Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...

Sensorless Speed Direct Torque Control with Space Vector Modulation (DTC-SVM)
I sA
ABC
Is
α
I sB
αβ
Is
β
R s
U sA
U sB
ABC
αβ
U
s α
U
s β
R s
Es
α
Es
β
∫
∫
Ψ sα
Ψ sβ
Ψ s
θ Ψs
Figure 6.8. Voltage model based estimator with ideal integrator.
There are proposed many improvements of the classical voltage model. Some of them
are presented bellow.
6.3.4 Voltage model based flux estimator with low pas filter
A common way to improve the stator flux voltage based model is to use a first-order
low-pass filter (LP) instead of the pure integrator. The equations (6.7 and 6.8) are
transferred to the form:
dΨ sα
= ( Us α − RsIs α)
+ Fc Ψ
sα
(6.9)
dt
dΨ sβ
= ( Usβ − RsIsβ)
+ Fc Ψ
sβ
(6.10)
dt
The block diagram of the estimator is presented in Fig. 6.9. Discrete time
implementation of the integrator becomes:
zΨ ( z) =Ψ ( z) + ( U − R I ) T
(6.11)
sα sα sα s sα
s
zΨ ( z) =Ψ ( z) + ( U − R I ) T
(6.12)
sβ sβ sβ s sβ
s
A LP filter does not give high accuracy at frequencies lower than cutoff frequency
ω = 2π F . There will be errors both in the magnitude and in the phase angle. As
c
c
results, the proposed voltage estimator with LP filter can be used successfully only in a
limited speed range above cutoff frequency
129