Common Cure for Harmonics – ABB Ultra Low Harmonic Drive
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Transcript Common Cure for Harmonics – ABB Ultra Low Harmonic Drive
Common Cures for
Harmonics
© Copyright 2008 ABB.
All rights reserved. - 1 2/29/2008
Larry Stanley
RSE,Nashville,TN
Results-Driven Roadshow
Cincinnati, 2008
© Copyright 2008 ABB - 2 -
Harmonics —
What?
Harmonics — What?
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Non-linear loads draw non-sinusoidal current
from a sinusoidal line (current doesn’t look like voltage):
Non-incandescent lighting
Computers
Uninterruptible power supplies
Telecommunications equipment
Copy machines
Battery chargers
Electronic variable speed drives
Any load with a solid state AC to DC power converter
The Real World, 6- Pulse Drive
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PWM Drive Input Current
(
)
th and
f7 = 420
w 7 = 2pFundamental,
× f7
i7 ( t) = 0.09 × cos ( w5
)
7 ×t - p
The
Theory:
7th Harmonics
f5 = 300
w 5 = 2p × f5
i5 ( t) = 0.32 × cos w 5 × t - p
1
Fundamental
5th
0.5
i1 ( t)
i5 ( t)
Components
0
i7 ( t)
0.5
7th
1
iT ( t) = i1 ( t) 0+ i5 ( t) 0.005
+ i7 ( t)
0.01
0.015
0.02
0.025
0.03
t
1.5
1
0.5
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i T( t)
Summation
0
0.5
1
1.5
0
0.005
0.01
0.015
0.02
t
0.025
0.03
Harmonic Content, 6- Pulse Drive
PWM Drive Harmonic Input Spectrum
Fundamental
5th
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7th
11th
13th
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Harmonics —
Why worry?
Harmonics — Why worry?
Harmonic Current Distortion —
Added heating in transformers and cables, reduces
available capacity
May stimulate a PF correction resonance condition
Excessive voltage
Overheating of capacitors
Tripping of protection equipment
Shutdown / damage to electronic equipment
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May cause telephone or electronic interference
Harmonics — Why worry?
© Copyright 2008 ABB - 9 -
(cont.)
Harmonic Voltage Distortion —
Increased heating in motors and other
electromagnetic equipment
Noisy operation of electromagnetic equipment
Malfunction of sensitive electronics
Nuisance tripping of electronic circuit breakers
Equipment downtime
Premature component failures
Failed transformers, motors and capacitors
Compliance with codes or specifications
Harmonics — A System Issue!
Harmonics produced by an individual load are only important to
the extent that they represent a significant portion of the total
connected load (Harmonics are expressed as a percentage)
Linear loads help reduce system harmonic levels (percentages)
TDD (Total Demand Distortion) equals the THD (Total Harmonic Distortion)
of the nonlinear load multiplied by the ratio of nonlinear load to
the total (demand) load:
NL
TDD = THD NL ×
TL
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Where
TDD
THDNL
NL
TL
=
=
=
=
TDD of the system
THD of the nonlinear loads
kVA of nonlinear load
kVA of total load
(nonlinear + linear)
Harmonics — By the Numbers
IEEE 519 - 1992
Table 10.2
Low-Voltage System Classification and Distortion Limits
Special
Applications
General
System
Dedicated
System
Notch Depth
10%
20%
50%
THD (Voltage)
3%
5%
10%
16,400
22,800
36,500
Notch Area, mVs
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Note: Notch area for other than 480 V systems should be multiplied by V / 480.
Harmonics — By the Numbers (cont.)
RSC
IEEE 519 - 1992
Table 10.3
Current Distortion Limits for General Distribution Systems
ISC / IL
<11
11£h<17
17£h<23
23£h<35
35£h
TDD
<20
4.0
2.0
1.5
0.6
0.3
5.0
20<50
7.0
3.5
2.5
1.0
0.5
8.0
50<100
10.0
4.5
4.0
1.5
0.7
12.0
100<1000
12.0
5.5
5.0
2.0
1.0
15.0
© Copyright 2008 ABB - 16 -
Note: All harmonic current levels are in percent with fundamental current IL as the base.
Harmonics —
© Copyright 2008 ABB - 17 -
Will it be a problem?
Harmonic Voltage, Will it be a problem?
THD (Voltage) will be acceptable (<5%) if the % drive
load times the % impedance feeding the drive load is
<3%
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%DriveLoad x %Impedance < 3%
E.g. a 45% drive load fed from 6% impedance feeder bus:
45% x 6% = 2.7% 2.7% < 3% Acceptable
E.g. a 70% drive load fed from 5% impedance feeder bus:
70% x 5% = 3.5% 3.5% > 3% Not Acceptable
(Approximate rule of thumb for 6-pulse drives with
3% reactor, all other loads assumed to be linear)
Harmonic Current, Will it be a problem?
THD (Current) on a network with a short circuit ratio <20
(20<50, 50<100, 100<1000) will be acceptable if the % drive load
times 45% is <5% (<8%, <12%, <15%)
© Copyright 2008 ABB - 19 -
%DriveLoad x 45% < 5% (RSC <20)
%DriveLoad x 45% < 8% (RSC 20<50)
%DriveLoad x 45% < 12% (RSC 50<100)
%DriveLoad x 45% < 15% (RSC 100<1000)
E.g. a network with a short circuit ratio of 35 has 15% drive load:
15% x 45% = 6.75% 6.75% < 8% Acceptable
E.g. a network with a short circuit ratio of 65 has 30% drive load:
30% x 45% = 13.5% 13.5% > 12% Not Acceptable
(Rule of thumb for 6-pulse drives with 3%
reactor,, all other loads assumed to be linear)
© Copyright 2008 ABB - 20 -
Harmonics —
What can I do?
© Copyright 2008 ABB - 21 -
Harmonics — What can I do?
Reactors (Chokes)
Passive Filters
Harmonic Trap
Hybrid
High Pulse Count Rectification
Active Filters
Drive Front End
Stand Alone
Reactors, AC Line or DC Link
AC Line
Reactor
Different design
techniques
Equal harmonic
reduction for same
normalized
% reactance
Typical full load
THD (current) at
drive input terminals
28% 46%
M
DC Link
Reactor
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M
Existence not position is what is important
Reactor Effectiveness
THD (Current) vs. % Reactor
120
Current harmonic content (THD) at drive
input terminals as a function of normalized %
reactance and network short circuit ratio
%THD (Current)
100
80
60
40
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20
0
0
1
2
3
4
5
6
% Reactor
Rsc = 20
Rsc = 60
Rsc = 200
7
8
9
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Swinging Chokes
Provide increased inductance at
reduced current
Reduce harmonics up to 30%
more than traditional designs
“Swing” portion of choke
characteristic significantly
improves harmonic performance
at reduced loads
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Swinging DC Link Choke
Designed to reduce harmonics at full
and partial loads
Perfect for Variable Torque
Centrifugal Loads
Equivalent to 5% line reactor
More inductance per volume/weight
of material
Swinging Choke Vs. Fixed Choke
Current Distortion vs % Speed for Variable Torque Load
45
40
%TDD (Current)
35
30
25
20
15
10
5% Swinging Choke
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5
3% Fixed Choke
0
0%
20%
40%
60%
% Speed
80%
100%
120%
© Copyright 2008 ABB - 27 -
High Pulse Count Rectification
Typical configurations are either 12 pulse or 18 pulse
Phase shifting transformer is required
Additional drive input bridges are needed
Typical full load THD (current) at transformer primary
8% 12% (12 pulse), 4% 6% (18 pulse)
Performance significantly reduced by line imbalance
(voltage or phase)
Excellent choice if stepdown transformer is already
required
Active Filter Front End with LCL Filter
Drive
DC
Link
L
L
C
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LCL filter
M
Line
inverter
(rectifier)
Motor
inverter
Motor
Active Filter Line Inverter (rectifier) removes low
frequencies < 1kHz
LCL Filter (passive filter) removes high frequencies >1
kHz. (Current and voltage)
Full output voltage is available with 80% input voltage
(400VIn = 480VOut)
Full regenerative capability (ACS800-U11/-17)
No transformer required
Not affected by line imbalance
Beauty Instead of Beast
IGBT line supply controls the
current
Active supply
Sinusoidal line current
Low distortion below
switching frequency
Current spectrum of low harmonic drive
100
LCL Line filter removes high
frequency distortion
1
0,1
0,01
0,001
0,0001
Diode supply
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Cleans the waveform above
switching frequency
10
Percentage [%]
0
1000
2000
3000
4000
5000
6000
Frequency [Hz]
7000
8000
9000
10000
Impressive Numbers
THD (current) and harmonic components
5
4
3
2
Total current distortion less than
3.5% to 4.5%
1
0
1
Total voltage distortion less than
5%
Power factor adjustable from
0.85 (leading or lagging) to 1.0
7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97
%THD (Voltage) = f(RSC)
5
4
3
© Copyright 2008 ABB - 31 -
2
1
0
10
20
30
40
50
60
70
80
90
100
RSC
Product offering
Wall-mounted low harmonic
drive ACS800-U31
© Copyright 2008 ABB - 33 -
10 – 125 HP
Cabinet-built low harmonic
drive ACS800-37
75 - 2800 HP
Low Harmonic vs 18-Pulse
Area Plot
9000
8000
7000
ABB
Square D
6000
SQ IN
Robicon/Siemens
5000
4000
Eaton/CH
3000
2000
1000
Horsepower
90
0
10
00
80
0
70
0
60
0
50
0
40
0
35
0
30
0
25
0
20
0
15
0
12
5
Results-Driven Roadshow
Cincinnati, 2008
10
0
75
60
50
40
30
25
20
© Copyright 2008 ABB.
All rights reserved. - 34 2/29/2008
0
Low Harmonic vs 18-Pulse
Volume Plot
300000
250000
ABB
Cubic In
200000
Square D
150000
Robicon
100000
Eaton/CH
HP
10
00
90
0
80
0
70
0
60
0
50
0
40
0
35
0
30
0
25
0
20
0
15
0
12
5
10
0
75
60
50
40
30
25
0
20
© Copyright 2008 ABB - 35 -
50000
18-Pulse Impedance and Imbalance Dependencies
Current Distortion Vs. Line Imbalance
25%
12/18-Pulse drives have 3% internal reactance.
Drives are only load present.
%TDD Current Distortion
20%
ULH Clearly Superior
12-Pulse
0% Voltage Imbalance Reference Curve
10% Total Network Impedance
18-Pulse
5% Total Network Impedance
(Utility + Multi-Phase Transformer)
15%
18 Pulse with
12 Pulse Performance
18-Pulse
10% Total Network Impedance
(Utility + Multi-Phase Transformer)
10%
ULH
1% Total Network Impedance
© Copyright 2008 ABB - 36 -
5%
ULH
10% Total Network Impedance
0%
0.0%
0.5%
1.0%
1.5%
2.0%
2.5%
Voltage Imbalance
12-Pulse Reference
18-Pulse Direct
18-Pulse Xfmr
ULH 1% Net Imp
ULH 10% Net Imp
3.0%
Harmonic Reduction Summary
Effectiveness of Harmonic Mitigation Techniques
(Assuming 100% Nonlinear Loading, ISC / IL = 60)
THD
(Current)
Harmonic
Reduction
No mitigation (reference level)
72%
3% line reactors (or equivalent DC link reactor)
39%
45.8%
5% line reactors (or equivalent DC link reactor)
33%
54.2%
5% line reactors + 5th harmonic trap filter
12%
83.3%
12 pulse input rectifier with 5% impedance transformer
10%
86.1%
Hybrid filter
7%
90.3%
18 pulse input rectifier with 5% impedance transformer
5%
93.1%
12 pulse input rectifier with 5% impedance transformer
+ 11th harmonic trap filter
4%
94.4%
3.5%
95.1%
Technique
© Copyright 2008 ABB - 37 -
Active harmonic filter
Remember!
An 80% THD nonlinear load which a will result in only 8%
TDD if the nonlinear load is 10% and the linear load is 90%.
(80%•(10%/(10%+90%))=8%)