TELKOM
NIKA Indonesia
n
Journal of
Electrical En
gineering
Vol. 13, No. 1, Janua
ry 201
5, pp. 65 ~ 7
5
DOI: 10.115
9
1
/telkomni
ka.
v
13i1.690
4
65
Re
cei
v
ed O
c
t
ober 2
4
, 201
4; Revi
se
d Novem
b
e
r
25, 2014; Accept
ed De
cem
b
e
r
15, 2014
A Review Paper on Torque Ripple Reduction in
Brushless DC Motor Drives with Different Multilevel
Inverter Topology
S. Arunkum
ar*, S. Thangav
e
l
Dep
a
rtment of Po
w
e
r El
ectron
ics and Dr
ives,
K.S.Rangas
a
m
y
Co
lle
ge of
T
e
chnolog
y (A
utonom
ous)
K.S.R Kalvi Na
gar, T
i
rucheng
ode, Nam
a
kkal
,
T
a
milnad
u, India, Ph./F
ax: 0
428
8 27
474
1-4
4
/042
88 2
7
4
8
6
0
*Corres
p
o
ndi
n
g
author, e-ma
i
l
: akumar5
989
@gmai
l
.com*
A
b
st
r
a
ct
T
h
is pa
per
pr
esents th
e ov
erall
revi
ew
of torqu
e
rip
p
l
e
reducti
on tec
h
niq
ues
in
brus
hless
D
C
motors (B
LDC)
and d
i
fferent
mu
ltilev
e
l i
n
ver
t
er topol
ogi
es
suitab
le for BL
DC motor driv
es. BLDC
mot
o
rs
are w
i
dely us
ed for ho
useh
old a
ppl
icati
o
n
s
due to its
features of h
i
g
h
reli
abi
lity, simp
le fra
m
e, h
i
g
h
efficiency, fast
dynamic re
s
p
o
n
se, co
mpact s
i
z
e
and
l
o
w
ma
inten
anc
e, etc.. T
he sw
itches
are
electro
n
ic
al
ly
co
mmu
ta
te
d ba
se
d o
n
th
e
i
n
fo
rm
a
t
io
n
o
f
roto
r p
o
s
i
t
io
n d
e
t
e
c
ti
o
n
.
The
posi
t
i
o
n
o
f
th
e roto
r i
s
de
te
rm
i
ned
w
i
th the h
e
l
p
of the s
ens
or
or se
nsorl
e
ss
techni
qu
es
. H
ence
it is
a
n
electro
n
ically c
o
mmutated
motor.
Becaus
e of
thi
s
co
mmutati
on,
the ri
pp
les are
ge
nerate
d
in
t
he electro
m
ag
netic tor
que
a
n
d
the
pow
er f
a
ctor
of AC mai
n
s
gets affected.
So, in or
der t
o
i
m
pr
ove
the
perfor
m
a
n
ce
of these
mot
o
rs the rip
p
le
in
th
e
electro
m
agn
eti
c
torque
cou
l
d
be re
duc
ed
an
d the
pow
er
fa
ctor of the A
C
ma
ins s
h
o
u
ld
be i
n
cre
a
sed.
A
n
enor
mous revi
ew
of different torque ri
ppl
e re
ductio
n
tech
n
i
q
ues an
d differe
nt multi
l
ev
el in
verter topol
ogi
e
s
suitab
le for torque ri
ppl
e min
i
mi
z
a
t
i
o
n
and
p
o
w
e
r qual
it
y impr
ove
m
ent w
i
th different co
nverter topo
lo
g
i
es
are disc
ussed
Ke
y
w
ords
:
brush
l
ess dir
e
ct current mot
o
r (BLDC), mult
ilev
e
l i
n
vert
er (MLI), back EMF
,
pow
er
factor
corrected (PF
C
), pow
er quality
,
discontin
uo
us
inductor curr
e
n
t mo
de (DICM
)
, bridge l
e
ss (BL)
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
Hou
s
e
hold a
pplian
c
e
s
li
ke
wa
shin
g
m
a
chin
es, roo
m
air con
d
itione
rs, refrig
erato
r
s,
fan
s
,
water
pump
s
,
vacuum
clea
ner a
nd free
zer are to
be
expecte
d one
of the fastest growi
ng en
d
prod
uct
s
in
the ma
rket ov
er the
next fe
w yea
r
s
[1-4]. Conve
n
tion
ally DC moto
rs li
ke
shunt
and
seri
es moto
rs are widely u
s
ed in the
s
e applia
nc
e
s
a
nd due to so
me dra
w
ba
cks like freq
ue
nt
maintena
nce and spa
r
king
in
brus
he
s, con
s
um
ers a
r
e switchi
ng o
v
er to si
ngle
pha
se in
du
ction
motors. Squi
rrel
ca
ge i
ndu
ction
motors
are
po
pula
r
due to
its ru
gged
con
s
tru
c
tion. But th
e
s
e
motors offe
rs poo
r
po
wer
factor an
d eff
i
cien
cy
comp
ared
to
syn
c
hron
ou
s m
o
tor. O
n
the
ot
her
hand the sy
nch
r
on
ou
s motors a
r
e affected with
speed limitatio
ns, noise problem an
d EMI.
These moto
rs operate at co
nstant spee
d dire
ctly
from AC
main
s wit
h
low effici
en
cy. No
w-a
-
da
ys
con
s
um
ers a
r
e dema
nd for high efficie
n
c
y, low
co
st, low a
c
o
u
sti
c
n
o
ise
and b
e
tter pe
rforman
c
e
motors for th
ese
applia
nces. The
co
nventional te
ch
nologi
es d
o
e
s
n’t meet the
s
e d
e
man
d
s.
The
use
of sp
eci
a
l ele
c
trical
machi
n
e
s
like br
u
s
hl
ess
DC m
o
tors (BLDC), pe
rmanent m
a
g
net
synchro
nou
s
motors (PMS
M) in these a
pplian
c
e
s
ar
e
a better choi
ce du
e to the feature
s
of high
reliability, hig
h
efficiency, low mainte
n
ance,
high flux density per unit volu
me, high po
wer
den
sity due t
o
ab
sen
c
e
of
field win
d
ing
and lo
w el
ect
r
oma
gneti
c
in
terfere
n
ce p
r
oblem [5
-6].
The
spe
ed
adju
s
ti
ng p
e
rfo
r
man
c
e
and
po
we
r den
sity of BL
DC moto
r i
s
high
com
p
a
r
e
d
to PMSM.
So
BLDC moto
r i
s
p
r
efe
r
abl
e i
n
num
erou
s
applia
nce
s
.
T
he BL
DC mot
o
rs a
r
e
also
use
d
in
ro
boti
cs,
medical equi
pment, pre
c
i
s
e motion
co
ntrol sy
st
ems, industrial to
ols, heatin
g and ventilatio
n
sy
st
em
s.
Typically a BLDC m
o
tor is an elect
r
onically com
m
utated mot
o
r. It has three
ph
ase
distrib
u
ted wi
nding on
the
stator, whi
c
h is
ma
de
u
p
o
f
stacked
ste
e
l laminatio
n
and p
e
rm
ane
nt
magnet
on
ro
tor. Depen
din
g
up
on th
e a
pplication
req
u
irem
ents the
pe
rman
ent
magnet
s
on
rotor
is either in
surface mou
n
ted type or b
u
ried ty
pe. As the name i
ndicates it ha
s no brushe
s fo
r
comm
utation.
The BLDC
motor is po
wered
with
the help of VSI
or CSI. Base
d on rotor p
o
s
ition
obtaine
d by rotor p
o
sitio
n
sen
s
o
r
s like
hall sen
s
ors,
re
solvers
or optic
al
en
co
ders, the p
o
w
er
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 : 65 – 7
5
66
electroni
c swi
t
che
s
are
co
mmutated. T
he sh
ape of
the gen
erate
d
back EMF in these moto
rs are
depe
nd
s on
stator
co
nst
r
uction. In
BL
DC moto
rs, t
he g
ene
rated
ba
ck EMF i
s
in
trap
ezoi
dal
sha
pe a
nd in
PMSM the ge
nerate
d
ba
ck
EMF is in
sin
u
soi
dal
wave
sha
pe. Depe
nding
upon th
e
rotor
po
sition
, the stator
windi
ng
s are
energiz
ed b
y
rectan
gula
r
curre
n
t wav
e
form
s which
is
displ
a
ced wit
h
120
0
[7].
2. State o
f
th
e Art on To
r
que Ripple Reduc
tion Te
chniques
Due
to en
ormous ap
plications of BL
DC mo
to
rs
i
n
indu
stri
es as well as
h
ousehol
d
appli
c
ation
s
,
the pe
rforma
nce
of th
ese
motors a
r
e
consi
dered to
be q
u
ite
signi
ficant. Norm
a
lly
the gen
erate
d
ba
ck EMF
waveform is
not ideal
i
n
t
hese moto
rs
becau
se of it
s ma
nufa
c
turi
n
g
limitation and
desig
n co
nsi
deratio
n of magneti
c
ma
terials. The ba
ck EMF wavef
o
rm is d
epa
rted
from its o
r
igin
al shap
e. As
said
ea
rlier,
the
BL
DC mot
o
r i
s
a
n
el
ect
r
oni
cally
com
m
utated m
o
tor,
due to
com
m
utation of
power el
ect
r
onic
swit
ch
e
s
the g
ene
rated ele
c
tro
m
agneti
c
torque
contai
ning ri
p
p
le in its wav
e
form [8]. Thes
e torque ri
pple produ
ce
s noi
se whi
c
h degrade
s the
perfo
rman
ce of
the
motor and compli
ca
tes
the sp
e
e
d
-control cha
r
acte
ri
stics e
s
pe
cially at l
o
w
spe
ed. So commutation t
o
rqu
e
rip
p
le,
torque ri
ppl
e prod
uced
by diode fre
e
wh
eeling in
an
inactive ph
ase are the research hot
spot
in rece
nt years [9].
The pra
c
tical
BLDC motor setup and trape
zoid
al ba
ck EMF waveform
s are shown in
Figure 1
and
Figu
re 2. T
h
e squa
re
wa
ve output of
the VSI is fe
d to the
stat
or
windi
ng of
the
motor. Ba
se
d upo
n the
roto
r po
siti
on the
po
wer el
ect
r
oni
c switch
es i
n
the inve
rter are
comm
utated.
Figure 1. BLDC Moto
r Set
u
p
Figure 2. Tra
pezoidal ba
ck EMF wavefo
rm
Conve
n
tional
control tech
nique
s en
erg
i
ze the
stator windin
g
s
by in
jecting th
e
similar
recta
ngul
ar p
hase cu
rrent
comma
nd without the
kn
owle
dge of n
on-lin
ea
rity in the back EMF
waveform whi
c
h ori
g
inate
s
more am
ount
of ri
pple in the gene
rated
electroma
gne
tic torque.
Cal
s
on et al.
analyzed that
the rippl
e in t
he gen
erated
torque
due t
o
pha
se
com
m
utation
is relate
d to the ene
rgi
z
ing
phase
cu
rre
nt and varies with spee
d. To minimize the torqu
e
rip
p
le
in BLDC m
o
tor two level
s
of the
control
schem
e
i
s
p
r
opo
sed fo
r
st
ator
cu
rre
nt. The first met
hod
employs the
positio
n sen
s
or to determi
ne the pha
se
seq
uen
ce of the re
ctang
ula
r
cu
rre
nt sign
als
and the mo
ment of current comm
uta
t
ion from
on
e pha
se to anothe
r pha
se and the ot
her
method controls the en
ergi
zing
curre
n
t amplit
ude by PWM switchin
g of the inverter [10].
Chu
ang
et al
. discu
s
sed
different P
W
M techniqu
e
s
suitabl
e fo
r co
mmutatio
n
torque
ripple
re
du
ction in BL
DC
motor d
r
ive a
nd p
r
op
osed
that PWM_
O
N
meth
od i
s
t
he be
st
choi
ce for
BLDC m
o
tors. But in
this discussio
n
the BLDC m
o
tor i
s
assum
ed wi
th ideal back
EMF waveform
and the no
n-li
nearity is n
o
t con
s
id
ere
d
[11]. Zhang et al. analyze
commutation t
o
rqu
e
rip
p
le
and
prop
osed th
a
t
the rippl
e in
the ele
c
tro
m
agneti
c
to
rqu
e
is mi
nimi
ze
d by re
gulati
ng the
DC li
nk
voltage
with t
he h
e
lp
of b
u
c
k conve
r
ter
as f
r
ont
end
conve
r
ter of t
he VSI. With
the hel
p of
b
u
ck
conve
r
ter, th
e sup
p
ly voltage is
step d
o
wn a
nd
fed t
o
the VSI whi
c
h results in
minimum am
ount
of rip
p
le i
n
th
e loa
d
to
rqu
e
.
PWM_
ON switchi
ng
pattern
is
a
bette
r
choi
ce
for
commutation
of
VSI. The propo
sed
meth
od effe
ctively red
u
ced t
h
e
torqu
e
spi
k
es
and
dip
s
, but it do
esn’t
con
s
id
ere
d
th
e ban
dwi
d
th
of the bu
ck
converte
r,
so i
t
is suita
b
le
at the low
sp
eed rang
e on
ly
[12].
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
A Revie
w
Pa
per on T
o
rq
u
e
Rippl
e Red
u
ction in
Brushless DC Mot
o
r Drives… (S.Arunkum
ar)
67
Che
n
et al.
d
e
scrib
e
s that
the bu
ck con
v
erte
r i
s
suita
b
le for low po
wer ap
plications only
and it is repl
ace
d
with Su
perlift luo co
nverter
top
o
l
ogy for DC li
nk voltage re
gulation
which is
suitabl
e for hi
gh p
o
wer
app
lication
s
to
o.
But the
ci
rcuit
co
nfiguration
is
more
com
p
lex compa
r
e
d
to buck
conv
erter
and
give better p
e
rfo
r
man
c
e
und
e
r
high
-spe
ed
operation o
n
l
y
. To overco
me
these
drawbacks, the luo conv
erter is replaced
with SEPIC c
onverter. B
u
t it needs t
h
ree
addition
al switch
es an
d
their corre
s
po
ndin
g
ind
u
ctan
ce, cap
a
citan
c
e an
d
diodes, wh
ich
increa
se the
co
st and swit
chin
g losse
s
[13].
Another
majo
r re
ason fo
r
torque
rip
p
le
in BLDC m
o
tor i
s
du
e t
o
diod
e fre
e
w
he
eling
curre
n
t in inactive pha
se. This wa
s analyzed
with differen
t
modulation
techniqu
es for
comm
utation
torque
ri
pple
and
while
co
nsid
erin
g the
po
wer di
ssi
p
a
tion PWM_
ON_P
WM i
s
the
better m
odul
ation meth
o
d
[14-15].
While
con
s
id
ering
the
no
n-line
a
rity in
the b
a
ck
EMF
waveform, there a
r
e o
n
ly two ki
nd
s of resolvent
s to
minimize th
e com
m
utati
on torq
ue
rip
p
le.
One m
e
thod
regul
ate the
armatu
re
cu
rrent of the
mo
tor by empl
oying direct to
rque
cont
rol [
16-
19] and the o
t
her on
e is to
apply the m
o
tor’s
ba
ck E
M
F as a
cont
rol pa
ram
e
ter to regulate t
he
c
u
rrent. In direc
t
torque
control, the back
EMF esti
mation
a
nd p
hase curre
n
t
mea
s
u
r
eme
n
ts
increa
se the
compl
e
xity of
the circuit [20
-
23].
Fang
et al.
pro
p
o
s
ed
novel a
u
tom
a
tic
cu
rre
nt
control m
e
th
od for torqu
e
rip
p
le
minimization i
n
gyro/BL
DC
motor d
r
ive. The no
n-
li
ne
arity in the ba
ck EM
F wa
s
con
s
id
ere
d
a
s
a
control functi
on for cu
rre
n
t control a
nd PWM_
O
N
_PWM mo
dulation met
hod is u
s
ed
for
comm
utation
whi
c
h minimi
ze
s the torq
u
e
rippl
e
due t
o
the diod
e freewheelin
g i
n
inactive p
h
ase
[24]. Now-a
-
days
several
artificial int
e
lligen
ce
b
a
s
ed co
ntrol algorith
m
s a
r
e
p
r
op
osed
to
minimize the
torque
rip
p
le
with no
n-lin
e
a
rity in the b
a
ck EMF
wa
veform. In ha
rmoni
c inj
e
cti
on
method the
ripple in th
e
gene
rated
el
ectro
m
ag
neti
c
torque
due
to back EM
F harmoni
cs are
eliminated. B
u
t this metho
d
ignores the
higher o
r
d
e
r fourier
seri
e
s
term
s used
for harm
onics
cal
c
ulatio
ns
becau
se of its com
p
lexity and ti
me-con
sumi
ng calcul
ation
s
a
l
so it is mo
re
compli
cate
d for re
al time impleme
n
tatio
n
due to its h
a
rmo
n
ics calculation [25-26
].
Torq
ue
control in multiph
a
s
e BL
DC
mo
tor ca
n be
achieved
with the hel
p of in
equality
con
s
trai
nts via Kuhn-T
u
cker theo
rem which le
ad
s to copp
er lo
ss
and torq
ue ri
pple re
du
ctio
ns.
But the ineq
uality con
s
traints requi
re
s feedb
ac
k sensors like h
i
gh re
solutio
n
encode
rs
and
torque tran
sd
uce
r
whi
c
h i
n
crea
se the
overall co
st
of the syste
m
[27
]. In direct torque a
n
d
indire
ct flux control meth
od, the flux and tor
que
e
s
timation
s a
r
e ca
rri
ed o
u
t with the h
e
l
p
of
Clarke
an
d P
a
rk tra
n
sfo
r
m
a
tions. But
th
ese
tran
sfo
r
mations
a
r
e more
time co
nsumi
ng be
cause
of the difficulty in accu
ra
cy of
the param
eter estim
a
tio
n
s [28-29].
3. Rev
i
e
w
on
Differ
e
n
t
Mu
ltile
v
e
l In
v
e
rter Topolog
y
Normally the
BLDC moto
r is
po
wered
by ei
ther V
S
I or CSI. T
he two l
e
vel
inverter
prod
uces
sq
u
a
re
wave o
u
tput with ha
rmonic
dist
ortions
in its
waveform, which res
u
lts
in total
harm
oni
c di
stortion
s (THD) in the
outp
u
t. Due to th
ese
effects the ri
pple
s
a
r
e create
d
in
the
output ele
c
tromagn
etic t
o
rqu
e
an
d distortio
n
in
the trape
zoidal ba
ck
EMF wavefo
rm.
Conve
n
tionall
y
controlle
d rectifier
with large valu
e of
inducto
r in serie
s
a
c
t as
a cu
rre
nt sou
r
ce
whi
c
h in
cre
a
se the overall
co
st of the syst
em a
s
well
as the sy
ste
m
looks so b
u
lky.
Whe
n
the
level of the
outp
u
t voltage i
s
i
n
crea
sed, th
e ha
rmo
n
ic
content g
e
ts
redu
ced.
The wavefo
rm is in stairca
s
e shape.
The disto
r
tions in the stator cu
rre
nt as well a
s
the
electroma
gne
tic torq
ue
get re
du
ced
with
high
levels. T
h
ese
cau
s
e
s
the g
ene
rated
electroma
gne
tic torqu
e
co
ntains mi
nim
u
m rippl
e in
its waveform. Also the two level inverter is
not suitabl
e for hig
h
po
we
r appli
c
atio
ns but the mu
ltilevel inverter is suita
b
le f
o
r hig
h
po
we
r
appli
c
ation
s
b
y
increa
sin
g
the level of the output voltage.
A compa
r
ativ
e analysi
s
be
tween two le
vel invert
er a
nd multilevel
inverter
with different
modulatio
n te
chni
que
s a
r
e
ca
rrie
d
out
a
nd the
re
su
lt
s a
r
e d
epi
cte
d
as graphi
cal view in
Fig
u
re
3(a
)-3
(d
). Fro
m
the grap
hi
cal re
pr
esent
ation, it was
clea
r that th
e multilevel inverter is the
best
choi
ce fo
r m
o
tors. Th
e p
e
rform
a
n
c
e a
nd efficien
cy
of the motor
is incre
a
sed
with the help
o
f
increa
sing th
e output level
s
of the invert
er. Even
thou
gh increa
sin
g
the numbe
r of levels re
su
lts
in more
num
ber of
swit
ch
es and
the
control will be more
compli
cated, which i
s
often a limitation
for the use
of the multilevel inverter,
better
qualit
y of load torque is con
s
i
dere
d
to be th
e
outcom
e
of the MLI fed BLDC moto
r.
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5
68
(a)
(b)
(c
)
(d)
Figure 3. Co
mparative an
alysis of (a
) P
mech ,
(b) efficiency, (c) Spe
ed and (d) torque of the two
level and mul
t
ilevel inverter
The multilev
e
l inverter i
s
grou
ped int
o
th
ree type
s of co
nfiguration namely
,
Diode
clamp
ed m
u
ltilevel inverte
r
, flying capa
ci
tor multilevel
inverter
and
cascad
ed
H-b
r
idge multilev
e
l
inverter.
3.1.
Diode Clamped Multilev
e
l
In
v
e
rter
The sin
g
le ph
ase five level diode clam
p
ed multilevel inverter is
sh
own in Figu
re
4. The
voltage stress on th
e po
wer devi
c
e i
s
li
mited with
th
e help
of the diode
s i
s
the
major
co
ncep
t of
these i
n
verte
r
s. The th
ree
pha
se inve
rte
r
out
p
u
t voltage shares co
mmon
DC
bu
s voltage
and
it
is divide
d for five level with the hel
p of
the ca
pa
cito
rs. Th
e volta
ge a
c
ro
ss ea
ch
cap
a
cito
r
and
swit
che
s
is V
dc
which i
s
same as the
supply voltage
. So there is no po
ssi
ble for high volta
ge
stre
ss a
c
ro
ss device
s
. Ea
ch le
g a
s
co
nsi
s
t of switches,
clam
pin
g
diod
es, fre
e
wh
eeling
di
ode
s
and also cap
a
citors.
It
i
s
a
l
so nam
ed as
neut
ral cla
m
ped
i
n
verte
r
. The
m
a
jo
r
d
r
awb
a
ck of
th
ese
inverter i
s
DC link voltage u
nbala
n
cin
g
. The co
m
pon
en
ts requi
re
d for n-level inve
rter is:
a)
Voltage so
urces: (n
-1
)
b)
Switchin
g de
vices: 2
(
n-1)
c)
Diod
es:
(n
-1
)
*
(n-
2
)
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A Revie
w
Pa
per on T
o
rq
u
e
Rippl
e Red
u
ction in
Brushless DC Mot
o
r Drives… (S.Arunkum
ar)
69
Figure 4. Dio
de Clam
ped
Multilevel Inverter
The switchin
g pattern for five level d
i
ode cl
ampe
d multilevel inverter i
s
sh
own i
n
Table 1.
Table 1. Swit
chin
g States for 5-l
e
vel DCMLI
Voltage
Sw
itching States
S
1
S
2
S
3
S
4
S
5
S
6
S
7
S
8
Vdc/2
1
1
1
1
0
0
0
0
Vdc/4
0
1
1
1
1
0
0
0
0
0
0
1
1
1
1
0
0
-Vdc
/4
0
0
0
1
1
1
1
0
-Vdc
/2
0
0
0
0
1
1
1
1
In the lo
ok up
table ‘
1
’
rep
r
ese
n
ts th
at th
e corre
s
po
ndi
ng
swit
ch i
s
i
n
O
N
p
o
sitio
n
and
‘0’
rep
r
e
s
ent
s that the switch
is in OFF co
ndition. At
an instant four
swit
che
s
are in ON po
sitio
n
.
The up
pe
r a
r
m switche
s
are
comm
uta
t
ed at maximum po
sitive
voltage an
d
the lower a
r
m
swit
che
s
are
comm
utated at
neg
ative maximum
val
ue. At funda
mental frequ
enci
e
s, it i
s
more
ef
f
i
cien
cy
.
3.2.
Fl
y
i
ng Capacitor Multilev
e
l In
v
e
rter
The
circuit co
nfiguratio
n of
this inverte
r
i
s
si
milar to th
e neutral poi
n
t
clampe
d
co
nverter
but it require
s high num
b
e
rs of auxilia
ry capa
cito
rs which i
s
sh
own in Figu
re 5. It doesn’t
requi
re
s any
clampi
ng dio
des. As the
name indi
cat
e
s, the com
m
on DC bu
s voltage is di
vided
into five level with the hel
p of flying capa
citors. Th
e main a
d
va
ntage
s of thi
s
converte
r i
s
it
doe
sn’t
requi
re
any filters
for hi
gh l
e
vel
and
a
c
tive
a
nd
rea
c
tive p
o
we
r flo
w
i
s
possibl
e in
b
o
th
dire
ction
s
. Bu
t the cont
rol
of the syste
m
is co
mpli
cat
ed when th
e
output level i
s
in
cre
a
sed.
Th
e
comp
one
nts required for n
-
level inverter
is:
a)
Main c
a
pac
i
tors
: (n-1)
b) Auxiliary
capacito
r : (n-1)*(n-2)/2
The lo
ok
up
table fo
r th
ese i
n
verte
r
s are
simil
a
r
to that of n
eutral
point
clamp
e
d
multilevel inverter. Th
e onl
y difference i
s
ab
sen
c
e of
the clampi
ng
diode
s.
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KA
Vol. 13, No. 1, Janua
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5
70
Figure 5. Flying Ca
pa
citor
Multilevel Inverter
3.3.
Cas
cade
d
H-Bridge Multil
ev
el In
v
e
rter
The ca
scad
e
d
H-b
r
idg
e
m
u
ltilevel inverters a
r
e b
u
ilt with se
rie
s
conne
ction of H-b
r
id
ge
inverter
with
sep
a
rate
DC
sou
r
ces. A
s
t
he na
me in
di
cate
s
H-b
r
idg
e
inverte
r
s are cascad
ed
with
each othe
r to pro
d
u
c
e st
aircase wave
form. Wh
e
n
the level gets incre
a
sed
the numb
e
r
of
inverters ca
scad
ed is al
so increa
sed.
It
doesn’t
need
s any clampi
ng dio
des an
d flying
cap
a
cito
rs. F
o
r thre
e pha
se configu
r
atio
n, the ca
scad
ed conve
r
ters can be lin
ke
d either in st
ar
con
n
e
c
tion o
r
delta conn
e
c
tion. Co
mpa
r
e to other to
pologi
es, it use
s
less com
pone
nts which
results in mi
n
i
mum amo
unt
of switching l
o
sse
s
. The control of the
s
e inverter i
s
a
l
so si
mple. B
u
t
it requi
re
s i
s
olated
DC source
s fo
r th
e po
we
r
con
v
ersio
n
, which limits it
s u
s
e. Fo
r
n-lev
e
l
inverter the n
u
mbe
r
of swit
chin
g device requi
re
d is
2(n-1
)
per le
g [30]. The circuit configu
r
ati
o
n
of single ph
a
s
e five level inverter a
nd its
output voltage waveform is sho
w
n i
n
Figure 6 and
Figure 7 re
sp
ectively. The swit
chin
g stat
es for five level inverter i
s
sho
w
n in Ta
b
l
e 2.
Figure 6. Ca
scad
ed H-b
r
id
ge Multilevel Inverter
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TELKOM
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ISSN:
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046
A Revie
w
Pa
per on T
o
rq
u
e
Rippl
e Red
u
ction in
Brushless DC Mot
o
r Drives… (S.Arunkum
ar)
71
Figure 7. Five level output voltage wavef
o
rm
Table 2. Swit
chin
g States for 5-l
e
vel CHBMLI
Sw
itches Tu
rn ON
Voltage Level
S1, S2
+Vdc
S1,S2,S5, S6
+2Vdc
S4,D2,S8,D6
0
S3,S4 -Vdc
S3,S4,S7,S8 -2Vdc
In the look up
table, diode free
whe
e
ling
occurs
at the zero voltage level. At
Vdc only two
swit
che
s
are
in
con
d
u
c
tin
g
mod
e
. Wh
en the
level
gets i
n
crea
sed, the
num
ber
of switch
es
con
d
u
c
ted is
also in
crea
se
d. Two switch
es from
u
ppe
r cell an
d the two switch
es
from lower ce
ll
are
co
ndu
cte
d
. Wh
en the
BLDC moto
r i
s
po
we
red
wi
th two level i
n
verter, the
g
e
nerated to
rq
ue
contai
ns
signi
ficant amou
nt of ri
pple whi
c
h is sh
own in Figure 8.
Figure 8 Electromag
netic T
o
rqu
e
Wavef
o
rm (T
wo lev
e
l Inverter)
Figure. 9 Electrom
agn
etic
Torq
ue Wave
form (Multilev
e
l Inverter)
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Vol. 13, No. 1, Janua
ry 2015 : 65 – 7
5
72
Whe
n
the BLDC moto
r is powered with
multilevel inverter, the generate
d
electroma
gne
tic torque
co
ntains mini
m
u
m amou
nt
of ripple in its waveform wh
ich is
sho
w
n
in
Figure 9.
Table 3. Co
m
parative Anal
ysis of Di
ffere
nt Multilevel Inverter T
opol
ogy
Terms
Diode
Clamped
Fl
y
i
ng
Capacitor
Cascaded H-
Bridge
Sourc
e
(n-1)
(n-1)
2(n-1
)
Clamping
diodes
(n-1)*
(n-2
)
-
-
Capacitors (n-1)
(n-1)*
(n-2
)/2
-
Component
Count
High High
Minimum
Sw
itching
Loss
Moderate
Moderate
High
Voltage Stress
Moderate
Moderate
Minimum
Among the
s
e
three top
o
lo
gies
singl
e so
urce,
multi DC link
ca
scad
ed H-bri
dge
multilevel
inverter is
the bes
t c
h
oice for torque rippl
e minimization in the BLDC motor drive.
4. Po
w
e
r F
a
c
t
or Co
rrec
t
io
n
The p
o
wer
q
uality has be
come
the m
o
st si
gnifi
cant
factor to
be
c
onsi
dered at the
point
of BLDC mot
o
rs. Th
e international
stan
dard
s
su
ch
a
s
Intern
ationa
l Electrote
c
hn
ical Commi
ssion
(IEC)
610
00-3-2,
sug
g
e
s
te
d su
ch th
at the ha
rmo
n
i
cs in the
sup
p
ly cu
rre
nt sh
ou
ld be
within t
he
accepta
b
le li
mit. For
cla
ss-A eq
uipme
n
t (< 6
00
W,
1
6
A p
e
r ph
ase)
whi
c
h
in
cl
ude
s h
o
u
s
eh
old
applia
nce
s
, t
he IEC
610
0
0
-3
-2 limit
s t
hat the T
H
D
of the supply
cu
rrent
shou
ld be
belo
w
19%
[31]. Conve
n
tionally dio
de
bridg
e
re
ctifier (DBR)
wi
th l
a
rge
value
of
DC lin
k
capa
citor i
s
used
a
s
a front-end
re
ctifier in VSI fed BLDC m
o
tors. T
h
is
circuit results in
highly dist
ort
ed supply
current
with THD of 65% and a p
oor po
we
r factor of 0.8
which i
s
not accepte
d
by Internatio
nal Po
wer
Quality (PQ
)
stan
da
rd
s
such
a
s
IEC-6100
0-3
-
2
[3
2]. Hen
c
e
a
power fa
cto
r
co
rrecte
d
(PFC)
frontend
re
cti
f
iers
are
ne
cessary to
im
prove th
e po
wer facto
r
in
ord
e
r to
im
prove th
e po
wer
quality (PQ) a
t
the AC mains.
Two stag
e
PFC conve
r
ters
a
r
e
in pra
c
ti
ce
in whi
c
h o
ne
PFC co
nverter co
ncent
rated
o
n
improvin
g the
power
qualit
y (PQ) at A
C
main
s wh
ich is typically a boost
converter an
d an
oth
e
r
one i
s
for vol
t
age control,
whi
c
h de
pen
ds u
pon t
he
choi
ce
of ap
plicatio
n. A si
ngle
stage P
F
C
conve
r
ters
h
a
sg
aine
d mu
ch m
o
re care be
cau
s
e
th
e PFC
ope
ra
tion and
the
DC-lin
k volta
ge
control ca
n b
e
achi
eved in
a single
stag
e [33-34].
In the
conve
n
tional PF
C
scheme
the
spe
ed
co
ntro
l ca
n b
e
a
c
hi
eved
with th
e hel
p of
pulsewi
dth-m
odulate
d
voltage
sou
r
ce i
n
verter
(PWM
-VSI) with
con
s
tant d
c
l
i
nk voltag
e. Thi
s
results hi
ghe
r switching lo
sse
s
in the VSI which
i
s
the sq
ua
re fu
nction of
swit
chin
g frequ
e
n
cy.
The
sp
eed
o
f
the BL
DC
motor i
s
dire
ctly propo
rtio
nal to th
e
DC lin
k volta
g
e
. So the
sp
ee
d
control ca
n be attained
by a variabl
e DC lin
k
voltage of VSI with funda
mental freq
u
ency
swit
chin
g (ele
ctroni
c
comm
utation). Thi
s
provide
s
mini
mum switchi
n
g losse
s
.
Singh and Si
ngh [35] have prop
osed the con
c
e
p
t of buck-bo
ost
conve
r
ter fed
BLDC
motor a
nd th
e sp
eed
co
ntrol ca
n be
ach
i
eved by PWM_
VSI with consta
nt DC li
nk voltag
e, which
offers high
switchi
ng l
o
sses. T
he
bu
ck-boo
st
conve
r
ter
i
s
re
pla
c
ed with singl
e-en
ded
p
r
im
ary-
induc
t
anc
e
converter
(SEPIC) based
VSI fed BLDC moto
r drive has been proposed by
Gopal
arath
n
a
m
and Taliya
t. But it requires m
o
re nu
mber of cu
rre
n
t and voltage sen
s
o
r
s wh
ich
rest
rict
s its applicability to lo
w power applicat
ions [36]
.
The
swit
chin
g lo
sses du
e
to fund
ame
n
tal freq
uen
cy swit
chin
g
of VSI for el
ectro
n
ic
comm
utation
of BLDC mot
o
r can be mi
nimize
d wi
th
the help of Cuk convert
e
r
fed BLDC m
o
tor
drive with a variabl
e DC lin
k voltage ha
s been pro
p
o
s
ed by Singh and Singh [3
2]. But it requires
three voltag
e
control sensors fo
r PFC
o
peratio
n
which is not
co
st effective and
suitabl
e for hi
gh
power ap
plications o
n
ly.
For fu
rthe
r im
provem
ent in
the efficien
cy
and
perfo
rm
ance of the B
L
DC moto
r th
e front
-
end b
r
idg
e
re
ctifiers
are re
placed with
b
r
idgel
ess
(B
L
)
topolo
g
ie
s. The BL top
o
logy provid
es
less
con
d
u
c
tion lo
sses a
c
ross
the swit
che
s
.
Jang an
d Jovanovic [37]
and Hub
e
r
et al. [38] ha
ve
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TELKOM
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ISSN:
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046
A Revie
w
Pa
per on T
o
rq
u
e
Rippl
e Red
u
ction in
Brushless DC Mot
o
r Drives… (S.Arunkum
ar)
73
prop
osed the
BL bu
ck
and
boo
st co
nvert
e
r for PFC
op
eration. But it
limits the o
p
e
rating
ra
nge
of
the dc lin
k voltage control
due to se
pa
rate ste
p
up
and ste
p
do
wn op
eratio
n
of the conve
r
ter.
Also large inrush
curre
n
t at the time of st
arting is m
a
jo
r dra
w
b
a
ck of
these converters.
Abbas A. Fordoun
et al. an
alyze the
Cuk deriv
e
d
conv
erters fo
r PF
C op
eration i
n
BLDC
motors. The
y
propo
sed
three types
of cuk
d
e
riv
ed co
nverte
rs. The Cuk converte
r h
a
s
cha
r
a
c
teri
ze
d
as natu
r
al p
r
otectio
n
ag
a
i
nst in
rush current and
o
v
erload
cu
rre
n
t, lower
ripp
le
conte
n
t in th
e
cu
rrent a
nd l
o
w
ele
c
trom
a
gnetic in
terfe
r
ence (E
MI) [3
9]. The
equiv
a
lent
circuit o
f
Cu
k derive
d
converte
rs i
s
shown in Figu
re 10(a
)
-(c).
(a)
(b)
(c
)
Figure 10. Equivalent circui
ts for (a) Ty
pe I. (b) Type II and (c) Type III Cuk deri
v
ed PFC
Conve
r
ters
Among th
e d
i
fferent BL
converte
r top
o
l
ogie
s
,
the b
r
idgele
s
s bu
ck-b
oo
st rectifi
e
r h
a
s
less co
mpon
ent cou
n
t co
mpared to cu
k de
rived
con
v
erters. To a
c
hieve in
here
n
t powe
r
fact
or
corre
c
tion
at
AC main
s, th
e re
ctifier i
s
func
tion
ed in
a di
scontinu
ous indu
cto
r
curre
n
t mod
e
(DIC
M). T
h
is
re
ctifier
offers
low switching losses in VSI, bec
au
se
th
e
VSI ope
r
a
tes
in low
freque
ncy fo
r elect
r
oni
c
commutation i
n
BLDC m
o
tor [40]. Th
e
equivalent
ci
rcuit for the
BL
buck-boo
st converte
r is
shown in Figu
re 11. The compa
r
at
ive analysi
s
betwe
en the differe
nt
PFC co
nverte
r topologi
es i
s
tabulate
d
in
Table 4.
Hen
c
e the B
L
buck-bo
ost
PFC co
nverter is a be
st
choi
ce for i
m
provin
g the
powe
r
factor at the
AC main
s in ord
e
r to o
b
tain the be
st power q
u
a
lity. Compa
r
ed to othe
r BL
topologi
es th
e buck-bo
ost
conve
r
ter h
a
v
e a minimu
m numbe
r of
comp
one
nts.
So the losses
asso
ciated
wi
th the switche
s
and
st
re
ss on switch
es g
e
ts red
u
ced.
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ISSN: 23
02-4
046
TELKOM
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KA
Vol. 13, No. 1, Janua
ry 2015 : 65 – 7
5
74
Table 4.Com
parative Anal
ysis of BL Co
nverter T
opol
ogie
s
Figure 11. Equivalent circui
t of
bridgele
s
s
bu
ck-bo
o
st conve
r
ter
5. Conclusio
n
An exhau
stive overview of torque
ripple
minimi
zation te
ch
ni
que
s with d
i
fferent
multilevel inverter to
polog
ies an
d po
wer qu
ality improvem
ent in
the bru
s
hle
ss
dc m
o
tors
(BLDC) h
a
s b
een presente
d
in this pape
r. Among
different torque
minimization tech
niqu
es, th
e
ca
scade
d
H-bridg
e
m
u
ltilevel inverte
r
gives
better
perfo
rman
ce
in the
efficie
n
cy a
s
well
as
smooth
e
r
distortion le
ss
stator current.
The h
a
rm
o
n
ics in the
stator current
are effe
ctively
redu
ce
d
whi
c
h minimi
ze th
e THD. Al
so
different
PF
C co
nverte
rs a
r
e a
nalyzed f
o
r p
o
wer
qual
ity
improvem
ent
at AC mai
n
s. From
this a
nalysi
s
the
B
L
bu
ck-boo
st co
nv
erte
r p
r
ovides re
du
ced
swit
chin
g lo
sse
s
an
d
stre
sses a
c
ro
ss t
he
switche
s
.
The BL
DC m
o
tor h
a
s inhe
rent h
o
u
s
eh
o
l
d
appli
c
ation
s
and the
pe
rforma
nce of t
hese mo
to
rs have b
een i
m
prove
d
by
BL bu
ck
boo
st
conve
r
ter a
s
front-en
d
re
ctifier an
d cascad
ed
H-b
r
idge m
u
ltilevel inverter fe
d BLDC mot
o
r
drive.
Referen
ces
[1]
Dai M, Ke
yha
n
i A, Sebastia
n
T
.
T
o
rque rippl
e
ana
l
y
sis
of a PM brushless DC mot
o
r using fin
i
te
elem
ent metho
d
.
IEEE Trans.
Energy Conver
s
. 2004; 19(
1): 40–
45.
[2]
W
ang HB, Li
u HP. A novel s
e
nsorl
e
ss contro
l method for
brushl
ess DC mo
tor.
IET Electr.
Power Appl.
200
9: 3(3): 240
–24
6.
[3]
Gan W
C
, Qiu L.
T
o
rque a
n
d
veloc
i
t
y
r
i
pp
le el
imin
atio
n of AC perma
n
ent
mag
net motor contr
o
l
s
y
stems usi
ng
the intern
al mo
del pr
inci
ple.
IEEE/ASME Tr
ans. Mechatron
. 2004; 9(
2): 436–
44
7.
[4]
T
abarraee K,
I
y
er J, Atig
he
chi H, Jatsk
e
vich
J. D
y
n
a
m
ic aver
age-v
a
lu
e mo
del
ing
of 12
0° VSI-
commutated br
ushl
ess DC motors
w
i
t
h
trap
ezoi
dal b
a
ck EMF
.
IEEE T
r
a
n
s. Energy Co
nvers
. 201
2
;
27(2): 29
6–
307
.
[5]
Kim T
H
and E
h
san
i
M. Se
ns
orless c
ontro
l
of t
he BL
DC m
o
tors from n
e
a
r-zero to
hig
h
spee
ds.
IEEE
T
r
ans. Pow
e
r Electron.
20
04;
19(6): 163
5–
1
645.
[6]
Ozturk SB, Alex
ander WC
, T
o
li
yat
HA. D
i
re
ct torque
co
ntrol
of four-s
w
i
tc
h br
ushl
ess
D
C
motor
w
i
t
h
non-s
i
nus
oi
dal back
EMF
.
IEEE T
r
ans. Pow
e
r Electron.
201
0; 25(2): 26
3–2
71.
[7]
Bhim Si
ngh, S
anj
eev Si
ng
h.
State of the A
r
t on Perma
ne
nt M
agn
et Bru
s
hless
DC Mo
tor Drive
s
.
Journ
a
l of Pow
e
r Electron
ics.
200
9; 9(1): 1-1
7
.
[8]
Haife
ng Lu, Le
i
Z
hang, W
enlo
ng Qu. A Ne
w
T
o
rque C
ontrol
Method
for T
o
rque
Ri
pp
le M
i
nimizati
on
of
BLDC Motors
w
i
t
h
Un-Ideal B
a
ck EMF.
IEEE
Trans. Power
Electron
. 20
08;
23(2).
[9]
Yand
amuri
H
ari
bab
u, Narasi
mha Murth
y
VV.
A Ne
w
T
o
rqu
e
Contro
l
Method for T
o
rque Ripp
l
e
Suppr
essio
n
in
BLDC Motor
w
i
th Non
i
de
al Ba
ck EMF
.
Indian
Streams R
e
se
arch Jour
nal.
2
013; 3(1
1
).
[10]
Calso
n
R, Milc
hel LM, F
agu
n
des
JC. Anal
ys
is of torque rip
p
le d
ue to ph
a
s
e commutatio
n
in brus
hles
s
dc machi
nes.
IEEE Trans. Ind. Appl.
199
2; 28(3): 632
–6
38.
Configuration
No. of Devices
S
u
itability
S
W
D L
C
T
OTAL
BL-BUCK
2
4 2 2
10
NO
BL-BOOST
2
2 1 1
6
NO
BL-CUK
T
-
1
2
3 3 3
11
Y
E
S
BL-CUK
T
-
2
2
2 3 4
11
Y
E
S
BL-CUK
T
-
3
2
4 4 3
13
Y
E
S
BL-BUCK-B
OOS
T
2
4 2 1
9
Y
E
S
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