Transcript High Power Converters and Applications

EE8407
Power Converter Systems
Topic 7
Graduate Course EE8407
Bin Wu
PhD, PEng
Professor
ELCE Department
Ryerson University
Contact Info
Office: ENG328
Tel:
(416) 979-5000 ext: 6484
Email:
[email protected]
http://www.ee.ryerson.ca/~bwu/
Ryerson Campus
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Topic 7
Multilevel Neutral Point Clamped (NPC)
Inverters
Courtesy of ABB (ACS1000)
Three-Level NPC Inverter Based MV Drive
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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Multilevel NPC Inverters
Topic 7
Lecture Topics
• Three-level NPC Inverter
• Space Vector Modulation
• Neutral Point Voltage Control
• High-level NPC Inverters
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Three-Level NPC Inverters
• Inverter Configuration
S1
D1
DZ 1
E
Vd
Z
Cd1
D2
S2
A
iA
iZ
iB
B
C
DZ 2 S 3
E
O
iC
LOAD
D3
Cd 2
S4
D4
Clamping diodes:
DZ1 and DZ2 (Phase A)
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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Three-Level NPC Inverters
Topic 7
• Switching State
Switching
State
Device Switching Status
(Phase A)
Inverter Terminal
Voltage
V AZ
S1
S2
S3
S4
P
On
On
Off
Off
E
O
Off
On
On
Off
0
N
Off
Off
On
On
E
Complementary Switch pairs:
S1 and S3; S2 and S4;
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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Topic 7
Three-Level NPC Inverters
• Gate Signal Arrangements
O P O
P
O P
O
N O
N
O N O
v g1
vg 2
vg 3
vg 4
E
v AZ
0


E
Inverter phase voltage vAZ has three levels: E, 0 and –E
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Three-Level NPC Inverters
• Inverter Output Waveforms
v AZ
E
0

E
2  t
v BZ
0
t
vCZ
0
t
v AB
2 E
E
0
v AB  v AZ  v BZ
2 E
t
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Space Vector Modulation
• Space Vectors
• Three-phase voltages
v AO (t )  vBO (t )  vCO (t )  0
• Two-phase voltages
2

cos
0
cos
v (t )
2
3

v (t )
3  sin 0 sin 2
  


3
4  v AO (t )
3  v (t ) 
4   BO 
sin

3  vCO (t ) 
(1)
cos
• Space vector representation

V (t )  v (t )  j v  (t )
(2)  (3)

2
V (t )   v AO (t ) e j 0  v BO (t ) e j 2 / 3  vCO (t ) e j 4 / 3 
3
(2)
(3)
(4)
where e jx  cos x  j sin x
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Space Vector Modulation
• Space Vectors (Example)
Switching state [POO]  on-state switches:
Phase A: upper two switches
[P]
Phase B: middle two switches [O]
Phase C: middle two switches [O]
from which
1
1
v AO (t )  Vd , vBO (t )   Vd
3
6
1
and vCO (t )   Vd
6
(5)
Substituting (5) to (4) gives a space vector
 1
V1  Vd e j 0
3
(6)
Total switching states: 27
Total space vectors:
19
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Space Vectors Diagram


V8

V15

V3

V9

V10

V2

V0

V4

V16

V5

V17

2
V14  Vd e j / 3
3

3
V7 
V d e j / 6
3

2

V13  V d
V1  V d / 3
3

V12

V6

V11

V18

19 space vectors:
Zero vector:
V0
Small vectors:
V1 – V6
Medium vectors: V7 – V12
Large vectors:
V13 – V18
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Space Vector Modulation
• Switching States and Space Vectors
Space
Vector

V0

V1

V2

V3

V4

V5

V6

V1P

V1N

V2 P

V2 N

V3 P

V3N

V4 P

V4 N

V5 P

V5 N

V6 P

V6 N
Switching State
Vector Classification
Vector
Magnitude
[PPP][OOO] [NNN]
Zero Vector (ZV)
0
P-type
[POO]
N-type
[ONN]
[PPO]
[OON]
[OPO]
Small Vector (SV)
[NON]
[OPP]
P-type Small Vector (PSV)
N-type Small Vector (NSV)
1
Vd
3
[NOO]
[OOP]
[NNO]
[POP]
Redundancy:
[ONO]
Zero vector – three switching states
Small vectors – two states per vector
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Space Vector Modulation
• Switching States and Space Vectors
Space
Vector

V7

V8

V9

V10

V11

V12

V13

V14

V15

V16

V17

V18
Switching State
Vector Classification
Vector
Magnitude
[PON]
[OPN]
[NPO]
[NOP]
Medium Vector (MV)
3
Vd
3
Large Vector (LV)
2
Vd
3
[ONP]
[PNO]
[PNN]
[PPN]
[NPN]
[NPP]
[NNP]
[PNP]
No redundant switching states for medium or large vectors
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
• Sector Definition
Sector III

V16
Sector II

V15

V9

V14

V8

V0

V4

V10

Vref

V2

V3

V5
q

V6
Topic 7

V1
 Sector I
V7

V13

V12
Sector IV
Sector VI

V11

V17
Sector V

V18
Vref : Reference vector, rotating in space at a certain speed;
All other vectors are stationary.
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
•
Space Vector Modulation
Topic 7
SVM Principle
•
For a given length and position in space, Vref can be approximated
by three nearby stationary vectors;
•
Based on the chosen stationary vectors, switching states are
selected and gate signals are generated;
•
When Vref passes through sectors one by one, different sets of
switches are turned on or off;
•
When Vref rotates one revolution in space, the inverter output
voltage varies one cycle over time;
•
The inverter output frequency corresponds to the rotating speed
of Vref ;
•
The inverter output voltage can be adjusted by the magnitude of Vref.
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Space Vector Modulation
• Dwell Time Calculation

V14 PPN
Ta
Dwell time is the duty-cycle time
of selected switches during the
sampling period Ts .
4

V2
• Select three nearest stationary vectors
 

V1 , V2 andV7
1
• Use volt-second balancing principle




Tb
V1 Ta  V7 Tb  V2 Tc  Vref Ts


(a)
V0
T  T  T  T
a
b
c
Tc
s
39° q
PPO
OON
Sector I

Vref
2

V7 PON
Tb
3
Ta
POO

V1 ONN
Tc
PNN

V13
Four Regions
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Dwell Time Calculation
From equation (a)

Ta  Ts [1  2 ma sin q ]



T

T
[
2
m
sin
(
 q )  1]
 b
s
a
3



T

T
[
1

2
m
sin
(
q )]
s
a
 c
3
Ta , Tb and Tc – dwell times for V1 , V7 and V2
ma 
3
Vref
– modulation index
Vd
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Switching Sequence (Seven-segment)
General Design Requirements
a)
b)
The transition from one switching state to the next involves only
two switches in the same inverter leg, one being turned on and
the other turned off; and
The transition for Vref moving from one sector (or one region)
to the next requires no or minimum number of switchings.
Note:
The switching sequence design is not unique, but the above
requirements should be satisfied for switching frequency
minimization.
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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Topic 7
Space Vector Modulation
• Switching Sequence (Seven-segment)
Assuming Vref is in Region 4 of Sector I,
three vectors are selected: V2 , V7 and V14
Voltage Vector

V2 N

V7

V14

V2 P

V14

V7

V2 N
Dwell Time
Tc
4
Tb
2
Ta
2
Tc
2
Ta
2
Tb
2
Tc
4
Phase A
O
P
P
P
P
P
O
Phase B
O
O
P
P
P
O
O
Phase C
N
N
N
O
N
N
N
Switching
State
[P]  E , [O]  0 , [ N]   E .
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Switching Sequence (Seven-segment)

V2 N

V7

V14

V2 P

V14

V7

V2 N
OON
PON
PPN
PPO
PPN
PON
OON
Ta
2
Tb
2
Tc
4
v AZ
E
0
vBZ
E
0
0
E
vCZ
v AB
E
0
Tc
4
Tb
2
Ta
2
Tc
2
Ts
Switching sequence requirement a) is satisfied.
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Switching Sequence (Seven-segment)
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Switching Sequence (Seven-segment)

V15

V14
SECTOR II
Extra
Switching
3
4
2b
4
2a
SECTOR III
SECTOR I
2b
1b 1a
1b

V16
2a
1a
3
1b
2b
SECTOR IV

Vref
f sw,dev  f sp / 2  f1 / 2

V13
Sampling frequency:

Vref
1a
2a
3
Device switching
frequency:
f sp  1/ Ts
SECTOR VI
Fundamental frequency:
4

V17
SECTOR V

V18
f1
Switching sequence requirement b) is satisfied.
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Simulated Waveforms (Seven-segment)
vg1
vg 4
2

3
v AZ
+E
0
-E
v AB
+2E
0
-2E
f1 = 60Hz, Ts = 1/1080 sec, ma = 0.8, fsw = 570Hz
vAB is not half wave symmetrical; and
contains both even- and odd-order harmonics.
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Space Vector Modulation
• Simulated Waveforms (Seven-segment)
V AZn / Vd
THD = 69.8%
0.15
0.1
0.05
0
1
5
10
15
20
25
30
35
40
45
50
55
60
n
V ABn / Vd
THD = 41.0%
0.15
0.1
14 16
20 22
26 28
0.05
0
1
5
10
15
20
25
30
35
40
45
50
55
60
n
f1 = 60Hz, Ts = 1/1080 sec, ma = 0.8, fsw = 570Hz
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Harmonic Content (Seven-segment)
V AB n / V d
0.08
n =1
20
0.06
n=2
4
8 10 16 20 14
16
0.04
10 16 20
14
0.02
10
0
0
0.2
0.4
0.6
0.8
ma
(a) Even order harmonics
V AB n / V d
THD
(%)
0.08
200
THD
0.06
n = 19
0.04
17 13 11 7
150
5
19
n =1
17
0.02
0
100
50
0
0.2
0.4
0.6
(b) Odd order harmonics
0.8
ma
0
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Laboratory Prototype at Ryerson
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Measured Waveforms
v AZ
v AB
Waveforms (2ms/div)
Waveforms (2ms/div)
V AZ n
Vd
18
18
0.1
3
35
77
9
V AB n
Vd
35
3
54
71
9
35
37
0.1
35
37
14 16 20 22
17
29
47
61 65
Spectrums (500Hz/div)
( a ) m a  0 .8
77
54
29
71
47
61 65
Spectrums (500Hz/div)
( b ) m a  0 .9
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Space Vector Modulation
Topic 7
• Measured waveforms (with even-order harmonic elimination)
v AZ
v AB
Waveforms (2ms/div)
Waveforms (2ms/div)
V AZ n
Vd
0.1
15 21
15 21
35
3
27
V AB n
Vd
3
45
57
35
27
77
35
37
0.1
17 19
29
47
61 65
Spectrums (500Hz/div)
( a ) m a  0 .8
77
13
17
19
29
57
45
71
35
37
71
47
61 65
Spectrums (500Hz/div)
( b ) m a  0 .9
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Neutral Point Voltage Control
• Neutral Point Voltage Deviation

Cd 1
Vd
B
Z

vZ
Cd 2
[ PPP] Þ

A
L
O
A
D
Vd
Vd

Z
vZ
B
Cd 2
[ONN ] Þ
vZ ¯
(c) N-type small vector
B
Cd 2

C
vZ ­
Vd

vZ
B
[ PON] Þ
Cd 2
Cd 2
L
O
A
D
C
A
Cd 1
Z
B
Z
vZ

A
Cd 1

Vd
C
L
O
A
D
(b) P-type small vector
A
iZ
iZ
[ POO] Þ
vZ not affected
L
O
A
D
Z
vZ
(a) Zero voltage vector
Cd 1

C

A
Cd 1
[ PNN] Þ
L
O
A
D
vZ not affected
(e) Large vector
C
vZ not defined
(d) Medium vector
The neutral point voltage vz can be controlled by
P- and N-types of small vectors
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Neutral Point Voltage Control
Topic 7
• Neutral Point Voltage Control
Ta  TaP  TaN
Ta

1   t 
T

 aP
2

T
TaN  a  1   t 

2
1  T  1
Neutral Point Deviation
Level
Motoring Mode
Regenerating Mode
(vd1  vd 2 )  Vd
t  0
t  0
(vd 2  vd1 )  Vd
t  0
t  0
vd1  vd 2  Vd
t  0
t  0
id  0
id  0
V  maximum allowed voltage deviation ( Vd  0 ).
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
Neutral Point Voltage Control
• Neutral Point Voltage Control
Without Neutral Point
Voltage Control
With Neutral Point
Voltage Control
vd 1 , vd 2
vd 1
(V )
vd 1
A
Vd
(5600V)
Z
2900
iZ
2800
R
vd 2
2700
2600
(a)
vZ  vd 2
0
0.01
0.02
0.03
0.04
0.05
t (sec)
(b)
R is used on purpose to make the dc voltage unbalance.
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
High-Level NPC Inverters
• Inverter Topologies
P
P
S1
S1
E
E
Cd
D1
Cd
S2
D1
S2
X
S3
D2  2
E
X
S4
D3  3
iA
Vd E
A
D1  2
iA
Vd
Y
D1  3
D2
S 2
A
S1
E
S1
Y
E
S3
D2  2
v AN
D2  2
Z
D3
E
S 3
S 2
S3
v AN
S 4
N
(a) Four-level (m = 4)
N
(b) Five-level (m = 5)
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
Topic 7
High-Level NPC Inverters
• Switching State
Switch Status
S1
S2
1
0
0
0
1
1
0
0
v AN
Four-level Inverter
S3
S1
S1
S2
1
0
1
1
1
1
0
1
Five-level Inverter
S3
S4
S1
S 2
1
0
0
0
0
1
1
0
0
0
1
1
1
0
0
1
1
1
1
0
0
1
1
1
1
0
0
1
1
1
S 2
S 3
0
0
1
1
0
0
0
1
3E
2E
E
0
S 3
S 4
v AN
0
0
0
1
1
0
0
0
0
1
4E
3E
2E
E
0
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
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EE8407
High-Level NPC Inverters
Topic 7
• Component Count
Voltage
Clamping
dc
Switches
Level
Diodes*
capacitors
m
6(m-1)
3(m-1)(m-2)
(m-1)
3
12
6
2
4
18
18
3
5
24
36
4
6
30
60
5
* The clamping diodes have the same voltage rating as
other switches.
Note:
The number of clamping diodes increases substantially
with the voltage level.
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
33
EE8407
High-Level NPC Inverters
Topic 7
• IPD Modulation (four-level)
1.0
vcr1
vcr 2
0
vcr 3
-1.0
v g1
vg 2
vg 3
v AN
3E
0
v AB
THD = 25.2%
3E
0
VABn / Vd
THD = 25.2%
0.10
0.05
0
1
5
10
15
20
25
30
35
40
45
50
55
60
n
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
34
EE8407
Topic 7
High-Level NPC Inverters
• Harmonic Content (four-level, IPD Modulation)
V AB n / V d
0.2
v = 3-level
v = 5-level
AB
7-level
AB
0.1
n=1
n=13,17
n=11,19
n=5
n=7
0
0
0.2
0.4
0.6
0.8
ma
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
35
EE8407
High-Level NPC Inverters
Topic 7
• APOD Modulation (four-level)
1.0
vcr1
vcr 2
vcr 3
-1.0
v AB
3E
0
iA
0
2

3
V AB n / Vd
0.15
0.10
n = 11
13
17th 19th
23rd
0.05
0
1000
37th
29th
2000
47th
53rd
3000
61st
f (Hz)
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
36
EE8407
Topic 7
High-Level NPC Inverters
• Harmonic Content (four-level, APOD Modulation)
V AB n
Vd
0.3
y
x
n=1
y
 0.612
x
0.2
n=13,17
n=11
0.1
n=19
0
0
0.2
0.4
0.6
0.8
Ma
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
37
EE8407
Summary
Topic 7
• The 3-level NPC inverter widely used in MV drives
Main features
- Low device count
- No switches in series
- Suitable for medium voltage operation
• The practical use of 4- or 5-level NPC inverters not reported
Main reasons
- Difficulties in dc capacitor voltage control
- Large number of clamping diodes
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
38
EE8407
Topic 7
Textbook: Bin Wu, ‘High-Power Converters and AC Drives’, Wiley - IEEE Press, 2006
39