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1
High-Power Converters and AC DrivesIEEE PESC2005 Tutorial
Bin Wu PhD, PEng
ProfessorRyerson University Toronto, Canada
Presentation material extracted from ‘High Power Converters and AC Drives’To be published by IEEE Press / Wiley November 2005, ISBN: 0-4717-3171-4
Ryerson Campus
Email: [email protected]://www.ee.ryerson.ca/~bwu/
2
High-Power Converters and AC Drives
1. Introduction2. Cascaded H-Bridge Multilevel Inverters3. Neutral Point Clamped Multilevel Inverters4. Other Multilevel Inverters5. PWM Current Source Inverters6. PWM Current Source Rectifiers
7. Voltage Source Inverter (VSI) Fed Drives8. Current Source Inverter (CSI) Fed Drives
Main Topics
High-Power Converters and AC Drives Bin Wu
3
Topic 1Introduction
Main Topics • Medium Voltage (MV) Drive Overview• High Power Converter Topologies • MV Industrial Drives• High-Power Semiconductor Devices
High-Power Converters and AC Drives Bin Wu
4High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Drive Overview
• MV Drive Power and Voltage Ratings
Majority of installed MV drives:
1MW to 4MW 3.3KV to 6.6KV
5High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Drive Overview
• MV Drive Market Survey
Main purpose for high-power fan/pump drives: Energy conservation
6High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Drive Overview
• General Block Diagram
Line- and motor-side filters: Optional, depending on converter topologies and harmonic requirements
2
7High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Drive Overview
• MV Drive ApplicationsIndustry Application Examples
Petrochemical Pipeline pumps, gas compressors, brine pumps, mixers / extruders, electrical submersible pumps, induced draft fans, boiler feed water pumps, water injection pumps.
Cement Kiln induced draft fans, forced draft fans, baghouse fans, preheat tower fans, raw mill induced draft fans, kiln gas fans, cooler exhaust fans, separator fans.
Mining & Metals
Slurry pumps, ventilation fans, de-scaling pumps, tandem belt conveyors, baghouse fans, cyclone feed pumps, crushers, rolling mills, hoists, coilers, winders.
Water / Wastewater
Raw sewage pumps, bio-roughing tower pumps, treatment pumps, freshwater pumps, storm water pumps.
Transportation Propulsion for naval vessels, shuttle tankers, icebreakers, cruisers. Traction drives for locomotives, light-track trains.
Electric Power Feed water pumps, induced draft fans, forced draft fans, effluent pumps, compressors.
Forest Products Fan pumps, induced draft fans, boiler feed water pumps, pulpers refiners, kiln drives, line shafts.
Miscellaneous Wind tunnels, agitators, test stands, rubber mixers.
Source: Rockwell Automation
8High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Drive Overview
• Technical Requirements and Challenges
• Line-Side RequirementsLow line current THDHigh input power factor
• Motor-Side ChallengesHigh dv/dt and wave reflectionMotor derating due to harmonicsCommon-mode voltage stress
9High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Drive Overview
• Technical Requirements and Challenges• Switching Device Constraints
Low device Switching frequency (<1000Hz)Reliable series connection
• Drive System RequirementsHigh efficiencyLow manufacturing costHigh reliability Effective fault protectionSelf commissioningMinimum down-time for repairsSmall footprintN+1 redundancy (optional)Dynamic braking / four-quadrant operation (optional)
10High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Converter Topologies
• Multipulse Diode/SCR Rectifiers
Main Feature: To reduce line current THD.
Six-pulse rectifiers can be in series or isolated at their outputs, depending on inverter topologies
11High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Converter Topologies
• Multilevel Voltage Source Inverters
N
dC
CascadedH-bridge (CHB)
Inverter
dC
Two LevelInverter
dC
Flying CapacitorInverter
dC
Neutral PointClamped (NPC)
Inverter
dC
~ ~
~
~
12High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Converter Topologies
• PWM Current Source Inverters
fC fC
dL dL dL
3
13
Topic 1 IntroductionMV Industrial Drives
• NPC Inverter Fed MV Drive
ACS1000, Courtesy of ABB
GCT based three-level NPC inverter fed drive (4.16KV and 1.2MW)
High-Power Converters and AC Drives Bin Wu
14High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Industrial Drives
• NPC Inverter Fed MV Drive
IGBT based three-level NPC inverter fed drive
SIMOVERT MVCourtesy of Siemens
15High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Industrial Drives
• CHB Inverter Fed MV Drives
Perfect Harmony, Courtesy of ASI Robicon
IGBT based cascaded H-bridge inverter fed MV drive (4.16KV and 7.5MW)
16High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionMV Industrial Drives
• PWM Current Source Inverter Fed Drive
PowerFlex 7000, Courtesy of Rockwell Automation
GCT based current source based MV drive(Frame C, 2.3 MW to 7MW)
17
4500V/800A press-pack and 1700V/1200A module diodes
High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Switching Devices
• Power Diode
18
4500V/800A and 4500V/1500A SCRs
High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Switching Devices
• Silicon Controlled Rectifier (SCR)
4
19
4500V/800A and 4500V/1500A GTOs
High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Switching Devices
• Gate Turn Off Thyristor (GTO)
20
6500V/1500A Symmetrical GCT
GCT = Improved GTO + Integrated Gate + Anti-parallel Diode (optional)
High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Switching Devices
• Integrated Gate Controlled Thyristor (IGCT/GCT)
21
1700V/1200A and 3300V/1200A IGBT modules
High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Switching Devices
• Insulated Gate Bipolar Transistor (IGBT)
22High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Switching Devices
• Device Voltage/Power Ratings
23High-Power Converters and AC Drives Bin Wu
Topic 1 IntroductionHigh-Power Switching Devices
• ComparisonItem GTO GCT IGBT
Maximum voltage and current ratings
High High Low
Packaging Press pack Press pack Module or Press pack Switching speed Slow Moderate Fast Turn-on (di/dt) snubber Required Required Not required Turn-off (dv/dt) snubber Required Not required Not required Active overvoltage clamping No No Yes Active di/dt and dv/dt control No No Yes Active short circuit protection No No Yes On-state loss Low Low High Switching loss High Medium Low Behavior after destruction Short circuited Short circuited Open circuited
Gate Driver Complex, separate
Complex, integrated
Simple, compact
Gate Driver Power Consumption High Medium Low
24
• H-Bridge Inverter• CHB Inverter Topologies• Phase Shifted PWM• Level Shifted PWM• PWM Scheme Comparison
Topic 2 Cascaded H-Bridge (CHB) Multilevel Inverters
High-Power Converters and AC Drives Bin Wu
5
25
• 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?
Device Switching frequency: fsw < 1000Hz
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel Inverters
26
Topic 2 CHB Multilevel InvertersH-Bridge Inverter
• H-bridge Inverter Circuit
High-Power Converters and AC Drives Bin Wu
dC∞dV
1S
2S
3S
4S
1D
2D
3D
4D
1g 3g
2g4g
A
B
P
N
ABv
27
°= 0δ
°= 0δ
°= 0δ
M
°= 30δ
°= 30δ
°= 30δ
A
B
C
Neutral
H-bridge
Phase ShiftingTransformer
UtilityGrid
Five-level cascaded H-bridge inverter H-bridge Power Cell
• CHB Inverter Fed MV Drive
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersH-Bridge Inverter
dC∞dV
1S
2S
3S
4S
1D
2D
3D
4D
1g 3g
2g4g
A
B
P
N
ABv
28
• Bipolar Modulation
Bipolar PWM:vAB from -Vd to +Vd
or from +Vd to -Vd
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersH-Bridge Inverter
dC∞dV
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
π π2
mv crv
0
0.2
0.4
0.6
12 ±fm32 −fm 32 +fm
2−fm 2+fm 23 ±fm 14 ±fm1=n
dn VV AB /
0
(a) W avefo rm s
(b ) H arm on ic spectrum
dV−
n1 10 20 30 40 50 60
29
• Bipolar Modulation (FFT)
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersH-Bridge Inverter
d
n
V
V AB
0.2
0.4
0.6
0.8
0.2 0.4 0.6 0.8
2±fm
00
32 ±fm
12 ±fm
0.707
fm
am
1=n
30
• Unipolar Modulation (1)
• Two modulation wavesvm and vm-
• One carrier wave vcr
• Unipolar PWM:vAB from 0 to +Vd
or from 0 to -Vd
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersH-Bridge Inverter
dC∞dV
1S
2S
3S
4S
1D
2D
3D
4D
1g 3g
2g4g
A
B
P
N
ABv
0
-1.0
1.0
−mv
π π2
1gv
3gv
0
BNv
ANvdV
dV
0
ABvdV
0
0.2
0.4
dn VV AB /
32 −fm 32 +fm14 ±fm
0.6
12 ±fm
mv crv
1=n
(b) Harmonic spectrum
(a) W aveform s
n1 10 20 30 40 50 60
6
31
• Unipolar Modulation (2)
• One modulating wave vm
• Two carrier wavesvcr and vcr-
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersH-Bridge Inverter
dC∞dV
1S
2S
3S
4S
1D
2D
3D
4D
1g 3g
2g4g
A
B
P
N
ABv0
-1.0
1.0
0
ABvdV
mv crv
−crv
1gv
3gv
32
• Five-Level Inverter
Converters in cascade, but no switching devices in series.
ComplementarySwitch pairs:S11 and S41;S31 and S21;
S12 and S42;S32 and S22;
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersCHB Inverter Topologies
1Hv
2Hv
N
21S
11S
41S
31S
22S42S
32S12S
E
E
E
E
E
E
A B C
O
LOAD
33
• Output Voltage and Switching Status (five-level)
Waveform of vAN is composed of five voltage levels: 2E, E, 0, -E, and -2E
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersCHB Inverter Topologies
1Hv
2Hv
21S
11S
41S
31S
22S42S
32S12S
E
E
A
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
34
• Seven- and Nine-Level Inverters (Per phase diagram)
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersCHB Inverter Topologies
1Hv
2Hv
21S
11S
41S
31S
22S42S
32S12S
E
E
A
3Hv
23S43S
33S13S
E
N
1Hv
2Hv
E
E
A
3HvE
4HvE
N
35
• Unequal dc Bus Voltage
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersCHB Inverter Topologies
1Hv
2Hv
21S
11S
41S
31S
22S42S
32S12S
E
E2
A
N
1Hv
2Hv
21S
11S
41S
31S
22S42S
32S12S
E
E3
A
N
36
• Unequal dc Bus Voltage (Two-cell seven-level topology)
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersCHB Inverter Topologies
1Hv
2Hv
21S
11S
41S
31S
22S42S
32S12S
E
E2
A
N
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
7
37
• Multicarrier Based PWM – Phase Shifted
Amv
1crv 2crv 3crv
11gv
31gv
1Hvπ
12gv
32gv
2Hv
13gv
33gv
3Hv
π0
A Nv
E
3E
0
1.0
-1.0
E
−1crv−2crv −3crv
E
π
π
321 HHH vvvvA N ++=
• # of voltage levels: m = 7• # of carriers: mc = m - 1 = 6
• Phase shift: 360°/ mc = 60°
Carriers for H1 bridge:vcr1 and vcr1-
Carriers for H2 bridge:vcr2 and vcr2-
Carriers for H3 bridge:vcr3 and vcr3-
m = 7
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersPhase Shifted PWM
38
• 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
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersPhase Shifted PWM
39
• 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
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersPhase Shifted PWM
12 ±fm14 ±fm 16 ±fm
36 ±fm96 −fm 96 +fm
16 ±fm76 −fm 76 +fm
dn VV /H1
dANn VV /
dABn VV /
40
• Harmonic Content (7-level, phase shifted)
00.2 0.4 0.6 0.80 am
0.1
0.2
0.3
d
n
V
V AB
16 ±fm
56 ±fm 76 ±fm
116 ±fm
x∆
y∆ 2241.xy=
∆
∆
1=n
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersPhase Shifted PWM
41
• Multicarrier Based PWM – Level Shifted PWM
• # of voltage levels: m = 5
• # of carriers: mc = m - 1 = 4
• IPD provides the best harmonic profile.
mv
π2π
π3
1crv
2crv
3crv
4crv
π π2 π3
mv
ππ2
mv
1crv
2crv
3crv
4crv
1crv
2crv
3crv
4crv
IPD
APOD
POD
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersLevel Shifted PWM
42
• Gating Arrangement (7-level)cr1v
cr2v
cr3v
π
π
π
π
g11v
g31v
1Hv
12gv32gv
2Hv
13gv33gv
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.
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersLevel Shifted PWM
8
43
• Inverter Output Voltages (seven-level)
• m = 7
• vAB close to a sinusoid
• Low THD, low EMI
• Equivalent fsw(inv) = fc = 3600Hz
• Switching occurs at different times
• fsw(device) = fcr /mc =600Hz (avg)
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersLevel Shifted PWM
1Hv
2Hv
3Hv
ANv
ABv
2±fm8+fm8−fm
16+fm16−fm
π2 π4
π2 π4
6−fm 6+fm
dABn VV /
dANn VV /
44
• Measured Waveforms (IPD, 7-level)
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersLevel Shifted PWM
Inverter phase voltage vAZ Line-to-line voltage vAB
45
• PWM at Low ma
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersPWM Scheme Comparison
- Phase shifted PWM: THD = 96.7%
- Level shifted PWM: THD = 48.8%
• At ma = 0.2:
1Hv2Hv3Hv
0
ANv
0
ABv
E
2E
1Hv
2Hv3Hv
0
ANv
0
ABv2E
E
(a) Phase-shifted modulation
(b) Voltage-shifted (IPD) modulation
THD = 96.7%
THD = 48.8%
θ
θ
46
• Total Harmonic Distortion (THD)
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersPWM Scheme Comparison
am
Hz600, =devswf
47
• Summary
High-Power Converters and AC Drives Bin Wu
Topic 2 CHB Multilevel InvertersPWM Scheme Comparison
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)
48
• Three-level NPC Inverter• Space Vector Modulation• Neutral Point Voltage Control • High-level NPC Inverter
Topic 3Neutral Point Clamped (NPC) Multilevel Inverter
High-Power Converters and AC Drives Bin Wu
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49
• Inverter Configuration
Clamping diodes: DZ1 and DZ2 (Phase A)
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersThree-Level NPC Inverter
1dC
1S
2S
3S
4S
AB
CZ
2dC
1D
2D
3D
4D
1ZD
2ZD
E
E
ZidV
Ai
OBi
Ci
50
• Switching State
Complementary Switch pairs: S1 and S3; S2 and S4;
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersThree-Level NPC Inverter
Device Switching Status (Phase A) Switching
State 1S 2S 3S 4S
Inverter Terminal Voltage
ZAV
P On On Off Off E
O Off On On Off 0
N Off Off On On E−
51
• Gate Signal Arrangements
Inverter phase voltage vAZ has three levels: E, 0 and –E
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersThree-Level NPC Inverter
2π
ONONONOPOPOPO
π0
1gv
2gv
3gv
4gv
AZv
E+
E−
52
• Inverter Output Waveforms
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersThree-Level NPC Inverter
π π2
E+AZv
BZv
CZv
ABv
0
0
0
0
tω
tω
tω
tωBZAZAB vvv −=
E−
E2+
E2−
E+
53
• Space Vectors
• Three-phase voltages0)()()( =++ tvtvtv COBOAO
• Two-phase voltages
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡
=⎥⎦
⎤⎢⎣
⎡
)()()(
34sin
32sin0sin
34cos
32cos0cos
32
)()(
tvtvtv
tvtv
CO
BO
AO
ππ
ππ
β
α
• Space vector representation)()()( tvjtvtV βα +=
r
(2) → (3)
[ ]3/43/20 )()()(32)( ππ j
COj
BOj
AO etvetvetvtV ++=r
where xjxe jx sincos +=
(3)
(1)
(2)
(4)
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
High-Power Converters and AC Drives Bin Wu
54
Switching state [POO] → on-state switches:Phase A: upper two switches [P]Phase B: lower two switches [O]Phase C: lower two switches [O]
dBOdAO VtvVtv31)(,
32)( −==
dCO Vtv31)( −=and
Substituting (5) to (4) gives a space vector
(5)
(6)0
1 32 j
d eVV =r
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
High-Power Converters and AC Drives Bin Wu
• Space Vectors (Example)
from which
Total switching states: 27Total space vectors: 19
10
55
• Space Vectors Diagram
19 space vectors:Zero vector: V0Small vectors: V1 – V6Medium vectors: V7 – V12Large vectors: V13 – V18
High-Power Converters and AC Drives Bin Wu
αdVV
32
13 =r
6/
33
7πjedVV =
r
3/
32
14πjedVV =
r
0Vr
3Vr
2Vr
4Vr
5Vr
8Vr
6Vr
15Vr
18Vr
12Vr
11Vr
10Vr
9Vr
17Vr
16Vr
β
3/1 dVV =r
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
56
Space Vector Switching State Vector Classification Vector
Magnitude
0Vr
[PPP][OOO] [NNN] Zero Vector (ZV) 0 P-type N-type PV1
r [POO]
1Vr
NV1r
[ONN]
PV2
r [PPO]
2Vr
NV2
r [OON]
PV3
r [OPO]
3Vr
NV3
r [NON]
PV4r
[OPP] 4Vr
NV4
r [NOO]
PV5r
[OOP] 5Vr
NV5
r [NNO]
PV6r
[POP] 6Vr
NV6r
[ONO]
Small Vector (SV)
P-type Small Vector (PSV) N-type Small Vector (NSV)
dV31
• Switching States and Space Vectors
Redundancy: Zero vector – three switching statesSmall vectors – two states per vector
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
57
Space Vector Switching State Vector Classification Vector
Magnitude 7Vr
[PON]
8Vr
[OPN]
9Vr
[NPO]
10Vr
[NOP]
11Vr
[ONP]
12Vr
[PNO]
Medium Vector (MV) dV33
13Vr
[PNN]
14Vr
[PPN]
15Vr
[NPN]
16Vr
[NPP]
17Vr
[NNP]
18Vr
[PNP]
Large Vector (LV) dV32
No redundant switching states for medium or large vectors
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
• Switching States and Space Vectors
58
• Sector Definition
1Vr
13Vr
7Vr
14Vr
0Vr
3Vr
2Vr
4Vr
5Vr
8Vr
6Vr
15Vr
18Vr
12Vr
11Vr
10Vr
9Vr
17Vr
16Vr
refVr
θ
Vref : Reference vector, rotating in space at a certain speedAll other vectors are stationary
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
59
• SVM Principle
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
• For a given length and position, Vref can be synthesized by three nearby stationary vectors;
• Based on the selected stationary vectors, switching states can be designed and gate signals can be generated;
• When Vref passes through sectors one by one, different sets ofswitches can be 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.
60
• Dwell Time Calculation
θ
4
bT PNNcT
bT
3
PON
PPN
PPOOON
1
aT
ONNPOO
2
cT
°39
13Vr
7Vr
1Vr
14Vr
0Vr
2Vr
refVr
aT
• Use volt-second balancing principle
• Select three nearest stationary vectors
721 and, VVVrrr
Sector I
⎩⎨⎧
=++
=++
scba
srefcba
TTTT
TVTVTVTVrrrr
271
Four Regions
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
What is the dwell time?• Vref is synthesized by three stationary vectors.• The dwell time for the stationary vectorsessentially represents the duty-cycle time of selected switches during the sampling period Ts .
(a)
11
61
• Dwell Time Calculation
⎪⎪⎪
⎩
⎪⎪⎪
⎨
⎧
−−=
−+=
−=
])3
(sin21[
]1)3
(sin2[
]sin21[
θπ
θπθ
asc
asb
asa
mTT
mTT
mTT
Ta , Tb and Tc – dwell times for V1 , V7 and V2
d
refa V
Vm 3=
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
– modulation index
From equation (a)
62
• Switching Sequence (Seven-segment)
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
General Design Requirements:a) 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
b) 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.
63
• Switching Sequence (Seven-segment)
Voltage Vector NV2r
7Vr
14Vr
PV2r
14Vr
7Vr
NV2r
Dwell Time 4cT
2bT
2aT
2cT
2aT
2bT
4cT
Phase A O P P P P P O
Phase B O O P P P O O
Switching
State Phase C N N N O N N N
,0]O[,]P[ == E E−=]N[ .
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
Assuming Vref is in Region 4 of Sector I,
three vectors are selected: V2 , V7 and V14
64
• Switching Sequence (Seven-segment)
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
High-Power Converters and AC Drives Bin Wu
2aT
BZv
AZv
CZv
E+
4cT
2bT
sT
ABv
E+
E−
E+
2cT
2bT
4cT
NV2
r7Vr
14Vr
PV2
r14Vr
7Vr
NV2
r
2aT
Switching sequence requirement a) is satisfied
65
• Switching Sequence (Seven-segment)
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
Sector I Sgmt 1a 1b 2a 2b 3 4
1st NV1
r [ONN] NV2
r [OON] NV1
r [ONN] NV2
r[OON] NV1
r [ONN] NV2
r [OON]
2nd NV2r
[OON] 0Vr
[OOO] NV2r
[OON] 7Vr
[PON] 13Vr
[PNN] 7Vr
[PON]
3rd 0Vr
[OOO] PV1r
[POO] 7Vr
[PON] PV1r
[POO] 7Vr
[PON] 14Vr
[PPN]
4th PV1r
[POO] PV2r
[PPO] PV1r
[POO] PV2r
[PPO] PV1r
[POO] PV2r
[PPO]
5th 0Vr
[OOO] PV1r
[POO] 7Vr
[PON] PV1r
[POO] 7Vr
[PON] 14Vr
[PPN]
6th NV2r
[OON] 0Vr
[OOO] NV2r
[OON] 7Vr
[PON] 13Vr
[PNN] 7Vr
[PON]
7th NV1
r [ONN] NV2
r [OON] NV1
r [ONN] NV2
r[OON] NV1
r [ONN] NV2
r [OON]
Sector II Sgmt 1a 1b 2a 2b 3 4
1st NV2r
[OON] NV3r
[NON] NV2r
[OON] NV3r
[NON] NV2r
[OON] NV3r
[NON]
2nd 0Vr
[OOO] NV2r
[OON] 8Vr
[OPN] NV2r
[OON] 8Vr
[OPN] 15Vr
[NPN]
3rd PV3r
[OPO] 0Vr
[OOO] PV3r
[OPO] 8Vr
[OPN] 14Vr
[PPN] 8Vr
[OPN]
4th PV2r
[PPO] PV3r
[OPO] PV2r
[PPO] PV3r
[OPO] PV2r
[PPO] PV3r
[OPO]
5th PV3r
[OPO] 0Vr
[OOO] PV3r
[OPO] 8Vr
[OPN] 14Vr
[PPN] 8Vr
[OPN]
6th 0Vr
[OOO] NV2r
[OON] 8Vr
[OPN] NV2r
[OON] 8Vr
[OPN] 15Vr
[NPN]
7th NV2r
[OON] NV3r
[NON] NV2r
[OON] NV3r
[NON] NV2r
[OON] NV3r
[NON]
66
• Switching Sequence (Seven-segment)
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
14Vr
15Vr
17Vr
18Vr
13Vr
16Vr
refVr
refVr
Switching sequence requirement b) is satisfied
2/2/ 1, fff spdevsw +=
ssp Tf /1=
Device switching frequency:
Sampling frequency:
Fundamental frequency:
1f
12
67
AZv
ABv
0
1gv
4gv
0
π π2 π3
• Simulated Waveforms (Seven-segment)
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
High-Power Converters and AC Drives Bin Wu
f1 = 60Hz, Ts = 1/1080 sec, ma = 0.8, fsw = 570Hz
vAB is not half wave symmetrical; andContains both even- and odd-order harmonics
68
• Simulated Waveforms (Seven-segment)
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
High-Power Converters and AC Drives Bin Wu
f1 = 60Hz, Ts = 1/1080 sec, ma = 0.8, fsw = 570Hz
dAZ VV n /
dAB VV n /
69High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
dnAB VV /
am
am
dnAB VV /
• Harmonic Content (Seven-segment)
70
• Measured Waveforms
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
AZv
ABv
8.0)a( =am 9.0)b( =am
d
n
VVAB
d
n
VVAZ
71
• Measured waveforms (No even-order harmonics)
High-Power Converters and AC Drives Bin Wu
Topic 3 Multilevel NPC InvertersSpace Vector Modulation
AZv
ABv
8.0)a( =am 9.0)b( =am
d
n
VVAB
d
n
VVAZ
The SVM switching sequence can be modified for even-order harmonic elimination.
72
• Neutral Point Voltage Deviation
The neutral point voltage vz can be controlled byP- and N-types of small vectors
Topic 3 Multilevel NPC InvertersNeutral Point Voltage Control
High-Power Converters and AC Drives Bin Wu
ZdV dV
dV dV
++
+ +
1dC
2dC
1dC
2dC
1dC
2dC
1dC
2dC
Zv+
Zv+
Zv+
Zv+
Zi
Zi
Z
ZZ
A
B
C
A
B
C
A
B
C
A
B
C
↑⇒ Zv]POO[affectednot]PPP[ Zv⇒
↓⇒ Zv]ONN[ definednot]PON[ Zv⇒
dV
+
Zv+
1dC
2dC
Z
A
B
C
affectednot]PNN[ Zv⇒
13
73
• Neutral Point Voltage Control
aNaPa TTT +=
( )
( )⎪⎩
⎪⎨
⎧
∆−=
∆+=
tTT
tTT
aaN
aaP
12
12 11 ≤∆≤− T
Topic 3 Multilevel NPC InvertersNeutral Point Voltage Control
High-Power Converters and AC Drives Bin Wu
Neutral Point Deviation Level
Motoring Mode 0>di
Regenerating Mode 0<di
ddd Vvv ∆>− )( 21 0>∆t 0<∆t
ddd Vvv ∆>− )( 12 0<∆t 0>∆t
ddd Vvv ∆<− 21 0=∆t 0=∆t
V∆ − maximum allowed voltage deviation ( 0>∆ dV ).
74
• Neutral Point Voltage Control
R is used on purpose to make the dc voltage unbalance.
Topic 3 Multilevel NPC InvertersNeutral Point Voltage Control
High-Power Converters and AC Drives Bin Wu
1dv
(sec)t
)(V21, dd vv
2dZ vv =
A
Z
2dv
ZidV
1dv
R
75
• Inverter Topologies
Topic 3 Multilevel NPC InvertersHigh-Level NPC Inverters
High-Power Converters and AC Drives Bin Wu
1S
2S
3S
1S ′
A
1D
22 ×D
2D′
E
E
dV E
E
E
dV
E
E
A
2S′
3S′
21×′D
1S
2S
3S
4S
1S ′
2S ′
3S′
4S ′
1D
X
22 ×D
33 ×D
31 ×′D
22 ×′D
3D′
X
Y
Y
Z
dCdC
P
N
ANv ANv
N
P
Ai Ai
76
• Switching State
Topic 3 Multilevel NPC InvertersHigh-Level NPC Inverters
High-Power Converters and AC Drives Bin Wu
Switch Status
Four-level Inverter
1S 2S 3S 1S ′ 2S ′ 3S ′ ANv
1 1 1 0 0 0 3E 0 1 1 1 0 0 2E 0 0 1 1 1 0 E 0 0 0 1 1 1 0
Five-level Inverter
1S 2S 3S 4S 1S ′ 2S ′ 3S ′ 4S ′ ANv
1 1 1 1 0 0 0 0 4E 0 1 1 1 1 0 0 0 3E 0 0 1 1 1 1 0 0 2E 0 0 0 1 1 1 1 0 E 0 0 0 0 1 1 1 1 0
77
• Component Count
Voltage Level
Switches Clamping Diodes*
dc 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.
Topic 3 Multilevel NPC InvertersHigh-Level NPC Inverters
High-Power Converters and AC Drives Bin Wu
78
• IPD Modulation (four-level)
Topic 3 Multilevel NPC InvertersHigh-Level NPC Inverters
High-Power Converters and AC Drives Bin Wu
3gv2gv
1gv
ANv
ABv
1crv
2crv
3crv
dAB VV n /
14
79
• Harmonic Content (four-level, IPD Modulation)
Topic 3 Multilevel NPC InvertersHigh-Level NPC Inverters
High-Power Converters and AC Drives Bin Wu
am
dAB VV n /
80
• APOD Modulation (four-level)
1crv
2crv
3crv
ABv
Ai
π π2 π3
dn VVAB /
Topic 3 Multilevel NPC InvertersHigh-Level NPC Inverters
High-Power Converters and AC Drives Bin Wu
81
• Harmonic Content (four-level, APOD Modulation)
0.2 0.4 0.6aM
0.1
0.2
0.3
00
x∆
y∆ 612.0=∆
∆
xy
n=1
n=13,17n=11
n=19
0.8
d
n
V
VAB
Topic 3 Multilevel NPC InvertersHigh-Level NPC Inverters
High-Power Converters and AC Drives Bin Wu
82
• The three-level NPC inverter has found wide application in the MV drives.Main features:- Low device count- Good harmonic profile- Suitable for medium voltage operation
• The practical use of four- or five-level inverters has not been reported. Main reasons: - Difficulties in dc capacitor voltage control- Large number of clamping diodes
Topic 3 Multilevel NPC InvertersSummary
High-Power Converters and AC Drives Bin Wu
83
• NPC/H-Bridge Inverters • Flying-Capacitor Multilevel Inverters
Topic 4Other Multilevel Inverters
High-Power Converters and AC Drives Bin Wu
84
• Five-Level Topology
High-Power Converters and AC Drives Bin Wu
Topic 4 Other Multilevel InvertersNPC/H-bridge Inverters
1dV 2dV 3dV
11S
12S
13S
14S
21S
24S
22S
23S
dC
dC
E
E
ANv BNv CNv
Compared with three-level NPC Topology:- Voltage levels increases from three to five- Inverter output voltage and power are doubled - Device count is doubled
15
85
• IPD Modulation
High-Power Converters and AC Drives Bin Wu
Topic 4 Other Multilevel InvertersNPC/H-bridge Inverters
11gv
14gv
21gv
24gv
ANv
1mv
2mv
1crv
2crv π π2
π π2
mV̂crV̂
86
• Waveforms and FFT
High-Power Converters and AC Drives Bin Wu
Topic 4 Other Multilevel InvertersNPC/H-bridge Inverters
π2 π3
)(VANv
d
n
V
VAN
π
12 −fm
52 −fm 52 +fm 14 ±fm
12 +fm
π π2 π3
)(VABv
d
n
V
VAB
12 −fm 12 +fm
52 −fm 52 +fm 14 ±fm
Inverter phase voltage vAN : 5-levels Line-to-line voltage vAN : 9-levels
87
• Five-Level Topology
1S
2S
4S
3S
1S ′
2S ′
3S ′
4S ′)4( E
dV
ComplementarySwitch pairs:S1 and S’1;S2 and S’2;S3 and S’3;S4 and S’4;
High-Power Converters and AC Drives Bin Wu
Topic 4 Other Multilevel InvertersFlying Capacitor Multilevel Inverters
88
• Phase-Shifted PWM
High-Power Converters and AC Drives Bin Wu
Topic 4 Other Multilevel InvertersFlying Capacitor Multilevel Inverters
ABv
ANv
54 −fm14 ±fm
54 +fm
12=fmdAB VV n /
π2 π4
π2 π4
• fsw (device) = 60(mf ) = 720Hz • fsw (inverter) = 60(4mf ) = 2880Hz
89
Features:- Low harmonic distortion- Modular design
Drawbacks:- Large number of dc caps - Complex pre-charging circuits- Difficulties in dc cap voltage balancing control
• Summary
High-Power Converters and AC Drives Bin Wu
Topic 4 Other Multilevel InvertersFlying Capacitor Multilevel Inverters
90
Main Topics • Single Bridge Inverter • Trapezoidal Modulation (TPWM)• Selective Harmonic Elimination (SHE)• Space Vector Modulation (SVM)• Dual Bridge Inverter
Topic 5 PWM Current Source Inverters (CSI)
16
91
• Inverter Topology
Features:- Simple topology – no antiparallel diodes- Reliable short circuit protection – constant dc current- Very low dv/dt on motor terminals
Symmetrical GCTs
Topic 5 PWM CSISingle Bridge Inverter
High-Power Converters and AC Drives Bin Wu
1S
2S
3S 5S
4S 6S
dI
wi
ci
si
fC
4g 6g 2g
1g 3g 5g
A
B
C
fC fCLOAD
O
ABv
Function of Cf :- Assist GCT commutation- Reduce harmonic distortion
92
• DC Current Source Id
Implementation of dc current source:- use a large size dc choke – making Id smooth; - use dc current feed back control – keeping Id constant
Topic 5 PWM CSISingle Bridge Inverter
High-Power Converters and AC Drives Bin Wu
SCRor
PWMRectifier
PWMInverter
Controller
dIdL
*dI
UtilitySupply
M
asv
bsv
csv
fC
A
B
C
dI
93
• Trapezoidal PWM (TPWM)• Selective Harmonic Elimination (SHE)• Space Vector Modulation (SVM)
• Constraints on Switching Pattern Design- dc current Id cannot be interrupted- inverter output current waveform
must be defined.
• At any time instant, only two switches are turned on, one 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
Topic 5 PWM CSISingle Bridge Inverter
High-Power Converters and AC Drives Bin Wu
• Modulation Techniques
94
• Trapezoidal PWM (TPWM)
Number of pulses per half cycle: Np = 7
Topic 5 PWM CSI Trapezoidal Modulation
High-Power Converters and AC Drives Bin Wu
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
95
• Harmonic Content (TPWM)
• Np = 15
• Fundamental does notchange much with ma
• ma = 0.85
Topic 5 PWM CSI Trapezoidal Modulation
High-Power Converters and AC Drives Bin Wu
am
am
max,1wwn II
max,1wwn II
96
• Waveforms (TPWM)
Topic 5 PWM CSI Trapezoidal Modulation
High-Power Converters and AC Drives Bin Wu
Hz180
,13,Hz8.131
=
==
sw
p
f
Nf
Hz155
,31,Hz55
=
==
sw
p
f
Nf
17
97
• Selective Harmonic Elimination (SHE)
• Not all the switching angles are independent.• Only two harmonics can be eliminated with Np = 5.
• No modulation index control – the magnitude of inverter output current is controlled by Id
• Number of harmonics to be eliminated: 2/)1( −= pNk
Topic 5 PWM CSI Selective Harmonic Elimination
High-Power Converters and AC Drives Bin Wu
π3π
32π π21θ 2θ
6π
23θπ−
dI
tω
wi
13θπ−
0
98
• Fourier Analysis
∑=∞
=1)sin()(
nnw tnati ωω
⎪⎪⎪⎪⎪
⎩
⎪⎪⎪⎪⎪
⎨
⎧
=++
+++
=++
+++
×=
∫∫
∫∫
∫∫
∫∫
−
−
−
−
−
−
−
even.k )()sin(...)()sin(
)()sin(...)()sin(
;oddk )()sin(...)()sin(
)()sin(...)()sin(
4
2
3
3
6
2
3
3
3
6
1
1
2
1
1
1
2
1
π
θπ
θπ
π
θ
θ
θ
θ
π
θπ
θπ
θπ
π
θ
θ
θ
ωωωω
ωωωω
ωωωω
ωωωω
π
tdtntdtn
tdtntdtn
tdtntdtn
tdtntdtn
Ia
k
k
k
k
k
k
dcn
∫= 20
)()sin()(4 π
ωωωπ
tdtntia wn
Topic 5 PWM CSI Selective Harmonic Elimination
High-Power Converters and AC Drives Bin Wu
99
⎪⎪⎪⎪
⎩
⎪⎪⎪⎪
⎨
⎧
=+−−−
+−−−−+
=−−++
+−−−−+
×=
even.k )6
cos()]3
(cos[)cos(
...)]3
(cos[)cos()]3
(cos[)cos(
;oddk )6
cos()]3
(cos[)cos(
...)]3
(cos[)cos()]3
(cos[)cos(
4
2211
2211
πθπθ
θπθθπθ
πθπθ
θπθθπθ
π
nnn
nnnn
nnn
nnnn
nIa
kk
kkdc
n
Expression for an
• Fourier Analysis
Topic 5 PWM CSI Selective Harmonic Elimination
High-Power Converters and AC Drives Bin Wu
100
• Switching Angle Calculation
To Eliminate nth harmonic, set an = 0kiF ki ..., ,2 ,1 0) ..., , , ,( 321 ==θθθθ
For 5th, 7th and 11th harmonic elimination:
0)6
11cos()]3
(11cos[)11cos(
)]3
(11cos[)11cos()]3
(11cos[)11cos(
0)6
7cos()]3
(7cos[)7cos(
)]3
(7cos[)7cos()]3
(7cos[)7cos(
0)6
5cos()]3
(5cos[)5cos(
)]3
(5cos[)5cos()]3
(5cos[)5cos(
33
22113
33
22112
33
22111
=−−++
−−−−+=
=−−++
−−−−+=
=−−++
+−−−−+=
πθπθ
θπθθπθ
πθπθ
θπθθπθ
πθπθ
θπθθπθ
F
F
F
Topic 5 PWM CSI Selective Harmonic Elimination
High-Power Converters and AC Drives Bin Wu
101
• Switching Angles (SHE)
Switching Angles Switching Angles Harmonics Eliminated 1θ 2θ 3θ
Harmonics Eliminated 1θ 2θ 3θ 4θ
5 18.00 - - 7,11,17 11.70 14.12 24.17 - 7 21.43 - - 7,13,17 12.69 14.97 24.16 -
11 24.55 - - 7,13,19 13.49 15.94 24.53 - 13 25.38 - - 11,13,17 14.55 15.97 25.06 - 5,7 7.93 13.75 - 11,13,19 15.24 16.71 25.32 - 5,11 12.96 19.14 - 13,17,19 17.08 18.23 25.84 - 5,13 14.48 21.12 - 13,17,23 18.03 19.22 26.16 - 7,11 15.23 19.37 - 5,7,11,13 0.00 1.60 15.14 20.26 7,13 16.58 20.79 - 5,7,11,17 0.07 2.63 16.57 21.80 7,17 18.49 23.08 - 5,7,11,19 1.11 4.01 18.26 23.60 11,13 19.00 21.74 - 5,7,13,17 1.50 4.14 16.40 21.12 11,17 20.51 23.14 - 5,7,13,19 2.56 5.57 17.82 22.33 11,19 21.10 23.75 - 5,7,17,19 4.59 7.96 17.17 20.55 13,17 21.19 23.45 - 5,11,13,17 4.16 6.07 16.79 22.04 13,19 21.71 23.94 - 5,11,13,19 5.13 7.26 17.57 22.72 5,7,11 2.24 5.60 21.26 5,11,17,19 6.93 9.15 17.85 22.77 5,7,13 4.21 8.04 22.45 5,13,17,19 7.80 9.82 18.01 23.25 5,7,17 6.91 11.96 25.57 7,11,13,17 5.42 6.65 18.03 22.17 5,11,13 7.81 11.03 22.13 7,11,13,19 6.35 7.69 18.67 22.74 5,11,17 10.16 14.02 23.34 7,11,17,19 8.07 9.44 19.09 22.93 5,13,17 11.24 14.92 22.98 7,13,17,19 8.88 10.12 19.35 23.22 7,11,13 9.51 11.64 23.27 11,13,17,19 10.39 11.14 20.56 23.60
Topic 5 PWM CSI Selective Harmonic Elimination
High-Power Converters and AC Drives Bin Wu
102
• Inverter Waveforms (SHE)
Harmonic eliminated: 5th, 7th and 11th; fsw = 420Hz
Topic 5 PWM CSI Selective Harmonic Elimination
High-Power Converters and AC Drives Bin Wu
wi
π2 π4
dI
max,1wwn II
1)1(3 −−pN 1)1(3 +−pN
π6
18
103
• Waveforms (SHE)
07,20
)(
1175
1
===
==
www
p
IIINHzf
a
03,60
)(
5
1
=
==
w
p
INHzf
c
Topic 5 PWM CSI Selective Harmonic Elimination
High-Power Converters and AC Drives Bin Wu
05,35
)(
75
1
==
==
ww
p
IINHzf
b
104
• Space Vector Modulation
• Six active current vectors and one zero vector• Six sectors.
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
SECTOR I
SECTOR III
SECTOR IV
SECTOR VISECTOR V
α
βj
θ
ω
SECTOR II
1Ir
2Ir
3Ir
6Ir
5Ir
4Ir
refIr
0Ir
105
• Switching State
Leg A Switching State
1S 4S wI
[1] On Off dI
[-1] Off On dI−
[0] Off Off 0
[2] On On 0
1S
2S
3S 5S
4S 6S
dI
LOAD
wi
ci
oi
fC
4g 6g 2g
1g 3g 5g
A
B
C
fC fC
Z
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
106
• Switching States and Space Vectors
Space Vector Switching State On-state Switch Vector
Definition
[2 0 0] 41 S,S
[0 2 0] 63 S,S Zero Vector 0I
r
[0 0 2] 25 S,S
00 =Ir
1Ir
[1 -1 0] 16 S,S 6/1 3
2 π−= jd eII
r
2Ir
[1 0 -1] 21 S,S 6/2
32 π= j
d eIIr
3Ir
[0 1 -1] 32 S,S 6/32
32 π= j
d eIIr
4Ir
[-1 1 0] 43 S,S 6/54
32 π= j
d eIIr
5Ir
[-1 0 1] 54 S,S 6/75
32 π= j
d eIIr
Active Vector
6Ir
[0 -1 1] 65 S,S 6/96
32 π= j
d eIIr
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
[1]: Upper switch on
[-1]: Lower switch on
[0]: None of the switches in a leg turned on
[2]: Both switches in a leg turned on (bypass mode)
107
• Dwell Time Calculation
⎩⎨⎧
++=
++=
021
002211
TTTT
TITITITI
s
sref
rrrr
2Ir
refIr
22 I
TT
s
r
11 I
TT
s
rα
1Ir
θ
⎪⎩
⎪⎨⎧
+−=
+=
)(3
1)(sin
)()(cos
21
21
TTITI
TTITI
dsref
dsref
θ
θ
:Im
:Re
Following the same principleof SVM for the NPC inverter
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
108
• Dwell Time Calculation
⎪⎪⎪
⎩
⎪⎪⎪
⎨
⎧
−−=
+=
−=
210
2
1
)6
(sin
)6
(sin
TTTT
TI
IT
TI
IT
s
sd
ref
sd
ref
θπ
θπ
⎪⎪⎪
⎩
⎪⎪⎪
⎨
⎧
−−=
+=
−=
210
2
1
)6
(sin
)6
(sin
TTTT
TmT
TmT
s
sa
sa
θπ
θπ
→
d
w
d
refa I
II
Im 1
ˆ==
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
19
109
• Switching Sequence
Requirements: 1) Transition from one switching state to the next involves only
two switches2) At any time only two switches are on.
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
1Ir
16 , SS
1gv
2Ir
0Ir
1Ir
2Ir
0Ir
21 , SS 41 , SS 16 , SS 21 , SS 41 , SS
1T 2T 0T6gv5gv4gv3gv2gv
sT sT
110
• Switching Sequence (Over one cycle)
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
1gv
Sector1 0 6 1 0
6VI I II III IV V
2 0 1 2 01 3 0 2 3 02
wi0 π π2
dI
...3,2,1Ir
sT sT
)( 6Ir
2gv
3gv
4gv
5gv
6gv
111
• Inverter Output Waveforms (SVM)
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
wi
si
ABv
π2 π4
π2 π4
f1 = 60Hz, fsw = 540Hz, Np = 9 and ma = 1
112
• Harmonic Spectrum (SVM)
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
max,1/ ABABn VV
max,1/ ssn II
max,1/ wwn II
f1 = 60Hz, fsw = 540Hz, Np = 9 and ma = 1
113
• Harmonic Content (SVM)
Topic 5 PWM CSI Space Vector Modulation
High-Power Converters and AC Drives Bin Wu
9,Hz540(a) == psw Nf
114
• Dual-Bridge Inverter
Research focus- Increase converter power rating- Equal dc current sharing- Switching pattern optimization
CSI #1
M
fC
CSI #2
1di
2di
dL
dv
1dL
2dL
Topic 5 PWM CSI Dual Bridge Inverter
High-Power Converters and AC Drives Bin Wu
20
115
• CSI PWM Schemes
Topic 5 PWM CSI Summary
High-Power Converters and AC Drives Bin Wu
Item SVM TPWM SHE
DC Current Utilization
dw II /max,1 0.707 0.74 0.73 to 0.78
Dynamic performance High Medium Low
Digital Implementation Real time Real time or look-up table
Look-up table
Harmonic Performance Adequate Good Best dc Current Bypass Operation Yes No Optional
116
Topic 6 Current Source Rectifier
Topics • Single Bridge Rectifier• Dual Bridge Rectifier• Power Factor Control• LC Resonance and Active Damping
High-Power Converters and AC Drives Bin Wu
117
• Converter Configuration
• Switching devices:Symmetrical GCT
• Function CfTo assist GCT commutation;To reduce line current THD.
sLsvsi wi
A
B
C
dv
2S4S 6S
didL
UtilitySupply
1g
1S 3S 5S
fC
LOAD
Topic 6 PWM CSR Single Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
118
• Rectifier Input Current Waveform
• Constraints for Switching Pattern Design- dc current id should not be interrupted- waveform of iw should be defined
• Three independent angles to eliminate two harmonicsand make modulation index adjustable.
Topic 6 PWM CSR Single Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
tω
wi
1β 2β
06/ βπ +23/ βπ −
13/ βπ − 02β
6/π 3/π 2/π
π0
dI
3/2π 6/5π
119
• Switching Angles
• Bypass pulse (BP) - make iw adjustable
Topic 6 PWM CSR Single Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
wi
tωπ2dI
1β02β
1gv
4gv2θ
tω
tω
π2
π2
3θ 5θ 6θ 8θ 10θ 11θ 12θ1θ
BP BP
2β
120
• Switching Angles versus ma
0 0.2 0.4 0.6 0.8 1-50
0
50
100
150
200
250
1θ2θ
am
θ
3θ4θ5θ
6θ7θ8θ9θ10θ
11θ12θ
(5th and 7th harmonic elimination)
Topic 6 PWM CSR Single Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
21
121
• Harmonic Profile
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1w
wn
II
1=n
11=n
13=n17=n
19=n
am
(5th and 7th harmonic elimination)
Topic 6 PWM CSR Single Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
122
• Waveforms
(5th and 7th harmonic elimination)
1gv
4gv
0
2.0
-2.0
wi
0
2.0
-2.0
si
0
2.0
-2.0
pv
π2 π4
π2 π4
0
0.4
0.8
1wwn II
11 13 17 19 23 25 29 31 37 411 Harmonic n
1wi
Topic 6 PWM CSR Single Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
123
• Experiments
Trace A: current in switch S1Trace B: Rectifier input current iwTrace C: Line current is
ma = 0.7 ma = 0.95
Topic 6 PWM CSR Single Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
124
• Dual-Bridge Topology
• Use 12-pulse transformer to cancel the 5th and 7th harmonics• Use PWM to eliminate the 11th and 13th harmonics• The lowest harmonic in the line current is the 17th
• Very low line current harmonic distortion
dL
si wisL
sL
LOAD
fC
fC
°= 0δ
°= 30δ
si~ wi~
di
Av
Cv
Bv
ssA iii ~+=
Topic 6 PWM CSR Dual Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
125
• Switching Angles
• Bypass pulses (BP) – make iw adjustable• SHE modulation – eliminate the 11th and 13th harmonics
BP
BP
Topic 6 PWM CSR Dual Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
1gv
wi
wi
1gv
tωπ2
tωπ2
tωπ2
tωπ2
π
π
π
(a) Switching pattern A for a low ma
(b) Switching pattern B for a high ma
1θ 3θ 4θ 6θ 7θ 12θ
1θ 5θ 6θ 10θ 14θ11θ
dI
dI
-Id
-Id
126
• Switching Angles versus md
(11th and 13th harmonic elimination)
Switching pattern A Switching pattern B
0 0.2 0.4 0.6 0.8
50
100
150
200
250
0
°θ
am1θ
3θ
4θ
12θ
6θ
7θ
0.80 0.85 0.90 0.95 1.00 1.05
50
100
150
200
250
0am
1θ
10θ
6θ
5θ
11θ
14θ
12θ13θ
°θ
Topic 6 PWM CSR Dual Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
22
127
• Harmonic Profile
0 0.2 0.4 0.6 0.8 1.00
0.2
0.4
0.6
0.8
Pattern A Pattern B
1w
wn
II
1=n
5=n
7=n
17=n
19=n
am
(11th and 13th harmonic elimination)
Topic 6 PWM CSR Dual Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
128
• Experimental Waveforms
Trace A: iA - line current on transformer primary sideTrace B: is - line current on transformer secondary sideTrace C: iw - rectifier input current
Modulation index: 0.5 Modulation index: 0.9
Topic 6 PWM CSR Dual Bridge Rectifier
High-Power Converters and AC Drives Bin Wu
129
• Phasor Diagram
sLsvsi wi
A
B
C
dv
2S4S 6S
didL
UtilitySupply
1S 3S 5S
fC
LOAD
ci
cv
Lv
sI sV
cIcV
wI
cI′sI′
wI′
α
LV
Topic 6 PWM CSR Power Factor Control
High-Power Converters and AC Drives Bin Wu
• Cf produces leading PF
• Delay angle control produces lagging PF
• To improve PF, use maand delay angle control simultaneously
130
• Block Diagram
Topic 6 PWM CSR Power Factor Control
High-Power Converters and AC Drives Bin Wu
LOAD
Power FactorAngle Detector
LPF LPF
si
LPF
wi
PWMGenerator
sLsv
fC
PI
0* =φ
am α PI
*dI
dL di
VZD
...
...
0
0.5
1.0 °
°
°
0
90
160...
...
cv
φ∆ I∆φ
sVsI
dI
131
• Power Factor Profile
0 0.2 0.4 0.6 0.80
0.2
0.4
0.6
0.8
1P
Region A Region B
PF
am
controlandWith αam
only controlWith am
Topic 6 PWM CSR Power Factor Control
High-Power Converters and AC Drives Bin Wu
132
• Experiments
Topic 6 PWM CSR Power Factor Control
High-Power Converters and AC Drives Bin Wu
di
am
α
wi
5.0
°67
(pu)
0
.031
sv
si
wi
(a) Transient response (b) Steady state waveforms (PF = 1)
23
133
• LC Resonance
Resonant Mode: Resonance may be excited by - Supply voltage harmonics- Rectifier current harmonicsfs
res CLπω
21
=
sLsvsi wi
A
B
C
dv
2S4S 6S
didL
UtilitySupply
1S 3S 5S
fC
LOAD
ci
cv
Lv
Topic 6 PWM CSR LC Resonance and Active Damping
High-Power Converters and AC Drives Bin Wu
134
• Passive and Active Damping
• Passive damping: Rp – physical damping resistor
• Active damping:
- no physical resistor
- damping current ip is producedby CSR via ma control
- ip is in phase with vc
Topic 6 PWM CSR LC Resonance and Active Damping
High-Power Converters and AC Drives Bin Wu
si
pi
sL sR
pRfCwisv
sisL sR
fCwi
CSR
CSR
(a) Passive damping
(b) Active damping
cv
cv
sv pi
pR
135
• Block Diagram of Active Damping Control
Topic 6 PWM CSR LC Resonance and Active Damping
High-Power Converters and AC Drives Bin Wu
PLL
θ
HPF ÷pR
1dq
abc Space VectorModulator
LPF
PI
*dI
am′ am ′′
StationaryFrame
SynchronousFrame
LOADsi wisLsv
fC
dL di
cv
pi′cv′
SGCTGating Unit
dI
136
• Measured Waveforms
- Rectifier input current
- Line current
- Capacitor voltage
Without Active Damping
With Active Damping
- Rectifier input current
- Line current
- Capacitor voltage
Topic 6 PWM CSR LC Resonance and Active Damping
High-Power Converters and AC Drives Bin Wu
137
Topic 7 Voltage Source Inverter Fed Drives
Topics • Two-Level VSI Fed Drives• NPC Inverter Fed Drives• CHB Inverter Fed Drives
High-Power Converters and AC Drives Bin Wu
138
• Power Converter Building Block (PCBB)
Topic 7 VSI Drives Two-Level Inverter Fed Drives
High-Power Converters and AC Drives Bin Wu
dCdV
sR
pR
sC
⎪⎭
⎪⎬⎫
⎪⎭
⎪⎬⎫
24
139
• Drive Configuration
Topic 7 VSI Drives Two-Level Inverter Fed Drives
fC
fL
dC
High-Power Converters and AC Drives Bin Wu
140
• Features and Drawbacks
Topic 7 VSI Drives Two-Level Inverter Fed Drives
High-Power Converters and AC Drives Bin Wu
Features• Modular structure using PCBB• Simple PWM Scheme• Active voltage clamping for series connected IGBTs• N+1 Provision• Ease of dc capacitor precharging• Provision for four-quadrant operation and regenerative braking
Drawbacks• High dv/dt in the inverter output voltage• Large size output LC filter
141
• Drive Configuration (with GCT Inverter)
Topic 7 VSI Drives NPC Inverter Fed Drives
dCsC
sC
sD
sDsR
sL
dC
sL
sR
fC
fL
High-Power Converters and AC Drives Bin Wu
142
• Main Specifications (With GCT Inverter)
Topic 7 VSI Drives NPC Inverter Fed Drives
High-Power Converters and AC Drives Bin Wu
Nominal input voltage 2300V, 3300V, 4160V Output power rating 400 ~ 6700HP (0.3 ~ 5 MW) Output voltage rating 0 ~ 2300V, 0 ~ 3300V, 0 ~ 4160V Output frequency 0 ~ 66Hz (up to 200Hz optional)
Drive system efficiency Typically > 98.0% (including output filter losses but excluding transformer losses)
Input power factor > 0.95% ( Displacement power factor > 0.97) Output waveform Sinusoidal (with output filter) Motor type Induction or synchronous
Overload capability Standard: 10% for one minute every 10 minutes Optional: 150% for one minute every 10 minutes
Cooling Forced air or liquid Mean time between failure (MTBF)
> 6 years
Regenerative braking capability No
143
• Drive Configuration (With IGBT Inverter)
Topic 7 VSI Drives NPC Inverter Fed Drives
fC
fLdC
dC
High-Power Converters and AC Drives Bin Wu
144
• Main Specifications (With IGBT Inverter)
Topic 7 VSI Drives NPC Inverter Fed Drives
High-Power Converters and AC Drives Bin Wu
Rectifier Standard: 12-pulse diode rectifier Optional: 24-pulse diode rectifier or active front end (PWM IGBT rectifier)
Displacement power factor ( ϕcos ) > 0.96 (12-pulse diode rectifier)
Nominal utility/motor voltage 2300V, 3300V, 4160V, 6600V
Output power rating
0.8 ~ 2.4MW @2300V 1.0 ~ 3.1MW @3300V 1.3 ~ 4.0MW @4160V 4.7 ~ 7.2MW @4160V (Parallel converter configuration) 0.6 ~ 2.0MW @6600V
Output voltage range 0 ~ 2300V, 0 ~ 3300V, 0 ~ 4160V, 0 ~ 6600V Output frequency 0 ~100Hz (standard) Motor speed range 1:1000 (with encoder)
Drive system efficiency Typically > 98.5% (at rated operating point, excluding transformer losses)
25
145
• Drive Configuration
Topic 7 VSI Drives CHB Inverter Fed Drives
dC
°−= 20δ
°= 0δ
°+= 20δ
High-Power Converters and AC Drives Bin Wu
146
• Drive Configuration
Topic 7 VSI Drives CHB Inverter Fed Drives
High-Power Converters and AC Drives Bin Wu
Multipulse Diode Rectifier Multilevel CHB Inverter
Rated Utility/Motor
Voltage
Rectifier Pulses
Secondary Windings
Transformer Secondary
Cables
Power Cells
IGBTs Voltage Levels
Rated H-BridgeOutput
IGBTswf , invswf ,
2300V 18 9 27 9 36 7 480V 600Hz 3600Hz
3300V 24 12 36 12 48 9 480V 600Hz 4800Hz
4160V 30 15 45 15 60 11 480V 600Hz 6000Hz
Typical power range: 0.3 ~ 10MW (400 ~ 14000HP)
147
• Drive Configuration (6600V Drives)
Topic 7 VSI Drives CHB Inverter Fed Drives
High-Power Converters and AC Drives Bin Wu
UtilitySupply
PowerCell
M
Phase ShiftingTransformer
Two units of 3300V CHB inverter in cascade
148
• Features and Drawbacks
Topic 7 VSI Drives CHB Inverter Fed Drives
High-Power Converters and AC Drives Bin Wu
Features • Modular design for cost reduction• Nearly sinusoidal inputs and outputs without LC filters• Provision for N+1 design for high reliability
Drawbacks• Costly phase shifting transformers• Large number of cables between transformer secondaries andpower converters
• The transformer normally installed inside cabinet – larger footprint, more cooling requirement
149
Topic 8 Current Source Inverter Fed Drives
Main Topics • CSI Drive for Standard Motors• CSI Drive for Inverter-Duty Motors• Transformerless CSI Drives for Std Motors• CSI Drive with SCR Rectifiers
High-Power Converters and AC Drives Bin Wu
150
• Drive Configuration
Topic 8 CSI Drives CSI Drives for Standard Motors
High-Power Converters and AC Drives Bin Wu
dL
fC fC
di
wi si
26
151
• Inverter Switching Scheme
Topic 8 CSI Drives CSI Drives for Standard Motors
High-Power Converters and AC Drives Bin Wu
152
• Main Specifications
Topic 8 CSI Drives CSI Drives for Standard Motors
High-Power Converters and AC Drives Bin Wu
Nominal input voltage 2300V, 3300V, 4160V, 6600V Output power rating 200 ~ 9000HP (150 ~ 6700 kW) Output voltage rating 0 ~ 2300V, 0 ~ 3300V, 0 ~ 4160V, 0 ~ 6600V Output frequency 0.2 ~ 85 Hz Drive system efficiency > 96.0% (including transformer losses) Input power factor Typically >0.98% (with PWM rectifier) Line current THD Typically <5% (with PWM rectifier) Output waveform Near sinusoidal current & voltage Motor type Induction or synchronous Overload capability 150% - one minute (standard) Power loss ride-through 5 cycles Cooling Forced air or liquid
Regenerative braking capability Inherent. No additional hardware or software required.
153
• Drive Configuration
Topic 8 CSI Drives CSI Drives for Inverter-Duty Motors
High-Power Converters and AC Drives Bin Wu
fCfC
sL
dL
No isolation transformer for cost reduction
154
• Drive Configuration
Topic 8 CSI Drives Transformerless CSI Drives for Std Motors
High-Power Converters and AC Drives Bin Wu
fCfC
dL cmL
sL
Use Integrated DC choke to block common-mode voltages
Integrated dc choke
155
• Integrated dc Choke
Topic 8 CSI Drives Transformerless CSI Drives for Std Motors
High-Power Converters and AC Drives Bin Wu
1x 2x1y
2y
2/cmddc iii +=
cmi
si
2/cmddc iii −=
fC
1x
2x
1y
2y
Common-mode voltage: vo (motor neutral to GND)156
• Testing Results
Topic 8 CSI Drives Transformerless CSI Drives for Std Motors
High-Power Converters and AC Drives Bin Wu
ABv
si
dci
Av
ov
cmi
0(a) =cmL pu8.4(b) =cmL
CM Voltage →
Without CM inductance With CM inductance
27
157
• Drive Configuration
Topic 8 CSI Drives CSI Drive With SCR Rectifiers
High-Power Converters and AC Drives Bin Wu
dL
fC
SCR Rectifier
M
GCT CSI
Z
Z
UtilityGrid
6600V
Phase ShiftingTransformer
StandardMotor
158
• Features and Drawbacks of MVCSI Drives
Topic 8 CSI Drives Summary
High-Power Converters and AC Drives Bin Wu
Features• Simple converter structure with component count• Motor friendly waveforms• Reliable fuseless short circuit protection• N+1 provision for high reliability• Regenerative braking capability• Inherent four quadrant operation
Drawbacks• Limited dynamic performance• Potential LC resonances
159
Summary - MV Industrial Drives
High-Power Converters and AC Drives Bin Wu
Inverter Configuration
Switching Device
Power Range Manufacturer
Two-Level Voltage Source Inverter
IGBT 1.4MVA – 7.2MVA Alstom
(VDM5000)
GCT 0.3MVA – 5MVA 3MVA – 27MVA
ABB (ACS1000) (ACS6000)
GCT 3MVA – 20MVA General Electric
(Innovation Series MV-SP)
IGBT 0.6MVA – 7.2MVA Siemens
(SIMOVERT-MV)
Three-Level Neutral Point Clamped Inverter
IGBT 0.3MVA – 2.4MVA General Electric–Toshiba
(Dura-Bilt5 MV)
0.3MVA – 22MVA ASI Robicon
(Perfect Harmony)
0.5MVA – 6MVA Toshiba
(TOSVERT-MV) Multilevel Cascaded H-Bridge Inverter
IGBT
0.45MVA – 7.5MVA General Electric
(Innovation MV-GP Type H)
NPC/H-bridge Inverter IGBT 0.4MVA – 4.8MVA Toshiba
(TOSVERT 300 MV)
Flying-Capacitor Inverter IGBT 0.3MVA – 8MVA Alstom
(VDM6000 Symphony) PWM Current Source Inverter
Symmetrical GCT
0.2MVA – 20MVA Rockwell Automation
(PowerFlex 7000)
>10MVA Siemens
(SIMOVERT S) >10MVA ABB (LCI) Load Commutated Inverter SCR
>10MVA Alstom
(ALSPA SD7000)
160
High-Power Converters and AC Drives
High-Power Converters and AC Drives Bin Wu