marie curie presentation

8/3/2019 Marie Curie Presentation

1/19

IMPROVING

DIRECT TORQUE CONTROLUSING MATRIX CONVERTERS

Technical University of Catalonia.

Electronics Engineering Department.

Colom 1, Terrassa 08222, Catalonia, Spain

University of Malta.

Department of Electrical Power and Control

Engineering.

Msida MSD 06, Malta

Research Student:

Carlos Ortega Garca

Home Supervisor:

Dr. Antoni Arias Pujol

Malta Supervisor:

Dr. Cedric Caruana


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Index

Introduction

Matrix Converters.

Direct Torque Control.

Classical

Using Matrix Converters.

Sensorless Control of a DTC drive using hf injection

Conclusions.


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Introduction

Matrix Converters (MC)

Advanced circuit topology capable of generating AC-AC.

Load voltage with arbitrary amplitude and frequency, and

sinusoidal input/output waveforms.

Power Factor Correction (PFC).

No inductive or capacitive elements

are required, thus allowing a very

compact design.

A very good alternative to Voltage Source Inverters (VSI).


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Direct Torque Control (DTC).

Simple and robust signal processing scheme.

No coordinate transformation and no PWM generation areneeded.

Quick and precise torque response.

The torque and flux modulus values and sector of the flux are

needed.

High torque ripple.

Introduction


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High Frequency Signal Injection.

Non Model-Based method.

Avoids problems at low and zero speed due to the lack ofback-EMF.

No dependence of machine parameters.

Saliency required.

Introduction


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Main objectives:

Improve the Direct Torque Control, regarding torque ripple,

using small vectors of Matrix Converters.

Analysis of different High Frequency signal Injection

methods for sensorless Direct Torque Control.

Introduction


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A switch, Sij, i={A,B,C},j={a,b,c} can

connect phase i of the input to phasej

of the load.

Switches states characterized by:

closedisswitchif1

openisswitchif0

ij

ij

ijS

SS

A mathematical model of the MC can be derived: Voltage equations: Current equations:

)(

)(

)(

)()()(

)()()(

)()()(

)(

)(

)(

tv

tv

tv

tStStS

tStStS

tStStS

tv

tv

tv

C

B

A

CcBcAc

CbBbAb

CaBaAa

cN

bN

aN

)(

)(

)(

)()()(

)()()(

)()()(

)(

)(

)(

ti

ti

ti

tStStS

tStStS

tStStS

ti

ti

ti

c

b

a

CcCbCa

BcBbBa

AcAbAa

C

B

A

VSB

SAb

SAc

VSA

VSC

M

Lf

Lf

Lf

Rf

Rf

Rf

SAa

SBa

SBb

SBc

SCb

SCc

SCa

Cf

Cf

Cf

Matrix ConverterInput Filter

ISB

ISA

ISC

Ia

Ib

Ic

IB

IA

IC

VaN

VbN

VcN

State of the Art

Matrix Converters


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Since any output phase can be connected to any input phase, there are 27

possible switching configurations.

Applying Clarks transformation to all switching states, it can be found that

MC can generate:

18 active vectors, 6 rotating vectors, and 3 zero vectors.

Output line-to-neutral voltage vectors Input line current vectors

Matrix Converters

Sector

1

2

3

4

5

6

1,2,3

4,

5,

6

7,8

,9

a)

Sector

1

23

4

5 6

2,

5,

8

1,4,73,6

,9

b)

State of the Art


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Direct Torque Control

Stator flux y*sand torque T*e

references are compared with the

corresponding estimated values.

Both stator flux and torque errors,

EyandETe, are processed by meansof hysteresis band comparators.

A proper VSI voltage vector is

selected.

The flux vector reference and thehysteresis band tracks a circular

trajectory, thus, the actual flux

follows its reference within the

hysteresis band in a zigzag path.

Look-up table

Flux and Torque Estimator

yS

Hy

Te

Te*

yS*

Te

yS

Ey

HTe

ETe

Voltage Source Invert er

IA

IB

Vo

SA

SB

SC

S(n)

M

S(1)

S(2)S(3)

S(4)

S(5) S(6)

V3t

1

V4t

2

V3t3V

4

t4

yS

V1

V2

V3

V4

V5

V6

y1

y2

y3

y4

y5

y6

a) b)

yy sin||||'2

3sr

sr

me

LL

LpT


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Direct Torque Control using

Matrix Converters

Matrix converter generates a higher

number of output voltage vectors

with respect to a VSI.

Another variable, , is

introduced to control the input

power factor.

Keeping this variable close to zero,

unity power factor operation is

possible.

A new hysteresis comparator is introduced which controls this variable.

Classical DTC using Matrix Converters

Voltage VectorTable

MatrixConverter

Flux and Torque

Estimator

yS

Hf

Te

Te*

yS*

Te

yS

IA

IB

Vo

S(n)

SA

SB

SC

Hy

HTe

ETe

Ey

estimator

M

Direct Torque Control for Induction Motors Using Matrix Converters (CPE-05)


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A new torque hysteresis comparator will provide

four different levels instead of three to distinguish

between small and large positive and negative

torque errors.

ETe

HTe

HTe

ETe

Large vectors will be used when

large torque error is detected.

When torque error is small, the small

voltage vector will be applied.

Zero vectors will be applied if small

torque error is detected and back

EMF imposes a variation in torque

towards its reference value.

The use of small vectors of Matrix Converters

Zero vector applied Low torque slope

Small vecto r applied Medium torque slope

Upper to rque band

Lower torque band

Large vector applied High torque slope

Upper torque band

Lower torque band

a) b)


Matrix Converters


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Torque ripple performance.

Comparison between the classical use of MC in DTC and the proposed method.

Classical DTC using MC Proposed method

0.85 0.9 0.95 14

4.5

5

5.5

6

6.5

7

7.5

8

Time (s)

Torque

(Nm)

0.85 0.9 0.95 14

4.5

5

5.5

6

6.5

7

7.5

8

Time (s)

Torque

(Nm)


wref=100% rated speed and TL=100% rated torque.


Matrix Converters


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Torque ripple performance.

Comparison between the classical use of MC in DTC and the proposed method.


0 250 500 750 1000 1250 15000.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Speed (rpm)

rmsvalueofTe

ERROR(Nm)

Classcal DTC using MC

Proposed method

The use of zero and large vectors in

the classical method leads into an

over/undershoot, more pronounced

as the speed increases. Small vectors are more effective

keeping the torque within the its

reference bands.


Matrix Converters


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Sensorless Control

Saliency

a

b

gmaxgminqr

q

(a)

(b)

gmaxgmin

Lm

qr(elec)

Asymmetry in the machine.

Magnetizing inductance variation.

Asymmetry in the rotor Rotor Position.

t

tV

v

v

i

ii

si

si

w

w

b

a

cos

sin

tLtL

tLtL

LL

V

i

i

irsis

irsis

qsdsi

i

si

si

wqw

wqw

wb

a

2sinsin

2coscos


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Sensorless Control

ab frame rotating injection.

Straightforward in vector

controlled drives.

The carrier can be

superimposed to the

voltage reference.

vds

*

iqs

*

ids

*

Voltage

Source

Inverteriabc

iab

PMSM

flux position

estimate

+

-

-

+

abcab

qe

++

+

+

dq

ab

dq

ab

PI

PI

ids

iqs

vqs

*

vas

*

vbs

*

vasi

vbsi

iab

wi

wi

tan-1ej2wite-jwitiab

iiab

iipos

Synchronous filter

Band-pass

filterHigh-pass

filter

2qr


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Sensorless Control

ab injection in a DTC drive.

Flux and Torque processed

errors, Hys and HTe, converted

directly to switching signals.

No voltage command =>

Difficult to inject.

Injection directly modifying the

vector pattern imposed by the

DTC switching table.

V4

V5

V4

V6V

n

Vn

Vn+1

Vn+1

xK xK

Tz

Ti

Voltage VectorTable

Stator Fluxand

TorqueEstimator

yS

Hy

Te

Te*

yS

* Ey

HTe

ETe

VoltageSource

Inverteriabc

iab

SA

SB

SC

S(n)

PMSMInjectionalgorithm

VSI

+PMSM

hfModel

abc/ab

iiab

VSI+

FundamentalEstimator

Synchronousfilter

ifab

+

-

-

-

-

+

+

+

High bandwidth of hysteresis controllers.

Difficult to inject outside of this bandwidth.

Decoupling of fundamental and hfcurrents is necessary


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Sensorless Control

ab injection in a DTC drive.

Steady state at 375 rpm Speed reversal.

Comparison between real and estimated position

0 0.05 0.1 0.15 0.2-4

-2

0

2

4

Time (s)

Modelbased

angleestimate(rad)

0 0.05 0.1 0.15 0.2-4

-2

0

2

4

Time (s)

Injectionmethod

angleestimate(rad)

0 0.1 0.2 0.3 0.4 0.5 0.6-4

-2

0

2

4

Time (s)

Modelbased

angleestimate(rad)

0 0.1 0.2 0.3 0.4 0.5 0.6-4

-2

0

2

4

Time (s)

Injectionmethod

angleestimate(rad)


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Conclusions

Advantages of Matrix Converters over the traditional VSI has

been combined with the advantages of the DTC scheme.

The use of small vectors of the MC has been investigated.

High frequency injection in a DTC drive has been presented.


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Thank you.

marie curie presentation

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