Page 1 of 12
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online: https://ejbss.org/ P a g e | 1947
Direct Torque Control for Matrix Converter-fed
Three phase Induction Motor
VELMURUGAN .S
PG Student
PRIST Deemed to be University, Thanjavur
Abstract— This paper develops a direct torque control
method (DTC) using a matrix converter fed induction motor.
The advantages of matrix converters are combined with the
advantages of the DTC technique; under the constraint of the
unity input power factor, the required voltage vectors are
generated to implement the conventional DTC method of
induction motor. The proposed DTC algorithm is applied to
induction motors and the simulation results are given in
steady-state and transient conditions, while the discussion
about the trend of the DTC method using the MC is also
carried out.
Keywords- Matrix converte; induction motor; direct torque
control method
I. INTRODUCTION
In the past two decades, due to the need to increase
the quality and the efficiency of power supply and usage,
the three phase matrix converter has become a major
modern energy converter and has emerged from the
previously conventional energy conversion modules as
one of the best substitutions [1], [2].
Matrix converter fed motor drive is superior to pulse width
modulation (PWM) inverter drives because it provides
bidirectional power flow, sinusoidal input/output currents,
and adjustable input power factor [3], [4]. Furthermore,
matrix converter allows a compact design due to the lack
of dc-link capacitors for energy storage. However, only a
few of practical matrix converters have been applied to
vector control system of induction motors (IM) for the
reason: Modulation technique and commutation control
are more complicated than conventional PWM inverter
[4].
Since the Direct Torque Control (DTC) method has been
proposed in the mid 1980’s, The Direct Torque Control (DTC)
method for AC machines is prevalently utilized in
Page 2 of 12
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online: https://ejbss.org/ P a g e | 1948
√3
when it is comparing with the Field Oriented Control
method. Reducing the torque ripple in conventional
DTC has the cost of small sampling interval that may
lead to high switching frequency [7]. In recent years,
several investigations have been performed with the
aim of improving steady state performance of the
DTC method, e.g., Direct Self Control (DSC) [8],
utilizing Space Vector Modulation (SVM) [9],
utilizing multi level inverters [10],
[16] or Matrix Converter [17] and Predictive Torque
Control [13]-[14].
By combining the advantages of matrix converters
with the advantages of DTC schemes, it is possible to
achieve fast torque and flux responses in a wide speed
range.
In this paper, a new DTC control for matrix converter
is proposed which allows under the constraint of unity
input power factor, the generation of the voltage
vectors required to implement the DTC of three phase
induction motor. Depending on the induction motor
operating point such vectors might be applied and
consequently the electromagnetic torque ripple is reduced.
Simulation results demonstrate the effectiveness of the
proposed control scheme was presented. Both, steady-state
and transient behaviour have been investigated.
II. DTC AND DTC MATRIXCONVERTER
(DTC-MC) STRUCTURES
DTC STRUCTURES
The basic model of DTC induction motor scheme is
shown in Fig. 1. At each sample time, the two stator
currents ica and icb and the DC bus voltage Vdc are
sampled. Using the inverter voltage vector, the α, þ
components of the stator voltage space vector in the
stationary reference frame are calculated as follows.
many variable speed drives, especially in case the torque V = 2 V
(s − cb+cc
)
control is more desired than speed control. The DTC cαref { 3 dc a 2 (1)
method has the dominant advantages such as fast transient
toque response and low calculation burden [6]. However
because of “Bang-Bang”control characteristic and not
using modular regulators, conventional DTC has two
drawbacks. First, the switching frequency is variable and
dependent to the hysteresis bands and speed of the motor.
Second, the torque ripples are considerable especially
Vcþref =
1 Vdc(sb − sc
)
The α, þ components of the stator current space vector
are calculated using
Page 3 of 12
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online: https://ejbss.org/ P a g e | 1949
2
Icα = ica (cα = oLcIcα + M (rα
{ Icþ =
ica+2icb
√3
(2) {
Lr
(cþ = oLcIcþ + M (rþ
(3)
The stator flux is a function of the rotor flux which is
provides from the flux observer.
Lr
Then the magnitude of the stator flux is calculated by
|(c| = J(
2 + (
2
(4)
cα cþ
(cref
Tref
Figure. 1. Block diagram of classical DTC
The electromagnetic torque is calculated by
Te =
3 p((cαIcþ–
(cþIcα)
where p is the number of pole pairs.
The torque and flux errors are defined as
{
∆(c = |(cref| — |(c|
∆Te = Tref — Te
(5)
(6) (a) Flux comparator.
Te
(b) Three-level torque comparator.
The inverter switching states are determined by the
torque and flux errors according to the sector determined.
In order to maintain the estimated stator flux
and torque within their boundaries which are determined
by the two hysteresis bandwidths as shown in figure 2a &
2b, at each sampling period, the torque and the stator flux
are estimated and compared with the corresponding
reference values before passing the hysteresis comparator.
The position of the stator flux is detected, and the
most suitable space vector among 8 space
vectors generated by a VSI is selected from the switching
table given in Table 1 to compensate the load torque and the
stator flux.
Vdc
Switching Table
+ -
(c
Sa
Sb
Sc
1
-Th
+ -
T
T
Th
-1
est
(c
Torque and Flux
Estimator
Vdc
Ia
Ic
IM
VSI
Fh
-1
-Fh
1
1
-Fh F
s
h
-1
1
-Th
Th
-1
