Internati
o
nal
Journal of P
o
wer Elect
roni
cs an
d
Drive
S
y
ste
m
(I
JPE
D
S)
Vol
.
6
,
No
. 2,
J
une
2
0
1
5
,
pp
. 29
3~
30
4
I
S
SN
: 208
8-8
6
9
4
2
93
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
/
IJPEDS
Open-Switch Fault-Tolerant Cont
rol
of
a Grid-Side Converter
in a
W
i
nd P
o
wer
G
e
ne
ra
t
i
o
n
Sy
st
em
Partha Sarati
Das
,
Ky
eo
ng
-H
wa
K
i
m
Departem
ent
of
Ele
c
tri
cal
and
In
form
ation Eng
i
n
eering
Seoul National
University
of
Scie
nce
and Techn
o
log
y
, Seou
l, Korea
Article Info
A
B
STRAC
T
Article histo
r
y:
Received
Ja
n 14, 2015
Rev
i
sed
Ap
r
28
, 20
15
Accepted
May 12, 2015
A fault-
toler
a
nt techniqu
e of
a gr
id-sid
e
converter
(GSC) is a ver
y
important
task because th
e unbalan
ced gr
id
power
endang
er
s the overall s
y
s
t
em. Since
the GSC is ver
y
sensitive to gri
d
disturbance
,
th
e com
p
let
e
s
y
ste
m
needs to
be stopped suddenly
once
an open-switch fau
lt occurs.
To improve the
reliability
of s
y
s
t
em, the continu
ous operation s
hould be guaranteed. In this
paper, a r
e
dundant topolog
y
b
a
sed fault-
toleran
t
algorithm is proposed for a
GSC in a wind power gener
a
tio
n s
y
stem
. Th
e p
r
oposed scheme consists of
the fau
lt d
e
te
c
tion and f
a
ult
-
toler
a
nt algorithms. Th
e faul
t det
ect
ion
algorithm
em
ploys the durat
ions of positive and negaitiv
e c
y
c
l
e
s
of three-
phase grid currents as well as normalized
roo
t
mean square (RM
S
) currents.
Once a fault
is detected, the corres
ponding faulty
phas
e
is
id
entified
and
is
olated
to
enab
l
e
th
e fau
lt-to
ler
a
nt oper
a
tion
.
Th
e fau
l
t
y
ph
as
e is
repla
ced
b
y
redundant one r
a
pidly
to r
ecov
e
r the orig
inal
shape of the gr
id currents
,
which ensures the continu
i
ty
in
operati
on. In co
ntrast with th
e convention
a
l
methods, the proposed fault detection
and fau
l
t-tolerant algorithms
work
effec
tive
l
y even
in the presen
ce
of the
open fau
l
t
s
in m
u
ltiple switches in th
e
GSC. Sim
u
latio
n results veri
f
y
the e
ffec
tive
n
ess of the pro
posed fault
diagnosis and
fault-toleran
t
contr
o
l algorithms.
Keyword:
Fau
lt-to
leran
t
G
r
id
-
s
id
e
co
n
v
e
r
t
e
r
Machine-side c
o
nve
r
ter
Op
en-switch fau
lt
W
i
nd
en
e
r
g
y
co
nv
er
s
i
on
s
y
s
t
e
m
Copyright ©
201
5 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
:
Ky
eo
ng
-H
wa
Kim
,
Depa
rtem
ent of Electrical a
n
d
I
n
f
o
rm
at
i
on E
ngi
neeri
n
g
,
Seou
l Nation
a
l
Un
iv
ersity o
f
Scien
ce an
d Tech
no
log
y
,
2
3
2
Go
ngn
eung
-r
o, N
o
wo
n-
gu
, Seou
l, 13
9-74
3, K
o
r
ea.
Em
a
il: k
2
h
1
@
seou
ltech
.ac.kr
1.
INTRODUCTION
W
i
nd, s
o
lar, and
biom
ass are renewa
ble e
n
ergy sources that
replace c
o
nve
ntional fuels
such
as oil or
natural gas. T
h
e efficiency and pe
rform
ance of re
newa
ble energy system
s are still unde
r devel
o
pm
ent. Most
of
rene
wa
ble energy technol
ogies are
used i
n
grid c
o
nnect
ed power
gene
ration syst
em
.
The control structures
of t
h
e g
r
i
d
c
o
n
n
ect
ed c
o
n
v
e
r
t
e
r are a
vi
t
a
l
port
i
o
n f
o
r ene
r
gy
co
nve
rsi
o
n
and t
r
ansm
i
ssion
w
h
i
c
h
need
s t
o
b
e
i
m
p
r
ov
ed
t
o
meet th
e requ
iremen
ts for grid in
terc
onn
ection
.
A grid-sid
e
co
nv
erter (GSC) con
v
e
rts the DC
electric energy
from
the renewable en
e
r
gy source into AC
electric energy
, wh
ich
tran
sfers th
e DC lin
k
p
o
wer
to
grid.
W
i
n
d
e
n
er
gy
i
s
bec
o
m
i
ng m
o
re a
n
d m
o
re i
m
port
a
nt
t
o
re
duce
rel
i
a
nce
o
n
f
o
ssi
l
f
u
el
,
w
h
i
c
h l
e
a
d
s t
o
a vari
et
y
o
f
re
s
earch a
n
d
deve
l
opm
ent
of
wi
nd
p
o
we
r
gen
e
rat
i
on t
e
c
h
n
o
l
o
gy
. T
h
ere a
r
e t
w
o t
y
p
e
s o
f
i
n
vert
er
schem
e
depe
n
d
i
n
g
on
i
t
s
ope
rat
i
o
n
,
t
h
at
i
s
t
h
e st
a
n
d
-
al
o
n
e
i
nve
rt
er a
n
d
gr
i
d
c
o
n
n
ect
ed
i
nve
rt
er.
T
h
e
G
S
C
f
o
r
w
i
nd
tur
b
i
n
e co
nv
er
ts D
C
pow
er
pr
odu
ced
b
y
a
w
i
nd
tur
b
i
n
e
gene
rat
o
r t
o
AC
po
we
r
to
s
u
pply electrical load
o
r
t
r
an
sfer th
e
ex
cessiv
e
power to
u
tility g
r
id
.
In th
is
case, th
e inv
e
rter ou
tpu
t
vo
ltag
e
an
d frequ
e
n
c
y sh
ou
l
d
be sam
e
as t
h
o
s
e o
f
t
h
e
g
r
i
d
.
In
t
h
e
gri
d
c
o
n
n
ect
ed i
n
v
e
rt
er
, o
u
t
p
ut
s
h
oul
d
be
sy
nc
hr
oni
z
e
d
wi
t
h
t
h
e
g
r
i
d
t
o
meet th
e requ
ire
m
en
ts in
g
r
i
d
in
terconn
ection
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-86
94
I
J
PED
S
Vo
l. 6,
No
.
2,
Ju
ne 20
15
:
293
–
3
04
29
4
Th
e issu
e
on
t
h
e
reliab
ility, co
n
tinu
ity, and
fau
lt
h
a
s
receiv
ed
i
n
ten
s
i
v
e research in
terests in th
e
devel
opm
ent of electrical po
wer system
s. A fa
ult in the
powe
r system
p
r
odu
ces th
e safety p
r
ob
lem
as
well as
t
h
e i
n
c
r
ease
d
l
o
ss
d
u
e t
o
s
hut
do
w
n
of
sy
st
em
. Thus,
t
h
e c
o
r
r
ect
di
ag
nosi
s
an
d
rem
e
di
al st
rat
e
gy
t
h
r
o
u
g
h
t
h
e
early detection of faults a
r
e i
m
portant to
avoid
ha
rm
fu
l accidents a
n
d to
gua
ra
ntee a c
o
ntinuity
of
ope
r
ation.
Furt
herm
ore,
p
o
we
r sy
st
em
dow
nt
i
m
e for u
n
sc
hed
u
l
e
d m
a
i
n
t
e
nanc
e can
be m
i
nim
i
zed, whi
c
h res
u
l
t
s
i
n
l
e
ss
econom
i
cal losses. For this re
ason, m
a
ny
research wo
rks ha
ve
bee
n
i
nve
s
tigated in electric power system
s
or
powe
r electronics equipm
ents.
Tw
o
di
f
f
ere
n
t
t
y
pes
of faul
t
-
t
o
l
e
rant
pul
se wi
dt
h
m
o
d
u
l
a
t
e
d
(P
WM
)
i
n
v
e
rt
er-
f
ed AC
m
o
t
o
r
dri
v
e
sy
st
em
have be
en p
r
op
ose
d
i
n
t
o
det
e
rm
i
n
e t
h
e fa
ul
t
y
devi
c
e
i
n
P
W
M
vol
t
a
ge s
o
u
r
ce i
n
v
e
rt
er d
r
i
v
es
f
o
r
ope
n
-
switch
and
short-switch
failu
res [1
]. In
th
is sch
e
m
e
, th
e
ex
pen
d
iture in
two
fau
lt-to
leran
t
co
nfigu
r
ation
s
was
dem
onstrated
and e
x
perim
e
ntal resu
lts have been
prese
n
t
e
d to prove
the success
f
ul fa
ult com
p
ensation.
A
fuzzy
l
ogi
c ba
sed fa
ul
t
di
agn
o
si
s m
e
t
hod f
o
r t
h
ree pa
ral
l
e
l
con
v
ert
e
rs i
n
a wi
nd t
u
rbi
n
e
sy
st
em
was studi
e
d
[2]
.
Thi
s
m
e
t
hod
can
n
o
t
onl
y
det
ect
b
o
t
h
ope
n
-
swi
t
c
h
an
d shor
t-
sw
itch
fa
u
lts
b
u
t
can
also
id
en
tify fau
lty
swi
t
c
hi
n
g
de
vi
ces wi
t
h
o
u
t
ad
di
t
i
onal
vol
t
a
g
e
sens
or
o
r
a
n
analytical syste
m
m
odel. Open-s
witch a
n
d
short-
switch
fau
lts can
b
e
d
e
tected b
y
an
alyzin
g
th
e stato
r
curren
t p
a
ttern
s
with
in
th
e m
a
x
i
m
u
m
o
f
two
cu
rrent
peri
ods
. T
h
e l
o
cat
i
o
n
o
f
a
fa
ul
t
y
swi
t
c
h ca
n
be i
n
di
cat
ed
b
y
six p
a
tterns of
a stator
cu
rr
en
t
v
ector
an
d th
e
faul
t
y
swi
t
c
hi
n
g
devi
ce i
s
det
ect
ed by
a
n
al
y
z
i
ng t
h
e
cu
rren
t v
ect
o
r
.
A
d
i
ag
no
stic algorith
m
th
at allo
ws th
e
real-tim
e d
e
tec
tio
n
an
d lo
cali
zatio
n
o
f
m
u
lti
p
l
e op
en
-switc
h
fau
lts in inverter-fed AC
m
o
to
r d
r
i
v
es
has b
e
en
prese
n
t
e
d
[3]
.
Thi
s
m
e
t
hod i
s
qui
t
e
si
m
p
l
e
and
ju
st
req
u
i
r
es t
h
e m
easured m
o
t
o
r p
h
as
e cur
r
ent
s
a
n
d
t
h
ei
r
corres
ponding refe
rence signals,
whic
h a
r
e
already availa
ble from
the ma
in
co
n
t
ro
l syste
m
. Mo
reov
er, th
is
al
go
ri
t
h
m
does
n
o
t
de
pen
d
o
n
t
h
e m
o
t
o
r
p
o
w
er
, l
o
a
d
, a
n
d
spee
d.
Fo
r a
P
W
M
vol
t
a
ge
sou
r
ce i
nve
rt
er
base
d
i
n
d
u
ct
i
on m
o
t
o
r
dri
v
e, f
a
ul
t
det
ect
i
on a
n
d di
ag
no
si
s sche
m
e
s have
bee
n
st
u
d
i
e
d
usi
n
g t
h
e f
u
zzy
l
o
gi
c [
4
]
.
Th
is
work
requ
ires t
h
e m
easu
r
em
en
t o
f
th
e ou
tpu
t
inv
e
rt
er cu
rren
ts t
o
detect th
e in
termit
ten
t
lo
ss
o
f
firing
p
u
l
ses in inv
e
rter power swit
ch
es. Fau
lt-to
l
e
ran
t
st
rate
gi
es
f
o
r
ne
ut
ral
p
o
i
n
t
cl
am
ped (
N
PC
) i
n
ve
rt
er s
y
st
em
s
feedi
n
g
hi
gh
p
o
we
r i
n
d
u
ct
i
o
n
m
o
t
o
r dri
v
e
s
have
been p
r
o
pos
ed wi
t
h
ver
y
l
o
w cost
[5]
.
Two di
f
f
ere
n
t
faul
t
co
nv
erter strat
e
g
i
es h
a
v
e
b
e
en
co
m
p
ared
with
th
e u
s
e
o
f
ad
d
ition
a
l co
m
p
on
en
ts.
A com
p
arativ
e liter
a
tu
re
revi
e
w
o
n
t
h
e
exi
s
t
i
ng m
e
t
h
o
d
s wa
s di
sc
uss
e
d f
o
r
faul
t
di
agn
o
si
s a
nd
pr
ot
ect
i
on i
n
cl
udi
n
g
o
p
e
n
-s
wi
t
c
h,
sho
r
t
-
switch
,
an
d
g
a
te
m
i
sfirin
g
fau
lts in
three
-
phase power inverters [6].
Tw
en
ty-on
e
m
e
t
h
od
s for
op
en-sw
itch
faul
t
s
an
d t
e
n
m
e
t
hods f
o
r sho
r
t
-
s
w
i
t
c
h fa
ul
t
s
were ev
al
uat
e
d an
d s
u
m
m
a
ri
zed base
d
on t
h
ei
r
per
f
o
r
m
a
nce
and
i
m
pl
em
ent
a
t
i
on e
f
f
o
rt
s.
T
h
e
gat
e
-m
i
s
fi
ring
fa
ul
t
s
an
d c
o
r
r
es
po
n
d
i
n
g d
i
agn
o
st
i
c
m
e
t
h
ods
ha
ve al
s
o
be
e
n
d
i
scu
s
sed br
iefly.
A
t
h
ree
-
p
h
ase
FPG
A-
base
d f
a
ul
t
-
t
o
l
e
ra
nt
ba
ck-t
o-
back
c
o
n
v
ert
e
r
was pr
o
pos
ed
wi
t
h
a v
e
ry
fast
fa
ul
t
det
ect
i
on sc
he
m
e
[7]
.
The fa
ul
t
-
t
o
l
e
ra
nt
co
nve
rt
er
wo
rk
s l
i
k
e a con
v
e
n
t
i
onal
back
-t
o
-
b
ack si
x
-
l
e
g c
o
nve
rt
e
r
bef
o
re t
h
e fa
ul
t
occu
rre
nce
and i
t
w
o
r
k
s as a fi
ve
-l
eg converter a
f
ter the fa
ult
occurre
nce.
Design,
im
pl
em
ent
a
t
i
o
n, a
n
d e
xpe
ri
m
e
nt
al
veri
fi
c
a
t
i
on
of a
F
P
G
A
-
b
ase
d
re
con
f
i
g
ura
b
l
e
c
ont
rol
st
rat
e
g
y
wer
e
d
i
scu
s
sed
for
th
is co
nv
erter. Fo
r a
v
o
ltage so
urce in
verter feedi
ng
AC
m
achines, a
real-tim
e diagnostic
sch
e
m
e
h
a
s b
e
en
repo
rted
to
d
e
tect th
e op
en
fau
lt in
m
u
lt
ip
le switch
e
s
[8
]. In
co
n
t
rast with
th
e m
a
j
o
rity o
f
m
e
t
hods
, onl
y
t
h
ree-
p
h
ase m
o
t
o
r cur
r
e
n
t
s
are use
d
, w
h
i
c
h
are al
ready
av
ai
l
a
bl
e for t
h
e
m
a
i
n
cont
r
o
l
sy
st
em
,
avoi
di
n
g
t
h
e
u
s
e of e
x
t
r
a se
n
s
ors
.
T
h
i
s
m
e
tho
d
ca
n ha
n
d
l
e
l
a
rge t
r
a
n
si
ent
s
suc
h
as l
o
a
d
and
spee
d
vari
at
i
ons.
A t
w
o-l
e
vel
fa
ul
t
-
t
o
l
e
ra
nt
vol
t
a
ge s
o
u
r
ce i
n
vert
er
f
o
r
pe
r
m
anent
m
a
gne
t
dri
v
e h
a
s
bee
n
pr
op
ose
d
[9]
,
w
h
i
c
h
pr
o
v
i
d
es t
o
l
e
ra
nce t
o
bot
h s
h
ort
-
swi
t
c
h a
n
d
ope
n
-
swi
t
c
h
fa
ul
t
s
of t
h
e swi
t
chi
n
g de
vi
ces.
Ex
peri
m
e
nt
al
resul
t
s
show t
h
at the
c
o
m
p
ensation st
rategy is
fast e
n
ough and t
h
e
thyristors
can s
u
ccess
f
ully isolate the fa
ulty leg in
all th
e fau
lt cases.
Fau
lt-to
leran
t
o
p
e
ration
is v
e
ry i
m
p
o
r
tan
t
for h
i
gh
im
p
act
au
to
m
o
tiv
e app
licatio
n
s
su
ch as electrical
vehicles and hybrid electrical
vehi
cl
es. A
n
act
i
v
e faul
t
-
t
o
l
e
rant
co
nt
r
o
l
sy
st
em
has been prese
n
t
e
d f
o
r a hi
g
h
p
e
rform
a
n
ce in
du
ction
m
o
to
r driv
e t
h
at
propels a
n
electrical vehicle or
a hybrid
electrical ve
hicle [10].
A
fau
lt-to
leran
t
co
n
t
ro
l system
whi
c
h can c
h
a
nge t
h
e c
o
nt
rol
t
echni
q
u
e i
n
t
h
e eve
n
t
of se
nso
r
fai
l
u
res h
a
s bee
n
rep
o
rt
e
d
f
o
r a
n
i
n
d
u
ct
i
o
n m
o
t
o
r dri
v
e [1
1
]
, where f
o
ur
cont
r
o
l
sche
m
e
s have bee
n
use
d
t
o
ens
u
re t
h
e
co
n
tinu
ity in
m
o
to
r d
r
iv
e
o
p
eratio
n. A fau
l
t-to
leran
t
p
o
w
e
rtrain f
o
r se
ri
es hy
bri
d
electric vehicles wi
th two
di
ffe
re
nt
t
echn
i
ques
has
bee
n
st
udi
e
d
[
1
2]
.
The t
i
m
e-dom
ai
n si
m
u
l
a
ti
on
and
ex
peri
m
e
nt
al
res
u
l
t
s
evi
d
ent
l
y
p
r
ov
ed th
at these techn
i
qu
es wo
rk
well in
sh
ort-switc
h
an
d op
en
-switch
fau
lt.
A m
o
du
lar
po
wer electron
i
c
co
nv
erter with a cascad
ed
H-b
r
i
d
g
e
m
u
ltilev
e
l in
v
e
rter h
a
s b
e
en
prop
o
s
ed
[13
]
. Sev
e
ral fau
lt detectio
n
m
e
t
hods
we
re
anal
y
zed,
an
d
one
wa
s t
e
st
ed
base
d
on
m
oni
t
o
ri
ng
t
h
e
DC
l
i
n
k
v
o
l
t
a
ge.
A fa
ul
t
-
t
o
l
e
ra
n
t
schem
e
for a
do
ubl
y
-
fed i
n
duct
i
o
n ge
ne
ra
t
o
r (
D
F
I
G
)
wi
nd t
u
r
b
i
n
e wa
s prese
n
t
e
d
usi
n
g a
p
a
ral
l
e
l
gri
d
si
de
re
ct
i
f
i
e
r an
d
seri
es G
S
C
[
1
4]
.
A
faul
t
-
t
o
l
e
ran
t
co
nt
rol
has
been
pr
op
ose
d
f
o
r
a
battery energy stora
g
e syste
m
based on a cascade PW
M
co
nv
erter with
star co
nfig
urat
i
on [
1
5]
. O
p
en
-
s
wi
t
c
h
fault
detection and
replacement of t
h
e
faul
ty switches
ha
ve been
proposed [16].
T
h
e detection
of faulty
swi
t
c
hes was do
ne by
m
easuri
ng
t
h
e phas
e
an
d
l
i
n
e vol
t
a
ges of
i
nve
rt
e
r
.
T
h
e repl
ace
m
e
nt
of faul
t
y
swi
t
c
h
was
do
ne
by
u
s
i
ng t
h
e e
x
t
r
a
arm
.
Perfo
rm
ance a
n
al
y
s
i
s
of
t
h
ree
-
p
h
ase i
n
duct
i
o
n m
o
t
o
r
dri
v
e sy
st
em
und
e
r
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
PED
S
I
S
SN
:
208
8-8
6
9
4
Ope
n
-Sw
i
t
c
h F
aul
t
-
Tol
e
r
ant
C
ont
r
o
l
of
a G
r
i
d
-
S
i
d
e
C
o
nve
r
t
e
r
i
n
a
Wi
nd
Pow
e
r
…
(
K
yeon
g
-
Hw
a Kim)
29
5
ope
n
-
swi
t
c
h
fa
ul
t
has bee
n
di
scusse
d [
17]
,
whe
r
e t
h
e o
p
e
n
-s
wi
t
c
h fa
ul
t
was i
n
v
e
st
i
g
at
ed at
no
rm
al operat
i
n
g
co
nd
itio
n as well as fau
lty con
d
ition
.
Du
ring
th
e
o
c
cu
rr
ence o
f
a sing
le-co
n
v
e
rter-cell
o
r
si
n
g
l
e-b
a
ttery-un
i
t
fau
lt, th
e
fault-to
leran
t
contro
l en
ab
les co
n
tinuo
us op
eratio
n
wh
ich
en
h
a
n
ces syst
e
m
reliab
ilit
y
an
d
av
ailab
ility.
W
i
t
h
o
u
t
p
r
o
p
e
r
faul
t
det
ect
i
on a
nd
faul
t
-
t
o
l
e
ra
nt
ope
rat
i
o
n
,
t
h
e o
v
eral
l
sy
st
em
has t
o
be st
op
pe
d
sud
d
e
n
l
y
un
de
r t
h
e o
p
e
n
-s
wi
t
c
h fa
ul
t
i
n
a w
i
nd
po
wer
ge
n
e
rat
i
on sy
st
em
. Thi
s
i
s
not
ac
cept
a
bl
e beca
u
s
e t
h
e
sy
st
em
downt
i
m
e due t
o
t
h
e uns
che
d
ul
ed m
a
i
n
t
e
nan
ce
or s
hut
down m
a
y
decrease the sy
ste
m
perform
a
n
ce as
well as th
e reliab
ility an
d
co
n
s
isten
c
y of syste
m
. It is
v
e
ry i
m
p
o
r
tan
t
to
m
a
k
e
reliab
l
e d
e
tectio
n
and
fau
lt-
tolerant algorithm
s
because the sy
ste
m
restoration ca
n be acc
om
p
lished
quic
k
ly. From
the studie
s
i
nvest
i
g
at
e
d
ab
ove
, i
t
can be obs
er
ved t
h
at
t
h
e det
ect
i
o
n, i
s
ol
at
i
o
n
,
an
d r
econ
f
i
g
urat
i
o
n
t
echni
q
u
es o
f
ope
n
-
swi
t
c
h
fa
ul
t
i
n
a g
r
i
d
c
o
nn
ect
ed c
o
nve
rt
er
f
o
r
wi
n
d
po
we
r
gene
rat
i
o
n sy
st
em
are
not
s
u
ff
i
c
i
e
nt
fo
r i
m
pr
ovi
ng
th
e reliab
ility. Th
erefo
r
e, m
o
re research wo
rk
s
n
e
ed
to
b
e
do
n
e
,
wh
ich
is a ch
alleng
ing
task
for
researcher.
Thi
s
pa
pe
r p
r
o
pos
es fa
ul
t
-
t
o
l
e
rant
c
o
m
p
ens
a
t
i
on ap
p
r
oac
h
es fo
r a
GSC
i
n
wi
n
d
po
we
r
gene
rat
i
o
n
syste
m
. Th
e total co
nfigu
r
ati
o
n con
s
ists
of
th
e m
ach
in
e
-
s
i
d
e
co
nv
er
te
r
(MS
C
)
an
d GSC in
a b
a
ck
-
t
o-
b
a
ck
to
po
log
y
, wh
ere th
e GSC
h
a
s th
ree add
ition
a
l in
v
e
rter leg
s
to
b
e
u
s
ed
as redu
nd
an
t h
a
rdware system. Th
e
ope
n
-
swi
t
c
h
fa
ul
t
i
s
det
ect
ed
by
usi
ng t
h
e
no
rm
al
i
zed RM
S cur
r
e
n
t
s
.
The
pr
op
ose
d
faul
t
-
t
o
l
e
rant
s
t
rat
e
gy
u
s
es th
e i
n
fo
rmatio
n
o
n
t
h
e
d
u
ration
s
of
po
sitiv
e and
n
e
g
a
tiv
e cycles in
grid
cu
rren
ts to
find
th
e l
o
catio
n
of
ope
n
-
swi
t
c
h
fa
ul
t
.
Once t
h
e l
o
cat
i
on
of
ope
n-s
w
i
t
c
h fa
ul
t
i
s
obt
ai
ne
d, t
h
e faul
t
-
t
o
l
e
ra
nt
al
gori
t
h
m
m
a
kes t
h
e
syste
m
k
eep
ru
nn
ing
with go
od
p
e
rfo
r
m
a
n
ce. Th
e
p
r
op
osed
m
e
th
o
d
d
o
es no
t
n
e
ed
any ad
d
ition
a
l cu
rrent
sens
or bec
a
us
e i
t
uses onl
y
t
h
e durat
i
ons
of t
h
ree
-
p
h
as
e gri
d
cu
rre
nt
s
.
Three c
u
r
r
en
t
sensor
s are use
d
t
o
cont
rol
t
h
e i
n
v
e
rt
er. T
h
e
pr
o
p
o
se
d m
e
t
hod i
s
sim
p
l
e
eno
u
g
h
t
o
be i
m
pl
em
ent
e
d i
n
g
r
i
d
si
de co
nt
r
o
l
l
e
r,
whi
c
h
allo
ws th
e contin
u
o
u
s
op
erati
o
n
of en
erg
y
tran
sfer to
grid
ev
en
i
n
th
e
presen
ce
o
f
co
m
p
lete lo
ss in
m
u
ltip
l
e
i
nve
rt
er l
e
gs.
2.
FAULT
-
TOL
E
RA
NT
CO
N
T
ROL O
F
G
S
C I
N
W
I
N
D
E
N
ERG
Y
CO
N
V
ERS
I
O
N
Fi
gu
re 1 s
h
ows
t
h
e pr
op
ose
d
f
a
ul
t
-
t
o
l
e
ra
nt
wi
nd e
n
er
gy
co
n
v
ersi
on sy
st
em
(
W
EC
S
)
t
o
pol
ogy
,
whi
c
h
i
s
based
o
n
a c
l
assi
cal
back-t
o-
bac
k
co
n
v
ert
e
r an
d u
s
es co
m
m
on red
u
nda
nt
l
e
gs f
o
r t
h
e
GSC
.
T
h
e
pr
o
pos
ed
fau
lt-to
leran
t
syste
m
is co
m
p
o
s
ed
of three d
i
ffer
ent
uni
t
s
whi
c
h
a
r
e
t
h
e pha
se i
s
ol
at
i
on uni
t
,
pha
se
reconn
ectio
n un
it, and
add
itio
n
a
l leg
u
n
it.
Th
e
redun
d
a
n
t
leg
s
co
nsist of th
e
switch
e
s
S
7
,
S
8
,
S
9
,
S
10
,
S
11
, a
n
d
S
12
, and are us
ed to re
place the fa
ulty one of the
other
le
gs unde
r any powe
r switch
fa
ilure in the GSC. The
red
u
nda
nt
l
e
gs
are not
use
d
no
rm
all
y
when
t
h
e
GSC
w
o
r
k
s wi
t
h
o
u
t
a
n
y
fa
ul
t
.
Ph
ase iso
l
ation
un
it u
s
es three trio
d
e
for altern
atin
g
cu
rren
t
(TRIAC) switch
e
s,
wh
ich
is lo
cated
bet
w
ee
n t
h
e
o
u
t
p
ut
t
e
rm
i
n
al
s of t
h
e
GSC
a
nd t
h
e c
o
r
r
esponding phases in
grid
. Thes
e TRIAC
s
w
itches
are
u
s
ed
to
iso
l
ate
th
e switch
e
s i
n
fau
lty leg
.
The reconn
ectio
n u
n
it wh
ich
also
con
s
ists of three TRIAC switch
e
s
is lo
cated
b
e
t
w
een
th
e
o
u
t
p
u
t
termin
als o
f
the redu
nd
an
t leg
s
and
th
e correspo
nd
ing
ph
ases in
grid
as sh
own
in Figure 1. These TRIAC s
w
itches are use
d
in order to
i
n
s
e
rt the redunda
nt leg in place
of the
faulty phase.
Du
ri
n
g
t
h
e
no
r
m
al
operat
i
o
n,
t
h
ree
TR
IAC
s
w
i
t
c
hes i
n
th
e i
s
o
l
atio
n un
it are tu
rn
ed
ON whereas
three T
R
IAC
switch
e
s i
n
th
e reco
nn
ection
u
n
it are turned
OFF.
Fi
gu
re
1.
Pr
o
p
o
se
d fa
ul
t
-
t
o
l
e
r
a
nt
sc
hem
e
of
GSC
i
n
WEC
S
t
o
p
o
l
o
gy
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-86
94
I
J
PED
S
Vo
l. 6,
No
.
2,
Ju
ne 20
15
:
293
–
3
04
29
6
Fi
gu
re 2 s
h
ow
s t
h
e ope
rat
i
o
n o
f
t
h
e ent
i
r
e sy
st
em
duri
ng t
h
e
n
o
rm
al heal
t
h
y
ope
ra
t
i
on. D
u
ri
n
g
h
ealth
y op
erati
o
n, th
e add
itio
n
a
l leg
u
n
it
will b
e
in
activ
e.
Howev
e
r, as so
on
as t
h
e fau
l
t d
e
tectio
n
al
go
rith
m
d
e
tects th
e
o
p
e
n
fau
lt in
th
e
GSC, t
h
e fau
lty p
h
a
se
will
be iso
l
ated
. By
u
s
ing
th
e g
a
ting
sign
al, t
h
e iso
l
ated
fau
lty ph
ase is
rep
l
aced
with
t
h
e add
itio
n
a
l l
e
g
un
it to
allow co
n
t
i
n
uou
s
o
p
e
ration
o
f
the GSC
.
Th
e
switch
i
ng
pat
t
e
rns
are
det
e
rm
i
n
ed by
gat
i
ng
si
g
n
al
.
An
op
en-switch
fau
lt in
th
e i
n
su
lated
g
a
te
bip
o
l
ar
t
r
ansist
or (IGBT
)
m
a
y
occur
due t
o
the failure i
n
th
e gate dr
iv
e
cir
c
u
it or
t
h
e
br
eak of
bo
nd
w
i
r
e
s i
n
t
h
e
I
G
BT.
W
h
en
on
e of
th
e IG
BTs
can
no
t
b
e
t
u
rned
O
N
,
the c
o
rresponding phase
current is ze
ro
du
r
i
ng
a hal
f
cy
cl
e,
ei
t
h
er
posi
t
i
ve or
negat
i
v
e
hal
f
cy
cl
e dep
e
ndi
ng
o
n
th
e po
sition
o
f
th
e
IGBT switch.
As
a
resu
lt,
DC curren
t
o
f
fset is i
n
du
ced
i
n
th
e
fau
lty ph
ase an
d th
is
of
fset
i
s
u
n
i
f
o
r
m
l
y
di
vi
de
d
bet
w
ee
n t
h
e
h
eal
t
h
y
p
h
ases
.
As soo
n
as t
h
e op
en-switch
fau
lt in an
y
IGBT is
d
e
tected
, t
h
e
gatin
g
si
g
n
a
l i
n
fau
lty ph
ase is
sto
p
p
e
d
in
t
h
e
GSC an
d app
lied
to th
e
red
und
an
t leg
in additio
n
a
l
u
n
it.
At th
e same ti
me, th
e TRIAC switch
of th
e iso
l
atio
n
u
n
it is tu
rn
ed
OFF t
o
iso
l
ate th
e fau
lty leg
an
d
t
h
e
TRIAC
switch o
f
th
e reconn
ecetio
n
u
n
it
is
t
u
rn
ed
ON.
Fi
gu
re
2.
Fa
ul
t
-
t
o
l
e
ra
nt
t
o
p
o
l
ogy
d
u
ri
ng
n
o
r
m
al
operat
i
o
n
Fig
u
re 3
shows th
e fau
lt-t
o
leran
t
to
po
log
y
un
d
e
r th
e
switch
S
1
o
p
e
n
fau
lt.
Wh
en th
e fau
lt is
in
trodu
ced
i
n
to
system
, th
e p
r
op
o
s
ed
d
e
tectio
n
algo
ritm
e
ffectiv
ely fi
n
d
s ou
t th
e
fa
ult occurre
nce
as
well
as
its lo
catio
n
.
As so
on
as th
e
fau
lt lo
cation
is d
e
term
in
ed
, a rem
e
d
i
al s
t
rateg
y
is p
e
rform
e
d
to
g
u
a
ran
t
ee
a
co
n
tinu
ity o
f
op
eration
.
In
t
h
is case,
a
-p
hase
TR
IAC
of
t
h
e
i
s
ol
at
i
on uni
t
i
s
t
u
rne
d
OFF and
a
-ph
a
se TRI
A
C
of the
reconne
c
tion
unit is t
u
rned ON at t
h
e
sam
e
tim
e.
Fi
gu
re
3.
Fa
ul
t
-
t
o
l
e
ra
nt
t
o
p
o
l
ogy
u
nde
r t
h
e s
w
i
t
c
h
S
1
ope
n f
a
ul
t
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
PED
S
I
S
SN
:
208
8-8
6
9
4
Ope
n
-Sw
i
t
c
h F
aul
t
-
Tol
e
r
ant
C
ont
r
o
l
of
a G
r
i
d
-
S
i
d
e
C
o
nve
r
t
e
r
i
n
a
Wi
nd
Pow
e
r
…
(
K
yeon
g
-
Hw
a Kim)
29
7
Fig
u
re
4
shows th
e fau
lt-to
leran
t
topo
log
y
u
n
d
e
r th
e switch
e
s
S
1
and
S
3
ope
n
fault. B
ecause the
faults occ
u
r i
n
a
-
phase a
n
d
b
-phase sim
u
ltaneously,
a
-
p
h
a
se and
b
-ph
a
se TRIAC swit
ch
es of th
e isolatio
n
u
n
it are turn
ed OFF an
d
a
-phase an
d
b
-phas
e
TRIAC swit
ches of the re
co
nn
ection
un
it are tu
rn
ed
ON. Th
e
g
a
tin
g sign
als
o
f
t
a
,
t
b
, and
t
c
are u
tilized
t
o
tu
rn
ON and
OFF th
e
TR
IAC
switch
e
s, if an
y op
en
-switch
fau
lt
occu
rs.
These
gat
i
ng
si
g
n
al
s are det
e
rm
i
n
ed
usi
n
g t
h
e
d
u
r
a
t
i
ons
of c
o
r
r
e
s
po
n
d
i
n
g
phas
e
cur
r
ent
.
D
u
ri
ng t
h
e
no
rm
al
operat
i
o
n
,
t
h
e
val
u
e
s
of
t
a
,
t
b
, and
t
c
used
for t
h
e
gating signals
are zero t
o
turn
ON t
h
e T
R
IAC
switch
e
s i
n
th
e iso
l
atio
n
un
it. Un
d
e
r th
e fault co
nd
itio
n
,
on the
contra
ry, these
values a
r
e cha
n
ge
d to
one
t
o
tu
rn
OFF th
e
TRIAC switches in
th
e iso
l
at
io
n
u
n
it and
t
o
tu
rn
ON th
e
TRIAC switches in
th
e reconn
ectio
n
u
n
it sim
u
ltan
e
o
u
s
ly.
Fi
gu
re
4.
Fa
ul
t
-
t
o
l
e
ra
nt
t
o
p
o
l
ogy
u
nde
r t
h
e s
w
i
t
c
hes
S
1
an
d
S
3
ope
n faul
t
3.
PROP
OSE
D
FAULT
DET
E
CTION
A
N
D
TOLE
RA
N
T
ALGO
RIT
H
MS
The
v
o
l
t
a
ge m
odel
o
f
t
h
ree-
p
h
ase M
S
C
wi
t
h
a
pe
rm
anent
m
a
gnet
sy
nc
hr
on
o
u
s
ge
nerat
o
r (
P
M
S
G
)
i
n
t
h
e sy
nc
hr
o
n
o
u
s
re
fere
nce
fra
m
e
i
s
gi
ve
n as
fol
l
o
ws:
qm
dm
d
e
qm
q
qm
s
qm
v
i
L
dt
di
L
i
R
e
(1
)
dm
qm
q
e
dm
d
dm
s
dm
v
i
L
dt
di
L
i
R
e
(2
)
wh
ere th
e su
bscrip
t “m
” d
e
n
o
tes th
e v
a
riab
les in
th
e MSC,
e
qm
and
e
dm
are the
q
-a
xi
s and
d
-a
xi
s ge
ne
rat
e
d
v
o
ltag
e
s, resp
ectiv
ely,
i
qm
and
i
dm
are the
q
-axi
s an
d
d
-a
xi
s gene
rat
e
d c
u
rre
nt
s, res
p
ect
i
v
el
y
,
R
s
is th
e
stator
resistance,
L
q
and
L
d
are the
q
-a
xi
s an
d
d
-a
xis inducta
n
ce
s, res
p
ectively,
ω
e
is the electrical angular
velocity
of t
h
e
gene
rator.
If t
h
e PMSG is a surface
mounted type, t
h
en the
d
-axis a
n
d
q
-axis i
n
ductance are t
h
e
sam
e
wh
ich
is referred
as no
salien
c
y.
Wh
en
th
e g
e
n
e
rated
vo
l
t
ag
e is alig
n
e
d to
th
e
q
-
a
x
i
s in
th
e syn
c
hron
ou
s
refe
rence
f
r
am
e, t
h
e
ge
nerat
e
d
vol
t
a
ge
s
by
t
h
e PM
S
G
a
r
e
o
b
t
a
i
n
ed
as
fol
l
ows:
m
e
qm
E
e
(3
)
0
dm
e
(4
)
whe
r
e
λ
m
is the flux linkages. By controlling the DC
link voltage
constantly,
the GSC can
deliver the
gene
rated
po
w
e
r fr
om
the MSC
to gri
d
. T
h
e con
v
erte
r inp
u
t po
we
r can
b
e
exp
r
esse
d in
term
s of
d
-axis
and
q
-
axis variables
in
(2) as follows:
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN:
2
088
-86
94
I
J
PEDS Vo
l. 6,
No
.
2,
Ju
ne 20
15
:
293
–
3
04
29
8
qm
qm
qm
dm
dm
in
Ei
i
e
i
e
P
2
3
)
(
2
3
(
5
)
If t
h
e loss in converter input
resistor an
d i
n
duct
o
r
is ne
gle
c
ted, the
in
put
po
we
r
P
in
is equal to t
h
at of
co
nv
er
ter
o
u
t
pu
t
P
o
.
Th
us,
th
e co
nve
rter
o
u
t
put
p
o
we
r ca
n
be e
x
p
r
esse
d a
s
o
dc
o
i
V
P
(
6
)
whe
r
e
V
dc
is the DC link
voltage and
i
o
is the
converter
out
put current.
A fl
ow
c
h
art
of
the
pr
o
pose
d
f
a
ult detectio
n a
n
d
fa
u
lt-tolerant algorithm
s
is
p
r
ese
n
ted
i
n
Figu
re 5.
Figu
re
5.
Flo
w
cha
r
t o
f
the
p
r
op
ose
d
o
p
en
-s
w
itch
fault
detection and faul
t-tolerant
algorith
m
T
h
r
e
e-p
h
a
s
e
gr
id
cu
rr
en
ts
a
r
e
tr
ans
f
orm
e
d into t
h
e
valu
es o
n
t
h
e stationa
ry
re
fere
nc
e fram
e
a
s
follows:
cg
bg
ag
dg
i
i
i
i
3
1
3
1
3
2
(7
)
)
(
3
1
cg
bg
qg
i
i
i
(8
)
whe
r
e the s
ubs
cript “g”
denot
e
s
the variables in the GSC, and
i
ag
,
i
bg
, and
i
cg
are the three
-
phas
e grid c
u
rrents
,
respectively. Using these
values
, the Park’s
vector m
o
dulus
i
sm
is obtaine
d
by
2
2
qg
dg
sm
i
i
i
.
(
9
)
Three
-
phase
R
M
S g
r
id c
u
rre
n
t
s are
no
rm
alized
by
u
s
in
g thi
s
Par
k
’
s
vecto
r
m
odulus
as
fol
l
ows:
sm
arms
an
i
i
i
(
1
0
)
St
a
r
t
If
(
i
an
>
i
th
1
),
(
(
i
a
,
po
s
<
i
th
2
)
||
(
i
a
,
ne
g
<
i
th
2
))
YES
NO
Se
n
s
i
n
g
i
ag
,
i
bg
,
i
cg
N
o
r
m
a
l
i
zed
R
M
S
cu
rren
t
s
i
an
,
i
bn
,
i
cn
C
a
l
c
ul
at
e
t
h
e
dur
at
i
o
n
o
f
pos
i
t
i
v
e
an
d
n
e
g
a
t
i
ve cycl
es
i
n
each
p
h
a
s
e
i
a
,
po
s
,
i
b
,
po
s
,
i
c
,
po
s
,
i
a
,
ne
g
,
i
b
,
ne
g
,
i
c
,
ne
g
fa
u
l
t _
s
ta
tu
s
= 0
G
a
t
i
n
g
Si
gn
al
s
t
a
=
t
b
=
t
c
= 0
fa
u
lt_
s
t
a
t
u
s
=1
G
a
t
i
n
g
Si
gn
al
t
a
=1
If
(
i
bn
>
i
th
1
),
(
(
i
b
,
po
s
<
i
th
2
)
|| (
i
b
,
ne
g
<
i
th
2
))
If
(
i
cn
>
i
th
1
),
((
i
c
,
po
s
<
i
th
2
) |
|
(
i
c
,
ne
g
<
i
th
2
))
YES
YES
NO
NO
fa
u
lt_
s
t
a
t
u
s
=1
G
a
t
i
ng Si
gn
al
t
b
=1
fa
u
lt_
s
t
a
t
u
s
=1
G
a
t
i
ng Si
gn
al
t
c
=1
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
PEDS
I
S
SN:
208
8-8
6
9
4
Ope
n
-Sw
itch F
ault-
Toler
ant C
ontr
o
l
of a G
r
id-
S
ide
C
o
nve
r
ter
in a
Wi
nd
Pow
e
r
…
(
K
yeong-Hw
a Kim)
29
9
sm
brms
bn
i
i
i
(
1
1
)
sm
crms
cn
i
i
i
(
1
2
)
whe
r
e
i
arms
,
i
br
ms
, and
i
crms
are three
-
phase
RMS grid c
u
rre
nts, res
p
ecti
v
ely, and
i
an
,
i
bn
, and
i
cn
are the
norm
alized three-phase RMS
gr
i
d
c
u
rrents, respectively.
In the
pr
o
pose
d
fa
ult detection algo
rithm
,
three-phase
grid
currents
i
ag
,
i
bg
, and
i
cg
are se
nse
d
at first
by
usin
g the c
u
r
r
ent se
nso
r
.
From
these values, the
no
rm
a
lized three-pha
s
e RMS gr
id c
u
rrents are calculated
by usi
n
g three
-
phase RMS
grid c
u
rre
n
ts and Pa
rk’s
vect
or
m
odul
us. The
durations of positive
and negative
cycles in each pha
se curre
n
ts are
calculated from
the current
m
easurem
e
n
ts. Open-s
witch fa
ult detection i
s
acheive
d
by us
ing the norm
alized thr
ee-phas
e RMS gri
d
curre
nts.
Once t
h
e fa
ult is detect
ed, the faulty switch
identification algorithm
find
s the location
of
faulty switch
by usi
n
g
the
durations of positive and negative
cycles as the i
d
entification
va
riables.
Under the
normal operati
ng
conditio
n, t
h
e
norm
alized RMS current
va
l
u
es becom
e
0.5. On
t
h
e other
hand, t
h
ese val
u
es are si
gnifi
cantly in
creased for the
open-switc
h fault condition. For t
h
e fault detection, the
threshol
d
value for the
normali
zed RMS current is c
h
ose
n
as
i
th
1
= 5.
0.
Wh
en a
n
ope
n
-
switc
h
fault is
introduced i
n
any com
b
ination
of
s
w
itch, one of
t
h
ree detection vari
ables
w
h
ich
a
r
e
i
an
,
i
bn
, and
i
cn
is
increase
d
. T
o
m
a
ke sure of fault occu
rre
nc
e, the controlle
r judg
es the fa
ult event when
one of these values is
larger than t
h
e
threshol
d
value
i
th
1
.
Fault-tolerant algorithm
is
activ
ated once
the fa
ult is detected
. After the fault
detection, a
reconfi
g
uration is required
in
har
d
wa
re as w
e
ll as in softwa
re. Ha
rd
wa
re r
econ
f
ig
urati
on
is do
ne by
re
placing
the faulty phase with redund
a
n
t o
n
e
.
I
n
so
ft
ware
pa
rt, t
h
e i
s
olation
and re
connection si
gnals a
r
e
gene
ra
ted as
soon
as the faulty sw
itch is identified.
The durati
ons
of
positive and negative cycle are us
ed to trigger t
h
e gati
ng signal of
the TRIAC
switches. Because the
durati
ons
of
pos
itive a
n
d ne
gaitive cy
cles in three-phas
e gri
d
curre
n
ts
are va
ried due
to
the open-switch fault location,
they can be
utilized in order to find out
the faulty phase. For exam
ple
,
if the
open-switch fault occurs i
n
S
1
as sh
o
w
n i
n
Figu
re
1,
a
-
p
h
a
se cu
rre
nt ha
s
o
n
ly
the d
u
r
ation
of
ne
gative
cy
cle
because the fa
ulty switch
S
1
can
no
t cond
uct an
y cu
rrent. To distinguis
h the fa
ulty phase,
i
a
,
pos
,
i
b
,
pos
,
i
c
,
pos
,
i
a
,
neg
,
i
b
,
neg
, and
i
c
,
neg
are obtained
from
three
-
phase grid c
u
rrents,
whic
h are used as fa
u
lty phase identification
variables. By com
p
aring these faulty phase id
entification variables wi
t
h
the thre
sh
ol
d value
i
th
2
, the faulty
phase can be identified
and the gating signals
t
a
,
t
b
, and
t
c
c
a
n
b
e
d
e
t
e
r
m
i
n
e
d
a
s
s
h
o
w
n
i
n
F
i
g
u
r
e
5
.
T
o
f
i
n
d
out the fa
ulty
pha
se instan
tly, the threshol
d value of
i
th
2
is chose
n
as 4.
0.
The determ
ined gatin
g sig
n
a
ls are
used to trigger the TRIAC
switches
of t
w
o
different set, that is, th
e phase is
olatio
n u
n
it an
d the
phase
reconnection unit in Fi
gure
1
fo
r fault-tolerant
com
p
ensation.
4.
SIMULATION RESULTS
The effectiveness of the
fault detec
tion, identification, an
d
fault-tole
rant s
c
hem
e
s is prov
ed usi
ng th
e
si
m
u
lation results. In order t
o
eval
uate the perform
a
n
ce of t
h
e proposed fault-tole
ra
nt
cont
rol strate
gy
, the
sim
u
lations h
a
ve
been
car
rie
d
out
o
n
the
P
S
IM
platfo
rm
for
a
grid
co
n
n
e
c
ted wi
nd
p
o
w
er
gene
ratio
n s
y
stem
.
The pa
ram
e
ter
s
for a PM
S
G
,
grid v
o
ltage,
and c
u
r
r
ent ar
e given in the
Table 1. A
n
o
p
en
-s
witch fa
u
lt
S
1
is
introduced at
t
=0.
2
sec i
n
the
u
ppe
r s
w
itch
of
a
-
p
h
a
se
o
f
th
e
GSC as shown in
Fi
gure
3. The faulty condition
is created
by t
u
rni
n
g OFF t
h
e
gate
sign
als o
f
th
e
cor
r
e
spon
din
g
switch
e
s.
Table
1.
Param
e
ters o
f
a
PM
S
G
,
gri
d
v
o
ltage
, an
d c
u
rre
nt
Rated power
5 kW
Rated speed
300 r
p
m
Nu
m
b
er
of poles
24
Flux linkages
0.
36 W
b
T
o
r
que 156
Nm
Stator
r
e
sistance
0.
64
Ω
Stator
inductance
0.
82
m
H
Gr
id voltage
359.
2 V
Gr
id cur
r
ent
29.
2 A
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN:
2
088
-86
94
I
J
PEDS Vo
l. 6,
No
.
2,
Ju
ne 20
15
:
293
–
3
04
30
0
To detect the fault, the normali
zed three-pha
se gri
d
RMS currents
a
r
e use
d
. During the norm
al
ope
ratio
n, the
no
rm
alized grid R
M
S cu
rre
nt
values
beco
m
e
0.
5.
Ho
we
ve
r, w
h
e
n
th
e fault occurs
, thre
e
-
phase
n
o
r
m
alized
g
r
id
RMS cur
r
e
n
t
s ar
e in
cr
eased b
e
yond
the thr
e
sho
l
d v
a
lu
es
i
th
1
. Figure
6 shows the sim
u
lation
results of
three-phase grid
currents without fa
ult-tolerant schem
e
and
with
th
e pr
op
ose
d
fault-t
o
lera
nt
schem
e
. In t
h
e
s
e figures, t
h
e
term
“
fault_status
” indicates t
h
e
detection of fa
ult and
t
a
,
t
b
, and
t
c
represents the
gating si
g
n
als.
After t
h
e fa
ult detection, th
e pr
op
osed fault-tolera
nt sc
hem
e
is
im
plem
ented at
t
=0.217sec
.
The
gri
d
currents are
returned t
o
the re
gula
r
shape
a
g
ain within 0.0
096 sec
with the
activation of t
h
e
pr
o
pose
d
fa
ult-tolera
nt strate
gy
as
sh
o
w
n
in Fi
gu
re
6
(
b
)
.
Whe
n
the
fa
ult occ
u
rs
, t
h
e
gri
d
c
u
r
r
e
n
t wa
ve
fo
rm
s
diverge from
their
refe
rences instantly be
fore the fault-tol
e
rant
operation.
This is du
e to the
nonlinearities
introduced in the invert
er topologies with the fault
occu
rre
nce. This ki
nd
of p
h
enom
enon can be elim
inated
as soon as t
h
e
fault-tolera
nt
pr
oced
u
r
e is e
x
e
c
uted.
(a) Without fault-tolera
nt
sc
h
e
m
e
(b
) Wit
h
fault-t
o
lera
nt
schem
e
Figu
re 6.
R
e
sp
ons
es of
t
h
ree
-
pha
se grid
cu
rr
ents un
der
S
1
o
p
en
-s
witch
fau
l
t
Responses of the
d
-
a
x
i
s and
q
-axis cu
rre
nt
s for this case
are sho
w
n in
Figure
7.
Wit
h
o
u
t fault-
tolerant scheme, the
d
-a
xis a
nd
q
-axis c
u
rre
nts ha
ve
big
fl
uctuatio
n
as s
h
ow
n i
n
Fig
u
r
e
7(a
)
due t
o
S
1
ope
n
-
switch fault.
Ho
we
ver
,
sinc
e this
open-switch fault is well com
p
ensa
ted
usin
g t
h
e
pr
op
ose
d
al
go
rithm
,
th
e
currents
are
stabilized wit
h
in very
sh
ort ti
m
e
as sh
ow
n i
n
Fi
gu
re
7(
b)
,
once
the
fa
ult-tolerant al
go
rithm
is
applied.
(a) Without fault-tolera
nt
sc
h
e
m
e
(b
) Wit
h
fault-t
o
lera
nt
schem
e
Figu
re 7.
R
e
sp
ons
es of
d
-axis
an
d
q
-a
xis c
u
r
r
ents
u
nde
r
S
1
open-switch
fault
i
ag
i
bg
i
cg
N
o
rm
a
l
Op
er
a
t
io
n
F
a
u
l
t O
p
e
r
a
ti
on
i
ag
i
bg
i
cg
N
o
r
m
al
Op
e
r
at
i
o
n
T
o
ler
a
n
t
O
p
era
t
i
o
n
Fa
u
l
t
O
ccu
re
n
c
e
f
a
ult_s
t
a
t
us
t
a
t
b
t
c
Fa
u
l
t
D
e
t
e
c
t
i
o
n
T
o
le
ra
n
t
A
p
p
lie
d
i
dg
i
qg
d
an
d
q
-
a
x
i
s
cu
rren
t
f
l
u
c
t
u
a
t
io
n
s
i
dg
i
qg
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
PEDS
I
S
SN:
208
8-8
6
9
4
Ope
n
-Sw
itch F
ault-
Toler
ant C
ontr
o
l
of a G
r
id-
S
ide
C
o
nve
r
ter
in a
Wi
nd
Pow
e
r
…
(
K
yeong-Hw
a Kim)
30
1
Figure 8 and Figure 9 illust
rate the responses of the
DC link volta
ge and
gri
d
output power. In these
fig
u
res
,
V
dc
,
ref
represents the
DC link
volta
ge refe
rence
a
n
d
P
out
the gri
d
out
put p
o
we
r. Du
rin
g
t
h
e no
rm
al
ope
ratio
n bef
o
re
the fa
u
lt is introduced at
t
=0.
2
sec,
the
D
C
link
voltage
is well re
gulat
ed a
nd t
h
e
gri
d
o
u
tp
ut
power is constant.
As a resu
lt of the open-switch
fault
oc
c
u
rrence
,
howe
ver, the
DC
li
nk
voltage is increased
an
d th
e gr
id ou
tpu
t
power is d
e
cr
eas
ed gradually. With
t
h
e fault-t
o
lerant
operation, t
h
e
DC link
vol
tage and
gri
d
out
put power reac
h steady-state again
as like as th
e
no
rm
al operati
on
. Afte
r th
e fault detection, it
is
necessa
ry
to f
i
nd
out t
h
e fa
ulty
phase
q
u
ickly
to co
m
p
ensate the
fault
y
phase c
u
rre
nt. If the a
bnorm
al
operation lasts contin
uously, there is a high possi
bility of seconda
ry faul
ts in the GSC
syste
m
and load. To
find out the faulty phase
accurately, the durations of
positive
and negati
ve phase
currents are used. If the
ope
n
-
switch
fa
ult occ
u
rs
o
n
u
ppe
r s
w
itch, t
h
e cor
r
es
p
ond
ing
ph
ase
h
a
s
only th
e n
e
gative
current
beca
us
e the
faulty upper switch cannot conduct cu
r
r
e
n
t as sho
w
n in F
i
gu
re 6.
If th
e ope
n
-
switch fa
ult
o
ccur
s
on
bo
tto
m
switch, the correspondi
ng
phase has
only t
h
e
positive current.
Therefore, th
e fault detection and the fault-
tolerant c
ont
ro
l techniq
u
es a
r
e re
q
u
ire
d
to
m
a
ke the sy
stem
operatio
n
balance
d
.
If t
h
e single
ope
n
-
switch
fault occurs i
n
the GSC, a faulty
phase current can either
be positive or negative de
pending on the
damaged
switch.
(a) Without fault-tolera
nt
sc
h
e
m
e
(b
) Wit
h
fault-t
o
lera
nt
schem
e
Figu
re 8.
R
e
sp
ons
es of DC
li
nk
v
o
ltage u
n
d
e
r
S
1
o
p
e
n
-s
witch
fault
(a) Without fault-tolera
nt
sc
h
e
m
e
(b
) Wit
h
fault-t
o
lera
nt
schem
e
Figu
re 9.
R
e
sp
ons
es of g
r
id o
u
tp
ut
p
o
w
er
u
n
d
er
S
1
open-switch
fault
Fig
u
r
e
10
thr
o
u
g
h
Figur
e 13
sh
ows th
e simu
la
tion re
sults
un
de
r the
open-switch fault
in
S
1
and
S
3
,
which is created
by turnin
g
OFF the gate si
gnals in
a
-p
hase
an
d
b
-
pha
se u
ppe
r
s
w
itch
si
m
u
ltaneou
s
ly
. B
e
fo
re
the fault occurs, it is well ob
s
e
rve
d
i
n
these
figures t
h
at the
entire sy
stem
provides
balanced three-phas
e gri
d
cur
r
ents
, co
nst
a
nt re
gulated
DC
link
v
o
ltage, a
nd
co
nsta
nt g
r
id
out
put
po
we
r exce
pt
fo
r the s
h
ort tr
ansient
peri
ods
. H
o
we
ver
,
w
h
e
n
the
fault is
introduced into t
h
e
syste
m
, phase
cu
rrents a
r
e
distorted as s
h
own i
n
Figu
re
1
0
(a
).
Als
o
, as
can
be
o
b
ser
v
e
d
in Fi
gu
re
11(
a)
, Figur
e
1
2
(
a
)
,
and
Figu
re 13
(
a
)
,
sign
if
icant
distur
ba
nce is intr
od
uce
d
to th
e ove
rall sy
stem
respo
n
se. T
h
e
q
-axis c
u
r
r
e
n
t can
not be c
ont
rolled a
nd t
h
e DC
link
voltage is increased
sh
arp
l
y, wh
ich m
a
y yield
a severe second
ar
y
f
a
u
lt in
th
e
DC lin
k
cap
acitor
.
A
b
i
g
dr
o
p
in
the
gri
d
out
put
p
o
we
r
is o
b
se
rve
d
,
w
h
ich m
eans tha
t
a p
r
o
p
er
p
o
w
er tra
n
sfe
r
ca
n
not
be ac
hie
v
e
d
.
v
dc
v
dc
,
re
f
D
C
Li
n
k
V
o
l
t
age
V
a
r
i
ati
o
n
v
dc
v
dc
,
re
f
P
ou
t
P
o
w
e
r V
a
ri
a
t
io
n
P
ou
t
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN:
2
088
-86
94
I
J
PEDS Vo
l. 6,
No
.
2,
Ju
ne 20
15
:
293
–
3
04
30
2
(a) Without fault-tolera
nt
sc
h
e
m
e
(b
) Wit
h
fault-t
o
lera
nt
schem
e
Fig
u
r
e
10
. Resp
on
ses of
th
r
e
e-
ph
ase cur
r
e
n
t
s un
d
e
r
S
1
an
d
S
3
open-switch fault
On the co
ntra
r
y
, by
using th
e pro
p
o
se
d schem
e
, th
e fault is detected in 0.
1
94m
s and the faulty
switch is
reco
gnize
d in
0
.
0
1
64s
.
Once
the faulty switch
is
identified, t
h
e
c
o
r
r
esp
o
ndi
ng
fa
ulty
phas
e
s are
isolated usi
n
g the TRIAC switches.
T
o
restore the
syste
m
, the TRIA
C switch
e
s
f
o
r
th
e co
rr
esp
ond
ing
red
u
nda
nt
leg are
tur
n
e
d
ON and
t
h
e gate
signals fo
r
the
faulty leg are transferred to
th
e red
u
nda
nt leg.
As
a
result, three-phase grid
current waveform
s, the
d
-a
xis an
d
q
-a
xis cur
r
e
n
t wave
f
o
rm
s, and the DC
link volta
g
e
cont
rol performance
can be
recovered
from
the fault condition as s
hown i
n
Fi
gure
10(b) t
h
rough
Figure
12
(
b
).
T
h
e
grid
o
u
tp
ut p
o
w
er
contin
ues
to
ru
n as
the sam
e
as the
pre-fault situations.
(a) Without fault-tolera
nt
sc
h
e
m
e
(b
) Wit
h
fault-t
o
lera
nt
schem
e
Fig
u
r
e
11
. Resp
on
ses of
d
-a
xi
s an
d
q
-a
xis c
u
rre
nts
un
der
S
1
and
S
3
o
p
e
n
-s
witch
fault
(a) Without fault-tolera
nt
sc
h
e
m
e
(b
) Wit
h
fault-t
o
lera
nt
schem
e
Fig
u
r
e
12
.
Resp
on
ses
of
DC
lin
k
vo
ltag
e
und
er
S
1
and
S
3
o
p
en
-s
witch fau
l
t
i
ag
i
bg
i
cg
Nor
m
a
l
O
p
e
r
at
i
o
n
Fa
u
l
t O
p
e
r
a
t
io
n
i
ag
i
bg
i
cg
N
o
rma
l
Op
erat
i
o
n
T
o
l
e
ra
n
t
Op
erat
i
o
n
F
a
u
l
t
O
ccu
ren
ce
fault_s
t
atus
t
a
t
b
t
c
F
a
u
l
t D
e
te
c
t
i
o
n
T
o
l
e
r
a
n
t
A
p
p
lie
d
i
dg
i
qg
d
an
d
q
-
a
x
i
s
cu
rren
t
f
l
u
c
t
u
a
t
i
o
n
s
i
dg
i
qg
v
dc
v
dc
,
re
f
D
C
L
i
n
k
Vo
l
t
a
g
e
Va
r
i
a
t
i
o
n
v
dc
v
dc
,
re
f
Evaluation Warning : The document was created with Spire.PDF for Python.