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Abstract - This paper presents a comparative study on two most
popular control strategies for induction motor drives: field-ori
ented control (FOC) and direct torque control (DTC). The com
parison is based on various criteria including basic control
characteristics, dynamic performance, parameter sensitivity, and
implementationcomplexity. The study is done by simulation using
the Simulink Power System Blockset that allows a complete repre
sentation of the power section (inverter and induction motor) and
the control system. The simulation and evaluation of both control
strategies are performed using actual parameters of an 50-HP
induction motor fed by an IGBT PWM inverter.
S
I’
Ac drives
NOMENCLATURE
stator voltages
stator currents
direct- and quadrature-axis stator currents
stator voltage and current space vectors
stator electrical frequency (rad/s)
rotor speed (rad/s)
slip frequency (rads)
unit vector
rotor angle
slip angle
dc link voltage
inverter gating signals (0 or I)
stator and rotor flux linkages
stator, rotor, and mutual inductances
stator and rotor resistances
rotor time constant
total leakage factor
Laplace operator
number of poles
star denoting a reference value
I. INTRODUCTION
using induction machines are now finding
increasing acceptance in various industrial variable-speed
applications because of the performance they can provide. The
development of high-performance control strategies for ac
drives, driven by industry requirements, has followed a rapid
evolution during the last two decades. It is now recognized that
the two high-performance control strategies for induction
motor drives are field-oriented control (FOC) [l], [2], [7], [8],
[9] and direct torque control (DTC) [3], [4], [5], [6],[lo]. They
have been invented respectively in the 70’s and in the 80’s.
These control strategies are different on the operation principle
but their objectives are the same. They aim both to control
effectively the motor torque and flux in order to force the motor
to accurately track the command trajectory regardless of the
machine and load parameter variation or any extraneous distur
bances. Both control strategies have been successfully imple
mented in industrial products. The supporters of field-oriented
control and direct torque control claim the superiority of their
strategy versus the other. Up to now, the question has not been
clearly answered.
The purpose of this paper is to present a comparative study
on these two control strategies in order to clarify the “myth”.
The comparison is based on various criteria including basic
control characteristics, static and dynamic performance, param
eter sensitivity and implementation complexity. The study is
done by simulation using the Simulink Power System Blockset
(PSB) that allows a complete representation of the power sec
tion (inverter and induction motor) and the control system. The
simulation and evaluation of both control strategies are per
formed using actual parameters of the same drive consisting of
an 50-HF’ induction motor fed by an IGBT PWM inverter.
11. DESCRIPTION OF FIELD-ORIENTED CONTROL AND DIRECT
TORQUE CONTROL SCHEMES
In this paper, we consider the basic configuration of indirect
FOC and DTC schemes with two separate control inputs: flux
and torque.
Field-oriented control system
Fig. 1 shows a block diagram of an indirect field-oriented
control system for an induction motor. In this system, the d-q
coordinates reference frame is locked to the rotor flux vector
rotating at the stator frequency U,, as shown in Fig. 2. This
results in a decoupling of the variables so that flux and torque
can be separately controlled by stator direct-axis current id, and
quadrature-axis current i,, respectively.
The stator quadrature-axis reference iqs* is calculated from
torque reference input T,*as:
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Abstract - This paper presents a comparative study on two most
popular control strategies for induction motor drives: field-ori
ented control (FOC) and direct torque control (DTC). The com
parison is based on various criteria including basic control
characteristics, dynamic performance, parameter sensitivity, and
implementationcomplexity. The study is done by simulation using
the Simulink Power System Blockset that allows a complete repre
sentation of the power section (inverter and induction motor) and
the control system. The simulation and evaluation of both control
strategies are performed using actual parameters of an 50-HP
induction motor fed by an IGBT PWM inverter.
S
I’
Ac drives
NOMENCLATURE
stator voltages
stator currents
direct- and quadrature-axis stator currents
stator voltage and current space vectors
stator electrical frequency (rad/s)
rotor speed (rad/s)
slip frequency (rads)
unit vector
rotor angle
slip angle
dc link voltage
inverter gating signals (0 or I)
stator and rotor flux linkages
stator, rotor, and mutual inductances
stator and rotor resistances
rotor time constant
total leakage factor
Laplace operator
number of poles
star denoting a reference value
I. INTRODUCTION
using induction machines are now finding
increasing acceptance in various industrial variable-speed
applications because of the performance they can provide. The
development of high-performance control strategies for ac
drives, driven by industry requirements, has followed a rapid
evolution during the last two decades. It is now recognized that
the two high-performance control strategies for induction
motor drives are field-oriented control (FOC) [l], [2], [7], [8],
[9] and direct torque control (DTC) [3], [4], [5], [6],[lo]. They
have been invented respectively in the 70’s and in the 80’s.
These control strategies are different on the operation principle
but their objectives are the same. They aim both to control
effectively the motor torque and flux in order to force the motor
to accurately track the command trajectory regardless of the
machine and load parameter variation or any extraneous distur
bances. Both control strategies have been successfully imple
mented in industrial products. The supporters of field-oriented
control and direct torque control claim the superiority of their
strategy versus the other. Up to now, the question has not been
clearly answered.
The purpose of this paper is to present a comparative study
on these two control strategies in order to clarify the “myth”.
The comparison is based on various criteria including basic
control characteristics, static and dynamic performance, param
eter sensitivity and implementation complexity. The study is
done by simulation using the Simulink Power System Blockset
(PSB) that allows a complete representation of the power sec
tion (inverter and induction motor) and the control system. The
simulation and evaluation of both control strategies are per
formed using actual parameters of the same drive consisting of
an 50-HF’ induction motor fed by an IGBT PWM inverter.
11. DESCRIPTION OF FIELD-ORIENTED CONTROL AND DIRECT
TORQUE CONTROL SCHEMES
In this paper, we consider the basic configuration of indirect
FOC and DTC schemes with two separate control inputs: flux
and torque.
Field-oriented control system
Fig. 1 shows a block diagram of an indirect field-oriented
control system for an induction motor. In this system, the d-q
coordinates reference frame is locked to the rotor flux vector
rotating at the stator frequency U,, as shown in Fig. 2. This
results in a decoupling of the variables so that flux and torque
can be separately controlled by stator direct-axis current id, and
quadrature-axis current i,, respectively.
The stator quadrature-axis reference iqs* is calculated from
torque reference input T,*as:
Do Drive thay đổi chính sách, nên một số link cũ yêu cầu duyệt download. các bạn chỉ cần làm theo hướng dẫn.
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