slides topic 3 - Ryerson Universitybwu/courses_teaching/8412/x8412_slides_topic3.pdf · 1 1 EE8412...

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EE8412Advanced AC Drive Systems

Topic 3Power Converter Topologies

Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley-IEEE Press, 2006, ISBN: 0-471-73171-4

Courtesy of ABB

2

Lecture Topics

1) Two-level Voltage Source Inverters 2) Cascaded H-bridge (CHB) Inverters 3) Neutral Point Lamped (NPC) Inverters4) Current Source Converters

EE8412 Advanced AC Drive Systems

Power Converter TopologiesEE8412


2

3

• Inverter Configuration

dC∞dV

1S

2S

3S 5S

4S 6S

1D

2D

3D

4D

5D

6D

1g 3g 5g

2g4g 6g

AiA

BC

O

P

N

LOAD

Bi

Ci

Assumption: dc capacitor very large → dc voltage ripple free

Topic 3 Power Converter Topologies

Two-level Voltage Source Inverter

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4

• Square Wave Operation

Why called two-level? vAN = 0 or =Vd

tω

tω

tω

tω

tω

tω

tω

tωπ π2 π3

3π3π

dV

dVA Bv

B Nv

A Nv

0

C Nv

A Ov

0

0

0

0

0

Ai

1gv2gv

3gv

4gv

5gv

6gv

32 /dV 3/dV

2π

C urrent-carrying devices in leg A4S4D1S1D

1S

2S

3S 5S

4S 6S

1D

2D

3D

4D

5D

6D

1g 3g 5g

2g4g 6g

AiA

BC

P

N

Bi

CidC∞dV

• Gating arrangements60° apartConduction angle: 180°Complementary gating: S1 on → S4 offS3 on → S6 offS5 on → S2 off

• During first 60° periodS1 on , VAN = VdS6 on, VBN = 0S5 on, VCN = Vd



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5

• Inverter Output Voltage

• Line-to-line voltage

⎟⎠⎞

⎜⎝⎛ +⎟

⎠⎞

⎜⎝⎛= ∑

∞

=

)6

(sin6

cos4...,13,11,7,5,1

πωππ

tnnnVv

n

dAB

• Fundamental-frequency voltage

dd

AB VVV 78.06

cos2

41 ==

ππ

• rms voltage

dd

dd

ABAB

VV

tdVtdV

tdvV

816.032

)()()()(21

)(21

2/13/2

0

3/5 22

2/12

0

2

==

⎟⎠⎞

⎜⎝⎛

⎟⎠⎞⎜

⎝⎛ −+=

⎟⎠⎞

⎜⎝⎛=

∫ ∫

∫π π

π

π

ωωπ

ωπ



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• Load Phase Voltage

• Phase voltage calculation

⎪⎩

⎪⎨

⎧

−=−=−=

3/)(3/)(3/)(

BCCACO

ABBCBO

CAABAO

vvvvvvvvv

• Fourier expression

• rms value

( )tnVn

vn

dAO ωπ

sin2...,13,11,7,5,1

∑∞

=

=

ddAOAO VVtdvV 47.032)()(

21 2/1

2

0

2 ==⎟⎠⎞

⎜⎝⎛= ∫

πω

π

dC∞dV

1S

2S

3S 5S

4S 6S

1D

2D

3D

4D

5D

6D

1g 3g 5g

2g4g 6g

AiA

BC

O

P

N

LOAD

Bi

Ci



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4

7



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• Modulating and Carrier Waves

• vcr – Carrier wave (triangle) • Amplitude modulation index

cr

ma V

Vm ˆˆ

=

• Frequency modulation index

m

crf f

fm =

v mAv Bmv Cmvcrv

crV̂ mV̂tω

• vm – Modulating wave (sine)

8



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• Gate Signal Generation

1gv

4gv

dVANv

π π2

mAv crv

crmA vv > 01 >gv )0( 4 <gv 1S on )off( 4S dAN Vv = Phase A

crmA vv < 04 >gv )0( 1 <gv 4S on )off( 1S 0=ANv

Vg1 and Vg4 are complementary

5

9

ABv

BNv

ANv

0

0

0

v mAv Bmv Cmvcrv

crV̂ mV̂

dV

dV

dV

π π2tω

tω

tω

tω

1ABv

1S

2S

3S 5S

4S 6S

B

C

P

N

dV

A



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• Line-to-Line Voltage vAB

10



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• Low order harmonics, n < (mf -2), are eliminated


• Waveforms and FFT

• ma = 0.8, mf = 15, fm = 60Hz, fcr = 900Hz

• Switching frequencyfsw = fcr = 900Hz

dV

3/2 dV

ABv

AOv

Ai

2±fm

12 ±fm

23 ±fm 14 ±fm

π3

π3π2

π2π

π

dVVAB 49.01 =

dn VVAB /

6

11

• Harmonic Content

• VAB1 versus ma is linear

• VAB1,max = 0.612Vd



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am

12 ±fm2±fm

14 ±fm23 ±fm

43 ±fm

d

nAB

V

V

1=n


12

• Space Vector Modulation (introduction)

α1Vr

0Vr

3Vr

2Vr

4Vr

5Vr

6Vr

βj

POO

PPOOPO

OPP

OOP POP

refVr

θOOOPPP

SECTOR ISECTOR III

SECTOR IV SECTOR VISECTOR V

SECTORII

ω



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7

13

ABv

AOv

0

0

0

Ai

dV

3/2 dV

π π2 π3

π π2 π3

VIVISector

III

IIIIV

V

III

IIIIV

V

• f1 = 60Hz, fsw = 900Hz, ma = 0.696, Ts = 1.1ms

• Space Vector Modulation (introduction)



EE8412


14Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley-IEEE Press, 2006, ISBN: 0-471-73171-4

CHB Inverter Fed MV Drive Source: ASI Robicon


Cascaded H-bridge Inverters

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15


Cascaded H-bridge Inverters• Converter Topologies (5-level)

Converters in cascade, but no switching devices in series.

ComplementarySwitch pairs:S11 and S41;S31 and S21;

S12 and S42;S32 and S22;

1Hv

2Hv

N

21S

11S

41S

31S

22S42S

32S12S

E

E

E

E

E

E

A B C

O

LOAD

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1Hv

2Hv

21S

11S

41S

31S

22S42S

32S12S

E

E

A

3Hv

23S43S

33S13S

E

N

1Hv

2Hv

E

E

A

3HvE

4HvE

N


Cascaded H-bridge Inverters• Converter Topologies (7- and 9-levels)

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17



Amv

1crv 2crv 3crv

11gv

31gv

1Hvπ

12gv

32gv

2Hv

13gv

33gv

3Hv

π0

ANv

E

3E

0

1.0

-1.0

E

−1crv−2crv −3crv

E

π

π

321 HHH vvvvAN ++=

• # of voltage levels: m = 7• # of carriers: mc = m - 1 = 6

• Phase shift: 360°/ mc = 60°

Carriers:vcr1 and vcr1-



m = 7

• Phase Shifted PWM

EE8412

1Hv

2Hv

21S

11S

41S

31S

22S42S

32S12S

E

E

A

H1

H2

3Hv

23S43S

33S13S

E

H3 N


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• Inverter Waveforms (7-level, phase shifted)

1Hv

2Hv

3Hv

0

ANv

0

ABv

3E

6E

• Switching occurs at different times

• fsw(device) = 60 mf = 600Hz

• Inverter phase voltage levels: 7

• Low EMI

• Line-to-line voltage levels: 12

• Close to a sinusoid• Low THD



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•Lowest harmonics: around 2mf

• Lowest harmonics: around 6mf

• Containing triplen harmonics

• No triplen harmonics• Equivalent fsw(inverter)

= 60(6mf ) = 3600Hz


Cascaded H-bridge Inverters• Harmonic Spectrum (7-level, phase shifted)

EE8412

12 ±fm14 ±fm 16 ±fm

36 ±fm96 −fm 96 +fm

16 ±fm76 −fm 76 +fm

dn VV /H1

dANn VV /

dABn VV /


20

• Harmonic Content (7-level, phase shifted)

00.2 0.4 0.6 0.80 am

0.1

0.2

0.3

d

n

V

VAB

16 ±fm

56 ±fm 76 ±fm

116 ±fm

x∆

y∆ 2241.xy=

∆

∆

1=n

• Inverter equivalent switching frequency: fsw(inv) = 6 fsw(device)• Small filter size for sinusoidal outputs.



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• Level Shifted PWM• # of voltage levels: m = 5• # of carriers: mc = m - 1 = 4

• IPD provides the best harmonic profile.

-1.0

0

1.0mv

π2π

π3

1crv

(a) In-phase disposition (IPD)

2crv

3crv

4crv

π π2 π3

(b) Alternative phase opposition disposition (APOD)

mv

ππ2

(c) Phase opposition disposition (POD)

mv

-1.0

0

1.0

1crv

2crv

3crv

4crv

-1.0

0

1.0

1crv

2crv

3crv

4crv

IPD

APOD

POD



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• Gating Pulse Arrangement (7-level, IPD)cr1vcr2vcr3v

π

π

π

π

g11vg31v

1Hv

12gv32gv

2Hv

13gv33gv

3Hv

ANv

mAv

-cr1v

-cr3v-cr2v

3H2H1HAN vvvv ++=

• # of voltage levels: m = 7• # of carriers: mc = m - 1 = 6

• fsw(device) << fcr (900Hz)• fsw(device) – Not the same for

all switches.• Device conduction

angle – not equal.

• Necessary to swap switching pattern.

• m = 7

}



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• m = 7

• Close to a sinusoid • Low THD, low EMI

• Equivalent fsw(inv) = fcr = 3600Hz

• Switching occurs at different times

• fsw(device) = fcr /mc =600Hz (avg.)


Cascaded H-bridge Inverters• Inverter Output Voltages (7-level, IPD)

EE8412

1Hv

2Hv

3Hv

ANv

ABv

2±fm8+fm8−fm

16+fm16−fm

π2 π4

π2 π4

dABn VV /



NPC Inverter Fed MV Drive Courtesy of Siemens


Neutral Point Lamped (NPC) Inverters

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Neutral Point Lamped (NPC) Inverters• Inverter Topology (three-level NPC)

Six clamping diodes: DA1, DA2 , DB1, DB2 , DC1 and DC2

EE8412

1dC

1S

2S

3S

4S

AB

CZ

2dC

1D

2D

3D

4D

1ZD

2ZD

E

E

ZidV

Ai

OBi

Ci

di


26

Complementary Switch pairs:SX1 and SX3; SX2 and SX4;


Neutral Point Lamped (NPC) Inverters• Switching State

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27

• Space Vector Diagram

19 space vectors:Zero vector: V0Small vectors: V1 – V6Medium vectors: V7 – V12Large vectors: V13 – V18



1Vr

13Vr

7Vr

14Vr

0Vr

3Vr

2Vr

4Vr

5Vr

8Vr

6Vr

15Vr

18Vr

12Vr

11Vr

10Vr

9Vr

17Vr

16Vr

refVr

θ

Sector I

Sector II

Sector III

Sector IV

Sector V

Sector VI

Six sectors: I, II, III, IV, V, VI

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• Simulated Waveforms (Space vector Modulation)



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AZv

ABv

0

0

0.05

0.1

dAB VV n /

0.15THD = 41.0%

1gv

4gv

0+E

-E

+2E

-2E

n1 5 10 15 20 25 30 35 40 45 50 55 60

π π2 π3

14 16 20 22 26 28


15

29

dnAB VV /

am

am

dnAB VV /

• Harmonic Spectrum (Space vector Modulation)



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• Level-shifted PWM (four-level)1 .0

-1 .0

3gv2gv

1gv

0

A Nv

0

Ai

3E

0 π π2 π3

A Bv

(a )

(b )

(c)

(d )

(e)

1c rv

2crv

3c rv

3E



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• Harmonic Content (four-level, IPD Modulation)



EE8412

am

dAB VV n /



PWM Current Source Converter Fed MV Drive Courtesy of Rockwell Automation


Current Source Converters

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Current Source Converters• Current Source Inverter

Features:- Simple topology – no antiparallel diodes- Reliable short circuit protection – constant dc current- Very low dv/dt on motor terminals- Four quadrant operation

• Switching devices:- Reverse blocking GCT

Function of output capacitor C:- Assist GCT commutation- Reduce harmonic distortion

EE8412

1S

2S

3S 5S

4S 6S

dI

wi

ci

si

fC

4g 6g 2g

1g 3g 5g

A

B

C

fC fCLOAD

O

ABv


34

1) Trapezoidal PWM (TPWM)

2) Selective Harmonic Elimination (SHE)

3) Space Vector Modulation (SVM)


Current Source Inverter• PWM Techniques

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Current Source Inverter• Switching Constraints

- dc current Id cannot be interrupted,- Inverter output current waveform

must be defined.

At any time instant, only two switches are turned on,one switch connected to the positive dc bus, and the other to the negative dc bus.

1S

2S

3S 5S

4S 6S

dI

wi

4g 6g 2g

1g 3g 5g

A

B

C

P

N

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Current Source Inverter• Trapezoidal PWM (TPWM)

1gv

2gv

3gv

4gv

5gv

6gv

0

wi

3π

32π π π2

tω

tω

tω

tω

tω

tω

tωdI

π2

3π

32π

tω

crv mv

mV̂ crV̂

0π π2

• Number of pulses per half cycle: Np = 7

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Current Source Inverter• Harmonic Content

(TPWM) 1ˆw

wn

II

n = 5

0.2 0.4 0.6 0.80

0.04

0.12

0.08

0.16

29

23

250

0.2 0.4 0.6 0.80am

0.2

0.4

0.6

0.8

n = 7n = 11

n = 17n = 13

19

n = 5n = 7

n = 1

1ˆw

wn

II

am

• Np = 15

• Fundamental doesnot change muchwith ma

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Current Source Inverter• Inverter Waveforms (TPWM)

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Current Source Inverter• Selective Harmonic Elimination (SHE)

• Not all the switching angles are independent.• Only two harmonics can be eliminated with 5 pulses per half cycle.

• No modulation index control – the magnitude of inverter output current is controlled by the dc link current Id

• Number of harmonics to be eliminated: 2/)1( −= pNk

EE8412

π3π

32π π21θ 2θ

6π

23θπ

−

dI

tω

wi

13θπ −

0


40

Harmonic eliminated: 5th and 7th

• Inverter Waveforms (SHE)


Current Source Inverter

EE8412

Harmonic eliminated: 5th


21

41

• Definition of- six active current vectors and one zero vector; - six sectors.


Current Source Inverter• Space Vector Modulation (SVM)

EE8412

SECTOR I

SECTOR III

SECTOR IV

SECTOR VISECTOR V

α

βj

θ

ω

SECTOR II

1Ir

2Ir

3Ir

6Ir

5Ir

4Ir

refIr

0Ir


42

wi

si

ABv

π2 π4

π2 π4


Current Source Inverter• Simulated Waveforms (SVM)

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43

• Harmonic Content (SVM)

0

0.02

0.04

0.06

0.08

1wwn II

0 0.2 0.4 0.6 0.8

n = 1

n = 5

19

17

711

13

am


Current Source Inverter

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• Switching devices:Reverse blocking GCT

• Function of filter capacitor Cf:To assist GCT commutation;To reduce line current THD.

sLsvsi wi

A

B

C

dv

2S4S 6S

didL

UtilitySupply

1g

1S 3S 5S

fC

LOAD


Current Source Rectifier• Converter Topology

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Current Source Rectifier

1) Selective Harmonic Elimination (SHE)2) Space Vector Modulation (SVM)

• PWM Techniques

• Experimental Waveforms (SHE with 5th and 7th harmonic elimination)

Trace A: current in switch S1Trace B: Rectifier input current iwTrace C: Line current is

ma = 0.7 ma = 0.95

EE8412



EE8412 Advanced AC Drive Systems


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