Maximise Efficiency & Reliability - Maintain ‘healthy’ electrical network with harmonic-less

Maximise Efficiency & Reliability:
Maintain ‘healthy’ electrical network with
harmonic-less
Ch’ng Eng Yong, CEng MEI, CEM, CMVP, PEM
July 2016
Schneider Electric 1

What are we discussing today
● Solve the harmonic issue, if possible, starting from the root of the
problem.
●A cost effective solution requires the knowledge of the
electrical power system and it is often a combination of several
solutions.
●Harmonic mitigation solutions are available in market to
fulfill your needs.

Agenda
●Why is there harmonic in the electrical network?
●General waveform signature (IEC 61000-3-6)
●Typical harmonic mitigation solutions
●Solutions comparison
●What’s next?
●Conclusion

Why is there harmonic in the electrical
network?
●Look at the full-bridge rectifier schematic
●Diode forward bias:
● Anode is more positive than cathode
● DC bus voltage is less than supply voltage
DC bus voltage U
DC busiC
U
iC
DC bus
capacitor
current (IC)
Supply
voltage (V)
Supply
current
(i)
V = E - Zsi
iC
i
V

Why is there harmonic in the electrical
network?
iC
Vc
-Vc
t
e
i

Agenda
●What’s next?
●Conclusion

General waveform signature
(IEC 61000-3-6)
Current
Type of Load Typical Waveform Distortion
Single Phase 80%
Power Supply (high 3rd)
high 2nd, 3rd,
Semiconverter 4th at partial
loads
6 Pulse Converter,
capacitive smoothing, 80%
no series inductance
0 10 20 30 40
-1.0
-0.5
0.0
0.5
1.0
Time (mS)
Current
0 10 20 30 40
-1.0
-0.5
0.0
0.5
1.0
Time (mS)
Current
-0.5
0.0
0.5
1.0
Current
no series inductance
6 Pulse Converter,
capacitive smoothing 40%
with series inductance > 3%,
or dc drive
6 Pulse Converter
with large inductor 28%
for current smoothing
12 Pulse Converter 15%
AC Voltage varies with
Regulator firing angle
Fluorescent
Lighting 17%
0 10 20 30 40
-1.0
Time (mS)
0 10 20 30 40
-1.0
-0.5
0.0
0.5
1.0
Time (mS)
Current
0 10 20 30 40
-1.0
-0.5
0.0
0.5
1.0
Time (mS)
Current
0.0 10.0 20.0 30.0 40.0
-1.000
-0.500
0.000
0.500
1.000
Time (mS)
Current
0 10 20 30 40
-1.0
-0.5
0.0
0.5
1.0
Time (mS)
Current
0 10 20 30 40
-1.0
-0.5
0.0
0.5
1.0
Time (mS)
Current

Typical harmonic mitigation solutions
●Equipment based solutions
● DC/AC choke
● Passive filter
● Drive isolation transformer (DIT)
● Multi-pulse VSD
● Multi-pulse VSD
● Active front end (AFE)
● C-less technology
●System based solutions
● Passive filter (Tuned power factor correction)
● Phase shifting transformer
● Zero-sequence harmonic filter
● Active harmonic filter

DC choke & line choke (installation)

DC choke & line choke (performance)
● Effect of the choke:
dt
di
LVL =
0.0
0.5
1.0
Current
0.0
0.5
1.0
Current
Line current spectrum
1.211.54
4.51
6.77
12.36
15.32
20.77
22.88
25.16
0
5
10
15
20
25
30
1 3 5 7 9 11 13 15 17 19 21 23 25
Harmonic order
I(A)
Without additional choke
THDI = 100%
9.38
3.20
1.80
0.87 0.74 0.49 0.35 0.30
25.94
0
5
10
15
20
25
30
1 3 5 7 9 11 13 15 17 19 21 23 25
Harmonic order
I(A)
With additional choke 3%
THDI = 40%
With additional large choke (>5%)
0 10 20 30 40
-1.0
-0.5
Time (mS)
Current
THDI = 30%
1.211.54
4.51
6.77
12.36
15.32
20.77
22.88
25.16
0
5
10
15
20
25
30
1 3 5 7 9 11 13 15 17 19 21 23 25
Harmonic order
I(A)
Without additional choke
THDI = 100%
9.38
3.20
1.80
0.87 0.74 0.49 0.35 0.30
25.94
0
5
10
15
20
25
30
1 3 5 7 9 11 13 15 17 19 21 23 25
Harmonic order
I(A)
With additional choke 3%
THDI = 40%
With additional large choke (>5%)
0 10 20 30 40
-1.0
-0.5
Time (mS)
Current
THDI = 30%

DC choke vs. line choke
●Influence of the nature of reactors
● In terms of harmonics, the results are quite similar.
● DC bus choke is a little smaller and the voltage drop is lower.
Inductor 2mH in the DC busLine inductor 3 x 1mH Inductor 2mH in the DC busLine inductor 3 x 1mH
9,38
3,20
1,80
0,87 0,74 0,49 0,35 0,30
25,94
0
5
10
15
20
25
30
1
3
5
7
9
11
13
15
17
19
21
23
25
Harmonic order
I(A)
THDI = 39.16 %
6,65
4,14
2,23 1,73 1,39 1,12 0,99 0,81
25,80
0
5
10
15
20
25
30
1
3
5
7
9
11
13
15
17
19
21
23
25
Harmonic order
I(A)
THDI = 35.54 %
ChokeACChokeDC 3=
9,38
3,20
1,80
0,87 0,74 0,49 0,35 0,30
25,94
0
5
10
15
20
25
30
1
3
5
7
9
11
13
15
17
19
21
23
25
Harmonic order
I(A)
THDI = 39.16 %
9,38
3,20
1,80
0,87 0,74 0,49 0,35 0,30
25,94
0
5
10
15
20
25
30
1
3
5
7
9
11
13
15
17
19
21
23
25
Harmonic order
I(A)
THDI = 39.16 %
9,38
3,20
1,80
0,87 0,74 0,49 0,35 0,30
25,94
0
5
10
15
20
25
30
1
3
5
7
9
11
13
15
17
19
21
23
25
Harmonic order
I(A)
THDI = 39.16 %
6,65
4,14
2,23 1,73 1,39 1,12 0,99 0,81
25,80
0
5
10
15
20
25
30
1
3
5
7
9
11
13
15
17
19
21
23
25
Harmonic order
I(A)
THDI = 35.54 %
6,65
4,14
2,23 1,73 1,39 1,12 0,99 0,81
25,80
0
5
10
15
20
25
30
1
3
5
7
9
11
13
15
17
19
21
23
25
Harmonic order
I(A)
THDI = 35.54 %
ChokeACChokeDC 3=

DC choke & line choke
(practical considerations)
● Most cost effective solution (0-
20% of drive cost).
● Reduce THDI around 30 - 50%.
● Bulky and heavy.
● Proper ventilation.
Advantages Concerns
● Reduce THDI around 30 - 50%.
● Line chokes protects the drive
front end, limits voltage spikes
and short circuit current.
● Depending on load condition,
might not be able to meet
standard requirements.
● Voltage drop ( >5%) can affect
low line supply conditions.
Lowers torque performance at
full speed when voltage drop is
higher.

Harmonic mitigation solutions
I. DC/AC line chokes
Ii. Passive filters
Iii. Zero-sequence harmonic filter
Iv. Drive isolation transformer (DIT)
V. Phase shifting transformer
Vi. Multi-pulse VSD (12, 18, 24, …)
VII. Active harmonic filters (AHF)
Viii. Active front end (AFE)
Ix. C - less technology

Passive filter (tuned PFC)
●Two type of passive filter
● Load based passive filter
● Global passive filter
●Load based passive filter
● Designed & sized based on the load size (kW)
● Designed & sized based on the load size (kW)
● Operate when the connected load is in operation
●Global passive filter
● Designed & sized based on the system power factor requirements.
● Compensation is based on required kVAR (PF) in the system.
● Primary function: Harmonic filtering
● Secondary function: Power factor correction
● Different from Detuned Power Factor Correction (reverse role)

Passive filter – load based
(performance)
With simple choke THDI 48% With passive filter THDI 10%With simple choke THDI 48% With passive filter THDI 10%

Power factor – which component?
Power factor in
system with linear
loads only.
P = kW
(Real Power)
D = kVAH
(Distortion Power)
Q = kVAr
(Reactive Power)
S = kVA
(Apparent Power)
θTPF
(True/Total Power Factor)
Power factor component in
system with harmonics
(linear + nonlinear loads)

Power factor components in system with
harmonics
D = kVAH
(Distortion Power)
Q = kVAr
(Reactive
Power)
S = kVA
(Apparent Power)
θTPF
( )
22
1
22
222
11
k
kk
rmsrms
THDTHDIV
IV
IV
DQPkVAS
rmsrms
++=
=
=
++=
∑
∞
=
P = kW
(Real Power)
22
1
11
11
11
IV
IV
THDTHDS
THDTHDIV rmsrms
++=
++=
True/Total Power Factor : distPFdispPFTPF θθθ coscoscos ⋅=
Displacement Power Factor
(Fundamental Components):
1
cos
S
kW
dispPF =θ
Distortion Power Factor
(Harmonic Components): 22
11
1
cos
IV
distPF
THDTHD ++
=θ

Passive filter (load based)
Advantages Concerns
● Able to reduce THDI to around
5 - 16%.
● Line chokes protects the drive
● Expensive (50 - 80% drive
cost).
and short circuit current.
● Meet IEC 61000 requirements
● Designed for full load capacity
to obtain effective impedance.
● Filter capacitor (passive filter)
must be disconnected when
VSD operates at no load or
low load condition. (causing
leading PF & voltage
regulation concern is remain
connected)

Ii. Passive filters

Zero-sequence harmonic filter
●Issue with neutral overloading
Phase A (50 Amps)
Phase B (50 Amps)
Electronic
Loads
Phase B (50 Amps)
Phase C (57 Amps)
Neutral (82 Amps)

Zero-sequence harmonic filter
●Typical solution for neutral overloading:
● Upsize neutral: “200% Neutral” – 173% maximum current, so provides a
little extra margin
●Concern: All neutral connected components need to be upsized too.
● Zero-Sequence Harmonic Filter
● Zero-Sequence Harmonic Filter
●Installed close to the nonlinear loads (e.g. DB)
●Concern: Proper ventilation and bulky
● Active Harmonic Filter
●Installed at upstream (Global solutions)
●Concern: Expensive and bulky

Zero-sequence harmonic filter – principle

Zero-sequence harmonic filter –
performance
Reduction ratio = 1:10

Ii. Passive filters

Drive isolation transformer (DIT)
●Designed with oversized core & special windings
●Can withstand high heat & harsh operational environment
●Electrically isolation secondary (Wye) source from primary (Delta)
● Secondary source (Wye) is grounded
● Prevent transfer of common-mode noise and/or ground current
● Reduce transients and surges
●Four Basic Functions:
● Voltage change (Delta-Wye windings)
● Common-mode noise & impulse reduction
● Reduction of drive induced ground currents
● Reduction of drive distortion effects on system voltage

Drive isolation transformer (DIT)
Advantages Concerns
● Trap triplen harmonic order in
delta windings (zero-sequence
network)
● Protects the drive front end,
● Expensive (50 - 80% drive
cost).
limits voltage spikes and short
circuit current.
● Reduce common-mode noise,
induced ground current,
impulse from either both sides.
● Cannot completely isolate the
harmonic (positive-sequence
network)

Ii. Passive filters

Phase shifting transformer
30o with
respect to
0o with
respect to
primary
An angular
displacement
of 30o
( ) 





−+−≅ ...
11
11cos
7
7cos
5
5cos
cos
32
1
ttt
tti
ωωω
ω
π
ω
5th & 7th harmonics go away!
( ) 





−−+≅ ...
11
11cos
7
7cos
5
5cos
cos
32
2
ttt
tti
ωωω
ω
π
ω
respect to
primary
primary

Phase shifting transformer
Advantages Concerns
● Protects the drive front end,
limits voltage spikes and
short circuit current.
● Bulky, heavy
● Expensive (100% drive cost)
delta windings
● Attenuations of 5th and 7th
harmonic currents with an
angular displacement of 30o .
● Both transformers (same
rating) have to be loaded
equally to achieve optimum
harmonic attenuation.
● Transformer must be able to
withstand excessive heat due
to harmonic current.

Ii. Passive filters

Multi-pulse VSD
●Harmonics can be reduced by phase multiplication.
●If n six-pulse rectifier sections…
● have the same transformer ratios,
● have transformers with identical impedance's,
● have transformers with identical impedance's,
● are phase shifted exactly 60°/n degrees from each other (where n = set of
rectifiers) or 360o/m (where m = number of pulse)
●Then…
● 2 set of rectifier sections phase shifted by 30° result in 12-pulse row up H7
are slightly reduced
● 3 set of rectifier sections phase shifted by 20° result in 18-pulse row up to
H13 are slightly reduced

Multi-pulse VSD – 12 pulse VSD
●12 pulses supply structure
●Using the concept of phase-shifting transformer of 30o
Phase shifted by 30°
Delta
Star
6 pulses
rectifier
6 pulses
rectifier
M
Inverter
H5 and H7 attenuated

●18 pulses supply structure
●Using the concept of phase-shifting transformer of 20o

Multi-pulse VSD comparison (6, 12, 18
pulse)
● 12-Pulse converter
+
-
DC Bus Load
Delta
Delta
Wye
AC Line
A
B
C
DC+
DC-
Line
Reactor
Rectifier Assembly
Transformer
Tertiary
Multipulse
Transformer
A
BC
1
2
3
4
56
7
8
9
DC Link
Reactor
M
Externally mounted 3 winding
transformer; more wire and cabling;
complicated
Current slightly distorted
Ithd 8% to 15% (depending on
network impedance)
0
100
A
12 pulse
Large footprint, more steel &
copper (losses)
Current wave form good
Ithd 4% to 6% (depending on network
impedance)
0.0s 0.02s
0
100
A
18 pulse
Tertiary
“C-less” or 3% reactance min (if
included); small footprint, simplified
cabling
Current waveform distorted
Ithd 30% to 50% with 3% reactor
(depending on network impedance)
0
100
A
6 pulse

Multi-pulse VSD
Advantages Concerns
● Eliminates rows up to H7,(12p),
up to H13(18p)
● Reduces THD(I) down to
10-15%(12p), 5-3%(18p)
● Very Bulky and heavy
10-15%(12p), 5-3%(18p)
● Suppresses line voltage
transients
● Efficient on the all load range
● Needs 2 or 3 diodes bridge
rectifier
● Needs a specific transformer
windings
● More cost effective for high
power VSD ( >100kW)

Ii. Passive filters

Active harmonic filter (AHF)
●Leading-edge technology for harmonic filtering
●IGBTs, 20 kHz modulation, to synthesize the output current for injection
●Real time control algorithms
● Responds instantly to inrush situations (100µs)
● Full response in 8 msec for steady sate situations
● Full response in 8 msec for steady sate situations

Active harmonic filter – schematic
diagram
IGBTs manage the power flow
to/from the DC bus caps
decouples the filter board
inductor/capacitor circuit from the
AC lines
three phase AC line
connection
remove the carrier frequency from
the current waveform sent into the
AC lines.
200k AIC

Active harmonic filter – control block
AC Phase
VdcIGBT
Converter
Lext CTi Lin
K1
R1
Cdc
CB
Load
Notch
Filter
SMPS
Board
Control
Board
Regulation
&
Monitoring
Control
Signal
CTa

Active harmonic filter (performance)

Active harmonic filter (AHF)
Advantages Concerns
● Reduces THD(I) below 5%
● Several units can be installed
on the same supply
● Reliability (more components)
● Global solutions
● Resonance elimination
● Corrects displacement power
factor (cos θ)
● CT direction & location must
be correct

Ii. Passive filters

Active front end
●The solution use an active rectifier bridge made with IGBTs instead of
the standard 6 diodes rectifier.
●The rectifier is controlled in order to ‘create’ a sinusoidal current into the
network (THDI <5%)
●It has the advantage to reverse the power flow and allows the feedback
of energy into the network (regenerative mode when the motor slow
down or during braking phase).
Current
Voltage
Active Front End

Active front end – comparison
Current
THD (%)
Voltage
THD (%)
RSC=20
Voltage
THD (%)
RSC=100
+ Inductor

Active front end (AFE)
Advantages Concerns
● Nearly sinus supply
(THDI<5%)
● Very expensive if
reversibility not needed
(150% drive cost)
● Need additional EMC filter
● Reversible, allows to feedback
energy onto the network
● Can be embedded in the drive
● Need additional EMC filter
● Reliability (IGBT, more
components)

C-less technology - principle
●DC bus capacitor value is reduced to 2-3% of standard AC drive
capacitor value.
●Current only flows from the mains into the DC link when the mains
voltage exceeds that of the capacitor (diode forward bias).
●The larger the DC link capacitor, the shorter the period of current flow,
and the higher the peak current.
A non demanding load like a fan allows
95% reduction of the DC bus
capacitance without significant
reduction of performances.
Less capacitance --> less current
harmonics
Rectifier D C Link Inverter
Thre
ePhase Power
C
+
-

C-less technology – performance
comparison
0 10 20 30 40
-1.0
-0.5
0.0
0.5
1.0
Time (mS)
Current
0.0
0.5
1.0
Current
0 10 20 30 40
-1.0
-0.5
Time (mS)
Current
0 10 20 30 40
-1.0
-0.5
0.0
0.5
1.0
Time (mS)
Current

C-less technology
Advantages Concerns
● Reduces THD(I) below
35%without added filter
● Only for Fan, Pump and non
demanding applications
(HVAC)
● Lowest cost for harmonic
mitigation
● More DC bus ripple so more
torque ripple.
● More sensitive to network
voltage drop and perturbation

Agenda
●What’s next?
●Conclusion

Solutions comparison
●Comparison between harmonic mitigation solutions at drive level
Nil Choke
3%-5%
Passive
filter
C less
18
pulses
Active
front end
Active
filter
Current distortion THDI >80% <48% <5%-16% <30% <5%-10% <5% <5%
Meet IEEE519 gen. app. no System dependent yes System dependent yes (18p) yes yes
Mitigation solutions
Meet IEEE519 gen. app. no System dependent yes System dependent yes (18p) yes yes
Meet IEC 61000 3-12 no yes yes yes yes yes yes
Meet IEC 61000 3-2 no no no no no yes yes
Drop voltage no yes no no no no no
Power factor no/full load <0,8 0.75-0.95 0.75-1 0.95 0.90-0.99 1 1
Load influence on THDI no yes yes no no no no
Efficiency 100% 97% 98% 100% 96% 96% 96%
Reliability High High Good Good Medium Good Good
EMC Poor Good Good Medium Good Medium Medium
Influence on VSD perf. no weak no Strong no no no
Resonance risk no weak yes no no no no
Cost effective very good good <100kW very good >200kW Medium Low harmonic
Price ratio /drive cost 100% 110%-120% 150%-200% 95% 200%-250% 250% 250%
Foot print ration/drive 100% 120% 200% 100% 350% 150%-200% 300%-500%
Offer ATV <75kW
ATV >75kW
<75kW option
ATV option
ATV21
fan/pump only
Square D US
Sinewave
AccuSine
Altivar AFE

Where to install the solutions?

Solutions comparison
●Cost comparison between harmonic mitigation solutions at drive level
Harmonic Mitigation - Cost / Performance Comparison
300
5
Cost/VSD price
0
50
100
150
200
250
6 Pulse Drive C-Less DC chokes
AC chokes
Passive Filters Multi-Pulse
12p, 18p
Active
Filters
THDI %
60-130
30-35
35-48
5-16
5-10
5

What’s next?
1st Step – Measure
● Select a good PQ tools and software
●Portable power quality loggers
●Power Quality Monitoring System
& Power Quality Meter
3rd Step – Implement
2nd Step – Analyze
● Identify & Categorize the PQ
event according to standard
(e.g. IEEE Std 1159-1995)
● Know the waveform
signature
● Identify the severity of the
event (Magnitude and
duration)
3rd Step – Implement
● Understand the effect of the
events
● Propose solutions to apply

Agenda
●What’s next?
●Conclusion

What we were discussing
●Solve the harmonic issue, if possible, starting from the root of the
problem.
installation and it is often a combination of several solutions.
●Harmonic mitigation solutions are available in market to
fulfill your needs.
3 main
messages
3 main
messages

Ch‘ng Eng Yong
+6012 – 2750 876
eng-yong.chng@schneider-electric.com
You‘ve got questions?
Contact
eng-yong.chng@schneider-electric.com

TThank You
for your attention
TThank You

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