analysis of power converters

8/17/2019 Analysis of Power Converters

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LECTURE NOTES ON

PE2001-ANALYSIS OF POWER CONV

SRM UN

Prepared by

Mr. R. Sridha

Ms. A. Geet

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RECTIFIER CIRCUIT

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INTRODUCTION

IN THYRISTOR BASED RECTIFIERS, OUTPUT VOLTAGE CAN BE CONTROLLED. SO TH

TERMED AS CONTROLLED RECTIFIERS.

CONTROLLED RECTIFIERS PRODUCE VARIABLE DC OUTPUT, WHOSE MAGNITUDE I

PHASE CONTROL.

PHASE CONTROL

DC OUTPUT FROM RECTIFIER IS CONTROLLED BY CONTROLLING DURATION OF T

CONDUCTION PERIOD BY VARYING THE POINT AT WHICH GATE SIGNAL IS APPLI

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CONTROLLED RECTIFIERS ARE OF TWO TYP

1- FULLY CONTROLLED RECTIFIERS

DC CURRENT IS UNIDIRECTIONAL, BUT DC VOLTAGE HAS EITHER POLARITY. WITH

POLARITY, FLOW OF POWER IS FROM AC SOURCE TO DC LOAD---RECTIFICATIO

WITH THE REVERSAL OF DC VOLTAGE BY THE LOAD, FLOW OF POWER IS FROM

TO AC SOURCE---INVERSION.

2- HALF CONTROLLED RECTIFIERSHALF OF SCRS ARE REPLACED BY DIODES.

DC OUTPUT CURRENT AND VOLTAGE ARE UNIDIRECTIONAL. I.E., FLOW OF POW

AC SOURCE TO DC LOAD.

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6

Half-Wave Rectifier with R-L Load

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7

Half-Wave Rectifier with R-L Load (freewheeling diod

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Full controlled Rectifier with R-L Load (freewheeling diode

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9

Full controlled Rectifier with R-L Load

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Full controlled Rectifier with R-L Load with freewheeling diode(Bri

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Full controlled Rectifier with RLE Load(Bridge type)

Continuous current mode Discontinuous c

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Full controlled Rectifier with RLE Load(Bridge type)

Inversion mode of operation

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• IN FULLY-CONTROLLED RECTIFIER, ONLY RECTIFICATION CAN BE OBTAINED

CONNECTING A FREEWHEELING DIODE ACROSS THE OUTPUT TERMINALS OF TRECTIFIER.

• ANOTHER METHOD OF OBTAINING RECTIFICATION IN BRIDGE RECTIFIERS

REPLACING HALF OF THE SCRS WITH DIODES. THESE CIRCUITS ARE CALL

SEMICONTROLLED BRIDGE RECTIFIERS.

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Semi controlled Rectifier with R-L Load

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S i t ll d R tifi ith R L L d ith f h li di d



Semi controlled Rectifier with R-L Load with freewheeling diode

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S ll d R f h RLE L d (C d )



Semi controlled Rectifier with RLE Load (Continuous current mode)

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S i ll d R ifi i h RLE L d (Di i d



Semi controlled Rectifier with RLE Load (Discontinuous current mod

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WHY DUAL CONVERTER……?

• SEMI-CONVERTER ARE SINGLE QUADRANT CONVERTER (I.E) OVER ENTIRE FIRING ANG

LOAD VOLTAGE & CURRENT IS SAME POLARITY

• SEMI-CONVERTER OPERATES ONLY IN RECTIFICATION MODE

• FULL-CONVERTER ARE TWO QUADRANT CONVERTER

• HERE THE CURRENT DIRECTION CANNOT REVERSED DUE TO UNIDIRECTIONAL PROPERT

BUT VOLTAGE CAN BE REVERSED

• Α = 0 TO 90 -(VTG & CT IS + VE)-RECTIFIER

• Α = 90 TO 180 -(VTG IS -VE & CT IS +VE)-INVERTER

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WHAT …..?

• IN ORDER TO HAVE FOUR QUADRANT OPERATION WITHOUT ANY MECH CHANG

SWITCH WE GO FOR DUAL CONVERTER

• TWO CONVERTERS ARE CONNECTED BACK TO BACK TO THE LOAD CIRCUIT(IE)TW

CONVERTERS IN ANTI-PARALLEL & CONNECTED TO SAME DC LOAD

• BY THIS ARRANGEMENT WE CAN REVERSE BOTH VTG & CT

• THUS FOUR QUADRANT OPERATION IS OBTAINED

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SINGLE PHASE DUAL CONVERTER

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GATING SEQUENCE

1 1

2 2

The average dc output voltage of converter 1 i2

cos

The average dc output voltage of converter 2 i

2 cos

mdc

mdc

V V

V V

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GATING SEQUENCE

0

0

1

In the dual converter operation one

converter is operated as a controlled rectifie

with 90 & the second converter is

operated as a line commutated inverterin the inversion mode with 90

dcV V

2dcSRM UNIVERSITY



GATING SEQUENCE

1 2 2

1 2

2 1 1

2 1

1 2

2 1

2 2 2cos cos cos

cos cos

or

cos cos cos

or

radians

Which gives

m m mV V V

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OUTPUT WAVEFORM

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PRACTICAL DUAL CONVERTER

• THOUGH THEIR AVG OUTPUT VTG ARE EQUAL ,YET THEIR INST.VTG ARE OUT OF P

RESULT IN VTG DIFFERENCE

• SO LARGE CIRCULATING CT FLOW BETWEEN TWO CONVERTERS BUT NOT THROU

LOAD

• CIRCULATING CT CAN BE LIMITED BY INSERTING A REACTOR BETWEEN THE TWO C

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EXP FOR INST.CIRCULATING CURRENT

• V O1 = INSTANTANEOUS OUTPUT VTG OF CONVERTER 1

• V O2 = INSTANTANEOUS OUTPUT VTG OF CONVERTER 2

• THE CIRCULATING CURRENT IR CAN BE DETERMINED BY INTEGRATING THE INSTANTAN

VOLTAGE DIFFERENCE (WHICH IS THE VOLTAGE DROP ACROSS THE CIRCULATING CUR

REACTOR LR), STARTING FROM T = (2 - 1 ).

• IDEAL CONDTION AS T

AVERAGE OUTPUT VOLTAGES DURING THE INTERVAL T = ( + 1 ) TO (2 - 1 ) ARE

OPPOSITE THEIR CONTRIBUTION TO THE INSTANTANEOUS CIRCULATING CURRENT IR IS

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1

1

1 2

2

2

1 2

1 2

2

1 1

1 . ;

As the o/p voltage is negative

1. ;

sin for 2 to

t

r r r O O

r

O

r O O

t

r O O

r

O m

i v d t v v v L

v

v v v

i v v d t L

v V t t

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1 12 2

1

sin . sin .

2cos cos

The instantaneous value of the circulating current

depends on the delay angle.

t t

mr

r

mr

r

V i t d t t d t

L

V i t

L

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1For trigger angle (delay angle) 0,

the magnitude of circulating current becomes min.

when , 0,2,4,.... & magnitude becomes

max. when , 1,3,5,....

If the peak load current is , one of p

t n n

t n n

I

the

converters that controls the power flow

may carry a peak current of

4,m

p

r

V I

L

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max

max

where

,

&

4 max. circulating current

m

p L

L

m

r

r

V I I

R

V i

L

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MODES OF OPERATION

•DUAL CONVERTER WITHOUT CIRCULA

CURRENT

•DUAL CONVERTER WITH CIRCULATINGCURRENT

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DUAL CONVERTER WITHOUT CIRCULATIN

CURRENT

• IN THIS MODE ONLY ONE CONVERTER IS OPERATED AT A TIME & NO NEED OF REA

• WHEN CONVERTER 1 IS ON, 0 < 1 < 900

• V DC IS POSITIVE AND IDC IS POSITIVE

• ALLOW 10 TO 20MS TO LOAD CT TO REACH ZERO

• WHEN CONVERTER 2 IS ON, 0 < 2 < 900

• V DC IS NEGATIVE AND IDC IS NEGATIVE

• LOAD CT MAY DISCONTINUOUS OR CONTINUOUS BUT SATISFACTORY OPERATIO

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DUAL CONVERTER WITH CIRCULATING CUR

• IN THIS MODE, BOTH THE CONVERTERS ARE SWITCHED ON AND OPERATED AT THE SA

REACTOR IS INSERTED

• THE TRIGGER ANGLES 1 AND 2 ARE ADJUSTED SUCH THAT ( 1 + 2 ) = 1800 (IE) 2

• WHEN 0 < 1 <900, CONVERTER 1 OPERATES AS A CONTROLLED RECTIFIER AND CON

OPERATES AS AN INVERTER WITH 900 < 2<1800

• IN THIS CASE V DC AND IDC, BOTH ARE POSITIVE• WHEN 900 < 1 <1800, CONVERTER 1 OPERATES AS AN INVERTER AND CONVERTER 2

AS A CONTROLLED RECTIFIER BY ADJUSTING ITS TRIGGER ANGLE 2 SUCH THAT 0 <

• IN THIS CASE V DC AND IDC, BOTH ARE NEGATIVE

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FOUR QUADRANT OPERATION

Conv. 2Inverting2 > 900

Conv. 2

Rectifying

2 < 900

Conv. 1Rectifyin

1 < 900

Conv. 1

Inverting

1 > 900

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MERITS OF DUAL CONVERTER WITH CIRCULAT

• THE CIRCULATING CURRENT MAINTAINS CONTINUOUS CONDUCTION OF BOTH T

CONVERTERS OVER THE COMPLETE CONTROL RANGE, INDEPENDENT OF THE LOA

• ONE CONVERTER ALWAYS OPERATES AS A RECTIFIER AND THE OTHER CONVERTER

AS AN INVERTER, THE POWER FLOW IN EITHER DIRECTION AT ANY TIME IS POSSIB

• AS BOTH THE CONVERTERS ARE IN CONTINUOUS CONDUCTION WE OBTAIN FAS

RESPONSE. I.E., THE TIME RESPONSE FOR CHANGING FROM ONE QUADRANT OPE

ANOTHER IS FASTER

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DEMERITS OF DUAL CONVERTER WITH

CIRCULATING CT

• DUE TO REACTOR, SIZE & COST IS HIGH

• CIRCULATING CT GIVES RISE TO MORE LOSSES IN CONVERTER. SO THE EFFICIENC

FACTOR IS LOW

• THE CONVERTER THYRISTORS SHOULD BE RATED TO CARRY A PEAK CURRENT MUC

THAN THE PEAK LOAD CURRENT

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Effect of source Inductance in single phase rectifier



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Effect of source Inductance in single phase rectifier



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3-phase full controlled rectifier(RL)



40

• THE LINE-TO-NEUTRAL VOLTAGES ARE:

• THEN THE LINE-TO-LINE VOLTAGES ARE:

)3

2(sin

)3

2

(sin

sin

t V v

t V v

t V v

mcn

mbn

man

)6

5(sin3

)2

(sin3

)6

(sin3

t V vvv

t V vvv

t V vvv

mancnca

mcnbnbc

mbnanab

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3-phase full controlled rectifier(RL)



• THE AVERAGE OUTPUT VOLTAGE IS FOUND FROM :

• THE RMS VALUE OF THE OUTPUT VOLTAGE IS :

cos

33)(

3 2/

6/

mabdc

V t d vV

2/1

2/12/

6/

2

)2cos4

33

2

1(3

)(

3

mrms

abrms

V V

t d vV

41SRM UNIVERSITY

3-phase full controlled rectifier(RLE)



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3-phase full controlled rectifier(RLE)



Rectification mode Inversion mode

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Analysis for Rectification mode



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Analysis for Rectification mode



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Effect of source Inductance in three phase rectifier



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3 phase Dual Converter



48

Due to instantaneous voltage differences between the output

voltages of converters, a circulating current flows through the

converters.

This circulating current is limited by a reactor.SRM UNIVERSITY

12 PULSE CONVERTER



a) SERIES CONNECTION

b) PARALLEL CONNECTION

c) TRANSFORMER CONNECTIO

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12 PULSE CONVERTER



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DC-DC CONVERTERS (CHOPPERS)

• THE OBJECTIVE IS TO CONVERT A FIXED DC VOLTAGE TO A VARIABLE

DC VOLTAGE

• IT IS POSSIBLE TO STEP UP AND STEP DOWN VOLTAGE.

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VOLTAGE STEP DOWN (BUCK CONVERTE



VOLTAGE STEP DOWN (BUCK CONVERTE

First, suppose L=0, E=0.

The diode is not needed.

Va=(ton/T)Vs

VRMS=k

1/2

Vs

Pout=(kVs2)/R

k=ton/T is the duty cycle

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VOLTAGE STEP UP (BOOST) CONVERTER

“On” mode: VL=L(di/dt)

“Off” mode: Assume currentdecreases at a constant rate. Then

Vo=Vs+VL

To ensure continuous current flow, a

capacitor is included.

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AVERAGE VALUE OF THE OUTPUT VOLTAG1

1

0

0

11

1

1

t

a O

t

a S

a S S

a S

V v dt T

V V dt T

t V V ft V T

V kV

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Performance of a step up converter with resistive load



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DC-DC CONVERTER CLASSIFICATION

• FIRST QUADRANT CONVERTER

• SECOND QUADRANT

CONVERTER

• 1ST AND 2ND QUADRANT

CONVERTER

• 3RD AND 4TH QUADRANTCONVERTER

• FOUR QUADRANT CONVERTER

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FIRST QUADRANT CHOPPER



S QU N C O

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SECOND QUADRANT CHOPPER



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THIRD QUADRANT CHOPPER



THIRD QUADRANT CHOPPER

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FOURTH QUADRANT CHOPPER



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1-2 AND 3-4 QUADRANT CONVERTERS



Q

1st quad: S1, D4

2nd quad: S4, D1

3rd quad: S3, D2

4th quad: S2, D3

Polarity of the load EMF is reversed

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FOUR QUADRANT CONVERTER



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LOAD VOLTAGE EXPRESSIONS ARE

OU QU N CONV

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Step-Down/Up (Buck-Boost) Converter



• The output voltage can be higher or lower than the input voltage

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Buck-Boost Converter: Waveforms

C ti d ti d



• Continuous conduction mode

Switch closed:

di

dt

V

L

L CC

Switch open:

di

dt

v

L

L o

Inductor Volt-second balance:

D

DV V

L

T DV

L

DT V

CC o

oCC

1

0)1(

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Buck-Boost: Limits of Cont./Discont. Conduct



• The output voltage is held constant

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Buck-Boost: Discontinuous Conduction



• This occurs at light loads

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Cuk DC-DC Converter

• The output voltage can be higher or lower than the input voltage



• Capacitor C1 stores and transfers energy from input to output

• When switch is ON, C1 discharges through the switch and transfers

output

• When switch is OFF, capacitor C1 is charged through the diode by einput and L1

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Cuk DC-DC Converter: Waveforms

• The capacitor voltage is



• The capacitor voltage is

assumed constant (very large)

• Note phase inversion at the

output

D

D

V

V

d

o

1

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SEPIC Converter



• Single-ended primary inductance converter (SEPIC)• Can buck or boost the voltage

• Note that output is similar to buck-boost, but without a ph

inversion

• This circuit is useful for lithium battery powered equipmen

D

D

V

V

d

o

1

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SEPIC Converter

Circuits for 2 different switching states



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ZETA CONVERTER



A Zeta converter performs a non-inverting buck-boost function similar to that of a SEPIC, w

acronym for Single-Ended Primary Inductance Converter. The Zeta topology is also similar to t

in that it uses two inductors, two switches and a capacitor to isolate the output from the input.

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When analyzing Zeta waveforms it is helpful to keep in mind that at equilibrium, L1average curr

average current equals IOUT, since there is no DC current through the flying cap CFLY. Also there is

i h i d Th f CFLY d i l i l f id d VOUT i i h id

ZETA CONVERTER



either inductor. Therefore, CFLY sees ground potential at its left side and VOUT at its right side, r

across CFLY being equal to VOUT.

When M1 is on, L1 and L2 are energized. D1 sees a potential of VIN+VOUT across it (see figures 3

is off, energy stored in L1 and L2 is released. D1 is forward biased.

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ZETA CONVERTER



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ZETA CONVERTER



Output voltage is given by the following equation:

Where D is duty cycle. VOUT is plotted as a function of D in figure 6. As

can be seen, for D less than 0.5 the converter performs buck function and

for D larger than 0.5 it is a boost topology.

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RESONANT CONVERTER



INTRODUCTION

CLASSIFICATION

CONCLUSION

RESONANT CONVERTER

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INTRODUCTION



RESONANT INVERTERS ARE ELECTRICAL INVERTE

ON RESONANT CURRENT OSCILLATION. IT IS KNOWN AS DC TO DC CONV

TO AC PWM INVERTER.

MAIN FUNCTION IS TO REDUCE SWITCHING LOSSES OF THE DEVICES(MO

INTRODUCTION

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CLASSIFICATION



THE RESONANT CONVERTER BROADLY CLASSIFIED INTO EIGHT TYPES. THOS

1. SERIES RESONANT INVERTER

2. PARALLEL RESONANT INVERTER

3. CLASS E RESONANT CONVERTER

4. CLASS E RESONANT RECTIFIER

5. ZERO VOLTAGE SWITCHING(ZVS) RESONANT CONVERTER

6. ZERO CURRENT SWITCHING(ZCS) RESONANT CONVERTER

7. TWO QUADRANT ZVS RESONANT CONVERTER

8. RESONANT DC-LINK INVERTER

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SERIES RESONANT INVERTER



IT IS BASED ON RESONANT CURRENT OSCILLATION.

SWITCHING DEVICE ARE PLACED IN SERIES WITH LOAD.

THYRISTOR ARE WORK IN SWITCHING DEVICE.

THIS TYPE OF INVERTER PRODUCES AN APPROXIMATELY SINUSOIDAL W

A HIGH FREQUENCY ,RANGING FROM 200HZ TO 100KHZ.

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CIRCUIT DIG OF SERIES RESONANT CONVERTER



CIRCUIT DIG. OF SERIES RESONANT CONVERTER

Equivalent circuit dig. Waveform

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PARALLEL RESONANT INVERT



PARALLEL RESONANT INVERTER IS DUAL OF SERIES RESONANT INVERTE

CURRENT IS CONTINUOUSLY CONTROLLED , THAT GIVES BETTER SHORT

PROTECTION UNDER FAULT CONDITION

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CLASS E RESONANT CONVERT



IT HAS LOW SWITCHING LOSSES , YIELDING A HIGH EFFICIENCY OF MOR

USED IN LOW POWER APPLICATION & HIGH FREQUENCY ELECTRIC LAMP

CLASS E RESONANT CONVERT

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CIRCUIT DIG. OF CLASS E RESONANT INVERTER & WAVE FORM

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CLASS E RESONANT RECTIFIE



CLASS E RESONANT RECTIFIER IS BASED ON THE PRINCIPLE OF ZE

SWITCHING(ZVS) .

THE DIODE TURN OFF AT ZERO VOLTAGE.

A HIGH FREQUENCY DIODE RECTIFIER SUFFERS FROM DISADVANT

SWITCHING LOSSES , HARMONIC CONTENT.

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ZERO VOLTAGE SWITCHING(ZVRESONANT CONVERTER



THE ZVS RESONANT CONVERTER TURN ON & TURN OFF AT ZERO VOLTAG

OUTPUT VOLTAGE CONTROL CAN BE ACHIEVED BY VARYING THE FREQU

OPERATES WITH CONSTANT OFF TIME CONTROL .

RESONANT CONVERTER

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ZERO CURRENT SWITCHING(ZCRESONANT CONVERTER



ZERO CURRENT SWITCHING(ZCS) RESONANT CONVERTER TURN ON & TU

ZERO CURRENT.

THIS CONVERTER CAN OPERATE AT HIGHER RANGE FREQUENCY THAT IS

2MHZ.

RESONANT CONVERTER

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TWO QUADRANT ZVS RESONACONVERTER



IN THIS CONVERTER THE ZVS CONCEPT IS EXTENDED

HERE FO > FS

= 1

2Π

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C S S A O

RESONANT DC-LINK INVERTE



THE DC LINK INVERTER IS SIMILAR TO THE PWM INVERTER .

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CONCLUSION



IT IS USED FOR HIGH FREQUENCY APPLICATION.

ZCS&ZVS BECOMES POPULAR AND THEY CAN TURN ON &TURN OVOLTAGE&CURRENT AND ALSO ELIMINATE SWITCHING LOSSES.

IN DC-LINK INVERTERS , A RESONANT CIRCUIT IS CONNECTED B

INVERTER & DC SUPPLY.

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UNIT 4

AC VOLTAGE CONTROLLERS

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INTRODUCTION



• THE POWER FLOW INTO A LOAD CAN BE CONTROLLED BY VARYING THE RMS VALUE

VOLTAGE.

• THIS CAN BE ACCOMPLISHED BY THYRISTORS, AND THIS TYPE OF POWER CIRCUIT IS

VOLTAGE CONTROLLERS.

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• THE MOST APPLICATION OF AC VOLTAGE CONTROLLERS ARE:



• INDUSTRIAL HEATING

• ON-LOAD TRANSFORMER TAP CHANGING

• LIGHT CONTROLS

• SPEED CONTROL OF INDUCTION MOTORS

• AC MAGNET CONTROLS

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• FOR POWER TRANSFER, TWO TYPES OF CONTROL ARE NORMALLY USED:

• ON-OFF CONTROL



• PHASE ANGLE CONTROL

• IN ON-OFF CONTROL, THYRISTOR SWITCHES CONNECT THE LOAD TO THE AC SOU

CYCLES OF THE INPUT VOLTAGE AND THEN DISCONNECTED FOR A FEW CYCLES.

• IN PHASE CONTROL, THYRISTOR SWITCHES CONNECT THE LOAD TO THE AC

PORTION OF EACH CYCLE.

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• THE AC VOLTAGE CONTROLLERS CAN BE CLASSIFIED INTO TWO TYPES:

• SINGLE-PHASE CONTROLLERS



• THREE-PHASE CONTROLLERS

• EACH TYPE CAN BE SUBDIVIDED INTO:

• UNIDIRECTIONAL OR HALF-WAVE CONTROL

• BIDIRECTIONAL OR FULL-WAVE CONTROL

• SINCE THE INPUT VOLTAGE IS AC, THYRISTORS ARE LINE COMMUTATED.

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PRINCIPLE OF ON-OFF CONTROL



• THE PRINCIPLE OF ON-OFF CONTROL CAN BE EXPLAINED WITH THE FOLLOWING SIN

FULL-WAVE CONTROLLER.

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• THIS TYPE OF CONTROL IS APPLIED IN APPLICATIONS WHICH HAVE HIGH MECHANIC

HIGH THERMAL TIME CONSTANT.



•TYPICAL EXAMPLES ARE INDUSTRIAL HEATING AND SPEED CONTROL OF MOTORS.

• IF THE INPUT VOLTAGE IS CONNECTED TO LOAD FOR N CYCLES AND IS DISCONNEC

CYCLES, THE OUTPUT LOAD VOLTAGE IS FOUND FROM:

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n

2/12

22



• NOTE THAT K IS CALLED THE DUTY CYCLE, AND THE POWER FACTOR AND OUTPUT VO

WITH THE SQUARE ROOT OF K.

k V nm

nV V

t d t V mn

nV

s srmso

srmso

2

0

22 )(sin2)(2

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PRINCIPLE OF PHASE CONTROL

• THE PRINCIPLE OF PHASE CONTROL CAN BE EXPLAINED WITH THE FOLLOWING CIRC



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• DUE TO THE PRESENCE OF DIODE D1, THE CONTROL RANGE IS LIMITED.



• THE RMS OUTPUT VOLTAGE CAN ONLY BE VARIED BETWEEN 70.7 TO 100%.

• THE OUTPUT VOLTAGE AND INPUT CURRENT ARE ASYMMETRICAL AND CONTAIN A D

• THIS CIRCUIT IS A SINGLE-PHASE HALF-WAVE CONTROLLER AND IS SUITABLE ONLY F

POWER RESISTIVE LOADS, SUCH AS HEATING AND LIGHTING.

• SINCE THE POWER FLOW IS CONTROLLED DURING THE POSITIVE HALF-CYCLE OF INP

THIS TYPE OF CONTROLLER IS ALSO KNOWN AS UNIDIRECTIONAL CONTROLLER.

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• THE RMS VALUE OF THE OUTPUT VOLTAGE IS FOUND FROM:

222

22 (sin2)(sin2[2

1{

s so td t V t d t V V



• THE AVERAGE VALUE OF THE OUTPUT VOLTAGE IS:

2/1)]

2

2sin2(

2

1[

2

so V V

)1(cos2

2

(sin2)(sin2[2

1 2

so

s sdc

V V

d t V t d t V V

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• THE FIRING PULSE OF T1 AND T2 ARE 180 DEGREES APART.



• THE RMS VALUE OF THE OUTPUT VOLTAGE IS:

•BY VARYING

Α FROM 0 TO

Π, VO CAN BE VARIED FROM VS TO 0.

2/1

2/122

2

2sin(

1

)(sin22

2

so

so

V V

t d t V V

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SINGLE-PHASE AC VOLTAGE CONTROLLERS INDUCTIVE LOAD



• IN PRACTICE, MOST LOADS ARE INDUCTIVE TO A CERTAIN EXTENT.

• A FULL-WAVE CONTROLLER WITH AN INDUCTIVE LOAD IS SHOWN NEXT.

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SINGLE PHASE AC VOLTAGE REGULATOR WITH RL LOAD



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• THE GATING SIGNALS OF THYRISTORS COULD BE SHORT PULSES FOR A CONTROLLE

RESISTIVE LOAD.



• HOWEVER, THEY ARE NOT SUITABLE FOR INDUCTIVE LOADS.

• WHEN THYRISTOR T2 IS FIRED, THYRISTOR T1 IS STILL CONDUCTING DUE TO THE INDU

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• BY THE TIME THE CURRENT OF T1 FALLS TO ZERO AND T1 IS TURNED OFF, THE GATE C

HAS ALREADY CEASED.



HAS ALREADY CEASED.

• CONSEQUENTLY, T2 WILL NOT BE TURNED ON.

• THIS DIFFICULTY CAN BE RESOLVED BY USING A CONTINUOUS GATE SIGNAL WITH A

Π - Α.

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• HOWEVER A CONTINUOUS GATE PULSE INCREASES THE SWITCHING LOSS OF THYR



• IN PRACTICE A TRAIN OF PULSES WITH SHORT DURATION ARE USED TO OVERCOME

PROBLEM.

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• THE RMS VALUE OF THE OUTPUT LOAD VOLTAGE IS FOUND FROM:



2/1

2/1

22

2

2sin

2

2sin(

1

)(sin22

2

so

so

V V

t d t V V

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THREE-PHASE FULL-WAVE CONTROLLERS



• THE UNIDIRECTIONAL CONTROLLERS, WHICH CONTAIN DC INPUT CURRENT AND HIG

CONTENT DUE TO THE ASYMMETRICAL NATURE OF THE OUTPUT VOLTAGE WAVEFOR

NORMALLY USED IN AC MOTOR DRIVES.

• A THREE-PHASE BIDIRECTIONAL CONTROL IS COMMONLY USED.

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30o

120SRM UNIVERSITY

• FOR 0 < Α < 60O:

2/1

)2sin

(1

6

VV



• FOR 60O < Α < 90O:

• FOR 90O

< Α < 150O

:

)846

(6

so V V

2/1

)16

2cos3

16

2sin3

12(

16

so V V

)16

2cos3

16

2sin

424

5(

16

so V V SRM UNIVERSITY

THREE-PHASE BIDIRECTIONAL DELTA-CONNECONTROLLERS

IF THE TERMINALS OF A THREE PHASE SYSTEM ARE ACCESSIBLE THE CONTROL ELEME



• IF THE TERMINALS OF A THREE-PHASE SYSTEM ARE ACCESSIBLE, THE CONTROL ELEME

LOAD MAY BE CONNECTED IN DELTA.

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• SINCE THE PHASE CURRENT IN A NORMAL THREE-PHASE DELTA SYSTEM IS ONLY 1/√3



CURRENT, THE CURRENT RATINGS OF THE THYRISTORS ARE LESS.

• THE FOLLOWING FIGURE SHOWS THE WAVEFORMS FOR A DELAY ANGLE OF 120 D

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60o



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UNIT 5CYCLOCONVERTER

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SINGLE PHASE CYCLOCONVERTER

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INTRODUCTION



• A DEVICE WHICH CONVERTS INPUT POWER AT ONE FREQUENCY TO THE OUT PU

DIFFERENT FREQUENCY WITH ONE STAGE CONVERSION IS CALLED A CYCLOCON

• TYPES

STEP-UP CYCLOCONVERTER( FO > FS)

STEP-DOWN CYCLOCONVERTER ( FO < FS)

• DUE TO HIGH COST, NOT SPREAD WIDELY IN EARLY DAYS

• NOW WITH ADVENT OF HIGH POWER THYRISTOR, CYCLOCONVERTER BECOME P

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APPLICATION OF CYCLOCONVERTER



• SPEED CONTROL OF HIGH POWER AC DRIVE

• INDUCTION HEATING

• STATIC VAR COMPENSATION

• FOR CONVERTING VARIABLE SPEED ALTERNATOR VTG TO CONT FREQ OUTPUT VT

AS POWER SUPPLY IN AIRCRAFT OR SHIPBOARDS

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SINGLE PHASE TO SINGLE PHASE MID POINTSTEP-UP CYCLOCONVERTER WITH R LOA



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WAVEFORM



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SINGLE PHASE TO SINGLE PHASE BRIDGE TSTEP-UP CYCLOCONVERTER WITH R LOA



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WAVEFORM



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1-Φ TO 1-Φ MID POINT TYPE STEP-DOWCYCLOCONVERTER WITH R LOAD



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OUTPUT VOLTAGE (VO) AND CURRENT (IO) WAV



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1-Φ TO 1-Φ MIDPOINT TYPE STEP-DOWCYCLOCONVERTER WITH R-L LOAD



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OUTPUT VOLTAGE (VO) AND CURRENT (IOWAVEFORM FOR DISCONTINUOUS CONDUC

MODE



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OUTPUT VOLTAGE (VO) AND CURRENT (IOWAVEFORM FOR CONTINUOUS CONDUCTION



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1-Φ TO 1-Φ BRIDGE TYPE STEP-DOWNCYCLOCONVERTER WITH R LOAD



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OUTPUT VOLTAGE (VO) AND CURRENT (IOWAVEFORM



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1-Φ TO 1-Φ BRIDGE-TYPE STEP-DOWNCYCLOCONVERTER WITH R-L LOAD



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OUTPUT VOLTAGE (VO) AND CURRENT (IOWAVEFORM FOR DISCONTINUOUS CONDUC

MODE



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OUTPUT VOLTAGE (VO) AND CURRENT (IOWAVEFORM FOR CONTINUOUS CONDUCTION



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THREE PHASE CYCLOCONVERTER

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THREE PHASE TO SINGLE PHASE CYCLOCONVTOPOLOGY 1



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TOPOLOGY 2



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OUTPUT VOLTAGE



THE INPUT AND OUTPUT VOLTAGES ARE ADJUSTED TO BE EQUAL AND THE LOAD CU

FLOW IN EITHER DIRECTION. THUS,

WHERE VD0 IS THE DC OUTPUT VOLTAGE OF EACH CONVERTER AT ZERO FIRING A

P AND N ARE THE INPUT AND OUTPUT FIRING ANGLES. FOR A 3 HALF-WAVE

VD0 =0.675VL AND VD0 = 1.35VL FOR THE BRIDGE CONVERTER (VL IS THE RMS LIN

0 0 0cos cosd d p d nV V V V

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THREE PHASE TO THREE PHASE CYCLOCONV

EACH PHASE GROUP FUNCTIONS AS A DUAL CONVERTER BUT THE FIRING ANGLE



• EACH PHASE GROUP FUNCTIONS AS A DUAL CONVERTER BUT THE FIRING ANGLE

GROUP IS MODULATED SINUSOIDALLY WITH 2/3 PHASE ANGLE SHIFT -> 3 BAVOLTAGE AT THE MOTOR TERMINAL.

• AN INTER-GROUP REACTOR (IGR) IS CONNECTED TO EACH PHASE TO RESTRICT CI

CURRENT.

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TOPOLOGY 1



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WAVEFORM



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TOPOLOGY 2



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REFERENCES

• 1 RASHID M H "POWER ELECTRONICS CIRCUITS DEVICES AND APPLICATIONS"



1. RASHID M.H., POWER ELECTRONICS CIRCUITS, DEVICES AND APPLICATIONS ,

HALL INDIA, THIRD EDITION, NEW DELHI, 2011.

• 2. P.C. SEN, “MODERN POWER ELECTRONICS”, WHEELER PUBLISHING CO, THIRD E

DELHI, 2008.

• 3. NED MOHAN, UNDELAND AND ROBBIN, “POWER ELECTRONICS: CONVERTERS,

AND DESIGN”, JOHN WILEY AND SONS.INC, NEWYORK,REPRINT - 2009.

•4. CYRIL W.LANDER, “POWER ELECTRONICS”, THIRD EDITION, MCGRAW HILL- 199

• www.nptel.ac.in, www.ieee.com, www.ocw.mit.edu

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http://www.nptel.ac.in/

http://www.ieee.com/

http://ocw.mit.edu/

http://ocw.mit.edu/

http://ocw.mit.edu/

http://www.ieee.com/

http://www.nptel.ac.in/

analysis of power converters

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