**HIGH – PERFORMANCE ADAPTIVE INTELLIGENT DIRECT**

TORQUE CONTROL SCHEMES FOR INDUCTION MOTOR DRIVES

TORQUE CONTROL SCHEMES FOR INDUCTION MOTOR DRIVES

**ABSTRACT**This study presents a detailed comparison between

viable adaptive intelligent torque control strategies of induction

motor, emphasizing advantages and disadvantages. The scope

of this study is to choose an adaptive intelligent controller for

induction motor drive proposed for high performance applications.

Induction motors are characterized by complex, highly non-linear

and time varying dynamics and inaccessibility of some states and

output for measurements and hence can be considered as a

challenging engineering problem. The advent of torque and flux

control techniques have partially solved induction motor control

problems, because they are sensitive to drive parameter

variations and performance may deteriorate if conventional

controllers are used. Intelligent controllers are considered as

potential candidates for such an application. In this paper, the

performance of the various sensorless intelligent Direct Torque

Control (DTC) techniques of Induction motor such as neural

network, fuzzy and genetic algorithm based torque controllers

are evaluated. Adaptive intelligent techniques are applied to

achieve high performance decoupled flux and torque control.

The theoretical principle, numerical simulation procedures and

the results of these methods are discussed.

Figure 1 Basic configuration of DTC scheme

Figure 3 Schematic of DTC using Neural-Network controller

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and stator flux control. Very fast torque response -- typically less

than 2ms -~ can be obtained. A very accurate stator flux observer is

an essential part of the complete concept. Due to this observer no

speed sensor is needed.

**DIRECT TORQUE CONTROLLED INDUCTION MOTOR DRIVE**

UTILIZED IN AN ELECTRICAL VEHICLE

A new developed Direct Torque Control principle is used for torqueUTILIZED IN AN ELECTRICAL VEHICLE

and stator flux control. Very fast torque response -- typically less

than 2ms -~ can be obtained. A very accurate stator flux observer is

an essential part of the complete concept. Due to this observer no

speed sensor is needed.

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Abstract. In this paper, a three-level inverter-fed induction motor

drive operating under Direct Torque Control (DTC) is presented

.Atriangularwave is used as dither signal of minute amplitude

(for torque hysteresis band and flux hysteresis band respectively)

in the error block. This method minimizes flux and torque ripple in a

three-level inverter fed induction motor drive while the dynamic

performance is not affected. The optimal value of dither frequency

and magnitude is found out under free running condition. The

proposed technique reduces torque ripple by 60% (peak to peak)

compared to the case without dither injection, results in low acoustic

noise and increases the switching frequency of the inverter. A

laboratory prototype of the drive system has been developed and

the simulation and experimental results are reported.

**Improved direct torque control of induction motor with**

dither injectiondither injection

Abstract. In this paper, a three-level inverter-fed induction motor

drive operating under Direct Torque Control (DTC) is presented

.Atriangularwave is used as dither signal of minute amplitude

(for torque hysteresis band and flux hysteresis band respectively)

in the error block. This method minimizes flux and torque ripple in a

three-level inverter fed induction motor drive while the dynamic

performance is not affected. The optimal value of dither frequency

and magnitude is found out under free running condition. The

proposed technique reduces torque ripple by 60% (peak to peak)

compared to the case without dither injection, results in low acoustic

noise and increases the switching frequency of the inverter. A

laboratory prototype of the drive system has been developed and

the simulation and experimental results are reported.

Block diagram of three-level inverter-fed DTC induction motor drive.

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Abstract

Induction motor drive based on direct torque control

(DTC) allows high dynamic performance to be obtained

with very simple hysteresis control scheme. Direct

control of the torque and flux is achieved by proper

selection of inverter voltage space vector through a

lookup table .In this paper apart from six sector look up

table used for classical DTC, a modified look up table,

which also use six sectors but with different zones and a

twelve sector table are presented .This paper also

presents the application of neural networks to control

induction machines with DTC. Neural network is used to

emulate the state selector of the DTC. In this paper

Levenberg-Marquardt algorithm is used to train the

neural network. Finally DTC is simulated with and

without neural networks and results are compared.

**Direct Torque Control of Induction Motor Using**

Sophisticated Lookup Tables Based on Neural NetworksSophisticated Lookup Tables Based on Neural Networks

Abstract

Induction motor drive based on direct torque control

(DTC) allows high dynamic performance to be obtained

with very simple hysteresis control scheme. Direct

control of the torque and flux is achieved by proper

selection of inverter voltage space vector through a

lookup table .In this paper apart from six sector look up

table used for classical DTC, a modified look up table,

which also use six sectors but with different zones and a

twelve sector table are presented .This paper also

presents the application of neural networks to control

induction machines with DTC. Neural network is used to

emulate the state selector of the DTC. In this paper

Levenberg-Marquardt algorithm is used to train the

neural network. Finally DTC is simulated with and

without neural networks and results are compared.

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Vector Modulation (DTC– SVM) controlled induction motor for

tram drive is presented. Thanks to its advantages like: excellent

dynamics, low torque ripples, insensitivity for motor parameters

changes, constant switching and low sampling frequency,

DTC–SVM is used in various applications. In proposed case

DTC–SVM is used for tram traction drive based on PWM Voltage

Sourced Inverter Fed Induction Machine. This method was chosen

after comparison with Field Oriented Control (FOC), Switching

Table Direct Torque Control (ST–DTC) and Direct Self Control

(DSC). DTC–SVM combines advantages and eliminates

drawbacks commonly used methods like FOC and ST–DTC.

There are no hysteresis controllers, what gives possibility to

reduce sampling and also switching frequency. It leads to reduce

switching loses (important in high power applications).

Constant switching frequency is ensured by using Space Vector

Modulation strategy. In DTC–SVM linear PI regulators are used.

Both stator flux and electromagnetic torque are controlled directly.

High dynamics is achieved and also good stationary operation

performance is kept. This advantages allow to implement

DTC–SVM for traction drives. The paper presents parallel structure

of DTC–SVM. Operating ranges, including field weakening

region, are described. Some experimental results of the 75kW

induction motor drive which illustrate its performance are attached.

**DIRECT TORQUE CONTROLLED PWM**

INVERTER FED INDUCTION MOTOR DRIVE FOR

CITY TRANSPORTATION

In this paper an application of Direct Torque Control with SpaceINVERTER FED INDUCTION MOTOR DRIVE FOR

CITY TRANSPORTATION

Vector Modulation (DTC– SVM) controlled induction motor for

tram drive is presented. Thanks to its advantages like: excellent

dynamics, low torque ripples, insensitivity for motor parameters

changes, constant switching and low sampling frequency,

DTC–SVM is used in various applications. In proposed case

DTC–SVM is used for tram traction drive based on PWM Voltage

Sourced Inverter Fed Induction Machine. This method was chosen

after comparison with Field Oriented Control (FOC), Switching

Table Direct Torque Control (ST–DTC) and Direct Self Control

(DSC). DTC–SVM combines advantages and eliminates

drawbacks commonly used methods like FOC and ST–DTC.

There are no hysteresis controllers, what gives possibility to

reduce sampling and also switching frequency. It leads to reduce

switching loses (important in high power applications).

Constant switching frequency is ensured by using Space Vector

Modulation strategy. In DTC–SVM linear PI regulators are used.

Both stator flux and electromagnetic torque are controlled directly.

High dynamics is achieved and also good stationary operation

performance is kept. This advantages allow to implement

DTC–SVM for traction drives. The paper presents parallel structure

of DTC–SVM. Operating ranges, including field weakening

region, are described. Some experimental results of the 75kW

induction motor drive which illustrate its performance are attached.