Internati
o
nal
Journal of Ele
c
trical
and Computer
Engineering
(IJE
CE)
Vol
.
3
,
No
. 5, Oct
o
ber
2
0
1
3
,
pp
. 61
8~
62
8
I
S
SN
: 208
8-8
7
0
8
6
18
Jo
urn
a
l
h
o
me
pa
ge
: h
ttp
://iaesjo
u
r
na
l.com/
o
n
lin
e/ind
e
x.ph
p
/
IJECE
Power System Stability Enhanc
ement and Improvement of
LVRT Capability of a DFIG
Based Wind Power System by
Using S
M
ES an
d SFCL
Anj
u
M
1
, R.
R
a
j
a
sek
a
r
a
n
2
Department o
f
EEE, SNS Colleg
e
of
Technolog
y
,
Coimbatore, Ind
i
a
email: anju5101
1@gmail.com
1
, rare457@gmail.com
2
Article Info
A
B
STRAC
T
Article histo
r
y:
Received J
u
n
6, 2013
Rev
i
sed
Ju
l 21
,
20
13
Accepte
d Aug 2, 2013
This paper proposes a exhaustive stud
y
about the performance
analy
s
is of
Doubly
Fed In
duction (DFIG) under
abnormal condition. N
o
w a day
,
majority
of
pow
er network coun
tenan
c
e
the prob
lem of ov
er curr
ent
and gr
id
connectivity
iss
u
es. SFCL (Sup
erconduc
ting Fault Curr
ent
Limiter)
, which
have th
e
com
p
etenc
e
to
lim
it
th
e fau
lt
current
a
nd prote
c
t th
e
e
quipm
ents
from damage. SMES (Superc
onducting Magnetic Energ
y
Storag
e) is main
ly
us
ed to com
p
ens
a
te both re
al a
nd react
ive po
wer variat
ions
,
thus
power
qualit
y
can b
e
e
nhanced
. Co-ord
inat
ed
operation
of SFCL - SME
S
thus used
to enhan
ce th
e p
o
wer s
y
stem
sta
b
ilit
y
and im
prove the
LVRT (L
ow Voltage
Ride Th
rough)
cap
ability
of
wind
power generation
s
y
stems. LVRT
capab
ili
t
y
of wi
nd turbine
is ref
e
rs to th
e ab
ili
t
y
of wind
powe
r
s
y
stem
to
conquer th
e voltage v
a
riations
if ther
e is an
y
unwanted cond
itions. Her
e
DFIG based wi
nd turbine plant is used
for consideration, because it will
provide smoothened power ou
tput nearly
do
uble th
an a
convention
a
l
generator. And it hav
e
more sim
p
le
a
nd rugg
ed
construction also. Design
of
DFIG based wind power gen
e
r
a
tion s
y
stems under fau
lt
condition with
th
e
help of SMES and SFCL is analy
s
ed
b
y
m
eans
of MATLAB/S
I
MULINK
block set.
Keyword:
DFI
G
D
oub
ly f
e
d
indu
ctio
n g
e
n
e
r
a
to
r
Low
v
o
ltag
e
r
i
d
e
thro
ugh
LVRT
SCFL
SMES
Copyright ©
201
3 Institut
e
o
f
Ad
vanced
Engin
eer
ing and S
c
i
e
nce.
All rights re
se
rve
d
.
Co
rresp
ond
i
ng
Autho
r
:
An
ju. M
,
Depa
rtm
e
nt
of EEE, SNS
Coll
ege of
Technol
ogy
Co
im
b
a
to
re, Ind
i
a
Em
a
il: an
j
u
5
101
1@g
m
ai
l.co
m
1.
INTRODUCTION
In rece
nt
y
ears
m
o
re at
t
e
nt
i
on has
been
gi
v
e
n t
o
induction
m
achines bec
a
use they are
use
d
for low
and m
e
di
um
powe
r
ap
pl
i
cat
i
o
n
.
At
t
r
act
i
v
e
adva
nt
age
s
o
v
e
r co
nve
nt
i
o
na
l
generat
o
r
s
ar
e l
o
wer
u
n
i
t
cost
, l
e
ss
main
ten
a
n
ce an
d ro
bu
st co
nstru
c
tion
etc.
Do
ub
ly-Fed
I
ndu
ctio
n G
e
n
e
rato
r
s
(D
FIG)
is p
a
rticu
l
arly
suitab
l
e
fo
r
i
s
ol
at
ed op
erat
i
o
n
l
i
k
e hy
dr
o
a
n
d wi
n
d
d
e
vel
o
pm
ent
s
[1
]
.
Do
u
b
l
y
fe
d i
n
duct
i
o
n
ge
nera
t
o
rs
(D
FI
Gs
) a
r
e c
u
r
r
ent
l
y
d
o
m
i
nat
i
ng t
h
e
rene
wa
bl
e ene
r
gy
m
a
rket
.
Ove
r
the last
decades,
DFIG-base
d
wi
nd t
u
rbines
ha
ve
bee
n
m
o
st prefe
r
red option for the hi
gh capacit
y
wind
farm
s because
it has the ability to c
ontrol the active and
re
active powe
r ex
cha
n
ge withi
n
the network.
DFIGs
h
a
v
e
t
h
e cap
abilit
y to
o
p
e
rate in
v
a
riab
le speed
reg
i
on
s so we h
a
v
e
to
ach
i
ev
e a sm
o
o
t
h
e
n
e
d
an
d
twi
ce th
e
p
o
wer th
an
any o
t
h
e
r co
nv
entio
n
a
l gen
e
rator
will p
r
o
d
u
c
e. In
th
e d
e
v
e
lop
m
en
t o
f
wind tu
rb
in
e techn
i
q
u
e
s,
DFI
G
i
s
bec
o
m
i
ng m
o
re p
o
pul
a
r
be
cause
of i
t
s
u
n
i
q
ue
c
h
aracteristics s
u
ch as
high efficiency, low c
o
st and
flex
ib
le con
t
ro
l [2
].
M
o
st
of t
h
e w
i
nd t
u
rbi
n
es fa
ce a pr
obl
em
of L
V
R
T
.
One
com
m
on LVR
T
sol
u
t
i
o
n i
s
t
o
i
n
st
al
l
a
crowbar circ
uit across the rot
o
r term
in
als. Whe
n
the
rot
o
r over c
u
rrent
is
detected, the
crowba
r circ
uit short
circu
its th
e roto
r term
in
als an
d
iso
l
ates th
e conv
erte
r
s
fr
om
t
h
e rot
o
r
.
A
nd t
hus R
o
t
o
r Si
de C
o
n
v
ert
e
r
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE
Vo
l. 3
,
N
o
. 5
,
O
c
tob
e
r
20
13
:
618
–
6
28
61
9
trig
g
e
ring
is
blo
c
k
e
d
.
Th
is
prov
id
es con
s
erv
a
tiv
e
p
r
o
t
ectio
n to
t
h
e
ro
t
o
r circu
it and
t
h
e RSC ch
an
ges th
e
DFI
G
t
o
a s
qui
rrel
ca
ge i
n
d
u
c
t
i
on m
achi
n
e,
whi
c
h a
b
so
rb
s reactiv
e p
o
wer
fro
m
th
e
g
r
id. As
a resu
lt d
yna
m
i
c
VAR c
o
m
p
ensators, s
u
c
h
as static VAR com
p
ensators
or static syn
c
h
r
on
ou
s co
m
p
ensators are s
o
m
e
tim
e
s
in
stalled
at th
e
DFIG term
in
al
s to
p
r
ov
id
e
re
activ
e
po
w
e
r
su
ppo
r
t
du
r
i
ng
a
gr
id
f
a
u
lt [
3
].
Un
bal
a
nce
d
gr
i
d
fa
ul
t
s
de
gra
d
e t
h
e
per
f
o
r
m
ance of
DF
I
G
-
b
ase
d
wi
nd
t
u
r
b
i
n
es.
I
n
fa
ct
, i
f
v
o
l
t
a
g
e
u
n
b
a
lan
c
e is no
t tak
e
n
in
to
acco
un
t th
e stat
o
r
and
ro
tor curren
t
s will b
e
hig
h
l
y un
balan
c
ed
even
with
a sm
a
l
l
u
n
b
a
lan
c
ed
stato
r
vo
ltag
e
. The u
n
b
a
lan
c
ed
cu
rren
ts will create u
n
e
qu
al heatin
g
on
stator an
d
ro
t
o
r wi
n
d
i
n
g
s
wh
ich
will p
r
od
u
c
e a co
m
p
let
e
ch
an
g
e
in
t
o
rq
u
e
and
po
we
r pu
lsatio
n
s
of t
h
e
g
e
n
e
rator
wh
ich
is t
w
ice the lin
e
fre
que
ncy
[4]
.
Seve
ral
co
nt
r
o
l
app
r
oac
h
es h
a
ve been p
r
ese
n
t
e
d fo
r DF
IG
sy
st
em
s
opera
t
i
ng wi
t
h
u
n
b
a
l
anced gri
d
fau
lts. Th
e
ro
to
r-sid
e
syste
m
is d
e
co
m
p
o
s
ed
in
t
w
o
se
p
a
rate
m
o
d
e
ls which
are
re
p
r
esen
ted
with
po
sitiv
e
and
negative
-
se
que
n
ce c
o
m
pone
nt
s res
p
ectively.
Two
pa
ralle
l cont
rollers
whic
h a
r
e e
x
presse
d i
n
the
positive and
n
e
g
a
tiv
e-syn
c
hrono
u
s
reference fram
e
are also
presen
te
d
.
Th
e go
al of the p
o
s
itiv
e-seq
u
en
ce con
t
ro
ller is to
regu
late th
e
ro
to
r sid
e
con
v
e
rt
er as i
n
th
e case of
n
o
rm
al o
p
e
ratin
g cond
itio
n
s
[5
].
2.
D
F
IG BA
SED WIND
POWER
GEN
E
RATION
Th
e m
a
j
o
rity o
f
wind
turb
i
n
es
are eq
ui
p
p
e
d
wi
t
h
Do
u
b
l
y
Fed I
n
duct
i
o
n
Gene
rat
o
rs (
D
FI
Gs
). T
h
e
wo
u
nd
r
o
t
o
r
i
n
duct
i
o
n
ge
nera
t
o
r
has st
at
o
r
whi
c
h i
s
di
rect
l
y
conn
ect
ed t
o
t
h
e
gri
d
a
nd
rot
o
r m
a
i
n
s ar
e do
ne
b
y
a Variab
le
Freq
u
e
n
c
y AC
/DC/AC Co
nverter (VFC).
Th
is h
a
s th
e ab
ility
to
h
a
nd
le a fraction
(2
5%-30
%
)
o
f
t
h
e to
tal power t
o
ach
iev
e
fu
ll con
t
ro
l of th
e g
e
n
e
rat
o
r. Th
e
Variab
le Freq
u
e
n
c
y Con
t
ro
ller con
s
ist
s
o
f
a
Ro
to
r sid
e
C
onv
erter (RSC
) an
d a
Grid-Si
d
e Co
nv
erter
(GSC) c
o
nnected bac
k
-t
o-back
by
a dc-l
i
n
k
ca
paci
t
o
r
in order t
o
m
eet powe
r fact
or
requirem
ent (e.g.
−
0
.
9
5
to
0
.
95
) at th
e
po
in
t
o
f
conn
ectio
n.
Fi
gu
re 1.
W
i
nd
t
u
r
b
i
n
e
m
odel
2.1.
Contr
o
lle
r Circuit of
Rotor Side Co
nverter
(RSC)
Th
e Ro
tor-Side Co
nv
erter (RSC) ap
p
lies
th
e v
o
lta
g
e
to th
e ro
tor wind
ing
s
of th
e Doub
ly-Fed
I
ndu
ctio
n G
e
ner
a
to
r. Th
e
p
u
rp
o
s
e of
t
h
e ro
t
o
r-
sid
e
con
v
er
t
e
r is to
con
t
ro
l
th
e ro
tor cu
rren
ts su
ch th
at the ro
t
o
r
flux
po
sition
is o
p
tim
all
y
o
r
ien
t
ed
with
respect to
th
e st
ator fl
u
x
i
n
ord
e
r
th
at th
e d
e
sired
torqu
e
is
d
e
velo
p
e
d
at the s
h
aft
of the m
achine.
Th
e
ro
to
r-sid
e
con
v
erter u
s
es a torq
u
e
contro
ller t
o
regu
l
a
te th
e
wind
t
u
rb
in
e
powe
r output
and m
easured
the volta
ge
or reactive
power at the m
achin
e stator terminals. The
powe
r is
m
easured i
n
o
r
der t
o
f
o
l
l
o
w a
pre
-
de
fi
ne
d t
u
rbi
n
e p
o
w
er-speed cha
r
acteris
tic to
obt
ai
n t
h
e
m
a
xim
u
m
pow
e
r
poi
nt
.
In
o
r
de
r to
re
d
u
ce the
p
o
we
r
err
o
r
o
r
r
o
to
r s
p
eed
er
ro
r to
z
e
ro
, a P
r
o
p
o
rti
onal
-
I
n
teg
r
al (
P
I)
re
gulato
r
is u
s
ed
at th
e ou
ter con
t
ro
l loo
p
. Th
e
o
u
t
p
u
t
o
f
th
e regu
lato
r is th
e referen
ce ro
to
r cu
rren
t ‘
i
rqref
’
th
at m
u
st b
e
in
j
ected
in
th
e ro
t
o
r
wind
ing b
y
ro
to
r-sid
e
co
nv
erter. Th
i
s
q
-a
xi
s c
o
m
pone
nt
co
nt
r
o
l
s
t
h
e el
ect
rom
a
gnet
i
c
t
o
r
que ‘
Te’
. The actual ‘
i
rq
’
co
m
ponent
o
f
r
o
t
o
r c
u
r
r
ent
i
s
co
m
p
ared wi
t
h
‘
i
rqref
’
and t
h
e er
ro
r i
s
m
i
nim
i
zed t
o
zero by
a cur
r
e
nt
PI re
gul
at
o
r
at
i
nne
r con
t
ro
l lo
op
. Th
e
ou
tpu
t
o
f
th
is cu
rren
t con
t
ro
ller lo
op
is th
e v
o
ltage
‘
v
rq
’
,
wh
ich
is
gene
rat
e
d
by
r
o
t
o
r-si
d
e c
o
n
v
e
rt
er
wi
t
h
a
not
her
si
m
i
l
a
rl
y
regul
at
ed
‘
i
rd
’
an
d ‘
v
rd
’
com
p
onent s
o
t
h
e re
q
u
i
r
ed
3
-
pha
se
vol
t
a
ges
appl
i
e
d
t
o
t
h
e
r
o
t
o
r
wi
n
d
i
n
g a
r
e
obt
ai
ne
d.
To desc
ri
be t
h
e cont
r
o
l
sche
m
e
, t
h
e genera
l
Park
’s m
o
d
e
l o
f
an
ind
u
c
ti
o
n
m
ach
in
e is in
trod
u
c
ed.
St
at
or-
o
ri
ent
e
d
refe
re
nce f
r
am
e wi
t
h
out
sat
u
r
a
t
i
on, t
h
e
v
o
l
t
a
ge
vect
o
r
e
quat
i
ons
are
V
s
=i
s
*R
s
+d
α
/d
t
(1
)
V
r
=i
r
*R
r
+ d
α
/d
t
(2
)
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
Po
wer S
y
stem S
t
ab
ility
En
han
cemen
t a
n
d
Imp
r
o
v
emen
t
o
f
LVRT Capa
b
i
l
ity o
f
a
DFIG
Ba
sed
… (An
j
u M)
62
0
whe
r
e ‘
V
s
’
i
s
t
h
e st
at
or
vol
t
a
ge i
m
posed by
t
h
e gri
d
. T
h
e
rot
o
r
vol
t
a
ge
,
‘
V
r
’
is con
t
ro
lled
b
y
th
e
r
o
to
r-si
d
e
con
v
e
r
t
e
r a
n
d
use
d
t
o
pe
rf
or
m
generat
o
r
c
o
nt
r
o
l
.
T
h
e
fl
u
x
vect
o
r
e
quat
i
o
ns a
r
e
α
s
= L
s
*i
s
+
L
m
*i
r
(3
)
α
r
=
L
m
*i
s
+
L
r
*i
r
(4
)
The stator a
n
d
rot
o
r
self-i
nductances are ‘
L
s
’
and ‘
L
r
’
:
L
s
=
L
m
+
L
ls
,
L
r
=
L
m
+
L
lr
(5
)
Defi
ning leaka
g
e
factor,
σ
=1-L
m
2
/L
r
*L
(6
)
L
0
=L
m
2
/L
s
(7
)
V
rd
=i
rd
*R
r
+
σ
L
r
*d
ird
/d
t
-
w
slip*
σ
L
r
*i
rq
(8
)
V
rq
=i
rq
*R
r
+
σ
L
r
*d
irq
/d
t
-
w
slip
(
σ
L
r
*i
rd
+L
0
*i
ms
) (
9
)
w
slip
=w
s
-w
r
(1
0)
The stator
flux
angle a
r
e calc
u
lated from
α
st
=
∫
(
V
st
-i
s
*R
s
)d
t (
1
1
)
α
sb
=
∫
(
V
sb
-i
s
*R
s
)dt
(1
2)
θ
s=tan
-1
(
α
st
/
α
sb
) (1
3)
The control schem
e
for the rotor-si
d
e conve
rter
is o
r
gan
i
zed
in
a gen
e
ric way with
two
PI-
cont
rol
l
e
rs
. Fi
gu
re
2 s
h
o
w
s
a schem
a
t
i
c
block
di
a
g
ram
for t
h
e r
o
t
o
r-
si
de c
o
n
v
ert
e
r c
ont
rol
.
The
o
u
t
e
r s
p
ee
d
cont
rol
l
o
o
p
o
r
a refe
rence t
o
r
que i
m
pose
d
on the m
achine
is us
ed f
o
r
the refe
rence
q
-
a
xi
s rot
o
r c
u
r
r
e
n
t ‘
i
rq
’.
These t
w
o
o
p
t
i
ons
m
a
y
be t
e
rm
ed as spee
d-
cont
rol
m
ode o
r
t
o
r
q
ue-c
o
n
t
r
o
l
m
ode f
o
r t
h
e
gene
rat
o
r, i
n
st
ead o
f
regu
latin
g
t
h
e
activ
e po
wer directly. Fo
r speed
-con
tro
l
m
ode
o
n
e
out
er
PI c
ont
r
o
l
l
e
r i
s
t
o
co
nt
r
o
l
t
h
e
spee
d
erro
r sign
al in
t
e
rm
s o
f
m
a
x
i
mu
m
p
o
w
er
po
int track
ing
.
Fi
gu
re 2.
The
R
o
t
o
r
-
Si
de
C
o
nve
rt
er (R
SC
)
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE
Vo
l. 3
,
N
o
. 5
,
O
c
tob
e
r
20
13
:
618
–
6
28
62
1
2.2. Contr
o
lle
r
circuit of
Gr
id-Side Conve
r
ter
(GSC)
Th
e grid-sid
e co
nv
erter aim
s
t
o
reg
u
l
ate th
e v
o
ltag
e
o
f
th
e
d
c
cap
acitor lin
k. Mo
reov
er, it is a
llo
wed
to
g
e
n
e
rate
o
r
ab
sorb
reactiv
e power
for
v
o
ltag
e
supp
ort req
u
i
rem
e
n
t
s. Th
e
fun
c
tion is realized
wi
th
two
in
tern
al con
t
rol lo
op
s as
wel
l
an
o
u
t
er regu
latio
n
l
o
op.
The
refe
rence
curre
n
t m
eas
ure
d
at the output
of
v
o
ltag
e
regu
lat
o
r is ‘
i
cdref
’
for the current re
gulator. T
h
e inne
r curre
nt
r
e
gul
at
o
r
l
o
op
con
s
i
s
t
s
of a c
u
r
r
en
t
reg
u
l
a
t
o
r t
o
co
nt
r
o
l
t
h
e m
a
gni
t
ude an
d
pha
s
e
of t
h
e ge
nera
t
e
d v
o
l
t
a
ge o
f
con
v
e
r
t
e
r. T
h
e
‘
i
cdref
’
is p
r
o
duced
by
th
e d
c
vo
ltag
e
regu
lato
r and
sp
ecified
q
-a
xis ‘
i
cqref
’
re
fere
nc
e is sh
o
w
n
in
F
i
gu
re
3.
Fig
u
r
e
3
.
Th
e
G
r
id
-
S
id
e Co
nv
er
ter (G
SC)
3.
SUPE
RC
ON
DU
CTI
N
G M
A
G
N
ETIC
E
N
ERG
Y
STO
R
A
G
E
(
S
ME
S)
A SMES
d
e
v
i
ce is a d
c
curren
t co
n
t
ro
lled d
e
v
i
ce t
h
at hav
e
th
e ab
ility
to
sto
r
es en
erg
y
in
t
h
e
mag
n
e
tic f
i
eld
.
Th
e d
c
cur
r
e
n
t
f
l
o
w
ing
thr
oug
h
a sup
e
r
c
ondu
ctin
g
co
il in
a lar
g
e
m
a
g
n
e
t cr
eates th
e
m
a
g
n
e
tic
field. T
h
e inductively store
d
energy (
E
i
n
Joul
e
)
an
d t
h
e
rat
e
d p
o
w
er
(
P
i
n
W
a
t
t
)
are
com
m
onl
y
given i
n
speci
fi
cat
i
o
ns f
o
r
SM
ES de
vi
c
e
s
an
d
t
h
ey can be e
x
pres
sed a
s
follows:
E=(1/2)
L
I
2
(1
4)
P=dE/d
t=LI d
i
/d
t=VI
(1
5)
whe
r
e ‘
L’
i
s
t
h
e coi
l
i
nduct
a
n
ce,
‘I
’
b
e
th
e
dc cu
rren
t fl
o
w
i
n
g
thro
ugh
th
e co
il an
d
‘
V’
is th
e v
o
ltag
e
acros
s the
coil.
Fi
gu
re
4.
C
o
m
p
o
n
e
n
t
s
of a
t
y
pi
cal
SM
ES
sy
st
em
A
SMES system co
n
s
ists o
f
a su
p
e
r
c
ond
u
c
t
i
n
g
co
il, cr
yogen
i
c syste
m
an
d
th
e po
w
e
r
con
v
e
r
s
ion
or
con
d
i
t
i
oni
n
g
s
y
st
em
(PC
S
) u
s
ed fo
r
c
o
nt
rol
and
p
r
ot
ect
i
on fu
nct
i
o
ns. SM
ES
c
onsi
s
t
s
o
f
1.
Po
wer C
o
ndi
t
i
oni
ng
Sy
st
em
(PC
S
)
2.
SMES Co
il.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
Po
wer S
y
stem S
t
ab
ility
En
han
cemen
t a
n
d
Imp
r
o
v
emen
t
o
f
LVRT Capa
b
i
l
ity o
f
a
DFIG
Ba
sed
… (An
j
u M)
62
2
3.
1. Pow
er C
o
ndi
ti
oni
n
g
Sy
s
t
em
The PCS provi
des a powe
r electro
nic interface betwee
n the WTG a
nd the Short circuit Coil whic
h
have
t
o
pe
rf
o
r
m
t
w
o g
o
al
s:
o
n
e i
s
t
o
c
o
nve
r
t
el
ect
ri
c p
o
we
r f
r
o
m
dc t
o
a
c
an
d t
h
e
ot
he
r i
s
t
o
c
h
a
r
ge/
d
i
s
char
ge
t
h
e coi
l
e
ffi
ci
e
n
t
l
y
. The
m
a
jor c
o
m
pone
nt
o
f
t
h
e
p
r
o
p
o
se
d
PC
S i
s
t
h
e
wel
l
-k
no
w
n
t
h
ree-
pha
se
vol
t
a
ge
sou
r
ce
i
nve
rt
er (
V
SI
)
or c
o
n
v
ert
e
r (
V
SC
) s
h
u
n
t
-
c
o
nnect
e
d
t
o
t
h
e
di
st
ri
but
i
o
n n
e
t
w
o
r
k
by
m
e
ans o
f
a st
ep-
u
p
Δ
–Y
cou
p
l
i
n
g t
r
ans
f
o
r
m
e
r as depi
ct
ed i
n
Fi
gu
re
5. The m
a
jor
com
pone
nt
of
a VSI i
s
t
h
e Is
ol
at
ed Gat
e
B
i
pol
a
r
Transisto
r
s (IGBTs).
Du
e to its lo
wer switch
i
ng
losses
a
n
d r
e
d
u
ce
d si
ze
whe
n
c
o
m
p
are
d
t
o
ot
her
de
vi
ces i
t
s
ope
rat
i
o
n ha
v
e
hi
g
h
p
r
i
o
ri
t
y
. Out
put
vo
l
t
a
ge cont
rol
of t
h
e VS
I ca
n be e
ffi
ci
ent
l
y
achi
e
ved t
h
ro
u
g
h
si
nus
oi
dal
p
u
l
s
e wi
dt
h m
o
d
u
l
a
t
i
on
(SP
W
M
)
t
ech
ni
q
u
es.
Th
is three-lev
e
l six
-
pu
lse
VSI to
po
log
y
g
e
nerates
m
o
re sm
oot
h
si
nus
oi
dal
out
put
vol
t
a
ge w
a
vef
o
rm
t
h
an
a con
v
e
n
t
i
o
nal
st
ruct
u
r
e
wi
t
h
o
u
t
i
n
c
r
easi
n
g t
h
e
sw
itch
i
ng
f
r
e
qu
en
cy.
3.
2. SME
S
C
o
i
l
An SM
E
S
sy
st
em
consi
s
t
s
of seve
ral
su
b-s
y
st
em
s whi
c
h m
u
st
be careful
l
y
desi
gne
d
i
n
or
der
t
o
obt
ai
n a
hi
g
h
-
p
erf
o
rm
ance co
m
p
ensat
i
on de
vi
ce u
nde
r t
h
e
phe
n
o
m
e
non
o
f
su
perc
o
n
d
u
ct
i
v
i
t
y
. The base
of t
h
e
SM
ES u
n
i
t
i
s
a l
a
rge Su
perc
on
d
u
ct
i
ng C
o
i
l
(SC
)
, w
h
ose
basi
c st
ruct
ure
consi
s
t
i
n
g o
f
t
h
e col
d
com
pone
nt
s
i
t
s
el
f (t
he SC
wi
t
h
i
t
s
s
u
p
p
o
rt
c
o
n
n
ect
i
o
n
com
pone
nt
s
and
t
h
e c
r
y
o
st
at
) an
d t
h
e
cr
y
oge
ni
c re
fri
g
e
rat
i
n
g
sy
st
em
i
n
Fi
gure
5. T
h
e eq
ui
val
e
nt
ci
rc
ui
t
of t
h
e SM
ES
coi
l
m
a
kes use of a l
u
m
p
ed
param
e
t
e
rs net
w
o
r
k
rep
r
ese
n
t
e
d by
a fou
r-se
g
m
e
nt
m
odel
com
p
ri
si
ng sel
f
i
n
du
ct
ances (
Li
),
m
u
t
u
al
coupl
i
n
gs bet
w
een se
gm
ent
s
(
i
and
j
,
Mij
), ac loss resistances (
Rp
), s
k
in
effect related
resistances (
Rp
i
)
,
tu
rn-
g
r
ound (
s
hun
t—
C
Shi
)
, and
tu
rn
– tu
rn
cap
a
citan
ces (series—
C
Si)
ar
e sh
ow
n in
Figu
r
e
5.
Fig
u
r
e
5
.
D
e
tai
l
ed
m
o
d
e
l of
the pr
opo
sed
SM
ES system
includi
ng the
PCS
and the
SC.
4.
SUPE
RC
ON
DU
CTI
N
G F
AULT
C
U
R
R
E
NT LIMITE
R (
S
F
C
L)
SFCLs
u
tilize su
perco
ndu
cting
m
a
terials to
li
m
i
t th
e cu
rrent d
i
rectly or t
o
su
pp
ly a
DC
bias curren
t
th
at affects t
h
e lev
e
l of m
a
g
n
e
tizatio
n
of a satu
rab
l
e
iron
co
re.
Wh
ile m
a
n
y
FCL
d
e
sign con
cep
ts are
b
e
ing
eval
uat
e
d f
o
r
com
m
e
rci
a
l
use and
i
m
prove
m
e
nt
s i
n
su
pe
rco
n
duct
i
n
g m
a
t
e
ri
al
s ove
r t
h
e l
a
st
3 y
ear
s ha
v
e
d
r
i
v
en
th
e techn
o
l
o
g
y
to
th
e
fo
refron
t. Th
is i
m
p
r
o
v
e
m
e
n
t
is
d
u
e
to
t
h
e ab
ility o
f
HTS m
a
terials to
o
p
e
rate at
t
e
m
p
erat
ures a
r
o
u
nd
7
0
K i
n
st
ead o
f
near
4K
w
h
i
c
h i
s
req
u
i
r
e
d
by
con
v
e
n
t
i
onal
s
upe
rc
on
d
u
ct
or
s. T
h
e
adva
ntage
is t
h
at the
refrige
r
ation
ove
rhead associated
wi
t
h
ope
rat
i
n
g at
t
h
e hi
ghe
r t
e
m
p
erat
ure i
s
ab
o
u
t
2
0
ti
m
e
s less co
stly th
an
t
h
e i
n
itial cap
ital co
st.
SFCLs
u
s
e th
e tran
sition
of su
p
e
rco
ndu
cto
r
s fro
m
zero
to
fin
ite resistan
ce to
li
m
it
th
e fau
lt cu
rren
ts
th
at resu
lt from sh
o
r
t circu
its in
electric
powe
r syste
m
s
.
Suc
h
short ci
rcuits can be
caused
by aged
or
accidentally da
maged i
n
sulation by
light
ning stri
king a
n
overhea
d
line
or
by ot
her unforesee
n fa
ults. If
not
deliberately checked, the s
ubs
eque
nt fa
ult curre
nt is li
m
i
t
e
d onl
y
by
t
h
e i
m
peda
nce
of t
h
e
sy
st
em
bet
w
een t
h
e
lo
catio
n
of th
e
fau
lt an
d th
e
po
wer sou
r
ces.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE
Vo
l. 3
,
N
o
. 5
,
O
c
tob
e
r
20
13
:
618
–
6
28
62
3
Fi
gu
re
6.
S
upe
rco
n
duct
i
n
g
Fa
ul
t
C
u
r
r
e
n
t
Li
m
iter connected in seri
es transmissio
n
lin
e
5.
R
E
SU
LTS AN
D D
I
SCU
SSSION
Th
e fau
lt-curren
t li
m
i
tin
g
p
r
i
n
cip
l
e o
f
th
e SFCL-MES is
th
e sa
m
e
as th
at o
f
th
e rectifier-bridg
e
-typ
e
fau
lt-cu
rren
t li
miter. Und
e
r
n
o
rm
al o
p
e
ratio
n, th
e SC
c
u
r
r
ent
i
s
re
gu
l
a
t
e
d t
o
be
hi
ghe
r t
h
an t
h
e
pea
k
am
pl
i
t
ude of ‘
n
i
sa
bc’
or ‘
n
i
rab
c
’
when the SFCL-MES is connect
ed on
the stator side or rotor side
respectively. Whe
r
e
i
sab
c
,
i
ra
bc
are
the stator and
rotor current and
‘
n’
b
e
th
e iso
l
ation
tran
sform
e
r tu
rns rat
i
o
(stato
r or
ro
t
o
r
sid
e
to th
e
rectifier si
d
e
)
resp
ectiv
ely.
D
u
ri
ng
no
rm
al
operat
i
on
, t
h
e SC
sho
w
s
no
n i
n
duct
i
v
e i
m
peda
nce a
nd t
h
e fo
rwa
r
d
v
o
l
t
a
ge d
r
o
p
o
f
th
e rectifier, the vo
ltag
e
d
r
op o
f
wi
ndi
ng re
sistance and le
akage
inducta
nce
of iso
l
ation
tran
sform
e
rs are th
e
onl
y
im
peda
nc
e of t
h
e ci
rc
ui
t
whi
c
h a
r
e ne
g
l
i
g
i
b
l
y
sm
all
.
During
a fau
lt, wh
en
th
e fau
lt cu
rren
t
in
creases in
a
m
plitude and reaches t
h
e val
u
e of ‘
i
sc
/
n’
(
is
c
is th
e cu
rrent o
f
th
e SC). Th
e SC will b
e
in
serted
in
to
stato
r
or
ro
t
o
r circu
it so
in
creasing
t
h
e fau
lt circuit i
m
p
e
d
a
n
ce
an
d
t
h
erefore li
mitin
g
th
e fau
lt curren
t
to
a
pre
d
et
erm
i
ned val
u
e.
Fi
gu
re
7.
D
F
I
G
i
n
c
o
rp
orat
e
d
wi
t
h
t
h
e S
F
C
L
-M
ES
(v
ol
t
a
ge
so
urce
t
o
pol
o
g
y
)
The DFIG current-s
o
urce in
co
rpo
r
ated
with th
e SFCL-MES is sh
own
in
Fig
u
re 7. Th
e d
c
term
in
als
of
t
h
e GSC, diode rectifier and
RS
C are
connected in s
e
ries with a
c
o
m
m
on dc-l
i
n
k ca
paci
t
o
r
.
T
h
e ac
termin
al o
f
th
e d
i
od
e rectifier is co
n
n
ected
in
series
wi
t
h
D
F
IG
by
t
h
ree i
s
ol
at
i
on t
r
a
n
sf
o
r
m
e
rs. Depe
nd
i
ng
o
n
th
e conn
ectio
n po
in
t of th
e iso
l
atio
n
t
r
an
sform
e
rs th
e SFC
L circuit ca
n be connecte
d
in
series with stator a
nd
SMES co
nn
ect
ed
in p
a
rallel to
stator
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
Po
wer S
y
stem S
t
ab
ility
En
han
cemen
t a
n
d
Imp
r
o
v
emen
t
o
f
LVRT Capa
b
i
l
ity o
f
a
DFIG
Ba
sed
… (An
j
u M)
62
4
Fi
gu
re
8.
M
o
d
e
l
l
i
ng o
f
DF
IG
base
d
wi
n
d
p
o
w
er
ge
nerat
i
o
n
u
nde
r
faul
t
Fi
gu
re 9.
To
r
q
ue Gene
rat
i
o
n
Fi
gu
re
1
0
. C
o
n
v
ent
i
o
nal
m
e
t
hod
f
o
r
p
r
ot
ect
i
o
n
(C
ro
w
bar
p
r
ot
ect
i
o
n Sc
he
m
e
).
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE
Vo
l. 3
,
N
o
. 5
,
O
c
tob
e
r
20
13
:
618
–
6
28
62
5
Fi
gu
re
1
1
. B
r
i
d
ge Ty
pe S
F
C
L
Fig
u
r
e
12
.
D
F
IG
w
ith
SFCL an
d SMES fo
r
V
o
ltag
e
regu
latio
n
an
d Fau
lt
cu
rren
t lim
ita
ti
o
n
5.
1.
Un
der F
a
ul
t C
o
n
d
i
t
i
o
n
Fig
u
r
e
13
.
Vo
ltag
e
an
d Cur
r
e
nt in
Stator
an
d
G
r
i
d
u
n
d
e
r fau
lted
co
nd
itio
n.
Fig
u
re
14
. R
o
to
r Vo
ltag
e
and Cu
rren
t
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
Po
wer S
y
stem S
t
ab
ility
En
han
cemen
t a
n
d
Imp
r
o
v
emen
t
o
f
LVRT Capa
b
i
l
ity o
f
a
DFIG
Ba
sed
… (An
j
u M)
62
6
Fig
u
re 15
.
Capacito
r Vo
ltag
e
5.
2. C
o
n
v
enti
o
n
al
Co
ntr
o
l
(
C
R
O
W
B
A
R
)
Fi
gu
re
1
6
. R
o
t
o
r
Fa
ul
t
cur
r
e
n
t
un
de
r c
o
n
v
e
n
t
i
onal
co
nt
r
o
l
t
echni
que
.
5.
3.
Un
der
the
Ac
ti
on
o
f
S
F
CL
Fi
gu
re
1
7
. Li
m
i
t
e
d R
o
t
o
r
vol
t
a
ge a
n
d
cu
rre
n
t
by
t
h
e e
ffe
ct
of
SFC
L
5.
4.
Un
der
the
Ac
ti
on
o
f
S
M
E
S
Fi
gu
re 1
8
. St
at
or
V
o
l
t
a
ge by
t
h
e
act
i
o
n of
S
M
ES
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE
Vo
l. 3
,
N
o
. 5
,
O
c
tob
e
r
20
13
:
618
–
6
28
62
7
6.
CO
NCL
USI
O
N
I
n
th
is
p
a
p
e
r
a n
e
w
topo
logy h
a
s b
een
p
r
o
p
o
s
ed
fo
r
g
r
i
d
con
n
ectio
n
d
u
r
i
ng
symme
tr
ical f
a
u
lt
co
nd
itio
n to
en
h
a
n
ce t
h
e v
a
riab
le sp
eed
d
r
i
v
en DFIG
fed
AC-DC-AC syste
m
fau
lt rid
e
-th
r
ou
gh
cap
a
bilit
y.
The
pr
op
ose
d
t
echn
o
l
o
gy
i
s
sim
u
l
a
t
e
d i
n
M
A
TLAB
usi
ng
p
o
we
rsi
m
tool
bo
x.
Si
m
u
lat
i
on res
u
l
t
s
p
r
ove t
h
at
th
e p
r
op
osed
co
n
t
ro
l strateg
y
is ab
le to
p
r
ov
i
d
e fu
ll ri
d
e
thro
ugh
to
th
e
g
e
n
e
rat
o
r an
d
power system
ca
p
a
b
ility
can
b
e
im
p
r
oved
.
An
SFCL-MES circu
it is v
e
ry in
tensiv
e
to
enh
a
n
ce th
e
LVRT cap
ab
ility an
d
sm
o
o
t
hed
th
e
po
we
r o
u
t
p
ut
o
f
a D
F
I
G
ba
se
d wi
nd t
u
r
b
i
n
e
.
The S
F
C
L
-M
ES has
n
o
i
n
fl
uence
o
n
t
h
e
p
o
we
r
gene
rat
i
o
n o
f
t
h
e
DFI
G
base
d
wi
n
d
t
u
r
b
i
n
e.
C
o
-
o
r
d
i
n
at
e
d
ope
rat
i
o
n of S
M
ES wi
t
h
SF
C
L
i
s
used t
o
im
prove t
h
e
ove
ral
l
per
f
o
r
m
a
nce.
APPE
NDI
X
Tabl
e 1. DF
IG
sim
u
l
a
t
i
on
val
u
es.
Tabl
e 2. Dri
v
e t
r
ai
n det
a
i
l
s
.
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