Recei ed 17 Feb ua y 2023, accep ed 15 Ma ch 2023, da e o publica ion 20 Ma ch 2023, da e o cu en e sion 23 Ma ch 2023.
Digi al Objec Iden i ie 10.1109/ACCESS.2023.3259323
An Adap i e Hyb id Con ol o Reduced Swi ch
Mul ile el G id Connec ed In e e o Weak
G id Applica ions
TILA MUHAMMAD1, ADNAN UMAR KHAN 1, YOUSRA ABID 1, MUHAMMAD HILAL KHAN2,
NASIM ULLAH 3, VOJTECH BLAZEK 4, LUKAS PROKOP 4, AND STANISLAV MISÁK 4
1Depa men o Elec ical and Compu e Enginee ing, In e na ional Islamic Uni e si y Islamabad, Islamabad 44000, Pakis an
2Depa men o Elec ical Enginee ing, Ci y Uni e si y o Science and In o ma ion Technology, Peshawa 25000, Pakis an
3Depa men o Elec ical Enginee ing, College o Enginee ing, Tai Uni e si y, Tai 11099, Saudi A abia
4ENET Cen e, VSB—Technical Uni e si y o Os a a, 708 00 Os a a, Czech Republic
Co esponding au ho s: Nasim Ullah ([email p o ec ed]) and Tila Muhammad ([email p o ec ed])
This wo k was suppo ed by he ollowing p ojec s: TN02000025 Na ional Cen e o Ene gy II and CK04000060 De elopmen o
analy ical ools o e ec i e ansi ion o elec omobili y. This wo k was also suppo ed in pa by he Tai Uni e si y Resea che s
Suppo ing P ojec (TURSP-2020/144), Tai Uni e si y, Tai , Saudi A abia.
ABSTRACT G id-connec ed in e e s ha e a e y signi ican ole in he in eg a ion o enewable ene gy
esou ces wi h u ili y g ids. Howe e , in ecen s udies, i is e ealed ha g id-connec ed in e e s a e
ulne able o ins abili y when he na u e o he g id changes om s ong o weak, which p oduces unce ain y
and pe o mance deg ada ion. An inc ease in g id impedance dec eases s abili y ma gins, emendously
inc eases o al ha monic dis o ion a e a ce ain limi , and ampli ies he ol age ha monics in he g id.
A cascaded educed swi ch symme ical mul ile el in e e along wi h an adap i e hyb id con ol echnique
is p oposed o injec ing powe gene a ed om dis ibu ed ene gy esou ces e icien ly and s ably o he
u ili y g id. This esea ch con ibu es wo old: a mul ile el in e e opology and he o he is i s con ol
me hod. The mul ile el in e e educes o al ha monic dis o ion and size o he il e while inc easing
powe handling capabili y. The con ol uni o he p oposed sys em u he consis s o wo pa s: one is he
synch onous ame cu en con olle , and he o he is s a iona y ame adap i e ha monic compensa o s. The
g id cu en con olle which is wo king in a synch onous e e ence ame ensu es egula ed cu en injec ion
o he g id. I is no a o able o implemen a ha monic compensa o in a synch onous e e ence ame due
o compu a ion complexi ies. The e o e, he s a iona y e e ence ame con olle s a e used o ha monic
compensa ions. Bu he esul an ha monic compensa o s ha e na ow bandwid h. Thus, hese a e no obus
agains a ia ion in g id equency. In his esea ch, his p oblem is esol ed by adding he adap i e ea u es
wi hin he ha monic compensa o s, which shi i s passing band acco ding o he equency o he g id while
emaining wi h he same bandwid h. The p oposed design o he hyb id ame con olle is alida ed by
conside ing a nine-le el in e e connec ed wi h a weak g id.
INDEX TERMS Adap i e ha monic compensa o s, g id-connec ed in e e s, ha monic compensa o s,
mul ile el in e e s, phase disposi ion le el shi ca ie pulse wid h modula ion, educed swi ch mul ile el
in e e s, o al ha monic dis o ion, weak g id.
I. INTRODUCTION
G id connec ed in e e s(GCIs) play an impo an ole in
enabling he use o enewable ene gy esou ces. I is used
The associa e edi o coo dina ing he e iew o his manusc ip and
app o ing i o publica ion was Snehal Gawande .
o connec Dis ibu ed Gene a o s(DGs) wi h he exis ing
g id o wi hin a mic og id. Mos o he enewable ene gy
esou ces a e in e mi en in na u e [1], [2]. Thus, he
ene gy p oduced is a ec ed by en i onmen al condi ions
like wea he , empe a u e, sunligh , speed o he wind and
humidi y can a ec i s ou pu . The e o e, s o age de ices
VOLUME 11, 2023
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T. Muhammad e al.: Adap i e Hyb id Con ol o Reduced Swi ch Mul ile el G id Connec ed In e e o Weak G id Applica ions
a e equi ed o make elec ici y a ailable when he e is less
powe gene a ion han demand o he powe gene a ion is
no possible [1]. The commonly used de ice o elec ical
ene gy s o age is a ba e y, which has ixed cycles o cha ge-
discha ge. A e hese cycles, he pe o mance o he ba e ies
deg ades and needs eplacemen . This p oblem is common
in he sys em whe e pho o ol aic gene a ion occu s because
sunligh is a ailable only in he day ime. Thus, he ene gy
has o be s o ed in o de o p o ide unin e up ed powe o
he use s a nigh e.g. in he case o he mal powe plan s
connec ed o he g id ese e ossil uels du ing he day ime
when ene gy en e s om sola panels, and a nigh he he mal
powe plan uns by using he uels ha we e ese ed in he
day ime. The heme looks like he ene gy is s o ed in he g id
indi ec ly du ing he day ime and used a nigh . Due o highe
u iliza ion, ba e ies need eplacemen which inc eases he
main enance cos o pho o ol aic sys ems. The cos -e ec i e
solu ion o his p oblem is o supply he excessi e ene gy
o he g id and ex ac i again when needed, by doing his
he equi emen s o s o age de ices like ba e ies can be
minimized. The co e componen used o his pu pose o
ans e ene gy om dis ibu ed sou ces o he g id is called
GCIs. Thus, he GCIs play an impo an ole in he in eg a ion
o dis ibu ed powe sou ces.
The GCIs a e no much di e en om isola ed in e e s
in ci cui pa ame e s, he main di e ence lies in hei con ol
and p o ec ion uni . Due o he inc ease in he u iliza ion o
enewable ene gy esou ces, he GCI is one o he ho a eas o
esea ch. Cu en ly, he esea ch is ocused on he e iciency
and s abili y o in e e s which is a challenging ask. The
g id i sel o which GCIs a e connec ed can be classi ied a a
ce ain locali y as s ong o weak. The s eng h o a g id can
be de ined in wo ways, g id impedance and sho ci cui a io
(SCR). The SCR is he a io o he sho ci cui powe a he
poin o common coupling (PCC) and he a ed powe o he
in e e . When he SCR is below 10, he g id is weak. In he
case when he SCR is abo e 20, he g id is s ong [3], [4], [5].
Mo eo e , he g id impedance o a s ong g id is conside ed
ze o while a weak g id has some conside able impedance.
Some con empo a y echniques ha e conside ed and es ed
o g id impedance up o 9mH [6] while in e e ence he
in e e is es ed up o 15mH [7].
The in eg a ion o GCIs wi h a weak g id becomes mo e
challenging. The g id impedance o a weak g id a ies due o
pa ame e s like dis ibu ion lines, line equency ans o me ,
dis ance om gene a ion uni s, and sho ci cui a io
[3], [4], [5]. The in e e con olle is designed by conside ing
a dynamic model wi h he assump ion ha g id impedance
does no a y bu in p ac ice, he impedance o weak g id
a ies [6], [8]. This a ia ion can change he s abili y ma gins
o he GCI which make he sys em a isk o become uns able.
The esea ch in his pape is ocused on: GCI opology
imp o emen s, de e mining he s abili y o he connec ed
GCI, and obus con ol echniques.
In [9], he GCI is o mula ed in he o m o a closed-
loop sys em which is used o he e alua ion o s abili y.
Mo eo e , i is ound ha he a io o g id impedance and
in e e ou pu impedance mus sa is y he Nyquis c i e ia o
s abili y. In [10] u he de ail o impedance-based s abili y is
discussed.
The de elopmen o GCI occu s ei he in o m o imp o e-
men s in opology o in i s con olle . Bo h pa s o GCI a e
o equal signi icance. The e o e, his esea ch con ibu es o
bo h domains by imp o ing he powe handling capabili y,
s abili y, and THD o he en i e sys em. The con ol uni o he
GCI plays a i al ole in he s abili y o he sys em. I usually
pe o ms h ee main unc ions: synch oniza ion, cu en
egula ion, and ha monic compensa ion. The synch oniza ion
uni ex ac s he phase o he g id ol age and o wa ds i o
he cu en con olle . The ex ac ed phase is u he used in
Di ec -Quad a u e-Ze o (DQZ) ans o ma ion and e e ence
gene a ion. The cu en con olle egula es he cu en and
gene a es he cu en ha is in phase wi h he g id ol age
which esul s in ac i e powe ans e .
The con olle mus be designed o injec pu e sine wa e
cu en s e en in he p esence o g id ha monics bu in mos
cases, he in e e con olle can no minimize hose ha monic
and he in e e injec s cu en pollu ed wi h low-o de
ha monics in o he g id. The e o e, ha monic compensa o s
a e used in addi ion o he cu en con olle o educe hese
ha monics’ con en in he g id cu en .
In he weak g id, any inc ease in impedance boos s he
ol age ha monics. These ha monics p opaga e h ough he
phase lock loop (PLL) ci cui and each he con ol uni .
Whe e i adds up o he g id cu en and inc eases he o al
ha monic dis o ion. In [7], PLL based on a second-o de
gene alized in eg a o (SOGI) il e is used which helps o
minimize he ha monic con en s in he phase gene a ed by
PLL. Mo eo e , he con olle used in PLL is P opo ional
In eg al (PI) which is a synch onous ame con olle and
equi es o hogonal signals o DQZ ans o ma ion. The
SOGI il e s also help in he gene a ion o he equi ed
o hogonal signals.
The PI con olle is one o he sui able and commonly used
cu en con olle s o PWM due o i s obus ness and ease o
implemen a ion bu he g id cu en is an AC signal which can
no be con olled wi h he PI con olle di ec ly. The e o e,
i s , he cu en signal is con e ed o a synch onous ame
using DQZ ans o ma ion and hen a PI con olle can
be used. DQZ ans o ma ion con e s he AC signal in o
DC o m and a e he p ocessing by he PI con olle , he
con olled signal con e s o AC o m wi h he help o in e se
DQZ ans o ma ion [11]. Addi ional eedback o capaci o
cu en is also used o wo k as ac i e damping and a oid
esonance c ea ed by a capaci o o LCL il e [12].
Al hough PI con ol educes he o al ha monic dis o ion
due o swi ching and dead ime he low-o de ha monics
a e s ill p esen . The e o e, addi ional PI con olle s o
P opo ional Resonance (PR) a e used as ha monic compen-
sa o s. Each echnique has i s own p os and cons. The PI
con olle s a e no app op ia e o ha monic compensa ion
because o a single ha monic wo PI con olle s in addi ion
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T. Muhammad e al.: Adap i e Hyb id Con ol o Reduced Swi ch Mul ile el G id Connec ed In e e o Weak G id Applica ions
o he complexi y o DQZ ans o ma ion a e equi ed [13].
The e o e, PI con olle s a e no ecommended o his
pu pose. PR con olle s a e sui able compensa o s bu hey
ha e na ow bandwid h. The e o e, e en a small a ia ion
in g id equency can a ec hei pe o mance [14]. This
p oblem o equency a ia ion can be ixed wi h he help o
inc easing he damping ac o and using adap i e ha monic
compensa o s [15].
The GCI is in insically a slow esponse sys em ha
p oduces many complica ions. The esponse ime o he
GCI can be imp o ed wi h he help o ol age eed o wa d.
In ecen s udies, ol age eed o wa d is conside ed an
in eg a ed pa o GCI. Mo eo e , g id ol age eed o wa d
minimizes he bu den on he cu en con olle and educes
he e ec o sag and spike in g id ol age [16]. The e
a e di e en echniques used o ol age eed o wa ds
like p opo ional ol age eed o wa d, undamen al ol age
eed o wa d, adap i e ol age eed o wa d [6] and ull
ol age eed- o wa d [17], [18] a e some o he commonly
used echniques. Al hough he ol age eed o wa d plays an
impo an ole in GCI bu i educes he s abili y ma gins
o he in e e . The e o e, di e en echniques a e p oposed
o o e come his limi a ion. The ull ol age eed o wa d,
p opo ional ol age eed o wa d, selec i e ha monic ol age
eed o wa d, and undamen al ol age eed o wa d a e he
commonly used echniques o his pu pose [18], [19].
In [20], i is ound ha undamen al ol age eed o wa d
has mo e s abili y ma gin as compa ed o o he s. The e o e,
undamen al ol age eed o wa d is used he e.
An in e e is he co e pa o a GCI and i is c i ical
o selec an app op ia e in e e opology. The e o e, he
in e e s can be classi ied on he basis o di e en pa ame e s
o ind he app op ia e opology. On he basis o , powe a ing
he e a e low, medium, and high powe in e e s like ly
back, push-pull, and hal -b idge in e e s a e used as low-cos
and low-powe in e e s. The H-b idge in e e s a e used as
medium powe in e e s and mul ile el in e e s a e sui able
o use in medium o high powe applica ions.
In a compa ison o he H-b idge and mul ile el in e e s,
he H-b idge in e e s ha e he ad an age o he minimum
numbe o powe elec onic swi ches, bu i equi es il e
componen s wi h highe alues which comp omises he
ad an age o he minimum numbe o powe elec onic
swi ches. The inc ease in he alues o il e componen s
inc eases he cos , size, weigh , and losses. Mo eo e ,
he minimum numbe o swi ches inc eases s ess on he
swi ches, hus i equi es swi ches wi h a highe a ing.
The e o e, conside ing hese cons ain s he smalle numbe
o swi ches does no look p omising [21], [22].
Ins ead o a ull b idge in e e , he mul ile el in e e
p oduces a sine wa e in s ai o m. Whe e each s ai is
encoded wi h pulse wid h modula ion(PWM). Hence, he
ol ages ac oss he swi ches p oducing PWM a y by a
smalle alue as compa ed o he ze o and peak alues in he
case o he ull b idge in e e . Due o his, he s ess on powe
swi ches educes and he ansien esponse imp o es.
The e a e many mul ile el in e e opologies a ailable in
li e a u e bu clamped diodes, lying capaci o s and cascaded
mul ile el in e e s a e he classical opologies [23], [24]. The
o he opologies a e de i ed o ms o hese in e e s. Each o
hese opologies has i s own ad an ages and disad an ages.
On he basis o be e ou pu wa e o m esolu ion, symme y
in he ci cui , simple PWM, and educed o al ha monic dis-
o ion, he cascaded mul ile el in e e is a good choice o
GCI. Mo eo e , i s s uc u e is mo e sui able o pho o ol aic-
based powe plan s, he e o e he cascaded mul ile el in e e
is conside ed sui able o he way o wa d o his esea ch.
The cascaded symme ical mul ile el in e e in eg a es
mul iple isola ed sou ces o gene a e di e en le els in he
ou pu wa e o m. The equi emen o isola ed sou ces limi s
i s usage. Bu in he case o PV panels as a sou ce o ene gy,
each panel o s ing o panels can be used as an isola ed
sou ce which makes i use ul. Ano he limi a ion o MLI is
he equi emen o many powe swi ches. To minimize his
limi a ion, many a ian s ha e been p oposed o educe he
numbe o swi ches. Simila ly, his esea ch is ocused on one
such a ian which uses a educed numbe o swi ches.
In [25] he au ho has p oposed a educed swi ch opology
wi h an addi ional ea u e o equal ol age sou ce sha ing.
This is u he ex ended in his esea ch, by p oposing an
adap i e hyb id ame con olle o make i p omising o
weak g id-connec ed applica ions.
The con ibu ions o his esea ch a e:
1) Designed and con olled educed swi ched cascaded
mul ile el in e e o g id-connec ed applica ions
ha ing he ea u e o u ilize sou ces equally.
2) A hyb id Adap i e con olle is implemen ed which is
wo king in bo h, synch onous and s a iona y ames
o e e ences simul aneously o pe o mance imp o e-
men .
3) The adap i e ha monic compensa o s a e designed
o minimize he e ec o g id equency and g id
impedance a ia ions on i s pe o mance and imp o e
he obus ness o he sys em.
Mo eo e , his pape is a anged such as Sec ion II
is ela ed o educed swi ch cascaded MLI, Sec ion III
consis s o ma hema ical modeling, Sec ion IV explains he
p oposed hyb id con ol, Sec ion Vdiscusses impedance-
based s abili y, Sec ion VI p esen s esul s and analysis, and
Sec ion VII consis s o conclusion.
Renewable ene gy esou ces can be connec ed o he AC
g id in ou possible con igu a ions as gi en in Figu e 1. The
me i s and deme i s o each con igu a ion a e summa ized in
Table 1. Table 1shows ha a mul ile el in e e is a sui able
solu ion. Because he DC sou ces can be used indi idually i
equi ed and hey can be combined by using he mul ile el
in e e o connec hem wi h he g id e ec i ely.
II. REDUCED SWITCH CASCADED MLI
The educed swi ch cascaded mul ile el in e e as shown
in Figu e 2consis s o wo s ages: s age 1 is a le el
syn hesizing cell, while s age 2 consis s o an H-b idge. The
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FIGURE 1. The a chi ec u e o GCI.
TABLE 1. The a chi ec u e o GCI.
le el syn hesizing cells a e used o gene a ing le els and he
H-B idge is used o pola i y in e sion. Each syn hesizing
cell can gene a e wo le els a posi i e and a nega i e le el.
Mo eo e , a single syn hesizing cell consis s o a disc e e
diode and a powe elec onic ansis o packed wi h an an i-
pa allel diode. The equi ed numbe o swi ches Nsw, diodes
Ndand isola ed DC sou ces NDC can be calcula ed om
(1), (2) and (3) espec i ely by using desi ed le el o he
in e e NL.
Nsw =NL−1
2+4.(1)
Nd=NL−1
2.(2)
NDC =NL−1
2.(3)
To demons a e he wo king p inciple o he p oposed
design we ha e conside ed an a bi a y nine-le el in e e
as a case s udy shown in Figu e 3. The numbe o con ol
swi ches (powe ansis o s) equi ed in he nine-le el in e e
a e eigh and he disc e e diodes a e compu ed om (1) and
(2). We ha e conside ed 4 dc sou ces Vdc1,Vdc2,Vdc3and Vdc4
o equal magni ude. Fou swi ches a e equi ed in s age 1,
namely S1,S2,S3and S4along wi h ou diodes D1,D2,
D3and D4, espec i ely while 4 swi ches in s age 2 deno ed
by A1,A2,A3and A4coupled wi h hei espec i e an i-
pa allel diodes.
FIGURE 2. Reduced Swi ch Cascaded N-Le el In e e .
FIGURE 3. Reduced Swi ch Cascaded 9-Le el In e e .
A. PHASE DISPOSITION PWM AND EQUAL SOURCE
SHARING
PWM plays an impo an ole in he con ol o any
powe elec onic con e e . The mos common o hese a e
a ailable in [26]. He e, he phase disposi ion Pulse Wid h
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TABLE 2. The speci ica ion o le el shi ed ca ie s used in PDPWM.
Modula ion(PDPWM) echnique is used which consis s o
le el-shi ed ca ie s wi h he same ampli ude and phase [27].
The ca ie s o he PDPWM is desc ibed he e by Ciwhich has
a equency ωc( he ωcis 1kHz in his sec ion II-A o ease
o demons a ion while in he emaining sec ions, he ωcis
10kHz). The ca ie s can be de ined as
Ci=E((−1) (i)yc(wc, ϕ)+i−N
2).(4)
whe e, E is ampli ude o a single iangula ca ie , N is he
numbe o le els, i=1, 2,..., N-1 and ycis a no malized
symme ical iangula ca ie de ined as
yc(wc, ϕ)=(−1)[α]((αmod2) −1) +1
2.(5)
whe e,
∝= wc +ϕ
π.(6)
The phase angle o ycis ep esen ed by ϕand mod
ep esen s he modulus unc ion. The ycis a pe iodic unc ion
ha ing he ime pe iod Tc=2π/ωc. Fo he PDPWM
echnique (i)=0. On he basis o hese assump ions
and speci ica ions he ou ca ie s which a e used he e a e
summa ised in Table2.
Figu e 4shows he classical PDPWM echnique o
mul ile el in e e and he swi ching signals gene a ed on
he basis o classical PDPWM o he ansis o s o le el
enhancemen cells. In Figu e 5, he p oposed modula-
ion echnique is p esen ed along wi h pseudocode which
makes he u iliza ion o sou ces on an equal basis. I is
shown in Figu e 5b ha in he posi i e hal cycle, he
u iliza ion o sou ce 1 o sou ce 4 is dec easing while
in he nega i e hal cycle, he u iliza ion o sou ce 4 o
sou ce 1 is dec easing. The swi ching signals o he
co esponding swi ches o le el enhancemen cells a e gi en
in Figu e 5b.
To minimize he ene gy losses in he ansis o swi ches
PWM signal is applied o any one ansis o in he ack o he
ON ansis o s a he same ime and he emaining ansis o s
o he same pa h will jus be kep ON. Simila ly, ze o is
applied o he es o he ansis o s o keep hem OFF a he
meanwhile. This pa e n o swi ching echnique is explained
wi h he help o Table 3.
On he basis o he modula ion echnique gi en in Figu e 4
he gene a ed ou pu o he in e e is gi en in Figu e 6a.
FIGURE 4. The PDPWM o 9-Le el GCI (a) Mul i ca ie s and e e ence
signal (b) Ga e signal gene a ed by con en ional PDPWM.
FIGURE 5. The PDPWM o 9-Le el GCI o equal sou ces sha ing (a)
Modula ion based on p oposed pseudocode (b) ga e signals gene a ed
o equal sou ce sha ing.
Simila ly, he swi ching pa e ns o S1 o S4a e gene a ed
on he basis o he modula ion echnique gi en in Figu e 5
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T. Muhammad e al.: Adap i e Hyb id Con ol o Reduced Swi ch Mul ile el G id Connec ed In e e o Weak G id Applica ions
TABLE 3. Ga e signals o o swi ches used in nine le el in e e .
FIGURE 6. Ou pu wa e o m o 9 le el in e e (a) Con en ional (b) Equal
ol age sou ce sha ing.
and he esul ing ou pu o he 9-le el in e e is gi en in
Figu e 6b.
III. SYSTEM MODELING
The p oposed model o he sys em is shown as a block
diag am in Figu e 7. He e he single-phase g id is conside ed
as mos ly esiden ial consume s a e connec ed wi h a single
phase. The model can be ex ended o a 3-phase in e e wi h
mino modi ica ions. The blocks o he p oposed GCI sys em
model consis o i) Mul ile el in e e , ii) induc o -capaci o -
induc o (LCL) il e , iii) Con ol uni which u he consis s
o a cu en egula o and ha monic compensa o , i ) Pulse
wid h modula o , ) A weak g id ( ep esen ed by The inen
ci cui o an impedance along wi h a ol age sou ce) a he
FIGURE 7. Mul ile el(9-Le el) weak GCI model.
FIGURE 8. The p oposed a e age swi ch con ol model o GCI.
poin o common coupling, i) A PLL used o he phase
de ec ion o g id ol age o gene a e e e ence cu en and
equency o he adap i e ha monic compensa o s and ii)
an ex a loop is used o ac i e damping.
IV. PROPOSED HYBRID CONTROL
The a e age swi ch con ol model o he p oposed in e e is
gi en in Figu e 8. Based on he unc ionali y o he sys ems
blocks can be di ided in o wo pa s as:
A ea A consis s o g id, in e e , LCL il e , modula o , ac i e
damping loop, ol age eed o wa d loop and eedback cu en
con olle designed in a synch onous ame o e e ence.
A ea B ep esen s he adap i e ha monic compensa o
wo king in he s a iona y e e ence ame and adap i e no ch
il e .
The impo an pa s o he a e age model a e elabo a ed in
he below subsec ions.
A. SYNCHRONIZATION
The in e e s ou pu cu en igmus be synch onized wi h
g ids ol age Vg o injec ing ac i e powe wi hin he g id.
He e, PLL is used o es ima e he phase and equency o g id
ol age Vg.
The PLL used he e uses a synch onous ame con olle ,
which needs di ec -quad a u e-ze o (DQZ) ans o ma ion
o AC signal bu DQZ ans o ma ion o single phase
sys em canno be implemen ed di ec ly like in he h ee-
phase sys em. In a single-phase sys em o hogonal signals
28108 VOLUME 11, 2023
T. Muhammad e al.: Adap i e Hyb id Con ol o Reduced Swi ch Mul ile el G id Connec ed In e e o Weak G id Applica ions
TABLE 4. Symbols, desc ip ion and alues o sys em pa ame e s.
FIGURE 9. PLL block diag am o ex ac ion o phase and equency o Vg
along wi h SOGI-based o hogonal signal gene a o .
a e equi ed o DQZ ans o ma ion which a e gene a ed
by SOGI-based o hogonal signal gene a ion me hod. The
ans e unc ion o SOGI il e s used he e a e gi en in (7) and
(8). The Gpllαgi en in (7) emo e high o de ha monics and
noise om Vgand allow Vαa he ou pu and Gpllβgi en in (8)
emo es high o de ha monic as well as p oduces a delay o
90oin Vg o make i o hogonal o Vα. The o hogonal signals
gene a ed a e con e ed om s a iona y e e ence ame o
synch onous e e ence ame by using DQZ ans o ma ion
which p oduces Vdand Vqas gi en in Figu e 9. Now, by using
PLL echnique g,i e and ωpll can be ex ac ed.
Gpllα=kpllωpll s
s2+kpllwplls+(ωpll )2.(7)
Gpllβ=
kpllω2
pll
s2+kpllwplls+(ωpll )2.(8)
The e a e o he ad anced echniques ha can be used o
imp o e he synch oniza ion o he GCI wi h g id ol age,
some o he la es a e [28], [29], [30], and [31]. The
ocus o his esea ch is on designing an adap i e ha monic
compensa o o mul ile el GCIs he e o e an exis ing PLL
echnique is implemen ed in [7] is used in his esea ch o
e alua e he pe o mance o he p oposed echnique.
B. CURRENT REGULATOR
The cu en egula o is used o con ol injec ed powe in o
he g id. The con olle used he e is he PI con olle , and i s
ans e unc ion is gi en in (9). The injec ed cu en wi hin
he g id is AC, i he PI con olle is implemen ed o con ol
he AC wa e o m i has educed bandwid h and can become
uns able. This issue can be o e come by con e ing he AC
signal om a s a iona y e e ence ame o i s co esponding
synch onous ame as discussed in subsec ion IV-A. Whe e,
he AC signal is con e ed in o i s co esponding DC, o his
pu pose, a DQZ ans o ma ion is used he e. The o hogonal
signal gene a o s a e again equi ed like in subsec ion IV-A o
con e a single phase cu en signal o wo o hogonal signals
bu he same echnique o hogonal signal gene a ion is no
app op ia e he e because he emo al o ha monic om he
inpu signal is no desi ed he e. The e o e, he g id cu en
igis conside ed as iαas gi en in (10) and he o he signal iβ
is p oduced by passing he g id cu en ig h ough wo low
pass il e s wi h a phase lag o 45◦pe il e as gi en in (11).
Then, wi h he help o Pa k ans o ma ion, he o hogonal
signals a e con e ed in o hei co esponding DC o m Id
and Iqwhich is gi en (12). The Idand Iqand a e sub ac ed
om hei espec i e e e ence signals and he e o signals
a e gene a ed. Bo h o he e o signals o he D-axis and
Q-axis a e passed h ough PI con olle which is exp essed
in (13) and (14) espec i ely. The in e se Pa k ans o m
is used o con e he con olled signals o hei espec i e
o hogonal signals in (17). This whole p ocess o cu en
con ol is desc ibed in a simpli ied o m in Figu e 10.
Gc(s)=Kp+Ki
s.(9)
iα(s)=ig(s).(10)
iβ(s)=(ig(s)) 1
1+Ts.(11)
Id
Iq=cosw sinw
−sinw cosw iα
iβ.(12)
Vcd (s)=(I∗
d−Id)Gc(s).(13)
Vcq(s)=(I∗
q−Iq)Gc(s).(14)
Vin _d=Vcd (s)−Iq(ω0(L1+L2)) +Vgd .(15)
Vin _q=Vcq(s)−Id(ω0(L1+L2)) +Vgq.(16)
Vin _α
Vin _β=cosw −sinw
sinw cosw Vin _d
Vin _q.(17)
The desi ed alues o Kpand Kia e selec ed wi h he help o
he MATLAB SISO ool, which is lis ed in Table 4.
C. ADAPTIVE HARMONIC COMPENSATORS
The ha monic compensa o s a e used o minimize he
ha monics con en s in he cu en eeding in o he g id.
The educ ion o ha monics in g id cu en enhances he
pe o mance and inc eases he s abili y o he GCIs. The g id
impedance a ia ion changes he ha monics con en in he
g id cu en . The e o e, ha monics compensa o s a e help ul
o p o ide obus ness agains he a ia ion o g id impedance.
VOLUME 11, 2023 28109
T. Muhammad e al.: Adap i e Hyb id Con ol o Reduced Swi ch Mul ile el G id Connec ed In e e o Weak G id Applica ions
FIGURE 10. Block diag am o synch onous ame cu en egula o along
wi h DQZ and in e se DQZ ans o ma ion.
The synch onous e e ence ame compensa o uses wo
con olle s o each ha monic. Hence, o ou ha monics
eigh con olle s a e equi ed bu ins ead o synch onous
only ou s a iona y e e ence ame con olle s a e equi ed.
The e o e, he esonan con olle s selec ed he e o his
pu pose a e s a iona y ame con olle s. The con olle s
es ima e he ha monic equencies p esen wi hin he g id and
mi iga e hem. The ealiza ion o he con olle in a digi al
domain is complex due o which i s usage is limi ed. This
limi a ion is o e come by adding a damping ac o which
no only makes i ealizable bu also inc eases i s bandwid h.
The ad an age o he b oad bandwid h is ha con olle s
can es ima e ha monics e en i he e exis small a ia ions
in undamen al and ha monic equencies. The limi a ion
o b oade bandwid h is ha con en s o undamen al can
also pass h ough he il e s because he magni ude o
he undamen al signal is e y la ge as compa ed o he
ha monics. To o e come his, and s op he undamen al signal
con en s om en e ing o he esonan il e s a no ch il e is
used he e. The no ch il e has a e y na ow bandwid h and is
di icul o ealize he e o e a damping ac o is also added o
he no ch il e o inc ease i s bandwid h o ealiza ion. Bo h
il e s wi h ela i ely la ge bandwid hs pe o m well wi hin
e y sligh a ia ions in equencies o he g id. Bu in he
case o li le la ge equency a ia ions, he pe o mance o
hese il e s signi ican ly deg ades and some imes p oduces
ad e se e ec s.
The no ch il e ans e unc ion Gno is gi en in (18) and
he ans e unc ion o esonan il e s G n is gi en in (19).
Bo h o hese il e s a e cascaded wi h gain KR o o m a ixed
alue ha monic compensa o GRwhich is gi en in (20). The
i s ou odd ha monic compensa o s a e shown in a ea B o
Figu e 8.
Gno =s2+0s+ω2
o
s2+kons+ω2
o
.(18)
G n =ko ωos
s2+ko wos+(nωo)2.(19)
GR=KRGno
n
X
i=3
G i.(20)
whe e iis an odd in ege s a ing om 3.
In his esea ch, o ix his p oblem o limi a ion ha
ix equency ha monic compensa o can no p ope ly wo k
when he e is a a ia ion in g id equency, he ixed alued
no ch and esonan il e s a e eplaced wi h adap i e il e s.
Some imes, a la ge a ia ion occu s in g id equency due
o apid a ia ions in load o gene a ing s a ions. In such
condi ions, he pe o mance o he ixed alue compensa o
deg ades o p oduces some ad e se e ec s. In his esea ch,
his limi a ion is o e come by designing adap i e il e s.
Al hough he bandwid hs o he adap i e il e s o es ima e
ha monics a e he same as ha o ixed alue il e s, bu
he adap i e il e s une hemsel es o he equencies o he
ha monics. The e o e, i is ound ha he a ia ion in he
undamen al equency has a mino e ec on he pe o mance
o compensa o s.
The designed adap i e il e s adap hemsel es acco ding
o equency es ima ed by PLL. The block diag ams o he
adap i e compensa o s a e gi en in Figu e 11(a) and (b). The
ans e unc ions o he il e a e gi en in (21) and (22). These
adap i e il e s a e cascaded wi h he gain KRand wo k as
adap i e ha monic compensa o s as gi en in (23).
Gnoad =
s2+ω2
pll
s2+kons+ω2
pll
.(21)
G nad =ko ωos
s2+ko wos+(nωpll)2.(22)
GRad =KRGnoad
n
X
i=3
G iad .(23)
whe e iis an odd in ege s a ing om 3.
Figu e 11(c) shows he equency esponse o adap i e
esonance compensa o s and no ch il e agains he g id
equencies o 49Hz, 50Hz o 51Hz labeled as blue, black
and ed espec i ely.
Thus, e e y adap i e ha monic compensa o wo k acco d-
ing o he g id equency and se he cu o alues o i s
il e such ha low-o de odd ha monics lies in he bandwid h
o i s co esponding compensa o . This phenomenon is
explained wi h he help o Figu e 11 which shows ha he
pe o mance o he ha monic compensa o depends on he
g id equency ha is i he g id equency is 51Hz hen
he equency o he 9 h odd ha monic is 459Hz. Thus,
in he case o ixed alues ha monic compensa o s he
esonance il e will no pass he ha monic bu in he case
o adap i e, i will pass h ough he il e as he esponse o
Figu e 11 shows he esul . The e in he case o equency
a ia ion ixed alued ha monic compensa o de alues i s
pe o mance, and a la ge a ia ion can make i uns able. The
ha monic compensa o akes equency as he inpu om PLL
con inuously.
The adap i e no ch il e is playing an impo an ole o
minimize he con en o g id equency in he ou pu signal
o he adap i e esonan il e s. The no ch il e blocks he
g id equency o en e in o he esonan il e as shown in
Figu e 11(a). The esul s o Figu e 12 show he no ch il e
has a signi ican ole o imp o e he esul .
28110 VOLUME 11, 2023
T. Muhammad e al.: Adap i e Hyb id Con ol o Reduced Swi ch Mul ile el G id Connec ed In e e o Weak G id Applica ions
FIGURE 11. Adap i e esonance ha monic compensa o (a) Adap i e
no ch il e (b) Adap i e esonance il e (c) F equency esponse o
adap i e ha monic compensa o o 49Hz, 50Hz and 51Hz.
D. PARAMETERS SELECTION OF CURRENT CONTROLLER
AND HARMONIC COMPENSATOR
To ind he app op ia e pa ame e s o he cu en con olle
and ha monic compensa o o he desi ed s abili y ma gin
(gain ma gin −3 o −5 dB and phase ma gin 30◦ o 60◦),
he open loop gain (24), as shown a he bo om o he page,
is de i ed om he p oposed sys em gi en in Figu e 8by
using block educ ion me hod. The alues o pa ame e s a e
ex ac ed wi h he help o Bode Plo and MATLAB SISO Tool
and lis ed in Table 4.
The Bode plo s o he open loop gain is gi en in Figu e 13
by using he pa ame e s gi en in Table 4. The esponses a e
o h ee di e en alues o g id impedance 5mH, 10mH, and
15mH. The esul s show ha he minimum phase ma gin and
gain ma gin a e 3dB and 50◦ espec i ely. The Ghin (24) is
gi en in (25):
Gh=kωos
s2+kωos+ω2
o
.(25)
FIGURE 12. Impac o adap i e no ch il e (a) 3 d ha monic wi hou
no ch il e (b) 3 d ha monic wi h no ch il e .
FIGURE 13. The open loop gain o he p oposed sys em.
V. IMPEDANCE-BASED STABILITY
The s abili y o he whole sys em is es ed wi h he help o
he impedance-based s abili y me hod. The p oposed sys em
gi en in Figu e 7is di ided in o wo equi alen subsys ems
he in e e side is ep esen ed in No on o m and he g id
along wi h g id impedance is ep esen ed in The enin o m
as gi en in Figu e 14.
The ne wo k o Figu e 14 can be sol ed wi h he help o
he supe posi ion heo em o ind he g id cu en gi en in
Gig
i e =Gckpwm
s3L1L2C1+s2L1ZgC1+s2L2C1kckpwm +sZgC1kckpwm +sL1+sL2+Zg−ZgG Ghkpwm +kpwmK GPR
(24)
VOLUME 11, 2023 28111
T. Muhammad e al.: Adap i e Hyb id Con ol o Reduced Swi ch Mul ile el G id Connec ed In e e o Weak G id Applica ions
ADNAN UMAR KHAN ecei ed he B.B. deg ee
in elec ical and elec onic enginee ing om Eas -
e n Medi e anean Uni e si y, Cyp us, in 1994,
he M.S. deg ee in communica ion sys ems om
he Uni e si y o Po smou h, U.K., in 1995, and
he Ph.D. deg ee om De Mon o Uni e si y,
U.K. He is cu en ly an Assis an P o esso wi h
he Depa men o Elec ical Enginee ing, In e na-
ional Islamic Uni e si y Islamabad, Pakis an.
YOUSRA ABID ecei ed he B.S. deg ee in
elec onic enginee ing om In e na ional Islamic
Uni e si y Islamabad, in 2018, and he M.S.
deg ee in elec ical enginee ing om Ai Uni e -
si y, Islamabad, in 2021. She is cu en ly pu suing
he Ph.D. deg ee wi h he Cen e o Ad ance
Elec onics and Pho o ol aic Enginee ing on he
Pakis an–U.K. mu ual p ojec o ene gy ha es -
ing and s o age a In e na ional Islamic Uni e si y
Islamabad. He esea ch in e es includes powe
elec onic con e e s.
MUHAMMAD HILAL KHAN ecei ed he B.Sc.
deg ee in elec ical enginee ing om he Uni e -
si y o Enginee ing and Technology, Peshawa ,
in 2007, he M.Sc. deg ee in elec ical enginee ing
om he Uni e si y o Enginee ing and Technol-
ogy, Taxila, in 2012, and he Ph.D. deg ee in
elec ical enginee ing om he CECOS Uni e si y
o IT and Eme ging Sciences, Peshawa , in 2021.
His esea ch in e es s include enewable ene gy,
mic og id, sma g ids, powe elec onic applica-
ions in powe sys ems, and sma ans o me s.
NASIM ULLAH ecei ed he B.Sc. deg ee in
elec ical enginee ing om he Uni e si y o
Enginee ing and Technology, Peshawa , in 2004,
and he Ph.D. deg ee in mecha onics enginee -
ing om Beihang Uni e si y, Beijing, China,
in 2013. He is cu en ly a P o esso wi h he
Elec ical Enginee ing Depa men , Tai Uni e -
si y, Saudi A abia. His esea ch in e es s include
enewable ene gy, mic og id, sma g ids, powe
elec onic applica ions in powe sys ems, sma
ans o me s, obo ics, and ligh con ol sys ems. He has comple ed se e al
esea ch p ojec s unded by he Deanship o Scien i ic Resea ch, Tai
Uni e si y, and he Minis y o Educa ion, Saudi A abia, as a P incipal
In es iga o (PI). He has au ho ed/coau ho ed mo e han 200 esea ch a icles
in pee - e iew jou nals and con ibu ed se e al book chap e s.
VOJTECH BLAZEK was bo n in he Czech
Republic, in 1991. He ecei ed he Ing. deg ee
om he Depa men o Elec ical Enginee ing,
VSB—Technical Uni e si y o Os a a, in 2016,
whe e he is cu en ly pu suing he in e nal doc o al
s uden deg ee. He is cu en ly a Junio Resea che
wi h he esea ch Cen e ENET—Ene gy Uni s
o U iliza ion o Non-T adi ional Ene gy Sou ces.
His cu en wo k includes de eloping mode n
and g een echnologies in o -g id sys ems wi h
ehicle- o-home echnologies.
LUKAS PROKOP g adua ed (Ing.) in elec ical
powe enginee ing om FEEC B no. He was an
Associa e P o esso wi h FEI TU Os a a. He is
cu en ly engaged in enewable ene gy sou ces,
mode n echnologies, and me hods in elec ical
powe enginee ing and elec ical measu emen s.
He is a esea ch eam membe o Czech and
in e na ional esea ch p ojec s. He se es as he
Depu y Head o he ENET Resea ch Cen e.
STANISLAV MISÁK was bo n in he Czech
Republic, in 1978. He ecei ed he Ing. and
Ph.D. deg ees om he Depa men o Elec i-
cal Enginee ing, VSB—Technical Uni e si y o
Os a a, in 2003 and 2007, espec i ely. He is
cu en ly a P o esso and he CEO o he Resea ch
Cen e ENET and he Cen e o Ene gy and
En i onmen al Technologies. He holds a pa en o
a aul de ec o o medium- ol age powe lines.
His cu en wo k includes he implemen a ion o
sma g id echnologies using p edic ion models and bio-inspi ed me hods.
28118 VOLUME 11, 2023