comparison of pi and ann control techniques for nine switches upqc to improve power quality

www.ijsetr.com

ISSN 2319-8885

Vol.03,Issue.33

October-2014,

Pages:6565-6581

Copyright @ 2014 IJSETR. All rights reserved.

Comparison of PI and ANN Control Techniques for Nine Switches

UPQC to Improve Power Quality SHAIK.MABUSUBANI

1, SURESH KORNEPATI

2

1PG Scholar, Dept of EEE, Sri Mittapalli College of Engineering, Guntur, AP, India, E-mail: [email protected].

2Associate Professor, Dept of EEE, Sri Mittapalli College of Engineering, Guntur, AP, India, E-mail: [email protected].

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

mailto:[email protected]

mailto:[email protected]

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 2cos cos cos

3 3

2 2 2sin 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 3

rd

harmonic.

Without UPQC utility side Current THD is 12.11% at

3rd

harmonic order.

Fig.34. without UPQC utility side current at 3

rd

harmonic.

Without UPQC utility side voltage THD is 4.15% at 5th

harmonic order.


th

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.


th & 9

th

harmonics.




Without UPQC Utility side Current THD is 12.17% at

7th

& 9th

harmonic orders.

Fig.38. without UPQC Utility side current at 7

th & 9

th

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 3

rd

harmonic.

Utility side voltage THD with PI 4.09% at 5th

harmonic

order.

Fig.41. Utility side voltage THD with PI at 5

th

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 7

th & 9

th

harmonics.




Utility side current THD with PI 2.26% at 7th

& 9th

harmonic orders.

Fig.44. Utility side current THD with PI at 7

th & 9

th

harmonics.

Utility side voltage THD with ANN 1.36% at 3rd

harmonic order

Fig.45. Utility side voltage THD with ANN at 3

rd

harmonic.

Utility side current THD with ANN 1.48% at 3rd

harmonic order.

Fig.46. Utility side current THD with ANN at 3

rd

harmonic.

Utility side voltage THD with ANN 1.35% at 5th

harmonic order.


th

harmonic.

Utility side current THD with ANN 1.31% at 5th

harmonic order.


th

harmonic.

Utility side voltage THD with ANN 1.37% at 7th

& 9th

harmonic orders.


th & 9

th

harmonics.




Utility side current THD with ANN 1.39% at 7th

& 9th

harmonic orders.


th & 9

th

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.

XI. REFERENCES

[1] H. Fujita and H. Akagi, ―The unified power quality

conditioner: The integration of series- and shunt-active

filters,‖ IEEE Trans. Power Electron., vol. 13, no. 2, pp.

315–322, Mar. 1998.

[2] L.H.Tey,P.L.So and Y.C.Chu,Unified power Quality

Conditioner for improving power Quality Using ANN

with Hysteresis Control, IEEE Tran. Power Electronics,

vol. 9, no.3, May 1994, pp. 1441-1446.

[3] V. Khadkikar and A. Chandra, ―A new control

philosophy for a unified power quality conditioner

(UPQC) to coordinate load-reactive power demand

between shunt and series inverters,‖ IEEE Trans. Power

Del., vol. 23, no. 4, pp. 2522–2534, Oct. 2008.

[4] M.F. Farias, P.E. Battaiotto, Investigation of UPQC

for sag compensation in wind farms to weak grid

connection, IEEE Conf., .2010.

[5] Vadirajacharya G. Kinhal, Promod Agarwal, and Hari

Oam Gupta, ―Performance Investigation of Neural

Network Based Unified Power-Quality Conditioner, IEEE

Transactions on power delivery, vol. 26, no. 1, Jan.

2011,pp.431-437

[6] D. Graovac, V. Katic, and A. Rufer, ―Power quality

compensation using universal power quality conditioning

system,‖ IEEE Power Eng. Rev., vol. 20, no. 12, pp. 58–

60, Dec. 2000.

[7]Hirofumi Akagi, Trends in Active Power Line

Conditioners, IEEE Tran. Power Electronics, vol. 9, no.3,

May 1994, pp. 263-268.

[8] Rvd Rama Rao And Dr.Subhransu.Sekhar.Dash,

Power Quality Enhancement By Unified Power Quality

Conditioner Using Ann With Hysteresis Control,

International Journal Of Computer Applications (0975 –

8887) Volume 6– No.1, September 2010.

[9] E. Destobbeleer and L.Protin, On the Detection of

Load Active Currents for Active Filter Control, IEEE

Trans. Power Electronics, vol. 11, no.6, Nov. 1996, pp.

768-775.

[10] Moleykutty George, Artificial Intelligence Based

Three-Phase Unified Power Quality Conditioner, Journal

of Computer Science 3 (7): 465-477, 2007 ISSN 1549-

3636 © 2007 Science Publications.

[11] Hideaki Fujita and Hirofumi Akagi, the Unified

Power Quality Conditioner: The Integration of Series- and

Shunt- Active Filters, IEEE Tran. Power Electronics, vol.

13, no.2, Mar. 1998, pp.315-322.

[12] Ahmet Tekel and Mhmet Tumayl, Upqc A

Literature Survey, Jes 7-1(2011): 122-130.

[13]Fang Zheng Peng, George W. Ott Jr., and Donald

J.Adams, ―Harmonic and Reactive Power compensation

Based on the Generalized Instantaneous Reactive Power

Theory for Three-Phase Four-Wire Systems, IEEE

trans,Power Electronics, vol.13, no.6, Nov. 1998, pp.

1174-1181.

[14] K.S. Ravi Kumar and S.V.A.R.Sastry,Application

of PI, Fuzzy Logic and ANN in Improvement of Power

Quality using Unified Power Quality Conditioner,ISSN :

2231-0711, IJCSET | June 2011 | Vol 1, Issue 5,214-217 .

[15]Kishore Chatterjee, B.G. Fernandes, and Gopal

K.Dubey, An Instantaneous Reactiv Volt Ampere

Compensator and Harmonic Suppressor System, IEEE

Trans. Power Electronics,vol. 14, no.2, Mar.1999, pp. 381

392.




[16] Saleha Tabassum and B.Mouli Chandra Power

Quality Improvement by UPQC Using ANN Controller,

International Journal of Engineering Research and

Applications (IJERA) ISSN: 2248-9622, Vol. 2, Issue4,

July August 2012, pp.2019-2024.

[17]Po-Tai Cheng, Subhashish Bhattacharya, and Deepak

D. Divan, Line Harmonics Reduction in High-Power

Systems Using Square-Wave Inverters-Based Dominant

Harmonic Active Filter, IEEE Trans. Power Electronics,

vol. 14, no.2, Mar. 1999, pp. 265-272.

[18] Seyedreza Aali Unified Power Quality Conditioner

Based on Neural-Network Controller for Mitigation of

Voltage and Current Source Harmonics, Journal of

Electrical Engineering.

[19] Ambrish Chandra, Bhim Singh, B.N.Singh, and

Kamal Al-Haddad, An Improved Control Algorithm of

Shunt Active Filter for Voltage Regulation, Harmonic

Elimination, Power-factor Correction, and Balancing of

Nonlinear loads, IEEE Trans. Power Electronics, vol. 15,

no.3, May 2000, pp. 495-507.

[20] Kolhatkar Y. Y. and Das S. P., ―Experimental

investigation of a single-phase UPQC with minimum

VA loading,‖ IEEE Trans. Power Deliv., vol. 22, no. 1,

pp. 373-380, 2007.

[21] M. George, C.L. Seen, Modeling and control of

zero-sequence current of parallel three-phase converters

using Matlab/power system blockset, IEEE Power

Systems Conf. and Exp. 2004, PSCE 2004, vol. 3, pp.

1440-1443.

[22] Basu M., Das S. P. and Dubey G. K., ―Comparative

evaluation of two models of UPQC for suitable interface

to enhance power quality,‖ Elect. Power Syst. Res., vol.

77, no. 7, pp. 821-830, 2007.

[23] Hyosung Kim, Sang-Joon Lee, and Seung-Ki

Sul, A calculation for the compensation voltages in

dynamic voltage restorers by use of PQR power theory,

19th Annual IEEE Applied PowerElectronics Conf. and

Expo. 2004, APEC '04, vol. 1, pp. 573-579.

[24] Sudeep Kumar. R, Ganesan. P ―250KVA unified

power quality controller‖ center for development of

Advanced computing, Trivandrum, IEEE2006.

[25] J. G. Nielsen, M. Newman, H. Nielsen, and F.

Blaabjerg, Control and testing of a dynamic voltage

restorer (DVR) at medium voltage level, IEEE Trans. on

Power Electronics, vol. 19, issue 3, May 2004, pp. 806-

813.

[26] G.Tulasi Ram Das, A.Jaya Laxmi, ―Different

control strategies for Unified Power Quality Conditioner

at load side‖, ICIEA 2006.

[27] E. K. K. Sng, S. S. Choi, and D. M. Vilathgamuwa,

Analysis of series compensation and DC-link voltage

controls of a transformerless self-charging dynamic

voltage restorer, IEEE Trans. Power Delivery, vol. 19,

[28 ]A. Kazemi, R. Rezaeipour ―Introducing a New

method for UPQC Control to Solve Power Quality

Problems‖ Center Of Excellence For Power System

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

shunt active power filter‟, IEE Proc.,-Gener. Trans. Distr.,

March, Vol. 147, No. 2

[30] H.Toodeji, S.H.Fathi, ―Power Management and

Performance Improvement in Integrated System of

Variable Speed Wind Turbine and UPQC‖ Amirkabir

University of Technology, Tehran, IEEE 2009.

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.

comparison of pi and ann control techniques for nine switches upqc to improve power quality

Engineering

power quality enhancement

power quality shaik

general power quality

switches power converter

switch power conditioner

power industrial power

reactive power

powerquality pq devices