EPCOS
Power Factor Correction &
Harmonic filter
Power Quality
Definition:
Power Factor, Harmonics, Transients,
Voltage and frequency variations and other
disturbances in electric power supply
networks
Examples for poor power quality
Adjustable Speed Drives
Flat topping of Drive input
voltage, heavily distorted
current
Notching on the input can
interfere with other loads on
the same branch circuit
Changing load structure
Past - load: most loads were linear
Induction-motors, heating, bulbs
voltage was followed by current - only a few problems
Features
Simple and rugged
design
Customer benefits
High reliability
Long lifetime
Favourably-priced
No commutator
Unrestricted operation for
partial- and overload
conditions
Low maintenance
(only the bearings)
High degree of protection
Can be universally used
Changing load structure
Todays - loads: most loads act non linear
Computer, motor-control, drives, etc.
Current is pulse shaped
Current is no longer following the sinusoidal wave shape
Result: Harmonics
- Increasing number of sources causing disturbances
- Equipment become more and more sensitive
- De-regulated energy market
Problems caused by harmonics
Origin of harmonics
Non linear loads
Loads which have non linear voltage-current characteristics are called non linear
loads. When connected to a sinusoidal voltage, these loads produce non
sinusoidal currents. Modern power electronic systems result into non sinusoidal
currents when connected to the sinusoidal networks.
The non linear devices can be classified under the following three major categories:
1. Power Electronics: e.g. rectifiers, variable speed drives, UPS systems, inverters, ...
2. Ferromagnetic devices: e.g. transformers (non linear magnetizing characteristics)
3. Arcing devices: Arcing devices, e.g. arc furnace equipment, generate harmonics due to the
non linear characteristics of the arc itself.
Harmonic disturbances are created by non-linear loads!
Modern drives a main source for harmonics
Voltage-source
DC link converter
Current-source
DC link converter
Cycloconverter
Design
~
~
=
=
~
=
~
M
3~
~
=
~
M
3~
Features
Voltage is impressed
in the DC link
Current is impressed
in the DC link
Drive
converter
SIMOVERT MASTERDRIVES
SIMOVERT MV
SIMOVERT ML
SIMOVERT A
SIMOVERT I
SIMOVERT S
M
3~
Cycloconverter, no DC link
SIMOVERT D
HARMONICS fed back by 6/12 pulse rectifier
Voltage
Voltagecharacteristic
characteristic
at
the
drive
at the driveconverter
converter
output
(PWM)
output (PWM)
100%
80%
6-pulse
12-pulse
60%
40%
20%
Current
Currentcharacteristic
characteristic
at
atthe
thedrive
driveconverter
converter
output
output
0%
6-pulse
11
13
17
19
23
25
100,00%
29,00%
9,00%
6,00%
3,50%
2,50%
2,00%
1,20%
1,10%
2,90%
0,90%
6,00%
3,50%
0,25%
0,20%
1,20%
1,10%
12-pulse 100,00%
Order number
Example for single phase Non-Linear load
Example of a non-linear load: Switched mode power supply
AC Current
Voltage
Current
LOAD
Understanding harmonics
Harmonic currents or voltages are integer
(whole number) multiples of the
fundamental frequency.
Harmonic
order
Frequency
3rd
5th
7th
50
150 250 350
Problems caused by HARMONICS
Overheating of transformers (K-Factor), and rotating equipment
Increased hysteresis losses
Neutral overloading / unacceptable neutral-to-ground voltages
Distorted voltage and current waveforms
HARMONICS
Fundame
Failed capacitor banks
h3
Breakers and fuses tripping
h7
Amplitude
Unreliable operation of electronic equipment,
h5
SUM
and generators
Erroneous register of electric meters
Time
Wasted energy / higher electric bills - KWD & KWH
Wasted capacity - Inefficient distribution of power
Increased maintenance cost of equipment and machinery
COST caused by HARMONICS
Additional investment due to faster equipment derating
Shorter life time of equipment
Higher energy consumption
Higher downtime of production equipment
Higher maintenance and repair cost
Reduced product quality
Reduced production output
Investment for stronger equipments/components
alternatively
One time investment for harmonic filter
Effect of harmonics
Tripping of circuit breakers and fuses
Due to resonance effects, the current levels may rise to multifold levels which results into tripping of
circuit breakers and melting fuses. This situation results into serious problems in industries which rely
on the quality of power for the continuous operation of their sensitive processes (e.g. semiconductor)
Overloading / decrease of life time of transformers
Transformers are designed to deliver power at network frequency (50/60Hz). The iron losses are
composed of the eddy current loss (which increase with the square of the frequency) and hysteresis
losses (which increase linearly with the frequency). With increasing frequencies the losses also
increase, causing an additional heating of the transformer.
Overloading of the capacitors
Capacitive reactance decreases with the frequencies. Even smaller amplitudes
of the harmonic voltages result into higher currents which are detrimental to
the capacitors: I = U * 2 * 3.14 * f * C.
Losses in distribution equipment
Harmonics in addition to the fundamental current cause additional losses in
the cables, fuses and also the bus bars.
Effect of harmonics
Excessive currents in the neutral conductor
Under balanced load conditions without harmonics, the phase currents cancel each other in neutral,
and resultant neutral current is zero. However, in a 4 wire system with single phase non linear loads,
odd numbered multiples of the third harmonics (3rd, 9th, 15th) do not cancel, rather add together in the
neutral conductor.
In systems with substantial amount of the non linear single phase loads, the neutral currents may rise
to a dangerously high level. There is a possibility of excessive heating of the neutral conductor since
there are no circuit breakers in the neutral conductors like in the phase conductors.
Malfunctioning of the electronic controls and computers
Electronic controls and computers rely on power quality for their reliable operation. Harmonics result
into distorted waveforms, neutral currents and over voltages which affect the performance of the
these gadgets.
Measurement errors in the metering systems
The Accuracy of metering systems is affected by the presence of harmonics. Watt-hour meters
accurately register the direction of power flow at harmonic frequencies, but they have magnitude
errors which increase with frequency.
The accuracy of demand meters and VAr meters is even less in the presence of harmonics.
Wrong multi meter readings. Use true RMS meter!
3rd harmonic in the neutral conductor
3rd harmonic in the neutral conductor
Synthesis of a wave form
Limit for harmonics
Summary
Consumer structure has changed from linear to non linear loads
Harmonics in the net are increasing
Increasing unknown energy losses
Unknown overloads
Problems in the net become more complex
Beside convent. PFC, filters become more and more important
De-tuned filters for most applications
Active filters for a niche market
EPCOS Harmonics solution
Unlike other solutions that:
Waste energy
Connect in series
Generate higher harmonics (through injection)
Have limited fixed sizes and are not expandable
Are bulky and expensive
The Solution EPCOS AG offers:
Specific harmonic filtering of any magnitude
Enhanced power quality
Elimination of associated wasted energy
Modular and expandable circuitry, to include additional load
Resonance
1. Harmonics can overload PFC capacitors due to over voltage and over
current created by the harmonic source and reduced reactance of PFC
capacitors at higher frequencies.
2. But more critical are applications in which the application configuration
(PFC capacitor and transformer) form a resonance circuit with an
frequency close to existing harmonic frequencies. In such a case
harmonic currents stimulate the resonance circuit and create resonance
amplification with harmful over voltages and over currents.
Resonance is one of the main reasons for failed PFC
capacitors or short life cycle of PFC capacitors!
Parallel resonance
Harmonics MAGNIFICATION
H#
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
100.0
0.4
2.1
1.6
0.2
0.4
0.7
0.1
0.2
0.1
0.1
0.0
0.1
0.0
0.1
0.2
0
1 16
2 72
41
1 33
11
36
68
37
69
3 27
69
301
158
319
20
K-f ac tor: 1.0 41
H#
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
Meter: 0001
H#
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
100.0
0.4
12.3
5.5
0.7
1.3
0.1
0.3
0.3
0.0
0.1
0.0
0.1
0.0
0.1
0.0
0
29
53
3 56
2 99
7
2 10
29
2 85
2 10
90
2 10
29
29
29
29
%
0.0
0.1
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
69
68
69
70
68
68
68
68
158
158
69
69
8
248
309
68
V olts : 27 7
T.H.D.:
K-f ac tor: 1.5 33
H#
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
%
0.5
0.1
0.4
0.1
0.2
0.1
0.0
0.0
0.0
0.1
0.0
0.0
0.1
0.1
0.1
0.0
1 00
119
66
91
29
29
29
119
29
90
29
119
29
119
119
209
2.8 %
Fr equenc y :60.01 Hz
max :
A mps : 17 16
T.H.D.:
13.6%
2 .9%
min:
0.5%
Frequenc y :60.01 Hz
max :
1 8.1%
min:
2.1%
Meter: 000 1
H#
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
100 .0
0.5
18.8
1.2
0.0
0.1
0.0
0.1
0.0
0.0
0.1
0.0
0.1
0.1
0.0
0.1
0
352
203
126
80
312
80
116
320
319
192
169
259
259
259
31
K-f a c tor : 1.829
H#
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
Meter: 000 1
H#
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
100 .0
1.0
150.0
8.7
1.5
1.6
1.7
1.2
0.5
1.0
1.5
1.2
0.5
0.9
0.7
0.6
0
169
263
141
280
259
279
79
260
331
259
339
180
182
349
292
%
0.1
0.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
26
31
25 9
25 9
20 0
25 9
80
20 0
16 9
25 9
25 9
34 9
25 9
34 9
25 9
79
K-f ac tor: 32.3 8
H#
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
%
2.3
2.9
3.8
1.2
1.5
0.8
0.5
1.1
0.3
0.5
0.5
0.1
0.6
0.3
0.2
0.0
9
79
25 9
30 0
25 9
31 0
25 9
29 4
8
25 9
31 2
25 9
34 9
30 7
19
25 9
V olts : 2 90
T.H.D.:
18.8%
A mps : 2033
T.H.D.:
89.5%
Frequen c y :5 9.97 Hz
max :
21.6%
min:
1.9%
Voltage
Meter: 0001
With PFC capacitors
Freq uenc y : 5 9.97 Hz
max : 152.3%
min:
3.6%
Current
No PFC capacitors
Real case of parallel resonance in KL/Malaysia
Parallel resonance
Harmonics present on LV side of the transformer
Transformer together with PFC capacitors on LV-side
acts as a parallel resonant circuit
X N , network
im pedance
At resonant frequency the inductive reactance is
equal the capacitive reactance
point of view
XT
transform er
In
The resultant impedance of the circuit increases to
very high value at resonant frequency
Excitation of a parallel resonant circuit results into a
high voltage across the impedances and very high
circulating currents inside the loop
Transformers and capacitors are additionally loaded
which may cause overloading of them
harm onic
load
XL
m otor
XC
cap acitor
Parallel resonance
What happens in case of parallel resonance?
1) I is constant and imprinted
2) Impedance Z
I
AC
DC
Ic
1) + 2) voltage U (ohmic law)
3) With U Ic = IL
IL
Parallel resonance: example
U = 20 KV
Sk = 500 MVA
S = 1000 kVA
Transformer
uk = 6%
U = 400 V
AC
Qc = 400kvar
DC
P = 500 KW, 6-pulse
I50 Hz = 720A
I250 Hz = 144A
I350 Hz = 103A
I550 Hz = 65A
I650 Hz = 55A
I850 Hz = 42A
I950 Hz = 38A
P = 100 KW
I350 Hz =
720
7
f R = 50
Parallel resonance: example
STr
SKLV =
ST 100
QC u K
100
uk
1000 kVA
AC
DC
SKLV =
100 = 16.67MVA
6
SKLV
frp = 50Hz
Qc
16.67 MVA
= 322 Hz
frp = 50 Hz
0.4 Mvar
Attention:
close to the 7th
harmonic!
Parallel resonance: example
51.5V
12.7%
400V
AC
DC
System bus bar:
impedance vs. frequency
I350 Hz = 103 Amp
0.5
322Hz
1,6
1,4
1,2
1
0,8
0,6
0,4
0,2
0
o
50
150
250
350
450
550
Frequency Hz
322 Hz is close to the 7th harmonic
350 Hz
Resulting harmonic voltage for 350 Hz :
U350 = 0.5 * 103A = 51.5V
Resonance?
if fr = f
132 kV level
Xc 0
Ic
11 kV level
Transformer
1000 kVA, uk = 5 %
415 V level
Transformer
630 kVA, uk = 5 %
Series
resonance
Parallel
resonance
415 V level
DC drive
600 kW
cos = 0.65
...
Capacitor
bank
300 kW
cos = 0.65
...
Capacitor
bank
Series resonance
Series resonant circuit formed by combination of inductive
Series resonant circuit
and capacitive reactance. The impedance behavior of this
circuit is as illustrated in the diagram. It is seen that at
resonant frequency the impedance reduces to a minimal
value. Thus the circuit offers very low impedance at the input
C
signal at this frequency which results into multiple fold
increase in the current. The voltage drop on the individual
component increases moving closer to resonant frequency.
S=signal source
Induc tanc e
Se rie s re so na nce
16
R eac tanc e
14
Im pedanc e
Impedance
12
fr
10
The point of series resonance is
given by the following formula:
100
vR = S N
QC1 eK
6
4
2
0
50
100
150
200
250
Freque ncy
300
350
400
Remedial measures
Limiting total output of harmonic sources
Limiting the number of simultaneously operating harmonic sources
Balanced connection of single phase loads to the three phases
Pull in extra neutral wires
Isolated ground separated from the safety ground
Tuned filter circuits
De-tuned HARMONIC filters
Using equipment with higher pulse number
Active harmonic filter
Harmonic proof capacitors
Various supplier of capacitors offer so called Harmonic proof capacitors.
Harmonic proof capacitors are special designed capacitors, e.g. mixed
dielectric, ALL PP or MPP with thicker dielectric
As explained before the main problem for capacitor failures is resonance
amplification due to series or parallel resonance
Both cases can not be solved with harmonic proof capacitors
From physical point of view only one passive solution is known:
Harmonic filter circuits (de-tuned or tuned)
Harmonic filter circuits
Filter circuits, which are in series connected reactors and capacitors, form a series
resonance circuit. Design and dimensioning of the components has to be done in such
a way, that one of the following points will be fulfilled:
De-tuned filter circuit
The main purpose of de-tuned filter is to avoid resonance condition of the capacitor
with the transformer inductance. Depending of the de-tuning frequency more or less
harmonic currents will be sucked from the grid. Very common is a de-tuning to a
frequency of 189 Hz (7 %) with a reduction of harmonics of app. 30-50 %.
Tuned filter circuit
The tuning has to be done for each harmonic frequency, means each harmonic
frequency requires its own filter circuit. The harmonic current will be reduced by
approximately 90 %.
For the fundamental frequency both types are reactive and are working with nearly its
full kvar load as a PFC capacitor.
De-tuned harmonic filters
Customer benefits of detuned filters
Improvement of Power Factor
Reduction of harmonics
Reduction of ohmic losses, real kW energy savings
Elimination of reactive energy consumption
Elimination of power utilities penalties on low power factor
Power Quality improvement
Climatic protection, reduction of greenhouse gas emissions
Reduction of new investment for distribution equipment
(transformers, LV switchgear, )
Reduction of equipment maintenance cost and down time of
production equipment
Improvement of production process stability
De-tuned harmonic filter
De-tuned harmonic filter
WHAT IS THE DEGREE OF DETUNING?
The most common degree of detuning is p = 7 %.
At fn=50Hz as the fundamental network frequency,
this degree of detuning corresponds to a resonance
frequency fres of 189 Hz, which can be calculated
as follows:
fres =
fn
p/%
100
p = (f / fres) 100 (in %)
EXAMPLES FOR
DETUNING-FACTORS (f=50Hz)
5%
5.5 %
5.67 %
6%
7%
8%
12.5 %
14 %
224 Hz
213 Hz
210 Hz
204 Hz
189 Hz
177 Hz
141 Hz
134 Hz
De-tuned harmonic filter
Calculation of a 7%-detuned filter:
Supply Voltage Un + Overvoltage:
fn:
50 Hz
p:
7%
400 V
Nc / kvar:
Uc:
430 V
25
50
440 V
Design: Ucr:
Qcr / kvar:
Un =
189 Hz
fres:
28.13
56.27
1.534
0.767
Cy / F:
462.78
925.56
C / F:
154.26
308.52
400 V
Ln / mH:
430 V
De-tuned harmonic filter
Previous Example, now for 7%-detuned filter
Resulting harmonic voltage e.g. :
AC
DC
Kvar: 400
5th (250Hz):
0.025 Ohm 144A = 3.6V 0.9%
7th (350Hz):
0.045 Ohm 103A = 4.6V 1.1%
System busbar: impedance vs. frequency
0,14
0,12
0,1
0,08
0,06
0,04
0,02
0
50
150
250
350
450
550
De-tuned harmonic filter
I m p e d a n c e b e h a v i o u r o f a s e r ie s i n d u c t a n c e c i r c u i t
3
c a p a c it iv e
b e h a v io u r
in d u c t iv e
b e h a v io u r
In d u c t iv e r e a c t a n c e
C a p a c it iv e r e a c t a n c e
R e s u lt a n t im p e d a n c e
0
0
100
200
300
400
-1
re s o n a n t fre q . f r
-2
-3
F re q u e n c y
500
600
700
800
De-tuned harmonic filter
Summary: detuned filter
Impedance
0,14
0,12
0,1
0,08
0,06
0,04
0,02
0
50
150
189Hz
250
350
5th
7th
450
550
11th
Summary: detuned filter
Resonance frequency not close to any harmonic
Filter frequency ffilter < fharmonic
A certain reduction of harmonic distortion
Export of some harmonics content to the HV-system
Capacitors are blocked against resonance, therefore de-tuned
filters are also known as anti-resonance- filter
Tuned harmonic filter
Power factor correction & Filtering harmonics (cleaning the grid)
Tuned harmonic filter
Tuned harmonic filter
A typical tuned filter bank at 50Hz fundamental frequency
consists of :
1 filter for the 5th harmonic ( 250Hz),
tuned to 245 Hz
1 filter for the 7th harmonic ( 350Hz),
tuned to 345 Hz
1 filter for the 11th harmonic (550Hz),
tuned to 545 Hz
Tuned harmonic filter
Previous Example, now for a TUNED FILTER
Resulting harmonic voltage e.g.:
5th (250Hz): 0.01 Ohm 144 A = 1.4V 0.4%
AC
DC
5 th
kvar: 200
7 th
400
11 th
100
7th (350Hz): 0.01 Ohm 103 A = 1.0V 0.2%
System bus bar: impedance vs. frequency
0,4
0,35
0,3
0,25
0,2
0,15
0,1
0,05
0
50
150
250
350
Frequency Hz
o
450
550
Tuned harmonic filter
Switching sequence of tuned filter: LIFO
Switching in:
3rd
5th
7th
11th
5th
7th
11th
Switching out:
3rd
Summary: tuned filter
Resonance frequencies of the series filter circuits are very close to
existing harmonics
Excellent reduction of harmonics on the bus bars
Capacitors are charged with high harmonic currents
cleaning of the network
No export of additional harmonic load to the HV-system
torture for the capacitors, if they are not rated for this high
effective current
Risk of sucking-off harmonic currents from HV side!!
Summary: tuned filter
Impedance
0,4
0,35
0,3
0,25
0,2
0,15
0,1
0,05
0
50
150
250
350
5th
7th
o
450
550
11th
Harmonic filters
FINAL COMPARISON:
Remaining harmonic voltage level,
for instance for the 7th harmonic:
Capacitor bank
without reactors:
12.7%
7% - detuned filter:
1.1%
tuned filter:
0.2%
Return on Investment
s
g
n
i
Sav
EPCOS
PFC
11--Reduces
ReducesKW
KWDemand
Demand
22--Reduces
ReducesKWH
KWHConsumption
Consumption
33--Eliminates
EliminatesPower
PowerFactor
FactorPenalty
Penalty
44--Reduces
ReducesMonthly
MonthlyElectricity
ElectricityBill
Bill
55--Reduces
ReducesMaintenance
Maintenance&
&Downtime
Downtime
Up
Le
to
ss
34
tha
%
Sa
n2
vin
Ye
gs
ar
Pa
yba
ck
Satisfied
Customer
Pow
er
Qua
lity
11--Improves
ImprovesVoltage
Voltage
22--Balances
BalancesThree
ThreePhases
Phases
33--Filters
FiltersSurges,
Surges,Transients
Transients
44--Filters
FiltersHarmonics
Harmonics
55--Improves
ImprovesPower
PowerFactor
Factor
lity nce
a
Qu tena
r
in
we
a
o
M
dP e&
e
c
tim
an
n
h
E n Do w
d
ce
u
d
Re
All components for harmonic filters
