TELKOM
NIKA Indonesia
n
Journal of
Electrical En
gineering
Vol. 13, No. 1, Janua
ry 201
5, pp. 76 ~ 8
4
DOI: 10.115
9
1
/telkomni
ka.
v
13i1.682
1
76
Re
cei
v
ed O
c
t
ober 1
0
, 201
4; Revi
se
d Novem
b
e
r
12, 2014; Accept
ed De
cem
b
e
r
6, 2014
Comparison of LS-PWM with Different Modulation
Strategies for SVC PLUS
S.A Kam
r
an*
,
Chengxion
g
Mao
State Ke
y
L
a
b
o
rator
y
of Adva
nced El
ectrom
agn
etic Eng
i
ne
erin
g and T
e
ch
nol
og
y (HUST
)
, China
*Corres
p
o
ndi
n
g
author, e-ma
i
l
: kame79
70@
ya
ho
o.com*,
c
x
mao@ma
il.h
u
s
t.edu.cn
A
b
st
r
a
ct
Urba
ni
z
a
ti
on is
contin
uin
g
ar
oun
d the w
o
rl
d acco
mpan
ie
d by a co
nsta
ntly grow
in
g d
e
man
d
fo
r
ener
gy. F
o
r th
ese re
aso
n
s, n
e
w
and
efficie
n
t
soluti
ons for
pow
er trans
mi
ssion
are r
e
q
u
i
r
ed. T
o
co
pe
w
i
th
these n
e
w
ch
alle
ng
es a
n
o
vel SV
C PL
US (Static V
a
r Co
mpens
ation SV
C) for
Reactiv
e
Po
w
e
r
Co
mp
ensati
o
n
is
desi
g
n
ed
a
nd r
e
searc
h
e
d
. SVC P
L
US
is
an
adv
anc
ed
ST
AT
COM (Static Sync
hron
o
u
s
Co
m
p
ensator)
w
i
th Modular
Multilev
e
l C
o
n
v
erter (MMC
) techn
o
lo
gy, als
o
call
ed (M-STATCOM). In
thi
s
pap
er the M-S
T
A
T
C
OM is simu
late
d in P
S
C
AD e
n
vir
o
n
m
ent w
i
th 10
0 s
ub-
mo
dul
es p
e
r
phas
e. Its static
and
dyn
a
m
ic
character
i
stics
are d
i
scusse
d. After comp
are a
nd c
ontr
a
st different
modu
latio
n
sch
e
m
es,
har
mo
nic co
ntents in L
e
ve
l-shift sine p
u
ls
e w
i
dth
modu
l
a
tion (L
S-PW
M) are foun
d
havi
ng l
east tota
l
har
mo
nic
disto
r
tions (T
HD)
a
nd w
i
th this
modu
latio
n
sch
e
m
e
conv
erter
can ac
hi
eve
more l
e
vels
so
it is
found fe
asib
le
to control the
converte
r. T
he beh
avi
our of
circulati
ng cu
rrent w
i
th leas
t ripples is a
l
s
o
observ
ed. In
this
pap
er, the
traditi
ona
l c
a
pacitor
ba
la
nc
e strategy
is
also
mod
i
fie
d
.T
he vi
abi
lity
o
f
the
MMCs as w
e
ll as the effective
ness of the LS-
P
W
M
control meth
od is co
nfi
r
me
d by si
mu
la
tion.
Ke
y
w
ords
:
SVC PL
US (S
tatic Var
Co
mpens
atio
n SV
C), LS-PW
M
mo
du
latio
n
str
a
tegy, the
circ
ulati
n
g
current
Copy
right
©
2015 In
stitu
t
e o
f
Ad
van
ced
En
g
i
n
eerin
g and
Scien
ce. All
rig
h
t
s reser
ve
d
.
1. Introduc
tion
Rea
c
tive p
o
w
er
comp
en
sation b
a
sed
on thyri
s
tor
controlle
d te
chnolo
g
y sta
r
t
ed in
the
mid 197
0s a
nd ha
s a
c
hie
v
ed a high d
egre
e
of ma
t
u
rity in many
application
s
, worl
dwi
de.SVC
PLUS [1] is
a
n
innovative
and u
n
iversal
l
y applic
able
solutio
n
for
g
r
id e
nhan
ce
m
ent. SVC PL
US
offers
convin
cing a
d
vanta
ges in all respect
s
:
a)
Improved dynamic st
ability
b)
Incre
a
sed po
wer q
uality
c)
Highly efficie
n
t flicke
r red
u
c
tion in ind
u
st
rial appli
c
atio
ns
d)
Low h
a
rm
oni
c gen
eratio
n
e)
Fast, efficient
, modular, an
d co
st-effe
ctive solution
It redu
ces th
e time and
re
sou
r
ces
re
qui
red fo
r proje
c
t developme
n
t. The relativ
e
ly low
numbe
r of compon
ents
simplifies d
e
si
gn, planni
ng,
and en
gine
ering ta
sks.S
V
C PLUS u
s
es
Voltage-So
urced
Conve
r
te
r (VSC) tech
nology ba
se
d
on Modul
ar
Multilevel Co
nverter
(MM
C
)
desi
gn.
a)
The MMC p
r
ovides a ne
a
r
ly ideal sinu
soid
al-sha
pe
d waveform
on the AC si
de.
Therefore, th
ere is o
n
ly little – if any
– need for hig
h
-f
requ
en
cy filtering an
d no n
eed
for low o
r
de
r harm
oni
c filtering.
b)
MMC allo
ws for low
swit
chi
ng frequ
en
cie
s
, whi
c
h re
du
ce
s syste
m
lo
sses.
MMC wa
s first introduced b
y
Marqua
rt and Lesnicar i
n
2003 [2], and sin
c
e then
several
resea
r
ch a
c
ti
vities have
been
carried
out fo
cu
sin
g
on
the
m
odulatio
n [3-4], control [5
-6],
modelin
g [7-8], design [9
-10] and p
r
o
t
ection [11-1
2
]. Possibility
of a commo
n
dc bu
s, simp
l
e
voltage scali
ng by a se
rie
s
co
nne
ction
of identical
cells, simpl
e
realization of redu
nda
ncy, etc
are
its
chi
e
f a
d
vantage
s. A
bove all,
MM
C offe
rs
a
practical a
p
p
r
o
a
ch
to
co
nstruct a
reliabl
e
and
c
h
eap
STATCOM (c
alled M-STATCOM)
with
incre
a
sed nu
mbe
r
of
le
vels,
capable of elimi
n
ating
interface tran
sform
e
rs and
repla
c
e the
m
by c
heap
reacto
rs to all
o
w po
we
r excha
nge
with the
power sy
ste
m
[13-14].
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
Com
pari
s
o
n
of LS-PWM with Different
Modulat
io
n Strategie
s
for S
V
C PLUS (S.
A
Kam
r
an)
77
In this pa
per,
in se
ction t
w
o, three p
h
a
s
e MMC to
pol
ogy and it
s o
peratin
g p
r
in
ciple i
s
studie
d
. Also differen
c
t mo
dulation st
rat
egie
s
for
mult
ilevel inverters are di
scu
s
sed.Section th
ree
descri
be di
re
ct cu
rrent co
ntrol st
rategy
for the bal
a
n
cin
g
of ci
rculation
curre
n
t and
capa
citors
voltage.Using
instantan
eo
us rea
c
tive theory,t
he ex
pre
ssi
on
s of the instanta
n
eou
s active
and
rea
c
tive po
wers i
n
the dq
coo
r
din
a
te system ar
e
de
rived. Simula
tion re
sults a
r
e di
scusse
d
in
se
ction four.
Section five concl
ude
s the
pape
r.
2. Structur
e And Principl
e Of MMC
Figure
1 explain
s
the st
ructu
r
e of
th
ree
-
ph
ase M
M
C. Six arm
s
of MM
C a
c
t as a
controllabl
e
voltage
sou
r
ce. Both
the
po
sitive an
d ne
gative a
r
ms compo
s
e a
pha
se.
Sub-
module
s
are i
dentical, eve
n
ly and
se
rial
ly conn
ecte
d
in both
arm
s
and o
p
e
r
ate i
nde
pende
ntly. A
small in
du
cto
r
is in
clu
ded i
n
ea
ch a
r
m to limit f
ault currents. F
r
om
Figure
1, it can be p
r
ove t
hat
the total voltages
of two a
r
ms in a
pha
se unit mu
st b
e
equal to th
e DC voltage
(call
ed p
r
in
ci
ple
of MMC), giv
en by equatio
n:
12
aa
d
c
uu
u
(1)
With a flexibl
e
co
ntrol of
sub-m
odul
es, t
he de
sired
si
nusoidal volta
ge at the AC
terminal
can b
e
achi
eved. Each
Sub-Mo
dule
con
s
i
s
ts of two IGBTs
wi
th anti-pa
rall
el diode
s an
d a
floating d
c
ca
pacito
r
V
c0
th
at form
a typi
cal
bi-di
r
e
c
tio
nal
cho
ppe
r, as sh
own
in
Figure
1
~
2.T
he
terminal volta
ge of e
a
ch sub-m
odul
e can be
eithe
r
i
t
s ca
pa
citor v
o
ltage o
r
ze
ro, depe
ndin
g
on
the three
swit
chin
g state
s
[15].
Figure 1. The
stru
cture of three
-
p
h
a
s
e
M-STATCOM
along with S
ub-M
odul
e
Figure 2. IGBT module (12
00V/50A)
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 13, No. 1, Janua
ry 2015 : 76 – 8
4
78
Several
different sub
-
mod
u
le top
o
logi
e
s
p
r
o
p
o
s
ed
i
n
the
literatu
r
e.The
mo
st
popul
ar
one is the hal
f-brid
ge ci
rcui
t including two powe
r
switc
hes an
d a dc
cap
a
cito
r. The other three
topologi
es a
r
e also ba
se
d the half-bri
dge
ci
rcuit, and the ope
rating prin
cipl
es du
ring
normal
con
d
ition
s
a
r
e ne
arly the
same. Th
e m
a
in differe
nce
of these fou
r
topologi
es is
the pe
rform
a
nce
durin
g fault condition
s [16]
.
The
sub
-
mo
d
u
le i
s
a
half-b
r
idge
sub
-
mo
dule
outfitted
with a
by-p
ass thyri
s
tor an
d a
by-
pass vacuum
switch.
2.1. Modulati
on Strategie
s
for Multile
v
e
l In
v
e
rters
A numbe
r
of mod
u
latio
n
st
rategi
es are u
s
e
d
in multilevel
po
we
r
con
v
ersio
n
appli
c
ation
s
. They can g
e
n
e
rally be cl
assified into three cate
gori
e
s:
a)
fundame
n
tal Freq
uen
cy switchi
ng strategie
s
b)
Space Ve
ctor PWM strate
g
i
es
c)
Car
r
ie
r ba
sed
P
W
M st
rat
e
g
i
es
Of all the
PWM metho
d
s for ca
scaded multile
vel inverter, carrie
r ba
se
d PWM
method
s an
d
spa
c
e ve
cto
r
metho
d
s
are often u
s
ed
but whe
n
th
e numb
e
r of
output level
is
more than
five, the
space
vector method
will be
very
com
p
licated
with the i
n
crease of
swit
chin
g
sta
t
es. So th
e
carrie
r
ba
se
d PWM
met
hod i
s
prefe
rre
d u
nde
r t
h
is
co
ndition
in
multilevel inverters. This
pape
r focu
se
s on Lev
el
-shift sine pulse width mod
u
lation (LS
-
PWM
)
[17].
3. Direct
Cur
r
ent Control Strateg
y
The dire
ct cu
rre
nt control comp
en
satio
n
is a smoot
h, fast and accurate te
ch
nique so
widely
use in
indu
strial
pro
ductio
n
a
s
it i
s
b
a
se
d
on
th
e rea
c
tive co
mpone
nt of th
e in
stantan
eo
us
c
u
rrent for the main variable
[18].
Dire
ct current
co
ntrol
schem
e
is i
m
plem
en
ted by va
rying
modulatio
n index in ord
e
r to get variation
in out
put voltage of STATCO
M while ke
e
p
ing
cap
a
cito
r voltage con
s
tant. Combin
ation
of active and rea
c
tive cu
rre
nt comp
on
ents u
s
ing L
S
-
PWM gen
erat
es the refere
nce valu
e of the insta
n
tane
ous
curre
n
t.
Assu
me that the three
-
p
h
a
s
e symm
etri
cal grid voltag
e as follo
ws:
co
s
(
)
2
2c
o
s
(
)
3
2
co
s
(
)
3
sa
sb
sc
t
U
UV
t
U
t
(15)
Whe
r
e, V
is the
RMS val
u
e of th
e volta
ge a
n
d
ω
i
s
t
he a
ngul
ar freque
ncy i
n
rad/se
c.Applyi
ng
KVL to Figure
1 the averag
e of three-
ph
ase system mathemati
c
al
model
is:
11
1
22
2
aa
s
a
m
a
bb
s
b
m
b
cc
s
c
m
c
ii
u
u
d
L
iR
i
u
u
dt
ii
u
u
(16)
Whe
r
e,
u
ma~
m
c
are the
out
put voltage f
o
r p
h
a
s
e
s
a,
b and
c
re
sp
ectively.
i
a~c
are M
-
STATCOM
output
cu
rre
n
t
s for ph
ases a, b
an
d
c
resp
ective
ly.
By tran
sferri
ng the
three
pha
se
grid
-si
d
e
voltages into
the synchro
n
ous d
-
q coo
r
d
i
nates a
s
:
3
0
sa
sd
sb
sq
sc
u
u
v
Tu
u
u
(17)
Whe
r
e, T is the tran
sform
a
tion matrix g
i
ven by:
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
Com
pari
s
o
n
of LS-PWM with Different
Modulat
io
n Strategie
s
for S
V
C PLUS (S.
A
Kam
r
an)
79
22
co
s(
)
c
o
s
(
)
co
s(
)
2
33
22
3
si
n(
)
s
i
n
(
)
s
i
n(
)
33
tt
t
T
tt
t
(18)
Acco
rdi
ng to
the d
e
finitio
n
of in
stanta
neou
s
rea
c
tive theo
ry
[11]
,the expressio
n
s of th
e
instanta
neo
u
s
active an
d reactive po
we
rs
in the dq
coordi
nate sy
stem are a
s
follows:
3
3
s
dd
d
s
dq
q
pU
i
V
i
qU
i
V
i
(19)
The in
stanta
n
eou
s a
c
tive p
o
we
r a
nd
rea
c
tive po
we
r e
x
chan
ge b
e
twee
n the
grid
and M
-
STATCOM
can be
co
ntroll
ed by adj
usti
ng
i
d
an
d
i
q
, separately. When
i
d
is
pos
i
t
i
ve, M-STATCOM
absorb
s
acti
ve
power an
d
the co
rre
spondi
ng cap
a
citors are
charg
ed.
If
i
d
is n
egative,
M-
STATCOM re
leases a
c
tive
powe
r
to the grid and the
corre
s
p
ondin
g
cap
a
cito
rs
are di
scha
rge
d
.
The M-STAT
COM relea
s
e
s
leadi
ng rea
c
tive power
whe
n
i
q
is positive, and
lagging
rea
c
tive
power when
i
q
is negative.
4. Simulation Stud
y
To prove th
at the M-STATCOM, ba
sed
o
n
pro
p
o
se
d co
ntrol
strategy, provides the
desi
r
ed
com
pen
sation
ef
fects
a th
re
e ph
ase, M
-
STATCOM
of Figu
re 1
is
simul
a
ted
in
PSCAD with
100Sub
-mo
d
u
les p
e
r ph
ase. Simulation
and loads’
param
eters are summa
ri
zed
in Table 1.
Table 1. Simulation an
d lo
ad paramete
r
s
Name
paramete
r
s
Active pow
er
200 MW
Sub-modules/ph
a
se 100
Reactive power
±10 MVar
Load inductance
15mH
Load resistance
0.1
Ω
DC capacitance
3nF
3-ph source volta
ge
10kv
Carrier f
r
eq.
5kHz
Dc resistance
2.8
Ω
Dc voltage
±40kv
IGBT mo
dule
1200V/50A
Amplitude modu rate
0.95
From Fi
gu
re
3~5,
after
comp
are an
d co
ntra
st o
n
ly Level-shi
ft sine p
u
lse width
modulatio
n (LS-PWM
)
is f
ound mo
re a
ppro
p
ri
ate as
it is providin
g an even power di
strib
u
tion
among
the
cell
s a
s
well
as it de
crea
ses p
o
wer l
o
sse
s
an
d imp
r
oves effici
en
cy so, it
can
be
use
d
to co
ntrol the co
nvert
e
r. It use
s
two reverse
d
si
ne wave
s to
comp
are with
some tri
ang
u
l
ar
wave
s who h
a
s the sam
e
amplitude a
n
d
phase but t
he vertical po
sition shifts a
level one by one
that is shown in Figure 6
(
a/b)
while Fi
gure 6
(
c) de
p
i
cts the eq
uivalent modul
ated sig
nal.
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 13, No. 1, Janua
ry 2015 : 76 – 8
4
80
Figur
e 3. Multi-ca
rri
er mo
d
u
lation w
a
v
e
form (a
) PD (
b
) POD (
c
) AP
OD (
d
) CPS, (e) SPS
0
0.
01
0.
02
0.
0
3
0.
04
0.
05
0.
06
-1.
5
-1
-0.
5
0
0.
5
1
1.
5
x 1
0
4
t(
s)
u(
V
)
0
0.
0
1
0.
02
0.
03
0.
0
4
0.
0
5
0.
06
-2
50
-2
00
-1
50
-1
00
-50
0
50
10
0
15
0
20
0
25
0
t(
s
)
i(
A
)
0
0.
01
0.
02
0.
0
3
0.
04
0.
05
0.
06
-1.
5
-1
-0.
5
0
0.
5
1
1.
5
x 1
0
4
t(
s)
u(
V
)
0
0.
0
1
0.
02
0.
03
0.
0
4
0.
0
5
0.
06
-2
00
-1
50
-1
00
-50
0
50
10
0
15
0
20
0
t(
s
)
i(
A
)
0
0.
0
1
0.
0
2
0.
0
3
0.
04
0.
05
0.
06
-1
.
5
-1
-0
.
5
0
0.
5
1
1.
5
x 1
0
4
t(
s)
u
(V
)
0
0.
01
0.
02
0.
03
0.
04
0.
05
0.
06
-
200
-
150
-
100
-5
0
0
50
100
150
200
t(
s
)
i(
A
)
Figure 4. PD, POD, APOD corre
s
p
ondin
g
output voltage and
curre
n
t
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
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ISSN:
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046
Com
pari
s
o
n
of LS-PWM with Different
Modulat
io
n Strategie
s
for S
V
C PLUS (S.
A
Kam
r
an)
81
Figure 5. PD, POD, APOD corre
s
p
ondin
g
output voltage and
curre
n
t harmo
nic
content
Figure 6(a
)
. Upp
e
r carrie
r and refe
re
nce sign
al
Figure 6(b
)
. L
o
we
r ca
rri
er a
nd refe
ren
c
e
sign
al
0
0.
0
0
2
0.
0
0
4
0.0
0
6
0.
0
0
8
0.
0
1
0.
0
1
2
0.
0
1
4
0.
0
1
6
0.
0
1
8
0.
0
2
-8
-6
-4
-2
0
2
4
6
8
Ti
m
e
(
s
)
Ca
r
r
i
e
r
w
a
v
e
s
0
0.
0
0
2
0.
0
0
4
0.
0
0
6
0.
0
0
8
0.
0
1
0.
0
1
2
0.
0
1
4
0.
0
1
6
0.
0
1
8
0.
0
2
-8
-6
-4
-2
0
2
4
6
8
Ti
m
e
(
s
)
ca
r
r
i
e
r
w
a
v
e
s
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TELKOM
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Vol. 13, No. 1, Janua
ry 2015 : 76 – 8
4
82
Figure 6(c). E
quivalent mo
dulated
sign
a
l
In Figure 7, single ph
ases
of voltage an
d cu
rrent at PCC
are
exami
ned b
e
fore
a
nd after
0.1s, without the
M-STAT
COM actio
n
. Before 0.1s,
as th
e loa
d
i
s
indu
ctive so
the current la
gs
the voltage b
y
a certain a
n
g
le. Due to th
e large
in
du
ctive reactive p
o
we
r the voltage drop is 5
%
of the rated voltage which is ma
king p
o
w
er
quality p
oor. After 0.1
s
, as the lo
ad
is cap
a
citive
the
curre
n
t lea
d
s the volta
g
e
by a
certai
n an
gle.
Du
e to
exce
ssi
v
e ca
pa
citive re
active
po
wer,
voltage ri
se
s
5% high
er th
an the
rate
d
voltage, whi
c
h is
also u
n
wanted
situatio
n. So, in both
the
ca
se
s for the
stable a
nd efficient gri
d
op
eration M
-
ST
ATCOM i
s
used.
Figure 7. Single pha
se
s of
voltage and
curre
n
t (witho
ut the M-STACOM a
c
tion
)
In Figure 8, singl
e pha
se
s of voltage and current a
t
PCC with M-STATCOM
action is
sho
w
n. After
the M-STAT
COM
is put i
n
to op
eratio
n
,
As
can
be
see
n
from th
e Fig
u
re
8,
either
before
o
r
after the
0.1
s
,
curre
n
t and
voltage a
r
e
su
bstantially in
pha
se a
nd th
e load
be
ca
me
equivalent to
a resi
stive load.Before 0.1s,
M-STA
T
COM o
pera
t
ed in the capa
citive mode,
gene
rated
ca
pacitive rea
c
tive powe
r
in o
r
de
r to
com
p
ensate the in
ductive rea
c
tive powe
r
, Th
us,
M-STATCOM
improve
d
the
power fa
ctor
and
redu
ce
d
the cu
rrent flowin
g thro
ug
h the line
s
. Due
to the pure a
c
tive cu
rre
nt, the line losses an
d voltage dro
p
s a
r
e
least and h
e
n
ce the volta
ge
level at PCC is im
proved
. After 0.1s,
M-STAT
CO
M ope
rate
d i
n
the i
ndu
ctive mode
so
it
absorb
ed in
d
u
ctive re
activ
e
power of th
e cha
r
gi
ng po
wer
ca
ble, an
d hen
ce redu
ced the
network
voltage level.
Figure 8. A single ph
ase of voltage and
curre
n
t at PCC with M-ST
ATCOM a
c
tio
n
0.
0
2
0.0
3
0.
0
4
0.
0
5
0.0
6
0.
0
7
0.
0
8
0.0
9
0.
1
0
2
4
6
8
10
12
14
Ti
m
e
(
s
)
0
0.
0
2
0.
04
0.
06
0.
0
8
0.
1
0.
1
2
0.
14
0.
16
0.
1
8
0.
2
-1
-0
.
8
-0
.
6
-0
.
4
-0
.
2
0
0.
2
0.
4
0.
6
0.
8
1
x 1
0
4
t(
s
)
u
(V
),
i
(
A
)
u
i
0
0.
02
0.
04
0.
06
0.
08
0.
1
0.
12
0.
14
0.
16
0.
18
0.
2
-1
-0
.
8
-0
.
6
-0
.
4
-0
.
2
0
0.
2
0.
4
0.
6
0.
8
1
x 1
0
4
u
i
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
Com
pari
s
o
n
of LS-PWM with Different
Modulat
io
n Strategie
s
for S
V
C PLUS (S.
A
Kam
r
an)
83
M-STATCOM
DC bu
s voltage and its F
FT analysi
s
shown in Figure 9. As can b
e
see
n
from Figu
re
9(a
)
, the DC bus voltage
fluctuat
ion i
s
small a
nd
has the d
oub
le freque
ncy
viz
.
100
HZ harm
onic waves,
with least ha
rmonic
co
mp
o
nents (THD=47.94%). Thi
s
prove
s
that
th
e
DC b
u
s volta
ge reg
u
lato
r control st
rateg
y
is good.
(a) M
-
STATCOM DC bu
s voltage
(b) FF
T analy
s
e
s
of M-STA
T
COM
DC b
u
s
voltage
Figure 9. M-S
T
ATCOM
DC bus voltage
and ha
rmo
n
ic content
The M
-
STAT
COM’S
cap
a
c
itor m
odul
es voltages fo
r
uppe
r an
d lo
wer
bri
dge
s a
r
e
sho
w
n
in Figure 10. As
it can
be
seen
from
Fig
u
re 10 t
hat th
e capa
citors’
voltage fluctuation
s
both for
lowe
r
and
up
per arm a
r
e
a
l
most
sam
e
a
nd of
very
sm
all value
a
r
ou
nd 0.1%.Th
u
s
,it verifie
s
th
at
the cap
a
cita
n
c
e voltage
co
ntrol
strategy is su
cce
ssful.
Figure 10. Ca
pacito
r
voltag
es of all the sub-m
odul
es i
n
a pha
se
0
0.
0
1
0.
0
2
0.
0
3
0.
0
4
0.
0
5
0.
0
6
0.
0
7
0.
0
8
0.
0
9
0.
1
2
2.
1
2.
2
2.
3
2.
4
2.
5
x 1
0
4
Ti
m
e
(
s
)
Vo
l
t
a
g
e
(
v
)
0
0.
0
5
0.
1
0.
1
5
0.
2
0.
2
5
0.
3
0.
3
5
13
00
14
00
15
00
16
00
17
00
18
00
19
00
20
00
Ti
m
e
(
s
)
V
o
l
t
ag
e(
V
)
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ISSN: 23
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046
TELKOM
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KA
Vol. 13, No. 1, Janua
ry 2015 : 76 – 8
4
84
5. Conclusio
n
The
com
pute
r
simulatio
n
i
n
the PS
CAD env
iro
n
me
nt co
nfirme
d th
e prope
r
ope
ration of
the three
-
ph
a
s
e SVC plu
s
.
T
he followi
ng
con
c
lu
sion
s
can b
e
dra
w
n
:
1)
The novel direct cu
rrent c
ontrol st
rateg
y
improved the tradition
al
capa
citor vol
t
age balan
ce
algorith
m
. The circulatin
g current rippl
es
found lo
wer.
2)
Level-shift
si
ne p
u
lse
widt
h mo
dulation
(LS-P
W
M) i
s
foun
d mo
re ap
propri
a
te
due
to l
e
a
s
t
total harmoni
c di
stortions(THD).It provi
ded
an
even
power
di
st
ribution
among
the cell
s
as well a
s
d
e
crea
sed the
power lo
sses and
im
proved efficien
cy. With this modulation
scheme
conv
erter a
c
hi
eve
d
more level
s
so it
is found
feasible to control the con
v
erter.
3)
Simulation of
large
numb
e
r of sub
-
mod
u
l
e
s in PSCA
D
environm
ent
is faste
r
a
s
compa
r
ed to
the MATLAB/SIMULINK en
vironme
n
t.
4)
SVC PLUS is an innovative and universally
appli
c
able solution for grid enhancement.It
improve
d
dyn
a
mic st
ability and po
we
r qu
ality of
power system
s in a new, hig
h
ly econ
omical
manne
r.
Referen
ces
[1] Information
on
h
ttp://
w
w
w
.
energy
.siemens.com/
hq/en/po
w
e
r
-
transmissio
n
/facts/
[2] M
Glinka,
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a
rquardt.
A ne
w
ac/ac-multi
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erter family a
ppl
ie
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h
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se conv
erter.
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e
r Electroni
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A Lesnicar, R
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An
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o
vativ
mo
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lar
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ev
el c
onverter to
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lo
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b
l
e
for
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i
de
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e
r
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e
. Proc. IEEE Po
w
e
rT
ech Confere
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[4]
E Solas, G Ab
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dul
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w
e
r El
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ar multi
l
e
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sy
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e vo
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o
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r
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u
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e
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[9]
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T
u
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u
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e
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w
e
r S
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e
chnol
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l
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b
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d
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e c
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l
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r
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l
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e
l
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ongr
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h
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