a simple indirect field oriented control of induction machines without speed measurement

8/10/2019 A Simple Indirect Field Oriented Control of Induction Machines Without Speed Measurement

1/5

A Simple Indirect Field Oriented Control of Induction Machines

Without Speed

Measurement

C.B. Jacobina', J. Bione F o . ~ ,.

alvadori3,A.M.N.

Lima1 and L.A.S. Ribeiro4

lUFPB/CCT/DEE/LEIAM

-

Campus

I1

-

Caixa Postal 10105

58.109-970 ampina Gr ad e , PB, Brazil.

Fax:

+55-83-3101015

{jacobina,marcusQdee.ufpb.br}

CEFET-PEUNED-Pesqueira, PE.

3UNIJUf/DeTEC/NEE Ijui,

RS.

*CEFET-MA - S i b Luis,

MA.

Abstmct: This

paper investigates

the use of the

model reference

control

strateg y for inductionmo

tor drive systems based on ndirect field oriented

control principles.

The

proposed control scheme

does not require

the

use of any electromechanical

sensor and is fairly independent of the rotor time

constant.

The

proposed scheme

is

well

suited

for

applications where there

is

n o

speed

control

but

it

is required to keep the indirect field orien ted con-

troller permanently tuned to obta in

a

high perfor-

mance

torque control.

The

parameter sensitivity

of the

control

scheme to changes

in

7 , and al,

is

also investigated

in this

paper.

Experimental re-

sults are

presented

and demonstra te the correct-

ness and feasibility of the proposed methodology.

I.

INTRODUCTION

The indirect field oriented control (IFOC) techniqueis

very useful for implementing high performance induction

motor drive systems [l-31. In general in the

IFOC

ech-

nique the shaft speed, that is usually measured, and the

slip speed, that is calculated based on the machine pa-

rameters, are added to define the angular frequency of the

rotor flux vector. The standard IFOC technique is essen-

tially

a

feedforward scheme and has the drawback of being

dependent

on

the motor temperature and the level of mag-

netic excitation of the motor. The use adaptive schemes to

compensatefor the parameter changes has been proposed

in

[4,5].

In this paper the model reference strategy is employed

to adapt the shaft speed instead of tracking directly the

rotor time constant changes. With this proposed scheme

the IFOC

can

be implemented without speed sensor. The

proposed scheme keeps the IFOC tuned even when the

rotor time constant changes. Moreover, there is no spe-

cial test signal being

used

and the machine is supplied

with three-phase sinusoidal pulse width modulated volt-

age waveforms. The paper evaluates d-axis voltage model

to be used within

the

adaptat ion scheme. Experimental

results are presented and demonstra te the correctness and

feasibility of the proposed methodology,

11. INDUCTIONOTOR M ODE L

For the purposes of the present investigation the induc-

tion machine is described by

1)

2)

d

dt

d

v:

=

T,i:+

-@, +jw,@:

0 = TA;

+

z@j ( w ,

uT @:

4: = lei:

+f&

3)

4;

= l,i:+lmit

4)

5)

(6)

Te =

P F i:q4:d

-

:d4Cq)

d

d t

Te

-

TL)

= Jm-wp Fmwp

The superscript

U

indicates the use ofa generic reference

frame and the variables and parameters used in the above

expressions are defined

as

follows: i) v = U + u t q ,

4

=

@,

+

q5&

are the sta tor voltage, the sta tor current,

the rotor current, the s tator flux and the rotorflux vectors,

respectively; ii) wp, w,,,

Te

and

TI

are the angular shaft

speed, the angular speed of the 4 coordinate system, the

electromagnetic torque

and

the load torque, respectively

and iii) P, m , Fm rsr r , l , , 1 and Zm rethe

number

of

pole pairs, the moment

of

inertia, the viscous friction

coefficient, the sta tor resistance, the rotor resistance, the

self inductance of the stator, the self inductance of the

rotor and the mutual inductance between stator and rotor,

respectively.

111. INDIRECT

I ELD

ORIENTED

CONTROL

The equations of the indirect field oriented control strat -

egy are defined from the equations tha t link the rotor flux

vector to stator current vector. This relationship, in

a

ref-

erence frame aligned with the rotor flux

vector

(superscript

e), is given by:

i

=

i t d

jifql : = i:d +

j i :q,

4;

= 4 t d

+ # t q

and

0-7803-6401-5/00/ 10.00

2000 IEEE

1809


2/5

i MRAC

Fig. 2. Block diagram of the proposed adaptive scheme

I v l

C ont r o l l e r

Mechan i sm

Fig.

1 .

Block

diagram

of

the model reference adaptive controller

where T , is the rotor time constant 7 , = Z,/r,), wol =

wc-w, is the slip frequency and w e is the angular frequency

of

the rotor flux vector with respect to the stator.

In the indirect field oriented strategy, the torque control

is

achieved through i , while the

rotor flux

is controlled

by i:d. The reference values of izd, and

w , ~

re given

bY

where the superscript indicates the reference variables.

Iv.

MODEL

REFERENCE

ADAPTIVE CONTROL

The model reference adaptive control can be regarded

as

an

ordinary feedback control loop that

has

another feed-

back loop to change the parameters of the controller. The

changes

of

the parameters of the controller is provided by

the adaptive mechanism that aims

at

minimizing the error

between the output

of

the system under control and the

output

of

the reference model

[SI.

1810


3/5

Figure

1

shows the basic block diagram

of

model refer-

ence adaptive strategy where the ordinary feedback loop

is the inner loop and the parameter adjustment loop

is

the

outer loop.

The use of the model reference adaptive schemes re-

quires the choice of

a

reference model to generate y* t)

tha t should be compared to the actual system output pro-

viding the adapting error.

The most common reference

models used with the model reference adaptive system

to

re tune the indirect field oriented controller are presented

in

[4,5].

In this paper we have chosen the d-axis voltage

model and consequently the reference model equation used

for y'(t) is given by

3/ t )= v. ;

=

rsi:: w al i:t;

13)

where U

= 1

-

g / ( l a l , . )

is the leakage factor.

v.

INDIRECT FIELD ORIENTED CONTROL

WITH

SPEED

ADAPTATION

Figure

2

shows the block diagram of the proposed adap-

tive scheme. In this scheme the adaptive mechanism pro-

vides the angular speed

;

that is added to the reference

slip frequency, issued from the indirect field oriented con-

troller, to determine the synchronous frequency of the r e

tor flux vector

3 =

w:, +

0 .

The key point in the proposed scheme is that the changes

of the rotor time constant that would be Compensated in

the computation of the slip frequency

w : ~

re compensated

by

Gr. This

alternative adaptation is viable since the slip

frequency and the shaft speed are simply added to yield the

synchronous frequency. Moreover, the same result of mm-

pensating for the rotor time constant changes is obtained

with the proposed scheme but without requiring the direct

measurement of the shaft speed and thus avoiding the use

of

any electromechanical sensing device.

In the scheme of Fig. 2,

VS

s y*(t) that is the output

of the reference model. The adaptation error is

Ay t)

=

y * ( t )

( t )

where y t ) is determined from the quantities

measured at the machine terminals. This error

Ay t)

is

multiplied by the torque command reference

is:

and is

supplied to a PI controller that provides

Gr

at its output.

VI. PARAMETERENSITIVITY

Variations in the parameters t hat directly influenceur

are normally tracked by adaptive mechanism described

above. However, if the parameters of the reference model

change (e.g., ul,, or r , ) , the performance of the MRAC

may deteriorate. Therefore, the sensitivities of the models

to variations in to nd ol,, have been evaluated at different

load conditions and for different shaft speeds.

The transient analysis examines the time evolution

of

the adapted quantity

w,., at

a given speed and load, in

response

to At, or A oZ,).

Figures 3(a) and 3(b) illustrate

the transient behavior of the performance of the d-axis

voltagezodel for Ar, = T,,

-

Fa = 0 . 7 ~ ~ ~nd A d e

=

uoLeoala =

0.7aOl,,,

espectively,at high frequency. The

subscript

o

in

r

and u,l,, indicates the nomkal value of

the parameter. The superscript

in Faand

ul,

indicates

the parameter estimated used in the MRAC strategy. In

the transient analysis, the

IF0

controller is correctly tuned

for

Os t

a simple indirect field oriented control of induction machines without speed measurement

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