Neutral Point Clamped Inverter
Do’s and Do Nots
25-Jan-08
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Agenda
– NPC Topology derivation
– Advantages , disadvantages of NPC inverter
– Operation modes of NPC
– FlowNPC 0 – A New Solution for UPS, Solar and drive
inverter Applications
– Conclusion
25-Jan-08
Page 2
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NPC topology derivation
Unipolar Output
Vout=D*Vin
Vout=Vin* sin(ωt)
with
D(t)=sin(ωt)
25-Jan-08
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NPC topology derivation
+
+
+
Adding components
25-Jan-08
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NPC topology derivation
Inserting polarity switches
25-Jan-08
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NPC topology derivation
Connecting blocks together
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NPC topology derivation
No path for rective current
Vout(t)*Iout(t)>0
NPC inverter
Bipolar output
unidirectional power
25-Jan-08
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NPC topology derivation
Inverse diodes create path for
rective current too
Vout(t)*Iout(t)<0
NPC inverter
Bipolar output
bidirectional power
4 quadrant operation
25-Jan-08
Page 8
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Advantage , disadvantage of NPC
Advantages Compared to 1200V IGBT halfbridge
•
•
•
•
Total +/- supply voltage is shared
3 level voltage on output - smaller output current ripple
All 600V components - are faster
All 600V components - have smaller voltage drop
Disadvantages Compared to 1200V IGBT halfbridge
• More components to handle – 10 against 4
• 4 IGBTs to drive (3 floating) against 2 (1 floating)
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Operation modes of NPC
Sine wave output
25-Jan-08
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Operation modes of NPC
Sine wave output real power
25-Jan-08
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Operation modes of NPC
Sine wave output real and reactive power
25-Jan-08
Page 12
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Operation modes of NPC
Current and commutation
loops at real power
25-Jan-08
Page 13
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Operation modes of NPC
Current and commutation
loops at reactive power
25-Jan-08
Page 14
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Operation modes of NPC
Waveforms of NPC inverter with reactive power
25-Jan-08
Page 15
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Operation modes of NPC
Standard splitted supply halfbridge
inverter
25-Jan-08
Page 16
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Operation modes of NPC
Comparison of
topologies
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Page 17
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Operation modes of NPC
Comparison of
waveforms
Halfbridge
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NPC
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Operation modes of NPC
Time
FFT
Distortion
Halfbridge
25-Jan-08
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NPC
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Solar inverter application
Optimal topology selection
•
•
NPC inverter supply is grounded to
eliminate common voltage problem
for transformatorless solar inverter
Splitted supply for multistring solar
panel connection
Optimal component selection
•
•
•
25-Jan-08
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High efficient switching buck stages
with 600V CoolMOS + 600V SiC Zero
Recovery rectifier
Low votage drop 600V trench IGBT
polarity switches
All in one module construction
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Solar inverter application
Positive
commutation
loop 3nH
Negative
commutation
loop 3nH
Layout optimization real load
25-Jan-08
Page 21
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Solar inverter application
§
§
§
§
§
§
§
§
§
3,4kW Static load (15A)
350V DC voltage
Fixed output frequency operation (50Hz)
Modulation frequency = 16kHz
Hard switching environment
Sinusoidal output voltage waveform (230VAC)
Sinusoidal output current waveform
Unity power factor (cosfi=1)
Installation cost is 3-5 Euro/Wp
Conditions for
optimization
25-Jan-08
Page 22
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Solar inverter application
Halfbridge
Halfbridge
(Trench IGBT) (Fast IGBT)
NPC
(Mixed)
T1,T2,FREDs
T1,T2,FREDs
T1,D1,T3, T2,D2,T4
Static losses
2*(11W+1W)=
24 W
2*(20W+1W)=
42 W
2*(8W+3W+8W)=
38 W
Switching
losses
2*(30W+12W)=
84 W
2*(15W+9W)=
48 W
2*(2W+0W+0W)=
4W
Total losses
108 W
90 W
42 W
Efficiency
96,8 %
97,4 %
98,8 %
25-Jan-08
Page 23
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Solar inverter application
1,00
NP C
0,99
0,98
0,97
half bridge
0,96
0,95
0,94
0,93
0,92
0,91
0,90
0,0
60
0,2
0,4
0,6
0,8
1,0
1,2
1,4
Pout/Pnom
European efficiency
(weighted)
Halfbridge
NPC
96,4%
99,3%
+230 Euro value
%
40
20
0
0,1
0,2
0,4
0,6
0,8
1,0
Efficiency weighting
1,2
1,4
Pout/Pnom
+1% power= 17W => 80 Euro
gain
Comparison of efficiencies
for optimization
25-Jan-08
Page 24
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flowSOL0-NP 6kW – Solar Inverter Modules
+
flowSOL0-NPI
flowSOL0-NPB
P
kW
flowSOL0-NPB: 1200V / 6kW
• NP-booster for transformer less input circuit
flowSOL0-NPI: 1200V / 6kW
• NP-inverter for transformer less output circuit
25-Jan-08
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f
kHz
serial
status
20..70
P05/08
S10/08
6..15 20.. 70
P05/08
S10/08
6
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
target market
UPS inverter application
Optimal topology selection
•
•
NPC inverter for one phase of 1 or 3
phase output of UPS
3 level operation for low noise and
easy filtering
Optimal component selection
•
•
High efficient switching buck stages
with all 600V IGBTs and FREDs
Low votage drop 600V trench IGBT
polarity switches for reactive current
switching
Low cost
•
All in one module construction
•
25-Jan-08
Page 26
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Drive application
Optimal topology selection
•
•
1 NPC inverter for each phase
of 3 phase output
3 level operation for low noise
and small distortion
Optimal component selection
•
•
25-Jan-08
Page 27
Fast switching over
audible noise (>16kHz)
Full regenerative mode
for braking
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
UPS inverter and drive application
Positive
commutation
loop 7nH
Negative
commutation
loop 7nH
Layout optimization reactive load
25-Jan-08
Page 28
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UPS inverter and drive application
PCB Layout for 3 phase NPC inverter
25-Jan-08
Page 29
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
UPS inverter and drive application
No good realization
NPC for high power
in 2 packages
flowSCREW with standard connection Not usable
not usable because of
overvoltage on
inductance in phase
output connection
25-Jan-08
Page 30
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UPS inverter and drive application
Overvoltage on polarity
switch
25-Jan-08
Page 31
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UPS inverter and drive application
Good realization
NPC for high power
in single package
25-Jan-08
Page 32
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Conclusion
Do
Do Not
• Learn
• Design
• Run
NPC inverter for
• Solar
• UPS
• Enhanced performance
Drive
Applications
25-Jan-08
Page 33
• Use
NPC inverter for
Low cost Standard
Drive Applications
Do Not
• Design
NPC inverter without
good Understanding
NPC operation
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.
Thank you for your attention
25-Jan-08
Page 34
Information is Vincotech Confidential & Proprietary. Do Not Reproduce or Distribute.