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i
u
i
u
A
A
a
i
i
u
B
B
i
u
u
b
⸙䱥ਈᦒಘ
C
N
i
u
D
D
i
u
i
u
c
E
E
O
i
NO
Fig. 4.
The common mode voltage of system
u
u
ac
bc
d
y
T
•
d
x
T
•
S
S
V
16
V
24
V
25
V
V
V
31
V
V
V
24
V
16
V
V
29
31
29
25
T
(a) SVPWM sequence before improvement
u
u
ac
bc
d
x
T
•
S
V
V
31
V
31
V
31
31
T
(b) The improved SVPWM sequence
Fig. 5.
SVPWM sequence
⎧
⎨
u
AO
=
u
AN
+
u
NO
u
BO
=
u
BN
+
u
NO
u
CO
=
u
CN
+
u
NO
u
DO
=
u
DN
+
u
NO
u
EO
=
u
EN
+
u
NO
(9)
⎩
From(9), the common mode voltage is
u
NO
=
1
5
(
u
AO
+
u
BO
+
u
CO
+
u
DO
+
u
EO
)
(10)
Assuming
U
im
= 100V, the input power factor is unity. When the input reference
current is in sector 2, the output reference voltage is in sector 1, from (10) it
can be found that, the maximal common-mode voltage
U
im
appears in zero
vector function of the moment. When the output voltage in other sectors it has
the same conclusion. Hence, the maximal CMV is
U
im
when the input current
sector is odd number; the maximal CMV is
−
−
U
im
when the input current sector
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