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POWER ELECTRONICSPOWER ELECTRONICS

AC VOLTAGE AC VOLTAGE CONTROLLERSCONTROLLERS

Dr. Adel GastliEmail: [email protected]

http://adel.gastli.net

Dr. Adel Gastli AC VOLTAGE CONTROLLERS 2

INTRODUCTIONINTRODUCTION

Purpose:Purpose: control the output rms voltage using SCR- or Triac-type switch.

Name:Name: AC Voltage Controller, AC to controlled AC converters or AC regulators

Types:Types: there are single-phase and three-phase types of ac voltage controllers


CHAPTERS CONTENTCHAPTERCHAPTERS CONTENTS CONTENT

1. 1-PHASE AC VOLTAGE CONTROLLERS2. 3-PHASE AC VOLTAGE CONTROLLERS3. CYCLOCONVERTERS4. APPLICATIONS & SUMMARY


Section 1Section 1

11--PHASE AC VOLTAGE PHASE AC VOLTAGE CONTROLLERSCONTROLLERS

LZ

)sin( tVv sms =Lv

Li

1T

2T

LZ

)sin( tVv sms =Lv

Li

Triac


SECTIONS CONTENTSSECTIONSECTIONS CONTENTSS CONTENTS

1. ON-OFF CONTROL2. PHASE CONTROL3. SECTION SUMMARY


ONON--OFF CONTROLOFF CONTROLIntegral half cycle control. Usually used for resistive load.

TN period during cycle half ofnumber :

kVNnV

NnVV ssmsrmsrms === 20

R

)sin( tVv sms =Lv

Li

TN

: period

sv

t0

smV

n

on switch during cycles half ofnumber :nSimilar to chopper principle.Duty

cycle


PHASE CONTROL: BIPHASE CONTROL: BI--DIRECTIONALDIRECTIONAL1.1. Resistive LoadResistive Load

sin 1 22

0

20 == dVdvV smLrms

R

)sin( tVv sms =Lv

Li sv

t0smV

+ +2

( ) 22sin-10

+= srms VV


SIMULINK SIMULATIONSIMULINK SIMULATION

vA

+i-

iA

g

+-

v+-

v

a

gk

Triac

g

v0vs

ia

Press toPlot Results

(sp_ac_regm.m)

R=10120V50Hz

(sp_ac_reg.mdl)


0 200 400 600 800 10000

0.5

1

1.5

Gat

e si

gnal

0 200 400 600 800 1000-200

0

200

Vol

tage

, (V

) vsv0

0 200 400 600 800 1000-20

0

20

Cur

rent

, (A

)

Angle, (Deg)

o45=


2.2. Inductive LoadInductive Load

sv

t0smV

R

)sin( tVv sms =0v

0i

L

+ +2

0v

Three cases to be distinguished:i. > ii. < iii. =

0i

i) i) > > : Discontinuous current

= RL 1tan

Current equation is obtained similarly to Chapter 10 (single-phase controlled rectifier).

is obtained by taking i1()=0.

+=22sin

22sin1

0srms VV

( ) ( )

=

tLR

s etZVi

sinsin21


Conduction in one alternance.

ii) ii) < < : / Not Practical because conduction angle cannot exceed

srmssm

rms VVV ==

20

+>To be avoidedTo be avoided

iii) iii) = = : Continuous conduction +=

If triac gate pulse is large enough then we will obtain continuous conduction.


SIMULINK SIMULATIONSIMULINK SIMULATION

R=10120V50Hz

(sp_ac_regm.m)

(sp_ac_reg.mdl)

+ i-

iA

g+- v

+- v

ag k

Triac

g

v0vs

ia

Press toPlot Results

R=10L=10mH

120V50Hz


0 200 400 600 800 10000

0.5

1

1.5

Gat

e si

gnal

0 200 400 600 800 1000-200

0

200

Vol

tage

, (V

) vsv0

0 200 400 600 800 1000-20

0

20

Cur

rent

, (A

)

Angle, (Deg)

o45=

oo 44.1745 =>=


0 200 400 600 800 10000

0.5

1

1.5

Gat

e si

gnal

0 200 400 600 800 1000-200

0

200

Vol

tage

, (V

) vsv0

0 200 400 600 800 1000-20

0

20

Cur

rent

, (A

)

Angle, (Deg)

oo 44.1710 =


oo 44.1710 =


SECTION SUMMARYSECTION SUMMARY

Single-phase AC voltage rms can be controlled by on-off control or phase delay control. By controlling the phase delay it is possible to

control the AC output voltage rms value between 0 and the source rms voltage value.It is important to know beforehand the load

angle in order to be able to control the output voltage properly.


Section 2Section 2

33--PHASE AC VOLTAGE PHASE AC VOLTAGE CONTROLLERSCONTROLLERS

LZ

AvAi0

Bv

CvLZLZ

Bi0

Ci0



1. TOPOLOGIES2. OPERATION3. SIMULINK SIMULATION


TOPOLOGIES TOPOLOGIES

LZ

AvAi0

Bv

CvLZLZ

Bi0

Ci0

1

2

3

1T

2T

3T

LZ

AvAi0

Bv

CvLZLZ

Bi0

Ci0

1

2

3

N

1T

2T

3TN

AvAi0

Bv

Cv

Bi0

Ci0

1

2

3

1T

2T

3T

LZ

LZLZ

Av

Bv

Cv2T

1

32

1T

3TLZ

LZ

LZ

Equivalent to 3 single-phases Is studied in this chapter


OPERATION OPERATION

line on line off v12 v1NA,B, C None VAB VAA,B C VAB VAB/2A,C B VAC/2 VAC/2B,C A -VBC/2 0None A,B,C 0 0A ImpossibleB ImpossibleC Impossible

LZ

AvAi0

Bv

CvLZLZ

Bi0

Ci0

1

2

3

N

1T

2T

3T

=>


0 50 100 150 200 250 300 350

-200

0

200V

olta

ge, (

V)

0 50 100 150 200 250 300 3500

0.5

1

1.5

Gat

e si

gnal

0 50 100 150 200 250 300 350-20

0

20

Cur

rent

, (A

)

Angle, (Deg)

avacv5.0

av

abv5.0

3 +

3 32 +

32

av

o30= Purely resistive load

Pulse width 50%


0 50 100 150 200 250 300 350

-200

0

200

Vol

tage

, (V

)

0 50 100 150 200 250 300 3500

0.5

1

1.5

Gat

e si

gnal

0 50 100 150 200 250 300 350-20

0

20

Cur

rent

, (A

)

Angle, (Deg)

o60= Purely resistive loadabv5.0 acv5.0

3

2 +3

2



0 100 200 300 400 500

-200

0

200V

olta

ge, (

V)

0 100 200 300 400 5000

0.5

1

1.5

Gat

e si

gnal

0 100 200 300 400 500-20

0

20

Cur

rent

, (A

)

Angle, (Deg)

+3 6

76

5

abv5.0 acv5.0



0 100 200 300 400 500

-200

0

200

Vol

tage

, (V

)

0 100 200 300 400 5000

0.5

1

1.5

Gat

e si

gnal

0 100 200 300 400 500-20

0

20

Cur

rent

, (A

)

Angle, (Deg)


MATHEMATICAL ANALYSIS: (Resistive Load)MATHEMATICAL ANALYSIS: (Resistive Load)

( )

+=

==

32sin2

32sin2

sin2

sBN

sBN

sAN

Vv

Vv

Vv

iaiL

vAN vanR=1o

T1

T4

vBN

vCN

T3

T6

T5

T2

R=1o

R=1o

ib

ic

NB

C

a

b

A

=

=

+=

6sin6

2sin6

6sin6

sCA

sBC

sAB

Vv

Vv

Vv


( )( ) ( ) ( ) ( ) ( )

++++=

=

++

++

tdvtdvtdvtdvtdv

tdvV

aac

aab

a

an

3/2

23/2

3/2

23/2

3/

23/

3/

23/ 2

2

0

20

441

21

o600


+=82sin

46160

sVV

RVI 00 = 000 3 VIP =

Output powerrms output Phase Current

rms Output phase voltage

( ) ( ) ( ) ( ) ( ) ( ) ( )

+++++= + + ++ 3/

3/

3/2

3/ 3/2

23/2

3/2

2223/ 2

0 3sin

46/sin

3sin

46/sin

3sin16 tdttdttdttdttdtVV s


( )( ) ( )

+=

=

++

+tdvtdv

tdvV

acab

an

3/2

3/

23/ 2

2

0

20

441

21

oo 9060


++=

162cos3

162sin3

12160

sVV

RVI 00 = 000 3 VIP =



( ) ( )

+= ++ ++ 2/

6/

2/

6/

22

0 4sin

4sin16 tdttdtVV s


( )( ) ( )

+=

=

+ tdvtdv

tdvV

acab

an

6/7

3/

26/5 2

2

0

20

441

21

oo 15090


++=

162cos3

162sin

4245160

sVV

RVI 00 = 000 3 VIP =



+= + + 6/ 6/22

0 )(4sin)(

4sin16 tdttdtVV s


Section 3Section 3

CYCLOCONVERTERSCYCLOCONVERTERS



1. SINGLE-PHASE2. THREE-PHASE


SINGLESINGLE--PHASE CYCLOCONVERTERPHASE CYCLOCONVERTER

+

sv 01v Load

3T1T

4T 2T

'4T

'2T

'3T

'1T

02v

+

P-converter N-converter

sv

t0

smV

P-converter on

N-converter on

cycles) half positive ofnumber (n ==nff sout

+=

=

2sin1

1 20

s

s

V

dvV

Variable voltage variable frequency converter output voltage.


THREETHREE--PHASE CYCLOCONVERTER PHASE CYCLOCONVERTER

+

A01v

Load

1T

4T

'2T

'5T

'6T

'3T

02v

+

P-converter N-converter

3T

6T

5T

2T

BC

'4T

'1T

ABC

Three-phase/single-phase cycloconverter


Three-phase/three-phase cycloconverter

P N P NP N

Phase a load

Phase b load

Phase c load

Neutral

Three-phase supply

18 thyristors are used to obtain a 3 full-wave three-phase converter.


Section 4Section 4

APPLICATIONS & SUMMARYAPPLICATIONS & SUMMARY


APPLICATIONSAPPLICATIONS

Light dimmer.

Soft starting of ac motors (compressors, pumps, etc.)

Variable speed drives for appliances an tools.

Transformer static tap changers.0v

pv


SUMMARYSUMMARYAc voltage controllers can use on-off control or

phase-angle control.The on-off control is more suitable for systems

having a high time constant.Due to the switching characteristics of thyristors,

an inductive load makes the solutions of equations describing the performance of controllers very complex and simulation is more convenient.The input power factor of controllers, which vary

with the delay angle, is generally poor, especially at low voltage output range.

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