Presentation on DTC_og

8/9/2019 Presentation on DTC_og

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Simulation Of Direct Torque Control Of

Three Phase Induction Motor

Presented By

Sandeep Guha NiyogiRoll No. 852010

M.Tech (Power Electronics & Drives)

Under the guidance

of

Mr. A.A.Nimje

Assistant Professor

School Of Electrical Engineering

KIIT University1


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OUTLINE

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INTRODUCTION

Torque control of induction motor based on DTC strategy has

been developed and the performance of this control method

has been demonstrated using Matlab/Simulink.

DTC (as the name indicates) is the direct control of torque &

stator flux of a drive by inverter voltage vector selection

through a look up table.

An advanced technique introduced for voltage fed inverter

drives & claimed to have comparable performance with

Vector Controlled Drives.

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Control Schemes of Induction Motor

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Direct Torque Control

Developed in the middle of 80s by I.Takahashi and T.Noguchi

as Direct Torque Control (DTC) and by M.Depenbrock as

Direct Self Control(DSC)

Stator flux is a time integral of stator emf and its magnitude

strongly depends on the stator voltage

Developed torque is directly proportional to the sine of anglebetween stator and rotor flux vectors

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BASIC DTC SCHEME

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Dynamic Machine model in stationary

reference frame

Q-axis equivalent Circuit D-axis equivalent Circuit

dt

dirV

dtdirV

sdss

dss

s

ds

s

qssqss

sqs

P

P

!

!

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Voltage Source Inverter

a, b and c are the mid

points of the three legs of

the inverter.

T1 to T6 are the switches

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Switching States of Phase Leg a ofVSI

T1 T4 Sa Va

On Off 1

Off On 0 0

dcVSa consisting of switching

devices T1 and T4

The total number of switching states possible with Sa, Sb and Sc are EIGHT

and are elaborated with the relation

baab VVV !

cbbcVVV !

accaVVV !

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Inverter switching states

STATE STATE No.SWITCH STATES

T1, T2, T6 are on 1 1 0 0

T2, T3, T1 are on 2 1 1 0

T3, T4, T2 are on 3 0 1 0

T4, T5, T3 are on 4 0 1 1

T5, T6, T4 are on 5 0 0 1

T6, T1, T5 are on 6 1 0 1

T1, T3, T5 are on 7 1 1 1T4, T6, T2 are on 8 0 0 0

aS

bS cS

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Switching States for the Voltage Source Inverter

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Switching States for the Voltage Source Inverter

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DTC development

The DTC scheme selects between the inverter's six non-zero voltagevectors and two zero vectors in order to keep the stator flux and torquewithin a hysteresis band around the flux and torque reference values.

Neglecting the stator resistance the stator voltage imposes directlythe stator flux in accordance with the following equation:

This equation shows that the applied voltage determines the change inthe stator flux vector.

tVss (!(.

P

ss

sssdt

diRV [P

P!

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DTC development

Stator flux vector locus and different possibleswitching voltage vectors.

5

6

4

3

2

1

V1

V3 V2

V4

V5 V6

rP

sPsP

V1(100)

V2(110)

V3(010)

V4(011)

V5(001)

V6(101)

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DTC CONTROLLER

Classical DTC look-up table

S1 S2 S3 S4 S5 S6

1

+1 V2 V3 V4 V5 V6 V1

0 V7 V0 V7 V0 V7 V0

-1 V6 V1 V2 V3 V4 V5

-1

+1 V3 V4 V5 V6 V1 V2

0 V0 V7 V0 V7 V0 V7

-1 V5 V6 V1 V2 V3 V4

edTPd

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STATOR FLUX & TORQUE CONTROLLER

! dtiV qssqsqsP dtiV dssdsds !P

!

!

ds

qs

fs

fsdsqss

P

PU

UPPP

1

22

tan

qsdsdsqse ii

PT ! PP

22

3

fluxstatoraxis-qqs !P

fluxstatoraxis-d!dsP

fluxstatoraxis-dV

fluxstatoraxis-q

ds !

!qsV

fluxstatorTotal!sP

dsqs &betweenangle PPU !fs

torqueneticelectromag!eT

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SIMULINK MODEL OF DIRECT TORQUE CONTROL OF

INDUCTION MOTOR

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FLUX CONTROLLER

!dtiR

VqssqsqsP

!

!

ds

qs

fs

fsdsqss

P

PU

UPPP

1

22

tan dtiV dssdsds !P

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TORQUE CONTROLLER

qsdsdsqse ii

PT ! PP

22

3

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Section.m

Section.m20


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swtable.m

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Simulation Results

Flux Magnitude Waveform (Weber)

The reference flux was set at 1.5 Wb and the reference torque is at 40 N-m

and the speed attained by the rotor is 960 rpm which is below the set speed

command of 1000 rpm.

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Actual Torque (N-m)

Speed of the motor (rpm)

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Comparison of actual torque obtained and the

reference torque

Reference Torque (N-m)

Actual Torque (N-m)

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Torque ripple and its effect on Speed

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Comparison between the reference flux and

actual stator flux linkage

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Locus of Stator Flux D & Q-Axis Stator Flux

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D & Q-Axis STATOR CURRENT

Three Phase Stator Current

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Inverter output line Current (Amp)

Inverter Output line Voltage (Volts)

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Sectors

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Pulses Generated

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CONCLUSION

The work carried out here is aimed and focused to develop a direct torquecontrol Simulink model. The DTC architecture allows the independent anddecoupled control of torque and stator flux.

DTC has some disadvantages, being one of the most important the torqueripple.

Only stator resistance is employed in the computation of stator flux linkages,thereby removing the dependence of mutual and rotor inductances of themachine on its calculation.

This scheme is also sensitive to stator resistance instrumented in the

controller. The stator resistance change has a wide variation from the set valuedue to the variation in temperature and to a smaller degree to statorfrequency variation, thus deteriorating the drive performance by introducingerror in the stator flux linkage magnitude and position hence in theelectromagnetic torque, particularly at low speeds.

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REFERENCES

Andrzej M. Trzynadlowski, Control Of Induction Motors, Academic Press

Publishers.

B.K.Bose, Modern Power Electronics & AC Drives, Prentice Hal PTR.

R.Krishnan, Electric Motor Drives- modelling, analysis and control,

Prentice Hall of India Pvt Ltd. Direct Torque Control- the world's most advanced AC drive technology

Technical Guide No. 1,ABB Finland

Giuseppe S. Buja, Fellow, IEEE, and Marian P. Kazmierkowski, Fellow, IEEE,

Direct Torque Control of PWM Inverter-Fed AC MotorsA Survey, IEEE

transactions on industrial electronics, vol. 51, no. 4, August 2004. H.F. Abdul Wahab and H. Sanusi, Simulink Model of Direct Torque Control

of Induction Machine, American Journal of Applied Sciences, Vol.5, and

No.8: Pgs. 1083-1090, 2008.

Hoang Le-Huy, Comparison of Field-Oriented Control and Direct Torque

Control for Induction Motor Drives, 1999

IEEE 34


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REFERENCES

Jagdish G. Chaudhari, Sandeep K. Mude and Prakash G. Gabhane, High

Performance Direct Torque Control of Induction Motor Using Space Vector

Modulation, IEEE CCECE/CCGEI, Ottawa, May 2006.

M. Lakshmi Swarupa, G. Tulasi Ram Das and P.V. Raj Gopal, Simulation and

Analysis of SVPWM Based 2-Level and 3-Level Inverters for Direct Torqueof Induction Motor, International Journal of Electronic Engineering

Research, Volume 1 Number 3, pp. 169184, 2009.

Nuno M. Silva, Antnio P. Martins, and Adriano S. Carvalho, Torque and

Speed Modes Simulation of A DTC-Controlled Induction Motor,

Proceedings of the 10th Mediterranean Conference on Control and

Automation - MED2002, Lisbon, Portugal, July 9-12, 2002.

Gopal K. Dubey, Fundamentals of Electrical Drives Second Edition, 2007.

Simulink-Dynamic System Simulation for MATLAB, the Mathworks Inc.

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THANK YOU

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