Environmental Engineering Reference
In-Depth Information
U
dc
-
*
l
s
V
d
+
PI reg.
Σ
Voltage
vector
selection
and
inverter
ΙΜ
-
*
V
q
V
dc
+
PI reg.
Σ
Figure 7.17 Induction generator under DTC voltage regulation
purpose of regulating output voltage and having machine flux regulated to a value
appropriate for both frequency and efficiency constraints.
In the method of Figure 7.17, the DTC of hybrid M/G output voltage does not rely
on the use of current sensors nor current regulators in the feedback control. It is also
apparent that with this method the speed of the M/G is also not required (i.e. from rotor
position sensor or speed observer) for proper control. The technique requires only
knowledge of the system voltage being regulated in response to some higher level
controller. Flux sensors in the machine stator that are wound with the same pitch as the
stator coils are used to provide the function of current and position sensors - that is, to
develop the magnitude and angle of the stator (or rotor) flux.
The method of DTC for the purpose of hybrid vehicle M/G voltage control in
generator mode is to again regulate the bus voltage as shown in Figure 7.18, but
with knowledge of M/G currents. Current sensors provide system protection and
improve overall system performance.
U
dc
-
*
V
d
l
s
+
d
-axis
current
dI
+
Σ
PI reg.
Σ
-
Voltage
vector
selection
and
inverter
I
d
ΙΜ
-
*
V
q
V
dc
+
+
Torque
regulator
d T
Σ
PI reg.
Σ
-
I
q
Current
feedback
Stationary
to sync.
transformation
Figure 7.18 Induction generator having DTC control and current measurements
The torque developed by an M/G, or required as input during generating mode,
is typically not available from knowledge of electromagnetic variables alone. For
example, the shaft torque of the M/G during engine cranking must be estimated
