
harmonic.
Without UPQC Utility side Current THD is 12.15% at
5th
harmonic order.
Fig.36. without UPQC Utility side current at 5th
harmonic.
Without UPQC Utility side voltage THD is 4.15% at 7th
& 9th
harmonic orders.
Fig.37. without UPQC Utility side voltage at 7th
& 9th
harmonics.

Without UPQC Utility side Current THD is 12.17% at
7th
& 9th
harmonic orders.
Fig.38. without UPQC Utility side current at 7th
& 9th
harmonics.
Utility side voltage THD with pi 3.99% at 3rd
harmonic
order.
Fig.39. Utility side voltage THD with PI at 3rd
harmonic.
Utility side current THD with PI 2.29% at 3rd
harmonic
order.
Fig.40. Utility side current THD with PI at 3rd
harmonic.
Utility side voltage THD with PI 4.09% at 5th
harmonic
order.
Fig.41. Utility side voltage THD with PI at 5th
harmonic.
Utility side current THD with pi 2.33% at 5th
harmonic
order.
Fig.42. Utility side current THD with PI at 5th
harmonic.
Utility side voltage THD with PI 3.88% at 7th
& 9th
harmonic orders.
Fig.43. Utility side voltage THD with PI at 7th
& 9th
harmonics.

Utility side current THD with PI 2.26% at 7th
& 9th
harmonic orders.
Fig.44. Utility side current THD with PI at 7th
& 9th
harmonics.
Utility side voltage THD with ANN 1.36% at 3rd
harmonic order
Fig.45. Utility side voltage THD with ANN at 3rd
harmonic.
Utility side current THD with ANN 1.48% at 3rd
harmonic order.
Fig.46. Utility side current THD with ANN at 3rd
harmonic.
Utility side voltage THD with ANN 1.35% at 5th
harmonic order.
Fig.47. Utility side voltage THD with ANN at 5th
harmonic.
Utility side current THD with ANN 1.31% at 5th
harmonic order.
Fig.48. Utility side current THD with ANN at 5th
harmonic.
Utility side voltage THD with ANN 1.37% at 7th
& 9th
harmonic orders.
Fig.49. Utility side voltage THD with ANN at 7th
& 9th
harmonics.

Utility side current THD with ANN 1.39% at 7th
& 9th
harmonic orders.
Fig.50. Utility side current THD with ANN at 7th
& 9th
harmonics.
IX. RESULT TABLE
X. CONCLUSION
The UPQC performance mainly depends upon how
accurately and quickly reference signals are derived. Then
conventional compensator was replaced with PI controller
and ANN. The simulation results have shown that the
UPQC perform better with ANN and PI controller
proposed scheme eliminates both voltage as well as
current harmonics effectively. The ANN controller also
performs in a similarly with slightly better voltage
compensation It is also observed that the response time
for derivation of compensation signals reduces
significantly with improved accuracy. the response of
ANN controller is faster and the THD is minimum for the
both the voltage and current which is evident from the
plots and comparison Table.1. Proposed model for the
Nine Switch UPQC is to compensate input voltage
harmonics and current harmonics caused by non-linear
load. The work can be extended to compensate the supply
voltage and load current imperfections such as sags,
swells, interruptions, voltage imbalance, flicker, and
current unbalance. Proposed Nine Switch UPQC can be
implemented using simple analog hardware, because it is
having PLL and Hysteresis blocks.
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Analysis of series compensation and DC-link voltage
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voltage restorer, IEEE Trans. Power Delivery, vol. 19,
[28 ]A. Kazemi, R. Rezaeipour ―Introducing a New
method for UPQC Control to Solve Power Quality
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Automation And Operation. Iran University of Science
and Technology, Iran pp 1528-1531, IEEE, 2008. issue
3,Jul. 2004, pp. 1511-1518.
[29] Elmitwally, A., Abdelkader, S. and EL-Kateb, M.
(2000) „Neural network controlled three-phase four-wire
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Author’s Profile:
Mr. SHAIK. MABUSUBANI is a
student of Sri Mittapalli College of
Engineering, Guntur, AP. Currently
he is pursuing M.Tech in Power
Electronics and Electrical Drives
(12U91D5408) from S.M.C.E. He
completed B.Tech (E.E.E.) in
Chalapati Institute of Technology.
His area of interests include Power Quality by Custom
Power Devices, controllers like controllers, Artificial
intelligence controlling techniques, power Electronics &
Drives, Neuro controller Neuro-fuzzy controllers,
renewable energy resources, Fuzzy controllers.
Mr. SURESH. KORNEPATI
presently working as Associate
Professor & Head, Deportment of
EEE in Sri Mittapalli College of
Engineering, Guntur, A.P. His area of
interests include renewable energy
resources, Power Quality by custom
Power Devices, Power System Operation, Control &
Stability, Intelligent controlling techniques and Power
Electronics & Drives.

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Comparison of PI and ANN Control Techniques for Nine Switches UPQC to Improve Power Quality