textbook: bin wu, ‘high-power converters and ac drives’, wiley - ieee press, 2006 ee8407 topic 6...

1 Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006

EE8407 Topic 6

Power Converter Systems

Graduate Course EE8407

Ryerson Campus

Bin Wu PhD, PEng

ProfessorELCE DepartmentRyerson University

Contact Info Office: ENG328Tel: (416) 979-5000 ext: 6484Email: [email protected] http://www.ee.ryerson.ca/~bwu/


EE8407 Topic 6

CHB Inverter Fed Drive Source: Toshiba - General Electric

H-bride power cells

Topic 6

Multilevel Cascaded H-Bride (CHB) Inverters


EE8407 Topic 6

Lecture Topics

• H-Bridge Inverter

• CHB Inverter Topologies

• Phase Shifted PWM

• Level Shifted PWM

• PWM Scheme Comparison

Multilevel CHB Inverters


EE8407 Topic 6

• To increase inverter operating voltage without devices in series

• To minimize THD with low switching frequencies fsw

• To reduce EMI due to lower voltage steps

Why Use Multilevel Inverters?

Switching frequency for high power converters:

fsw = 60Hz ~ 1000Hz

Multilevel CHB Inverters


EE8407 Topic 6

N

dC

CascadedH-bridge (CHB)

Inverter

dC

Two LevelInverter

dC

Flying CapacitorInverter

dC

Neutral PointClamped (NPC)

Inverter

dC

~ ~

~

~

• Per-Phase Diagram

Multilevel Inverter Topologies


EE8407 Topic 6

• H-bridge Power Cell

dCdV

1S

2S

3S

4S

1D

2D

3D

4D

1g 3g

2g4g

A

B

P

N

ABv

H-Bridge Inverter


EE8407 Topic 6

H-bridge Power Cell

• Typical Industrial Applications

0

0

0

M

30

30

30

A

B

C

Neutral

H-bridge

Phase ShiftingTransformer

UtilityGrid

Five-level CHB inverter

dCdV

1S

2S

3S

4S

1D

2D

3D

4D

1g 3g

2g4g

A

B

P

N

ABv

H-Bridge Inverter


EE8407 Topic 6

• Bipolar Modulation

Bipolar PWM:

vAB from -Vd to +Vd

or from +Vd to -Vd

dCdV

1S

2S

3S

4S

1D

2D

3D

4D

1g 3g

2g4g

A

B

P

N

ABv1gv

3gv

dV

dV

0

-1.0

1.0

0

BNv

ANv

0

ABv

dV

1ABv

2

mv crv

0

0.2

0.4

0.6

12 fm32 fm 32 fm

2fm 2fm 23 fm 14 fm

1n

dn VVAB /

0

(a) Waveforms

(b) Harmonic spectrum

dV

n1 10 20 30 40 50 60

H-Bridge Inverter


EE8407 Topic 6

• Bipolar Modulation (FFT)

d

n

V

VAB

0.2

0.4

0.6

0.8

0.2 0.4 0.6 0.8

2fm

00

32 fm

12 fm

0.707

fm

am

1n

H-Bridge Inverter


EE8407 Topic 6

• Unipolar Modulation (1)

0

-1.0

1.0

mv

2

1gv

3gv

0

BNv

ANvdV

dV

0

ABv

dV

0

0.2

0.4

dn VVAB /

32 fm 32 fm14 fm

0.6

12 fm

mv crv

1n

(b) Harmonic spectrum

(a) Waveforms

n1 10 20 30 40 50 60

dCdV

1S

2S

3S

4S

1D

2D

3D

4D

1g 3g

2g4g

A

B

P

N

ABv

• Two modulation waves

vm and vm-

• One carrier wave vcr

• Unipolar PWM:

vAB from 0 to +Vd

or from 0 to -Vd

H-Bridge Inverter


EE8407 Topic 6

• One modulating wave: vm

• Two carrier waves: vcr and vcr-

dCdV

1S

2S

3S

4S

1D

2D

3D

4D

1g 3g

2g4g

A

B

P

N

ABv

0

-1.0

1.0

0

ABv

dV

mv crv

crv

1gv

3gv

• Unipolar Modulation (2)

H-Bridge Inverter


EE8407 Topic 6

• Five-Level CHB Inverter

Converters in cascade, but no switching devices in series.

Complementary Switch 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

H1

H2

CHB Inverter Topologies


EE8407 Topic 6

• Output Voltage and Switching Status (five-level)

Waveform of vAN is composed of five voltage levels: 2E, E, 0, -E, and -2E

1Hv

2Hv

21S

11S

41S

31S

22S42S

32S12S

E

E

A

H1

H2 N

Switching State Output Voltage

ANv 11S 31S 12S 32S 1Hv 2Hv

2E 1 0 1 0 E E 1 0 1 1 E 0 1 0 0 0 E 0 1 1 1 0 0 E

E

0 0 1 0 0 E 0 0 0 0 0 0 0 0 1 1 0 0 1 1 0 0 0 0 1 1 1 1 0 0 1 0 0 1 E -E

0

0 1 1 0 -E E 0 1 1 1 -E 0 0 1 0 0 -E 0 1 1 0 1 0 -E

-E

0 0 0 1 0 -E -2E 0 1 0 1 -E -E



EE8407 Topic 6

• Seven- and Nine-Level Inverters (Per phase diagram)

1Hv

2Hv

21S

11S

41S

31S

22S42S

32S12S

E

E

A

H1

H2

3Hv

23S43S

33S13S

E

H3 N

1Hv

2Hv

E

E

A

3HvE

4HvE

N

(a) Seven-level inverter (b) Nine-level inverter



EE8407 Topic 6

• Unequal dc Bus Voltages

(a) Two-cell seven-leveltopology

(b) Two-cell nine-leveltopology

1Hv

2Hv

21S

11S

41S

31S

22S42S

32S12S

E

E2

A

H1

H2 N

1Hv

2Hv

21S

11S

41S

31S

22S42S

32S12S

E

E3

A

H1

H2 N



EE8407 Topic 6

Switching State Output Voltage

ANV 11S 31S 12S 32S 1HV 2HV

3E 1 0 1 0 E 2E

1 1 1 0 0 2E 2E

0 0 1 0 0 2E

1 0 1 1 E 0

1 0 0 0 E 0 E

0 1 1 0 -E 2E

0 0 0 0 0 0

0 0 1 1 0 0

1 1 0 0 0 0 0

1 1 1 1 0 0

1 0 0 1 E -2E

0 1 1 1 -E 0 -E

0 1 0 0 -E 0

1 1 0 1 0 -2E -2E

0 0 0 1 0 -2E

-3E 0 1 0 1 -E -2E

• Unequal dc Bus Voltages (Two-cell seven-level topology)

(a) Two-cell seven-leveltopology

1Hv

2Hv

21S

11S

41S

31S

22S42S

32S12S

E

E2

A

H1

H2 N



EE8407 Topic 6

• Carrier Based PWM – Phase Shifted

Amv

1crv 2crv 3crv

11gv

31gv

1Hv

12gv

32gv

2Hv

13gv

33gv

3Hv

0

ANv

E

3E

0

1.0

-1.0

E

1crv 2crv 3crv

E

321 HHH vvvvAN

• # of voltage levels: m = 7

• # of carriers: mc = m - 1 = 6

• Phase shift: 360° / mc = 60°

Carriers for H1 bridge:vcr1 and vcr1-



m = 7

Phase Shifted PWM


EE8407 Topic 6

• 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: 13• Close to a sinusoid• Low THD

Phase Shifted PWM


EE8407 Topic 6

• FFT (7-level, phase shifted)

• Lowest harmonics: around 2mf

• Lowest harmonics: around 6mf

• Containing triplen harmonics

• No triplen harmonics• Equivalent fsw(inverter)

= 60(6mf ) = 3600Hz

0

0.04

0.08 12 fm14 fm 16 fm

0

0.04

0.08

36 fm96 fm 96 fm

0

0.04

0.08 16 fm76 fm 76 fm

dn VV /H1

dANn VV /

dABn VV /

THD = 53.9%

THD = 18.8%

THD = 15.6%

1 n10 20 30 40 50 60 70 80

1 n10 20 30 40 50 60 70 80

1 n10 20 30 40 50 60 70 80

Phase Shifted PWM


EE8407 Topic 6

• 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.x

y

1n

Phase Shifted PWM


EE8407 Topic 6

• Carrier Based PWM – Level Shifted• # of voltage levels: m = 5

• # of carriers:

mc = m - 1 = 4

IPD provides the best harmonic profile.

-1.0

0

1.0mv

2

3

1crv

(a) In-phase disposition (IPD)

2crv

3crv

4crv

2 3

(b) Alternative phase opposite disposition (APOD)

mv

2

(c) Phase opposite disposition (POD)

mv

-1.0

0

1.0

1crv

2crv

3crv

4crv

-1.0

0

1.0

1crv

2crv

3crv

4crv

IPD

APOD

POD

Level Shifted PWM


EE8407 Topic 6

cr1v

cr2v

cr3v

g11v

g31v

1Hv

12gv

32gv

2Hv

13gv

33gv

3Hv

0

ANv3E

mAv

-cr1v

-cr3v

-cr2v

3H2H1HAN vvvv

E

E

E

• # of voltage levels: m = 7

• # of carriers: mc = m - 1 = 6

• fsw(device):

- not equal to fcr, and

- not the same for all switches.

• Device conduction angle:

- not equal.

• Necessary to swap switching

pattern.

• Gating Arrangement (7-level)

Level Shifted PWM


EE8407 Topic 6

• Inverter Output Voltages (seven-level)

• m = 7

• vAB close to a sinusoid • Low THD, low EMI

• fsw(inv) = fc = 3600Hz

• Switching occurs at different times

• fsw(device) = fcr /mc =

600Hz (avg)

1Hv

2Hv

3Hv

0

ANv

0

ABv

0

0.04

0.08

0

0.04

0.08

2fm8fm8fm

16fm16fm

3E

6E

2 4

2 4

THD = 18.6%

THD = 10.8%

6fm 6fm

dABn VV /

dANn VV /

1 n10 20 30 40 50 60 70 80

1 n10 20 30 40 50 60 70 80

Level Shifted PWM


EE8407 Topic 6

• Prototype at Ryerson (Seven-level CHB Inverter)

Level Shifted PWM


EE8407 Topic 6

• Measured Waveforms (IPD, 7-level)

Inverter phase voltage vAZ Line-to-line voltage vAB

Level Shifted PWM


EE8407 Topic 6

• PWM at Low ma

- Phase shifted PWM:

THD = 96.7%

- Level shifted PWM:

THD = 48.8%

• At ma = 0.2:

1Hv

2Hv

3Hv

0

ANv

0

ABv

E

2E

1Hv

2Hv

3Hv

0

ANv

0

ABv2E

E

(a) Phase-shifted modulation

(b) Level-shifted modulation (IPD)

THD = 96.7%

THD = 48.8%

PWM Scheme Comparison


EE8407 Topic 6

• Total Harmonic Distortion (THD)

am0.2 0.4 0.6 0.80

20

40

60

80

THD(%)

Phase-Shifted PWM

Level-Shifted PWM (IPD)

Hz600, devswfSeven-level Inverter



EE8407 Topic 6

Comparison Phase-shifted Modulation

Level-shifted Modulation (IPD)

Device Switching Frequency Same for all devices Different Device Conduction

Period Same for all devices Different

Rotating of switching patterns No required Required THD of inverter output

line-to-line voltage Good Better

Low Order Harmonics No Yes

(Very low amplitude)

• Summary



EE8407 Topic 6

textbook: bin wu, ‘high-power converters and ac drives’, wiley - ieee press, 2006 ee8407 topic 6...

Documents

highpower converters

ee8407 topic

ac drives

wiley ieee press

v d hbridge inverter

level chb inverter converters

e chb inverter topologies

high power converters