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6F3A4768
5.4.5 Voltage Reference
(1) Voltage reference
EQ_R and ED_R, the results of current control, are input. Then,
θ
, the information of magnetic flux, is input
and a 3-phase voltage reference is obtained. Since in this case an interval is provided between ON and
OFF of the IGBTs, a dead time compensation is inserted. Furthermore, another compensation is inserted
for when the output voltage of a specific phase is saturated to output the voltage reference for PWM
control.
(2) PWM control
The PWM control section outputs gate pulse signals based on the voltage reference of each phase.
(3) Gate board
The gate board insulates gate signals generated by the PWM section and amplifies them to drive the
IGBTs.
Gate Pulse
WV_REF
VV_REF
VU_REF
3 Phase Voltage Reference
Q
Q-axis Voltage
Reference
EQ_R
5.4.4
A-axis Voltage
Reference
ED_R
5.4.4
Flux Position
Q0CMP
D
θ
(
)
(
)
(
)
W
U
V
Y
2
3
2
X
W
X
U
)
cos(
Q
sin
D
Y
)
sin(
Q
cos
D
X
+
−
=
×
+
−
=
=
θ
×
+
θ
×
=
θ
×
−
θ
×
=
U
V
W
Dead Time Compensation
$DEAD_T_CMP
Maximum Voltage
Compensation
PWM
Control
Gate
Board
GDM
IGBT
Fig. 5.4.2 Voltage Reference
(4) Dead time compensation
In Fig. 5.4.2, the IGBTU and IGBTX are inserted in series between the "
+
" and "-" sides of the DC power
supply.
If both the IGBTU and IGBTX, are on at the same time, the DC power supply is shorted, causing an
overcurrent to flow in the IGBTU and IGBTX, which may destroy the main circuit. Moreover, the IGBT has
a nature that its on-state operation is quick, while its off-state operation is relatively slow. Therefore, on/off
control of the IGBTs works in such a way that when one IGBT is turned off, another IGBT is turned on after
a certain wait time. This wait time is called dead time.
Providing this dead time prevents DC short-circuits. However, this control prevents the desired voltage
from being output in the control circuit. This is why the dead time compensation is provided. However, the
Toshiba decides the settings and the user must not change them.
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