Mitsubishi Electric FR-A700 Technical Manual page 446

Block diagram of Real sensorless vector control
Magnetic
φ 2
ω
*
+
-
ω FB
ω FB
Since the current control loop is configured same as the
vector control with encoder, necessary excitation current
(current required to generate magnetic flux) and torque
current (current proportional to the load torque) can be
calculated separately by using the speed estimated value
found by the motor current and output voltage as the speed
feedback value.
[Speed control]
Speed control operation is performed to zero the
difference between the speed command
estimated value FB. At this time, the motor load is
found and its result is transferred to the torque current
controller as a torque current command iq
[Torque current control]
A voltage (Vq) is calculated for the current (iq) to flow
identical to the torque current command (iq*) found by
the speed controller.
[Magnetic flux control]
The magnetic flux 2 of the motor is derived from the
excitation current id. An excitation current command
(id*) is calculated for the motor magnetic flux 2 to be
the predetermined magnetic flux.
id
*
+
flux
control
-
id
iq
*
+
Speed
control
iq
ω 0
+
+
ω s
iq
Slip
calculation
φ 2
Magnetic
calculation
Speed estimation
and speed
*
.
*
Excitation
Vd
current
control
Torque
Vq
current
- control
iq
id
Vd
flux
Vq
[Excitation current control]
A voltage (Vd) is calculated to flow a current id
identical to the excitation current command (id*) found
by magnetic flux control.
[Output frequency calculation]
Motor slip
current value iq and magnetic flux 2. Output frequency
0 is found by adding the slip amount s to the speed
estimated value FB.
The above results are used to make PWM modulation and
run the motor.
480
PWM
modulation
Output
voltage
conversion
ω 0
id
Current
iq
conversion
s is calculated on the basis of the torque
SELECTION
IM
which is
*