Internati
o
nal
Journal of P
o
wer Elect
roni
cs an
d
Drive
S
y
ste
m
(I
JPE
D
S)
Vol
.
7
,
No
. 2,
J
une
2
0
1
6
,
pp
. 53
1~
54
2
I
S
SN
: 208
8-8
6
9
4
5
31
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
An Improved DTFC based Five
Levels - NPC Inverter Fed
Induction Motor for Torq
ue Ripple Minimization
P. Rajas
e
k
a
ran
*
, V.
Jaw
ah
ar Sen
t
hilkum
ar
**
*Department of Electrical
and
Electron
i
cs Eng
i
neering, Jawahar
l
al
Nehru
Technological University
, H
y
der
a
bad
,
Telangana - 500
085, India
**Department
of
Electron
i
cs and Communication Engi
neering, An
na University
, C
h
ennai – 600025
, India
Article Info
A
B
STRAC
T
Article histo
r
y:
Received Sep 30, 2015
Rev
i
sed
Ap
r
19
, 20
16
Accepte
d
May 2, 2016
This pap
e
r pres
ents a five lev
e
l Neut
ral Point
Clamped (NPC) inver
t
er f
e
d
IM (Induction
Motor) drive fo
r variab
le
speed
application. In
general th
e
stator curren
t
is ver
y
high
ly
affected
b
y
the har
m
onic components. It can be
affecting
the tor
que to
produce
high torq
u
e
ripp
le in
IM at maximum to low
s
p
eed reg
i
on. S
i
nce
the d
r
ive
perform
ances
ar
e dep
e
nds
on
m
a
them
atic
al
model contains the par
a
meters v
a
riati
ons, no
ise,
common mode v
o
ltag
e
, f
l
ux
variation and harmonic levels of the
machine.
Torque ripples and voltag
e
saturations
ar
e the most
significant
problem
s in drive applic
ation
.
To
overcome th
is problem the DTF
C
(direc
t torqu
e
and flux
contro
l) techniqu
e
based
fi
ve-level neutral-po
int-clamped (N
P
C
-5L) approach is
us
ed. The
proposed contro
l scheme uses to
stator
current err
o
r as var
i
able. Through the
res
i
s
t
anc
e
es
tim
ated P
I
contro
lle
r rule
s based th
e selection of v
o
ltag
e
space
vector modulation techniqu
e is optim
ized and
motor performance lev
e
l has
been im
proved
.
The
torque
&
s
p
eed ar
e s
u
cc
e
s
s
f
ull
y
control
l
e
d
with l
e
s
s
torque response. The results are compared and
verified with co
nvention
a
l
three phases VSI
under d
i
ffer
e
nt
cont
rol techniqu
e b
y
Matlab/Simulink.
Keyword:
Di
rect
t
o
rq
ue
a
n
d
fl
ux
co
nt
r
o
l
Fi
el
d o
r
i
e
nt
e
d
cont
rol
I
ndu
ctio
n m
o
to
r
Fi
ve l
e
vel
s
N
P
C
Space vector m
odulation
To
rqu
e
ripp
le min
i
mizatio
n
Vol
t
a
ge
s
o
u
r
ce
i
nve
rt
er
Copyright ©
201
6 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
:
P Rajase
ka
ran
Depa
rt
m
e
nt
of
El
ect
ri
cal
and
El
ect
roni
cs
E
n
gi
nee
r
i
n
g,
Jawa
harl
al
Ne
hr
u Tec
h
nol
ogi
cal
Uni
v
ersi
t
y
,
Hy
de
raba
d,
Tel
a
nga
na - 5
0
0
0
8
5
, I
ndi
a.
E-
m
a
i
l: r
a
j
a
sekar
a
nph
d12
3@g
m
ai
l.co
m
1.
INTRODUCTION
The rece
nt
y
ears, i
n
duct
i
on
m
o
t
o
rs has wi
del
y
pre
f
er
red
for m
o
st
i
n
d
u
st
ri
al
l
o
w t
o
hi
gh s
p
ee
d
ap
p
lication
d
u
e to
th
ei
r reliab
ility, afford
ab
le price,
t
h
e
rugg
ed con
s
tructio
n
an
d efficien
cy in
co
m
p
arison
with
DC m
o
tors
which suffer
from
the dra
w
backs
of
the brushes
-
c
o
ll
ector, c
o
rrosi
o
n and
necess
ity of
main
ten
a
n
ce.
Howev
e
r, indu
ctio
n m
o
to
rs are con
s
id
ered
as
no
n
l
i
n
ear, m
u
ltiv
ariab
l
e and
h
i
gh
ly co
up
led
sy
st
em
s [1, 2]
. For t
h
i
s
reas
o
n
, i
n
duct
i
o
n m
o
t
o
rs ha
ve bee
n
use
d
especi
al
l
y
i
n
cl
osed-l
o
op f
o
r vari
a
b
l
e
speed
ap
p
lication
.
Even
th
e ind
u
c
tion
m
o
to
r is
po
ssib
le fo
r
h
i
gh
p
r
ecision
t
o
rque and
sp
eed con
t
ro
l th
rou
g
h
hig
h
l
y
prese
r
ved
co
nt
rol
t
e
c
hni
que
[
3
]
.
Gen
e
rally, th
e
ad
ju
stab
le-sp
e
ed
d
r
iv
e op
eratio
n
sh
ou
ld meet fo
llowing
req
u
i
rem
e
n
t
su
ch
as
h
i
gh
ly
si
nus
oi
dal
o
u
t
p
ut
wa
vef
o
rm
s, whi
c
h ha
s ass
o
ci
at
ed wi
t
h
red
u
ced
v
o
l
t
a
ge/
c
ur
rent
harm
oni
c di
st
ort
i
ons
, l
o
we
r
el
ect
rom
a
gnet
i
c
i
n
t
e
rfere
nce
(EM
I
)
,
l
o
we
r com
m
on-m
ode v
o
l
t
a
ge, l
o
wer s
w
i
t
c
hi
n
g
l
o
sses an
d h
i
ghe
r
efficiencies [5]. Those
requi
r
em
ents are not fully satis
f
i
e
d
i
n
c
o
m
m
o
n
V
S
I
,
C
S
I
t
y
p
e
o
f
i
n
v
e
r
t
e
r
s
.
S
o
t
h
e
m
u
l
tilev
e
l in
v
e
rters are
p
r
eferred
fo
r
h
i
gh p
o
wer
d
r
i
v
e
ap
p
lication
.
C
o
mmercially
t
h
ree
b
a
sic m
u
ltilev
e
l
co
nv
erters are p
r
esen
ted
in
th
e literatu
re as d
i
od
e-
clamp
e
d
co
nv
erters cascad
ed
H-bridg
e
con
v
e
rters and
flying-ca
pacitor c
o
nverte
rs.
Am
ong t
h
e
va
ri
o
u
s M
L
I t
o
p
o
l
o
gi
es, t
h
e
ne
ut
ral
poi
nt
cl
am
ped (N
PC
) t
o
p
o
l
o
gy
i
s
m
o
st
use
d
one
.
Eve
n
i
f
t
h
e cond
uct
i
n
g po
w
e
r swi
t
c
hes and t
h
e dc-l
i
n
k capaci
t
o
rs have t
o
end
u
r
e
onl
y
one-
h
al
f of t
h
e
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-86
94
I
J
PED
S
Vo
l. 7,
No
.
2,
Ju
ne 20
16
:
531
–
5
42
53
2
dc-l
i
n
k v
o
l
t
a
ge
. As a resul
t
,
t
h
e conv
ert
e
r can be deal
wi
t
h
t
h
e do
ubl
e v
o
l
t
a
ge
and
po
wer
v
a
l
u
e
com
p
ared t
o
st
anda
r
d
t
w
o
-
l
e
v
e
l
VSI wi
t
h
t
h
e sam
e
swi
t
c
hi
ng
fre
que
ncy
.
In
gene
ral
t
h
e NPC
t
o
pol
ogy
has
b
een con
s
tru
c
t
e
d
b
y
h
i
g
h
e
r
nu
m
b
er of
p
o
wer switch
e
s
so th
us ad
d
ition
a
l co
n
t
ro
l sch
e
me requ
ired
.
Dc link
neut
ral
p
o
i
n
t
cl
am
pi
ng i
s
nee
d
f
o
r m
a
i
n
t
a
i
n
i
n
g
bal
a
nce
d
vol
t
a
ge
[4
-6]
.
Hi
g
h
n
u
m
b
er
of
fi
ve l
e
vel
NPC
i
n
ve
rt
er
fed
wi
t
h
hi
g
h
per
f
o
r
m
a
nce I
M
dri
v
es w
h
i
c
h i
s
re
q
u
i
r
es
deco
u
p
l
e
d t
o
rq
ue an
d fl
u
x
co
nt
r
o
l
.
DTFC
t
e
chni
que i
s
av
o
i
di
ng t
h
e st
at
o
r
cur
r
e
n
t
deco
upl
i
n
g p
r
obl
e
m
[13]
.
Add
itio
n
a
lly
DTFC
p
r
ov
id
es v
e
ry fast torq
u
e
and
sp
eed resp
on
se
with
ou
t an
y co
m
p
lex
i
n
inn
e
r
cu
rren
t
reg
u
l
a
t
i
on l
o
o
p
. DT
FC
–S
P
W
M
schem
e
has enha
nce
d
t
h
e fu
ndam
e
nt
al
out
put
v
o
l
t
a
ge
s by
ext
e
n
d
t
h
e l
i
n
ear
m
odul
at
i
on ran
g
e.
In t
h
i
s
pa
per
,
st
at
or re
si
st
ance est
i
m
at
i
on base
d DT
FC
by
i
n
c
o
r
p
o
r
a
t
i
ng SP
WM
s
c
hem
e
has
pr
o
pose
d
t
o
us
es st
at
or
cu
rre
nt
er
ro
r a
s
var
i
abl
e
t
h
r
o
ug
h
PI c
o
nt
rol
l
e
r
.
Fi
ve l
e
vel
s
N
P
C
i
n
vert
er
ha
s b
e
e
n
equate
d the
DC link voltage
into inverting AC volta
ge.
Space
vector e
s
tim
a
ted NPC inve
rters
have
been
min
i
mized
th
e
to
rq
u
e
ripp
les
an
d vo
ltag
e
satu
ration
s
. Th
e
vo
ltag
e
b
a
lan
c
i
n
g
cap
a
b
ility is also
im
p
r
o
v
e
d
.
2.
FIVE LEVEL
NP
C I
N
VER
TER
The
fi
v
e
-
l
ev
el
n
e
u
t
r
a
l-
po
in
ted cla
m
p
e
d
(N
PC-
5
L)
topo
logy is sh
own
in
f
i
gu
r
e
(
1
)
.
Each
leg of
th
e
NPC
has c
o
nst
r
uct
e
d by
ei
g
h
t
act
i
v
e swi
t
c
he
s (Q
1,
Q2
, Q
3
,
Q4,
Q
5
, Q
6
,
Q7 a
nd
Q
8
) a
n
d co
n
v
ert
e
r
[7
-
8
]
.
The
swi
t
c
hi
n
g
st
at
es are
gi
ve
n i
n
t
a
bl
e
1.
A
n
i
nve
rt
er
stage connecte
d
t
o
a
n
MV induction m
achine (IM
).
Gene
ral
l
y
a standa
r
d
di
rect
-
o
n
-
l
i
n
e (
DOL
)
m
e
t
hod can b
e
fol
l
o
we
d f
o
r
cont
r
o
l
pu
r
p
o
s
e. Si
nce t
h
e v
a
l
u
e o
f
leakage i
n
duct
a
nce is
x
σ
,
r
a
ng
e o
f
0.18
p
.
u
.
The
NPC
ca
n
be a
b
l
e
t
o
m
i
nim
i
ze t
h
e har
m
oni
c di
st
ort
i
o
n
o
f
t
h
e
st
at
o
r
cu
rre
nt
.
Fu
rt
her t
h
e act
i
v
e
swi
t
c
hes
of t
h
e
con
v
e
r
t
e
r are
ope
rat
e
d at
l
o
w f
r
eq
ue
ncy
.
T
h
e SP
WM
sc
h
e
m
e
has ov
erc
o
m
e
s t
h
e l
i
m
i
tat
i
ons
of
t
h
e m
odul
at
i
o
n i
n
de
x
ran
g
e
of
P
W
M
m
e
tho
d
s.
T
h
e S
P
W
M
c
ont
r
o
l
l
e
r i
s
s
u
i
t
a
bl
e t
o
ac
hi
eve t
h
e
cur
r
ent
harm
oni
cs [
9
-
1
0]
. The
5L
-N
P
C
i
nvert
e
r
de
ri
ved
fr
om
3L-
N
PC
i
n
vert
e
r
.
The T
h
ree
p
h
a
s
e NPC
-
5L
v
o
l
t
a
ge i
s
deri
ved from
phase ca
pacitor
C
ph
feed series connected
ca
pa
citor out
put voltage.
Fi
gu
re
1.
5L
-
N
PC
i
n
vert
er
ci
r
c
ui
t
di
ag
ram
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
PED
S
I
S
SN
:
208
8-8
6
9
4
An
Impr
ove
d
DTFC
base
d F
i
ve Levels - N
P
C In
ve
rter Fe
d Induction M
o
tor f
o
r Tor
que
…
(P Rajasek
a
ran)
53
3
Tabl
e 1. Swi
t
c
hi
n
g
Ta
bl
e
SWITCHING ST
ATES
OUTPU
T VOL
TA
GE
Q1
Q2 Q3 Q4 Q5 Q6 Q7
Q8
1
1 1 1 0 0 0
0
Vdc/2
0
1 1 1 1 0 0
0
Vdc/4
0
0 1 1 1 1 0
0
0
0
0 0 1 1 1 1
0
-
V
dc/4
0
0 0 0 1 1 1
1
-
V
dc/2
Th
e
d
e
sired d
c
lin
k vo
ltag
e
is Vd
c, each
cap
acito
r (C
1
,
C2
, C
3
, C4)
h
a
s b
e
en
sp
lits
v
o
ltag
e
(1
/
4
)
Vd
c. Th
e
d
c
lin
k cap
acitor cu
rren
ts are
flows thro
ugh
th
e activ
e switch
e
s b
y
n
a
m
e
d
as ic1
,
ic2, ic3 and
ic4.
This c
o
nverte
r ac voltages a
nd
curre
nts
of the each pha
s
e are
deri
ved by va
r,
vbr a
nd
vc
r (ia, ib
& ic)
connected to the induction
dri
v
e.
3.
MODEL OF INDUC
TION MOTOR
The t
h
ree
phas
e
i
nduct
i
o
n m
o
t
o
r has c
onst
r
u
c
t
e
d by
n num
ber o
f
st
at
or w
i
ndi
n
g
s t
h
at
ar
e di
spl
ace
d
by
(
3
6
0
˚
/n). It can process
at every 120
˚
.
A
typ
i
cal iso
l
ated
n
e
u
t
ral fi
v
e
-leg
inv
e
rter co
nfig
uratio
n is u
s
ed
t
o
dri
v
e a st
ar
-c
o
nnect
e
d
fi
ve-
p
hase s
q
ui
rrel
-
c
a
ge i
n
d
u
ct
i
o
n
m
o
t
o
r. Si
nce t
h
e c
onsi
d
ere
d
squi
rrel
-
ca
ge
s
t
at
or a
nd
rot
o
r c
a
n
be
re
prese
n
t
e
d
by
a
sh
ort
-
ci
rc
ui
t
e
d
t
h
ree
-
phase
roto
r
wind
ing
i
n
in
du
ctio
n m
o
to
r [11
-
12
]. Th
e
state
eq
u
a
tion
o
f
indu
ctio
n m
o
to
r written
b
y
stator
referen
c
e frame (
α
,
β
)
c
o
o
r
di
nat
e
s,
ca
n be g
i
ven fol
l
o
ws su
ch
as
st
at
or a
n
d
r
o
t
o
r
l
a
m
i
nat
e
d m
odel
s
h
o
w
n i
n
fi
gu
re
2.
Fig
u
re
2
.
Stator an
d ro
tor lamin
a
tio
n
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.
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42
53
4
U
B
X
A
X
.
.
(1
)
X
C
Y
.
(2
)
Whe
r
e
A, B and C a
r
e the
evolution
of the
co
n
t
ro
l and
ob
serv
atio
n m
a
trices
resp
ectiv
ely.
t
r
r
i
s
i
s
X
;
V
s
V
s
U
I
s
I
s
Y
(3
)
T
r
T
r
M
T
r
T
r
M
MT
R
M
T
r
T
S
M
MT
R
T
r
T
S
A
1
0
1
0
1
1
1
1
0
1
1
0
1
1
(4
)
Wi
t
h
,
ω
R
o
tor
spee
d a
n
d the
machine’s
pa
ra
meters
ar
e Rs,
Rr
,
M,
Ls, Lr an
d p ar
e g
i
v
e
n
b
y
,
R
s
Ls
T
s
Rr
Lr
T
r
,
(5
)
The m
echani
c
a
l
equat
i
o
n i
s
de
ri
ve
d i
n
eq
uat
i
o
n
(
7
)
.
.
f
c
r
C
e
dt
d
J
(6
)
J is the
ine
r
tia coefficient a
n
d usi
n
g the
Laplace trans
f
orm
,
the e
q
uation (8) shows t
h
at t
h
e
relation bet
w
ee
n
the stator
flux
and the
ro
tor flux re
pres
ents
a low
pass
wi
t
h
t
i
m
e const
a
n
t
.
T
h
e electromagnetic torque
can
be e
x
press
e
d as
,
s
T
r
s
L
S
M
r
1
(7
)
i
s
sa
i
s
sa
p
C
e
2
2
3
(8
)
4.
IMP
R
O
V
ED
DTFC
S
C
HE
ME FO
R
IN
D
UCTI
O
N
M
O
TOR
Th
e
DTFC m
e
th
od
is pro
p
o
s
ed
fo
r ind
u
c
tion
m
o
to
r con
t
ro
llin
g
pu
rp
ose sin
ce it can
be p
r
ov
id
e a
very accurate and
fast dec
o
upled c
ont
rol of the stator flux linka
ge an
d
the electrom
a
gnetic torque
without
h
e
lp
o
f
an
y curren
t
regu
lators [14
]
. Th
e
DTFC with
st
ato
r
resistan
ce esti
m
a
to
r is sh
own
in
figu
re
3. Th
is
strateg
y
of con
t
ro
l co
m
p
etiti
v
e
co
m
p
are to th
e
ro
t
o
r
flux orien
t
ed m
e
th
o
d
[15
]
. Th
e l
o
oku
p tab
l
e can
b
e
deri
ved
by
bas
e
d
on
t
h
e
sel
ect
ed t
o
rq
ue e
r
r
o
r si
g
n
al
i
n
i
n
pu
t
com
p
arat
or
si
de.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
PED
S
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:
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8-8
6
9
4
An
Impr
ove
d
DTFC
base
d F
i
ve Levels - N
P
C In
ve
rter Fe
d Induction M
o
tor f
o
r Tor
que
…
(P Rajasek
a
ran)
53
5
Fi
gu
re
3.
Im
pr
ove
d
DT
FC
bl
ock
di
a
g
ram
w
i
t
h
st
at
or
resi
st
ance est
i
m
at
or
Thi
s
c
ont
r
o
l
t
e
chni
que
i
s
f
u
l
l
y
depe
n
d
s
up
o
n
t
h
e c
o
nve
rt
e
r
act
i
v
e s
w
i
t
c
h
i
ng
o
p
erat
i
n
g l
e
vel
.
T
h
e
sel
ect
i
on o
f
co
nt
r
o
l
l
i
ng pa
rt
s
are ge
neral
l
y
b
a
sed o
n
t
h
e
us
e of
hy
st
eresi
s
reg
u
l
a
t
o
rs a
n
d
SP
W
M
t
ech
ni
que
,
am
pl
i
t
ude
of t
h
e st
at
o
r
fl
u
x
and
el
ect
rom
a
gnet
i
c
t
o
r
que
c
a
n
be c
ont
rol
l
e
d
by
t
h
i
s
m
odi
fi
ed st
at
e
of
s
y
st
em
.
The st
at
or
fl
u
x
i
s
deri
ve
d i
n
equat
i
o
n (
1
)
,
ca
n be ap
p
r
o
x
i
m
at
el
y
sim
p
l
i
f
i
e
d i
n
eq
uat
i
o
n (
2
) t
h
e st
at
o
r
re
si
st
ance
i
s
i
g
n
o
re
d si
nc
e
i
t
can be deri
ved
i
n
sh
ort
pe
ri
o
d
.
dt
t
I
S
R
S
V
S
S
s
0
(9
)
dt
t
V
S
so
s
0
(1
0)
During
sam
p
li
n
g
tim
e
Te p
e
riod
th
e v
ector ten
s
io
n
ap
p
lied
to
th
e m
ach
i
n
e rem
a
in
s co
n
s
tan
t
, an
d
th
u
s
on
e can
be written
as,
t
T
e
V
s
k
s
k
s
0
.
)
(
)
1
(
(1
1)
There
f
ore t
o
i
n
crease the stator fl
ux,
we ca
n
apply a
v
ect
o
r
o
f
ten
s
ion
t
h
at
is co
-lin
ear i
n
i
t
s d
i
rection
an
d v
i
ce-
v
er
sa. Figu
r
e
4 sh
ows th
e
st
ator flux increm
ent and s
p
atial pos
i
t
i
ons
of
t
h
e v
o
l
t
a
ge vect
o
r
s ke
epi
n
g
t
h
e fl
ux
i
n
si
d
e
of
t
h
e st
ri
p
hy
s
t
eresi
s
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
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:
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94
I
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S
Vo
l. 7,
No
.
2,
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ne 20
16
:
531
–
5
42
53
6
Fi
gu
re
4.
St
at
o
r
fl
ux
i
n
c
r
em
ent
an
d
spat
i
a
l
p
o
si
t
i
ons
o
f
t
h
e
vol
t
a
ge
ve
ct
or
s
Fi
gu
re 5.
C
o
m
p
o
n
e
n
t
s
of
t
h
e err
o
r
of
flux at
the tim
e
of t
h
e
app
lication
o
f
t
h
e v
ector V2
vo
ltag
e
If t
h
e e
r
r
o
r o
f
f
l
ux i
s
est
i
m
at
e
on t
h
e di
rect
i
o
n o
f
st
at
o
r
fl
u
x
and
o
n
a pe
r
p
endi
c
u
l
a
r
di
rec
t
i
on s
h
o
w
n
i
n
fi
gu
re
5,
o
n
e
p
u
t
s
i
n
evi
d
e
n
ce t
h
e
c
o
m
ponent
s
act
i
n
g
o
n
t
h
e t
o
r
que
an
d
o
n
t
h
e
fl
ux
. T
h
e c
o
m
pone
nt
sf
∆Φ
g
i
v
e
s th
e electro
m
a
g
n
e
tic To
rq
u
e
o
f
th
e
Indu
ctio
n
m
o
to
r
wh
ile th
e co
m
p
on
en
t sf
∆Φ
m
odi
fi
es t
h
e
m
a
gni
t
u
de
of
st
at
or
fl
u
x
.
The t
o
r
que
i
s
p
r
o
d
u
ced
by
t
h
e
i
n
d
u
ct
i
o
n m
o
t
o
r
can
be
ex
pre
ssed as
e
quat
i
o
n:
sin
2
3
r
s
r
L
s
L
M
p
Ce
(1
2)
The
t
o
rq
ue
de
pen
d
s
on
t
h
e
a
m
pli
t
ude
of
t
w
o
vect
ors
s
u
ch
as
st
at
or
fl
u
x
Φ
, rot
o
r
fl
ux
Φ
and
th
e
i
r
relativ
e po
sitio
n
γ
.
If
one suc
ceeds in
perfe
c
tly controlling the fl
ux
Φ
(st
a
rt
i
ng
wi
t
h
Vs
)
i
n
m
odul
e a
n
d i
n
p
o
s
ition
,
on
e can
sub
s
equ
e
n
tly co
n
t
ro
l t
h
e am
p
l
itu
d
e
an
d th
e
relativ
e po
si
tio
n
o
f
Φ
.
5.
PI RES
I
STA
NCE E
S
TIM
A
TOR
S
F
O
R
DTFC
D
R
I
V
E
B
a
sed o
n
t
h
e
rel
a
t
i
ons
hi
p
be
t
w
een c
h
an
ge
of
resi
st
ance
and c
h
a
n
g
e
of c
u
r
r
e
n
t
,
a
PI re
si
st
ance
est
i
m
a
t
o
r can
b
e
co
nst
r
uct
e
d i
n
e
quat
i
o
n
(
1
0
)
as s
h
o
w
n i
n
Fi
gu
re.
6
.
s
K
I
K
P
i
R
S
(1
3)
Whe
r
e
and
are
th
e pro
p
o
r
tion
a
l an
d in
tegral
gain
s
o
f
t
h
e PI esti
m
a
to
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
An
Impr
ove
d
DTFC
base
d F
i
ve Levels - N
P
C In
ve
rter Fe
d Induction M
o
tor f
o
r Tor
que
…
(P Rajasek
a
ran)
53
7
Fi
gu
re
6.
B
l
oc
k
di
ag
ram
of P
I
re
si
st
ance est
i
m
a
t
o
r
Whe
n
the
stator
resistance c
h
anges
,
the c
o
m
p
ensa
t
i
on p
r
ocess ca
n be
depi
ct
ed a
s
t
h
e chan
ge
of
stato
r
resistan
ce will ch
an
g
e
th
e am
p
l
i
t
u
d
e
of th
e cu
rren
t vecto
r
[1
6
]
. Th
e error of th
e am
p
l
itu
d
e
o
f
curren
t
v
ector and
t
h
at o
f
t
h
e
referen
c
e cu
rren
t v
ect
or will b
e
u
s
ed
t
o
co
m
p
en
sate th
e ch
ang
e
in stato
r
resistan
ce
u
n
til
the error in c
u
rrent
becom
e
s
zero. There
f
ore, the steady st
ate error
of this resistan
ce estimator is zero a
n
d t
h
e
refe
rence
cu
rre
nt
vect
or
can
b
e
de
ri
ve
d f
r
o
m
the re
fere
nce t
o
r
q
ue a
n
d
re
fer
e
nce
flu
x
as,
i
s
i
s
i
s
*
2
*
2
*
(1
4)
sref
C
eref
p
i
s
2
3
2
*
(1
5)
∗
i
s
deri
ved
f
r
om
t
h
e
fol
l
o
wi
n
g
equat
i
o
n,
w
h
i
c
h i
s
e
q
uat
e
d i
n
t
o
ze
ro
ex
pre
s
s
e
d as
,
0
2
*
2
*
.
1
*
2
L
S
sref
i
sa
L
s
i
sa
sref
i
sa
L
S
(1
6)
Th
e
filter ti
m
e
con
s
tan
t
sho
u
ld
b
e
sm
all co
m
p
ared
to
t
h
e
stato
r
resistan
ce esti
m
a
to
r time co
n
s
tan
t
because to ove
r
com
e
its effec
t
on the stat
or
resist
ance a
d
a
p
tation. T
h
e
final estim
a
ted stator
resistance
is
ag
ain
p
a
ssed
t
h
rou
g
h
a low
p
a
ss
filter to
hav
e
a sm
o
o
t
h
v
a
riation
of st
ato
r
resistan
ce
v
a
lu
e. Th
is up
d
a
ted
stator resistanc
e
can be
used
d
i
rectly in
th
e co
n
t
ro
ller.
A P
I
co
nt
r
o
l
l
e
r i
s
use
d
t
o
re
gul
at
e t
h
e out
put
vo
l
t
a
ge t
o
achieve t
h
e re
puted stator c
u
rrent and
also
torqu
e
.
Th
e
PI co
n
t
ro
ller lim
i
t
s th
e tran
sien
t respo
n
s
e
of th
e
to
rq
ue
cont
rol
l
e
r.
DT
FC
uses an i
n
d
u
ct
i
on m
o
t
o
r
m
odel
t
o
achi
e
ve a desi
re
d o
u
t
put
t
o
r
q
ue by
usi
n
g st
at
or
res
i
st
ance
esti
m
a
to
r.
An
indu
ctio
n
m
o
to
r
m
o
d
e
l i
s
u
s
ed
to
p
r
edict th
e v
o
ltag
e
requ
ired
to
d
r
iv
e th
e flux
and
to
rqu
e
to
dem
a
nded
val
u
es wi
t
h
i
n
a
fi
x
e
d t
i
m
e
peri
o
d
.
Thi
s
cal
cul
a
t
e
d v
o
l
t
a
ge a
n
d
cur
r
ent
a
r
e sy
n
t
hesi
zed
usi
n
g
space
vect
o
r
m
odul
at
i
on
(S
VM
).
6.
RESULT A
N
D
AN
ALY
S
IS
Thi
s
sect
i
on e
v
al
uat
e
s t
h
e per
f
o
r
m
a
nce of t
h
e di
rect
t
o
r
que
fl
u
x
co
nt
r
o
l
st
rat
e
gy
(DT
F
C
)
base
d NP
C
fi
ve l
e
vel
i
nve
rt
er f
o
r i
n
d
u
ct
i
on m
o
t
o
r o
p
e
r
at
i
on. T
h
e res
u
lts are veri
fied and com
p
are
d
with conve
n
tional
VSI
u
n
d
er
di
ffe
rent
c
ont
rol
t
echni
q
u
es i
n
M
A
T
L
AB
/SIM
UL
IN
K. In
d
u
ction
m
o
tor
s
p
ecificatio
ns o
f
pr
o
pose
d
t
o
pol
ogy
are l
i
s
t
e
d i
n
t
a
bl
e 1. I
f
t
h
e l
e
vel
of i
nve
rt
er i
n
crease
d
m
eans, cur
r
e
n
t
harm
oni
cs co
ul
d be
red
u
ce
d. T
h
e c
o
n
v
e
n
t
i
onal
V
S
I ba
sed i
n
d
u
c
t
i
on m
o
t
o
r has
been i
m
pl
em
ent
e
d
by
usi
ng
f
i
el
d ori
e
nt
ed c
ont
rol
and Di
rect Torque
control.
Th
e
d
y
n
a
m
i
c p
e
rfo
r
m
a
n
ce of
th
e IM
d
r
i
v
e syste
m
fo
r
v
a
ri
o
u
s
op
eratin
g
co
nd
itio
ns h
a
s
b
een stud
ied
wi
t
h
t
h
e uses
of D
T
FC
co
nt
rol
l
e
r. T
h
e p
r
o
pos
ed N
P
C
i
n
t
e
rface
d IM
dri
v
e arra
n
g
em
ent
i
s
show
n i
n
f
i
g:
7.
th
ree
ph
ase
NPC inv
e
rter stato
r
vo
ltag
e
s are illu
strated
i
n
fig
:
8
.
DTFC
b
a
sed
indu
ction
m
o
to
r
h
a
s ach
i
ev
es
sup
e
ri
o
r
c
ont
r
o
l
l
e
d co
nst
a
nt
spee
d, re
d
u
ced
ri
ppl
e c
o
nt
ent
i
n
st
at
or c
u
r
r
e
nt
an
d m
i
nimi
zed t
o
r
q
ue ri
p
p
l
e
s
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-86
94
I
J
PED
S
Vo
l. 7,
No
.
2,
Ju
ne 20
16
:
531
–
5
42
53
8
Th
is is illu
strated
in
fig
:
9
&
1
0
resp
ectiv
el
y. Fig
:
1
1
and
1
2
sh
ows th
e stato
r
cu
rren
t an
d
torqu
e
wavefor
m
and
di
ffe
rence
bet
w
ee
n t
h
e
si
gnal
s
o
f
t
o
r
que
.
Th
e D
i
ff
er
en
t k
i
nd
o
f
h
a
r
m
o
n
i
c
ord
e
r
of
the
to
rqu
e
sign
al
s
ar
e show
n
in
f
i
gu
r
e
13
. Th
e p
e
rf
or
m
a
n
ce
of c
o
n
v
e
n
t
i
ona
l
VSI ba
sed i
n
duct
i
o
n m
o
t
o
r
un
de
r DTC
an
d FOC
c
ont
rol
t
echni
q
u
es are
sho
w
n i
n
fi
g
u
r
es
1
4
& 15
. Fi
g
u
r
e
16 s
h
ows t
h
e THD i
n
p
h
ase
curr
ent
f
o
r el
im
i
n
at
i
on of
h
a
rm
oni
cs. The
Pro
p
o
sed t
o
p
o
l
o
gy
Sim
u
l
a
t
i
on res
u
l
t
s
ha
ve s
h
ow
s t
h
e sm
oot
h
a
n
d
i
m
prove
d
p
e
rf
orm
a
nce o
f
t
h
e m
o
t
o
r c
o
m
p
are
d
t
o
C
o
n
v
e
n
t
i
onal
VSI
base
d st
r
u
ct
ure. T
h
e t
o
t
a
l
harm
oni
c di
st
ort
i
o
n ca
n be
o
b
t
a
i
n
ed
suc
h
a
s
22
.
91%
f
o
r F
O
C
co
nt
r
o
l
sc
hem
e
and
7
8
.
87%
f
o
r
DTC
co
nt
r
o
l
schem
e
. Th
e cur
r
ent
ha
rm
oni
c
wo
ul
d
be
red
u
ced as
8.
29
% by
usi
n
g
DTFC
b
a
sed
f
i
v
e
levels N
P
C
o
f
inductio
n
m
o
to
r
.
Figu
re
7.
Sim
u
lation circ
uit di
agram
fo
r
NPC
-IM
Fi
gu
re
8.
Fi
ve
Level
-
NPC
i
n
v
e
rt
er
vol
t
a
ge
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
PED
S
I
S
SN
:
208
8-8
6
9
4
An
Impr
ove
d
DTFC
base
d F
i
ve Levels - N
P
C In
ve
rter Fe
d Induction M
o
tor f
o
r Tor
que
…
(P Rajasek
a
ran)
53
9
Fi
gu
re 9.
IM
d
r
i
v
e pe
rform
ance at starting time
Fi
gu
re 1
0
. IM
dri
v
e per
f
o
r
m
a
nce
at
ru
n
n
i
n
g t
i
m
e
Fi
gu
re
1
1
.
St
at
or
cu
rre
nt
a
n
d
t
o
r
q
ue
wave
fo
r
m
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-86
94
I
J
PED
S
Vo
l. 7,
No
.
2,
Ju
ne 20
16
:
531
–
5
42
54
0
Fi
gu
re
1
2
. E
r
r
o
r Si
gnal
of
T
o
r
que
Fi
gu
re
1
3
. T
o
r
que
wa
ve
fo
rm
s f
o
r
di
f
f
ere
n
t
h
a
rm
oni
c or
de
r
Fi
gu
re
1
4
.
DT
C
base
d i
n
d
u
ct
i
on m
o
t
o
r
pe
rf
orm
a
nce
Evaluation Warning : The document was created with Spire.PDF for Python.