Base PaPower Quality Improvement using MC-UPQC in a Deregulated Power Systems per

8/19/2019 Base PaPower Quality Improvement using MC-UPQC in a Deregulated Power Systems per

1/11

Power Quality Improvement using MC-UPQC in a

Deregulated Power Systems

P.CHINNAI! ".".SUPUA# Dr N."ISA$I% Dr &."..'.PASAD(

PG Student Asst.Prof Professor&Head Professor&Head 1&2 Annama)*arya Institute +, e)*nology S)ien)es /irupati 3 0NUA College o, 1ngineering/ Pulivendula 4 Madanapalle Institute +, e)*nology S)ien)e

/Madanapalle

Abstract—In this paper presents a Design of a Unified Power Quality conditioner (UPQC) connected to three phase four wire system (P!")# $he neutral of seriestransformer used in the fourth wire for the P!" system#$he neutral current that may flow toward transformer neutral point is compensated by using a four%leg &oltagesource in&erter topology for shunt part# $he seriestransformer neutral will be at &irtual 'ero potential during all operating conditions# In this simulation weobser&e the power uality problems such as unbalanced &oltage and current harmonics by connecting non linear load to P!" system with Unified Power Quality

conditioner# A new control strategy such as unit &ector template is used to design the series AP* to balance theunbalanced current present in the load currents bye+panding the concept of single phase P%Q theory# $he P%Q theory applied for balanced three phase system# And also be used for each phase of unbalanced systemindependently# $he ,A$-A./0imulin1 based simulationsare pro&ided the functionality of the UPQC

Inde+ $erms— Power quality (PQ), PSCAD/EMTDC, uniie!"ower#quality $on!itioner (%PQC), olta'e#our$e $onerter(SC)*

I. I N+DUCI+N

IH in)reasing appli)ations o, nonlinear and ele)tron-

i)ally swit)*ed devi)es in distri2ution systems and industries/

power-3uality 4PQ5 pro2lems/ su)* as *armoni)s/ ,li)6er/ andim2alan)e *ave 2e)ome serious )on)erns. In ad- dition/

lig*tning stri6es on transmission lines/ swit)*ing o, )apa)itor

2an6s/ and various networ6 ,aults )an also )ause PQ

pro2lems/ su)* as transients/ voltage sag7swell/ and interrup-

tion. +n t*e ot*er *and/ an in)rease o, sensitive loads

involving digital ele)troni)s and )omple8 pro)ess )ontrollers

re3uires a

pure sinusoidal supply voltage ,or proper load operation 9!:.

In order to meet PQ standard limits/ it may 2e ne)essary to

in)lude some sort o, )ompensation. Modern solutions )an 2e

,ound in t*e ,orm o, a)tive re)ti,i)ation or a)tive ,iltering 9#:.

A s*unt a)tive power ,ilter is suita2le ,or t*e suppression o, negative load in,luen)e on t*e supply networ6/ 2ut i, t*ere are

supply voltage imper,e)tions/ a series a)tive power ,ilter may

2e needed to provide ,ull )ompensation 9%:.

In re)ent years/ solutions 2ased on ,le8i2le a) transmission

systems 4;ACS5 *ave appeared. *e appli)ation o, ;ACS

)on)epts in distri2ution systems *as resulted in a new gener-

ation o, )ompensating devi)es. A uni,ied power-3uality )ondi-

tioner 4UPQC5 9(: is t*e e8tension o, t*e uni,ied power-,low

)ontroller 4UP;C5 99?:.

e)ently/ multi)onverter ;ACS devi)es/ su)* as an

interline power-,low )ontroller 4IP;C5 9@: and t*e generalied

uni,ied power-,low )ontroller 4BUP;C5 9!: are introdu)ed.

*e aim o, t*ese devi)es is to )ontrol t*e power ,low o, multilines or a su2networ6 rat*er t*an )ontrol t*e power ,low

o, a single line 2y/ ,or instan)e/ a UP;C.

*en t*e power ,lows o, two lines starting in one

su2station need to 2e )ontrolled/ an interline power ,low

)ontroller 4IP;C5 )an 2e used. An IP;C )onsists o, two series

"SCs w*ose d) )apa)itors are )oupled. *is allows a)tive

power to )ir)ulate 2etween t*e "SCs. it* t*is )on,iguration/

two lines )an 2e )ontrolled simultaneously to optimie t*e

networ6 utiliation.

*e BUP;C )om2ines t*ree or more s*unt and series )on-

verters. It e8tends t*e )on)ept o, voltage and power-,low )on-

trol 2eyond w*at is a)*ieva2le wit* t*e 6nown two-)onverter

UP;C. *e simplest BUP;C )onsists o, t*ree )onvertersE one )onne)ted in s*unt and t*e ot*er two in series wit* two

transmission lines in a su2station. *e 2asi) BUP;C )an

)ontrol total ,ive power system 3uantities/ su)* as a 2us

voltage and indepen- dent a)tive and rea)tive power ,lows o,

two lines. *e )on)ept o, BUP;C )an 2e e8tended ,or more

lines i, ne)essary. *e devi)e may 2e installed in some )entral

su2stations to manage power ,lows o, multilines or a group o,

lines and provide voltage sup- port as well. 'y using BUP;C

devi)es/ t*e trans,er )apa2ility o, transmission lines )an 2e

in)reased signi,i)antly. ;urt*ermore/ 2y using t*e multiline-

management )apa2ility o, t*e BUP;C/ a)tive power ,low on

lines )annot only 2e in)reased/ 2ut also 2e de)reased wit*

respe)t to operating and mar6et transa)tion re- 3uirements. In

general/ t*e BUP;C )an 2e used to in)rease t*e trans,er

)apa2ility and relieve )ongestions in a ,le8i2le way.

*is )on)ept )an 2e e8tended to design multi)onverter )on-

,igurations ,or PQ improvement in adFa)ent ,eeders. ;or e8-

ample/ t*e interline uni,ied power-3uality )onditioner

4IUPQC5/ w*i)* is t*e e8tension o, t*e IP;C )on)ept at t*e

distri2ution level/ *as 2een proposed in 9!!:. *e IUPQC

)onsists o, one series and one s*unt )onverter. It is

)onne)ted 2etween two ,eeders to regulate t*e 2us voltage o,

one o, t*e ,eeders/ w*ile regulating t*e voltage a)ross a

sensitive load in t*e ot*er ,eeder. In t*is )on,iguration/ t*e

voltage regulation in one o, t*e ,eeders is per- ,ormed 2y t*es*unt-"SC. However/ sin)e t*e sour)e impedan)e is very low/

a *ig* amount o, )urrent would 2e needed to 2oost t*e 2us

+


2/11

voltage in )ase o, a voltage sag7swell w*i)* is not ,ea- si2le. It also *as low dynami) per,orman)e 2e)ause t*e d)-lin6

)apa)itor voltage is not regulated.

;ig. !. Single-line diagram o, a distri2ution system wit* an MC-UPQC.

In t*is paper/ a new )on,iguration o, a UPQC )alled t*e

multi)onverter uni,ied power-3uality )onditioner 4MC-UPQC5

is presented. *e system is e8tended 2y adding a series-"SC

in an adFa)ent ,eeder. *e proposed topology )an 2e used ,or

simultaneous )ompensation o, voltage and )urrent

imper,e)tions in 2ot* ,eeders 2y s*aring power )ompensation

)apa2ilities 2etween two adFa)ent ,eeders w*i)* are not

)onne)ted. *e system is also )apa2le o, )ompensating ,or interruptions wit*out t*e need ,or a 2attery storage system and

)onse3uently wit*out storage )apa)ity limitations.

II. P+P+S1D MC-UPQC SGS1M

A. Circuit Configuration

*e single-line diagram o, a distri2ution system wit* an

MC-UPQC is s*own in ;ig. !.

As s*own in t*is ,igure/ two ,eeders )onne)ted to two di,-

,erent su2stations supply t*e loads $! and $#. *e MC-UPQC

is )onne)ted to two 2uses 'US! and 'US# wit* voltages o,

and / respe)tively. *e s*unt part o, t*e MC-UPQC is also

)onne)ted to load $! wit* a )urrent o, . Supply voltages are

denoted 2y and w*ile load voltages are and .

;inally/ ,eeder )urrents are denoted 2y and and load )ur-

rents are and .

'us voltages and are distorted and may 2e su2Fe)ted

to sag7swell. *e load $! is a nonlinear7sensitive load w*i)*

needs a pure sinusoidal voltage ,or proper operation w*ile its

)urrent is nonsinusoidal and )ontains *armoni)s. *e load $#

is a sensitive7)riti)al load w*i)* needs a purely sinusoidal

voltage and must 2e ,ully prote)ted against distortion/

sag7swell/ and interruption. *ese types o, loads primarily

in)lude produ)tion industries and )riti)al servi)e providers/su)* as medi)al )enters/ airports/ or 2road)asting )enters

w*ere voltage interruption )an result in severe e)onomi)al

losses or *uman damages.

B. MC–UPQC Structure

*e internal stru)ture o, t*e MC>UPQC is s*own in ;ig. #.

It )onsists o, t*ree "SCs 4"SC!/ "SC#/ and "SC%5 w*i)* are

)onne)ted 2a)6 to 2a)6 t*roug* a )ommon d)-lin6 )apa)itor.

In t*e proposed )on,iguration/ "SC! is )onne)ted in series

wit* 'US! and "SC# is )onne)ted in parallel wit* load $! at

t*e end o, ;eeder!. "SC% is )onne)ted in series wit* 'US# at

t*e ;eeder# end.

1a)* o, t*e t*ree "SCs in ;ig. # is realied 2y a t*ree-p*ase

)onverter wit* a )ommutation rea)tor and *ig*-pass output ,ilter

as s*own in ;ig. %. *e )ommutation rea)tor and *ig*-


3/11

;ig. #. ypi)al MC-UPQC used in a distri2ution system.

;ig. %. S)*emati) stru)ture o, a "SC.

pass output ,ilter are )onne)ted to prevent t*e ,low

o, swit)*ing *armoni)s into t*e power supply.

As s*own in ;ig. #/ all )onverters are supplied ,rom a

)ommon d)-lin6 )apa)itor and )onne)ted to t*e distri2ution

system t*roug* a trans,ormer. Se)ondary 4distri2ution5 sides

o, t*e series-)onne)ted trans,ormers are dire)tly )onne)ted in

series wit* 'US! and 'US#/ and t*e se)ondary 4distri2ution5

side o, t*e s*unt-)onne)ted trans,ormer is )onne)ted in

parallel wit* load $!. *e aims o, t*e MC-UPQC s*own in

;ig. # are

!5 to regulate t*e load voltage against sag7swell and

dis- tur2an)es in t*e system to prote)t t*e

nonlinear7sensitive load $!

#5 to regulate t*e load voltage against sag7swell/

interruption/ and distur2an)es in t*e system to prote)tt*e sen- sitive7)riti)al load $#

%5 to )ompensate ,or t*e rea)tive and *armoni) )omponents

o, nonlinear load )urrent .

In order to a)*ieve t*ese goals/ series "SCs 4i.e./ "SC! and

"SC%5 operate as voltage )ontrollers w*ile t*e s*unt "SC4i.e./ "SC#5 operates as a )urrent )ontroller.

C. Control Strategy

As s*own in ;ig. #/ t*e MC-UPQC )onsists o, two series

"SCs and one s*unt "SC w*i)* are )ontrolled independently.

*e swit)*ing )ontrol strategy ,or series "SCs and t*e s*unt

"SC are sele)ted to 2e sinusoidal pulsewidt*-modulation

4SPM5 voltage )ontrol and *ysteresis )urrent )ontrol/ respe)-

tively. Details o, t*e )ontrol algorit*m/ w*i)* are 2ased on t*e

> met*od 9!#:/ will 2e dis)ussed later.

Shunt-SC! ;un)tions o, t*e s*unt-"SC are

!5 to )ompensate ,or t*e rea)tive )omponent o, load $! )ur-rent


4/11

;ig. (. Control 2lo)6 diagram o, t*e s*unt "SC.

#5 to )ompensate ,or t*e *armoni) )omponents o, load $!

)urrent

%5 to regulate t*e voltage o, t*e )ommon d)-lin6 )apa)itor.

;ig. ( s*ows t*e )ontrol 2lo)6 diagram ,or t*e s*unt

"SC.

*e measured load )urrent is trans,ormed into t*e syn-

)*ronous re,eren)e ,rame 2y using

4!5

w*ere t*e trans,ormation matri8 is s*own in 4#5/ at t*e 2ottom

o, t*e page.

'y t*is trans,orm/ t*e ,undamental positive-se3uen)e )om-

ponent/ w*i)* is trans,ormed into d) 3uantities in t*e and

a8es/ )an 2e easily e8tra)ted 2y low-pass ,ilters 4$P;s5. Also/

all *armoni) )omponents are trans,ormed into a) 3uantitieswit* a ,undamental ,re3uen)y s*i,t

;ig. )omponents o, t*e

s*unt "SC re,eren)e )urrent are de,ined as ,ollows

;ig.


5/11

4#5

and are ,undamental ,re3uen)y positive-/ neg-

ative-/ and ero-se3uen)e )omponents/ respe)tively/ and is

t*e *armoni) )omponent o, t*e 2us voltage.A))ording to )ontrol o2Fe)tives o, t*e MC-UPQC/ t*e load

voltage s*ould 2e 6ept sinusoidal wit* a )onstant amplitude

even i, t*e 2us voltage is distur2ed. *ere,ore/ t*e e8pe)ted

load voltage in t*e syn)*ronous re,eren)e ,rame 4 5

only *as one value

4!%5

w*ere t*e load voltage in t*e a"c re,eren)e ,rame 4 5 is

4!(5

*e )ompensating re,eren)e voltage in t*e syn)*ronous

re,eren)e ,rame is de,ined as

4!


6/11

;ig. =. P*asor diagram o, 3uadrature )ompensation. 4a5 it*out voltagesag.425 it* voltage sag.

;ig. J. P*asor diagram o, inp*ase )ompensation 4supply voltage sag5.

t*e a)tive power re3uirement o, t*e load is only drawn ,rom

t*e utility w*i)* results in a unity input-power ,a)tor.

In an inp*ase )ompensation s)*eme/ t*e inFe)ted voltage is

inp*ase wit* t*e supply voltage w*en t*e supply is 2alan)ed.'y virtue o, inp*ase inFe)tion/ series "SC will mitigate t*e

voltage sag )ondition 2y minimum inFe)ted voltage. *e

p*asor diagram o, ;ig. J e8plains t*e operation o, t*is

s)*eme in )ase o, a voltage sag.

A )omparison 2etween inp*ase 4UPQC-P5 and 3uadrature

4UPQC-Q5 models is made ,or di,,erent sag )onditions and

load power ,a)tors in 9!%:. It is s*own t*at t*e power rating

o, t*e s*unt-"SC in t*e UPQC-Q model is lower t*an t*at o,

t*e UPQC-P/ and t*e power rating o, t*e series-"SC in t*e

UPQC-P model is lower t*an t*at o, t*e UPQC-Q ,or a power

,a)tor o, less t*an or e3ual to .@. Also/ it is s*own t*at t*e

total power rating o, UPQC-Q is lower t*an t*at o, UPQC-P

w*ere t*e "A demand o, t*e load is *ig*.

As dis)ussed in Se)tion II/ t*e power needed ,or

interruption )ompensation in ;eeder# must 2e supplied

t*roug* t*e s*unt "SC in ;eeder! and t*e series "SC in

;eeder#. *is implies t*at power ratings o, t*ese "SCs are

greater t*an t*at o, t*e series one in ;eeder!. I, 3uadrature)ompensation in ;eeder! and inp*ase )ompensation in

;eeder# are sele)ted/ t*en t*e power rating o, t*e s*unt "SC

and t*e series "SC 4in ;eeder#5 will 2e redu)ed. *is is an

important )riterion ,or pra)ti)al appli)a- tions.

'ased on t*e a,orementioned dis)ussion/ t*e power-rating

)al)ulation ,or t*e MC-UPQC is )arried out on t*e 2asis o,

t*e linear load at t*e ,undamental ,re3uen)y. *e parameters

in ;ig. = are )orre)ted 2y adding su,,i8 K!/L indi)ating;eeder!/ and t*e parameters in ;ig. J are )orre)ted 2y adding

su,,i8 K#/L indi)ating ;eeder#. As s*own in ;igs. = and J/ load

voltages in 2ot* ,eeders are 6ept )onstant at regardless o,

2us voltages variation/ and t*e load )urrents in 2ot* ,eeders

are assumed to 2e )onstant at t*eir rated values 4i.e./ and

/ respe)tively5

4!=5


7/11


8/11

;ig. ?. 'US! voltage/ series )ompensating voltage/ and load voltage in;eeder!.

I". SIMU$AI+N 1SU$S

*e proposed MC-UPQC and its )ontrol s)*emes *ave

2een tested t*roug* e8tensive )ase study simulations using

PSCAD7 1MDC. In t*is se)tion/ simulation results are

presented/ and t*e per,orman)e o, t*e proposed MC-UPQC

system is s*own.

A. #istortion and Sag$S%ell on the Bus oltage

$et us )onsider t*at t*e power system in ;ig. # )onsists o, two t*ree-p*ase t*ree-wire %?4v5 4rms/ $-$5/


9/11

;ig. !!. Simulation results ,or an upstream ,ault on ;eeder# 'US# voltage/)ompensating voltage/ and loads $! and $# voltages.

load $# is involved in sag7swell or interruption. *is voltage

imper,e)tion )an 2e )ompensated ,or 2y "SC#.

In t*is )ase/ t*e power re3uired 2y load $# is supplied

t*roug* "SC# and "SC%. *is implies t*at t*e power

semi)ondu)tor swit)*es o, "SC# and "SC% must 2e rated

su)* t*at total power trans,er is possi2le. *is may in)rease

t*e )ost o, t*e devi)e/ 2ut t*e 2ene,it t*at may 2e o2tained )an

o,,set t*e e8pense.

In t*e proposed )on,iguration/ t*e sensitive7)riti)al load on

;eeder# is ,ully prote)ted against distortion/ sag7swell/ and in-

terruption. ;urt*ermore/ t*e regulated voltage a)ross t*e

sensitive load on ;eeder! )an supply several )ustomers w*oare also prote)ted against distortion/ sag7swell/ and

momentary interruption. *ere,ore/ t*e )ost o, t*e MC-

UPQC must 2e 2alan)ed against t*e )ost o, interruption/ 2ased

on relia2ility indi)es/ su)* as t*e )ustomer average

interruption duration inde8 4CAIDI5 and )ustomer average

interruption ,re3uen)y inde8 4CAI;I5. It is e8pe)ted t*at t*e

MC-UPQC )ost )an 2e re)overed in a ,ew years 2y )*arging

*ig*er tari,,s ,or t*e prote)ted lines.

*e per,orman)e o, t*e MC-UPQC under a ,ault )ondition

on ;eeder# is tested 2y applying a t*ree-p*ase ,ault to ground

on ;eeder# 2etween s. Simulation results are

s*own in ;ig. !!.

C. *oad Change

o evaluate t*e system 2e*avior during a load )*ange/ t*e

nonlinear load $! is dou2led 2y redu)ing its resistan)e to *al,

at .< s. *e ot*er load/ *owever/ is 6ept un)*anged. *e

system response is s*own in ;ig. !#. It )an 2e seen t*at as

load $! )*anges/ t*e load voltages and remain

undistur2ed/


10/11

M+HAMMADI et al. MU$IC+N"11 UNI;I1D PQ C+NDII+NINB SGS1M

;ig. !#. Simulation results ,or load )*ange nonlinear load )urrent/ ;eeder!)urrent/ load $! voltage/ load $# voltage/ and d)-lin6 )apa)itor voltage.

t*e d) 2us voltage is regulated/ and t*e nonlinear load )urrent

is )ompensated.

#. Un"alance oltage

*e )ontrol strategies ,or s*unt and series "SCs/ w*i)* are

introdu)ed in Se)tion II/ are 2ased on t*e > met*od. *ey

are )apa2le o, )ompensating ,or t*e un2alan)ed sour)e

voltage and un2alan)ed load )urrent. o evaluate t*e )ontrol

system )a- pa2ility ,or un2alan)ed voltage )ompensation/ a

new simulation is per,ormed. In t*is new simulation/ t*e

'US# voltage and t*e *armoni) )omponents o, 'US! voltage

are similar to t*ose given in Se)tion I". However/ t*e

,undamental )omponent o, t*e 'US! voltage is an

un2alan)ed t*ree-p*ase voltage wit* an un2alan)e ,a)tor

o, (. *is un2al- an)e

voltage is given 2y

4#J5

*e simulation results ,or t*e t*ree-p*ase 'US! voltage/

series )ompensation voltage/ and load voltage in ,eeder ! are

s*own in ;ig. !%. *e simulation results s*ow t*at t*e

*armoni) )omponents and un2alan)e o, 'US! voltage are

)ompensated


11/11

;ig. !%. 'US! voltage/ series )ompensating voltage/ and load voltage in;eeder! under un2alan)ed sour)e voltage.

,or 2y inFe)ting t*e proper series voltage. In t*is ,igure/ t*e

load voltage is a t*ree-p*ase sinusoidal 2alan)e voltage wit*

regulated amplitude.

". C+NC$USI+N

In t*is paper/ a new )on,iguration ,or simultaneous )om-

pensation o, voltage and )urrent in adFa)ent ,eeders *as 2een

proposed. *e new )on,iguration is named multi)onverter

uni,ied power-3uality )onditioner 4MC-UPQC5. Compared

to a )onventional UPQC/ t*e proposed topology is )apa2le o,

,ully prote)ting )riti)al and sensitive loads against

distortions/ sags7swell/ and interruption in two-,eeder

systems. *e idea )an 2e t*eoreti)ally e8tended to

multi2us7multi,eeder systems 2y adding more series "SCs.

*e per,orman)e o, t*e MC-UPQC is evaluated under

various distur2an)e )onditions and it is s*own t*at t*e

proposed MC-UPQC o,,ers t*e ,ollowing advantages!5 power trans,er 2etween two adFa)ent ,eeders ,or

sag7swell and interruption )ompensation

#5 )ompensation ,or interruptions wit*out t*e need ,or a

2at- tery storage system and/ )onse3uently/ wit*out

storage )a- pa)ity limitation

%5 s*aring power )ompensation )apa2ilities 2etween two

ad- Fa)ent ,eeders w*i)* are not )onne)ted.

1;11NC1S

9!: D. D. Sa2in and A. Sundaram/ KQuality en*an)es relia2ility/L +,,, Sectr./ vol. %%/ no. #/ pp. %(>(!/ ;e2. !@@=.

9#: M. astogi/ . Nai6/ and N. Mo*an/ KA )omparative evaluation o, *armoni) redu)tion te)*ni3ues in t*ree-p*ase utility inter,a)e o, power ele)troni) loads/L +,,, rans. +nd. Al./ vol. %/ no. !!

9!!: A. &. 0indal/ A. B*os*/ and A. 0os*i/ KInterline uni,ied power 3uality)onditioner/L +,,, rans. Po%er #el./ vol. ##/ no. !/ pp. %=(>%J#/ 0an.#J.

9!#: M. Hu and H. C*en/ KModeling and )ontrolling o, uni,ied power

3uality )ompensator/L in Proc. /th +nt. Conf. Ad0ances in Po%er Syste' Control1 2eration and Manage'ent / Hong &ong/ C*ina/#/ pp. (%!>(%

Documents

Base PaPower Quality Improvement using MC-UPQC in a Deregulated Power Systems per