Course
Power Quality - 3
Ljubljana, Slovenia
2013/14
Prof. dr. Igor Papič
igor.papic@fe.uni-lj.si
Harmonics - design of power
factor correction devices
Content
1st day
2nd day
3rd day
Session 1
Introduction to
Power Quality
• what is PQ
• economic value
• responsibilities
Harmonics –
definitions
• calculations
• non-linear loads
• harmonic
sequences
Harmonics - design
of power factor
correction devices
• resonance points
• filter design
Session 2
Basic terms and
definitions
• voltage quality
• continuity of
supply
• commercial
quality
Propagation of
harmonics
• sources
• consequences
• cancellation
Flicker - basic
terms
• voltage variation
• flicker frequency
• sources
• flickermeter
Session 3
PQ standards
• EN 50 160
• other standards
• limit values
Harmonics resonances in
network
• parallel
resonance
• series resonance
Flicker spreading
• radial network
• mashed network
• simulation
• examples
Session 4
PQ monitoring
• measurements
• PQ analyzers
• data analyses
Harmonics case
study
• calculation of
frequency
impedance
characteristics
Flicker mitigation
• system solutions
– network
enforcement
• compensation
4th day
Flicker case study
• calculation of
flicker spreading
in radial network
• variation of
network
parameters
Voltage sags –
definitions
• characteristics
• types
• causes
Propagation of
voltage sags
• transformer
connections
• equipment
sensitivity
• mitigation
Other voltage
variations
• unbalance
• voltage
transients
• overvoltages
5th day
Interruptions
• definitions
• reliability indices
• improving
reliability
Consequences of
inadequate power
quality
• voltage quality
• interruptions
• costs
Modern
compensation
devices
• active and hybrid
compensators
• series and shunt
compensators
Conclusions
• PQ improvement
and costs
• definition of
optimal solutions
Power Quality, Ljubljana, 2013/14 3
1
Design of PFC devices
• influence of impedance change
– compensator impedance varies with the number of used
compensation stages (crossing of resonance points)
– network impedance change has large influence on
frequency response
– load impedance has minor influence on frequency
response
• detuned filter
– series connection of inductor and capacitor
– resonance frequency is below the characteristic harmonic
(141 Hz, 225 Hz)
– good response under different operating conditions
Power Quality, Ljubljana, 2013/14 4
Influence of network impedance change
• frequency impedance characteristics
– data for calculation of one supply transformer 20/0,4 kV
(two transformer in previous case)
– short-circuit voltage
usc = 4,13 %
– rated power
S n = 1 x 0,63 MVA
– rated voltage
U MV = 20 kV; U LV = 0,4 kV
– ratio R/X
( R / X )TR = 1 / 4
Power Quality, Ljubljana, 2013/14 5
Influence of network impedance change
• frequency impedance characteristics
– calculation of parameters of one supply transformer
20/0,4 kV
LTR =
2
U LV
u sc
1
= 32,4 μH
2
100 π S n 100 1 + ( R / X )TR
RTR =
2
U NN
u sc ( R / X )TR
= 2,54 mΩ
2
S n 100 1 + ( R / X )TR
Z TR ( j 2 π f ) = RTR + j 2 π f LTR
Power Quality, Ljubljana, 2013/14 6
2
Influence of network impedance change
• frequency impedance characteristics
– harmonic source
is on the network
side
• impedance
characteristics
as a function
of frequency
• one supply
transformer
100
10
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 7
Influence of network impedance change
• frequency impedance characteristics
– harmonic source
is on the network
side
• impedance
characteristics
as a function
of frequency
• two supply
transformers
(previous case)
100
10
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 8
Influence of network impedance change
• frequency impedance characteristics
– harmonic source
is on the network
side
• impedance
characteristics
as a function
of number of
used
compensation
stages
• one supply
transformer
10
1
0.1
0.01
0
0.2
0.4
0.6
0.8
1
Power Quality, Ljubljana, 2013/14 9
3
Influence of network impedance change
• frequency impedance characteristics
– harmonic source
is on the network
side
• impedance
characteristics
as a function
of number of
used
compensation
stages
• two supply
transformers
(previous case)
10
1
0.1
0.01
0
0.2
0.4
0.6
0.8
1
Power Quality, Ljubljana, 2013/14 10
Influence of network impedance change
• frequency impedance characteristics
– harmonic source
is on the load
side
• impedance
characteristics
as a function
of frequency
• one supply
transformer
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 11
Influence of network impedance change
• frequency impedance characteristics
– harmonic source
is on the load
side
• impedance
characteristics
as a function
of frequency
• two supply
transformers
(previous case)
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 12
4
Influence of network impedance change
• frequency impedance characteristics
– harmonic source
is on the load
side
• impedance
characteristics
as a function
of number of
used
compensation
stages
• one supply
transformer
1
0.1
0.01
0
0.2
0.4
0.6
0.8
1
Power Quality, Ljubljana, 2013/14 13
Influence of network impedance change
• frequency impedance characteristics
– harmonic source
is on the load
side
• impedance
characteristics
as a function
of number of
used
compensation
stages
• two supply
transformers
(previous case)
1
0.1
0.01
0
0.2
0.4
0.6
0.8
1
Power Quality, Ljubljana, 2013/14 14
Detuned filter
• frequency impedance characteristics
– equivalent circuit with detuned filter
Power Quality, Ljubljana, 2013/14 15
5
Detuned filter
• frequency impedance characteristics
– data for calculation of detuned filter
– rated voltage
U LV = 0,4 kV
– reactive power
Q f = 0,40 MVAr
– filter frequency
f r = 141 Hz (225 Hz)
– ratio R/X of C
( R / X ) fC = 1 / 50
– ratio R/X of L
( R / X ) fL = 1 / 10
Power Quality, Ljubljana, 2013/14 16
Detuned filter
• frequency impedance characteristics
– calculation of parameters of detuned filter
• detuned filter
• 141 Hz, p = 12,5 %
• 225 Hz, p = 5,0 %
p = ω 2Lf C f =
ω2
50 2
= 2
2
(2π f r ) f r
p(141 Hz ) = 0,05;
p (225 Hz ) = 0,125
Power Quality, Ljubljana, 2013/14 17
Detuned filter
• frequency impedance characteristics
– calculation of parameters of detuned filter
• detuned filter
Cf =
Q f (1 − p )
2
100 π U LV
C f (141 Hz ) = 6,96 mF ;
Lf =
C f (225 Hz ) = 7,57 mF
1
(2π f r )2 C f
L f (141 Hz ) = 0,183 mH ;
L f (225 Hz ) = 0,066 mH
Power Quality, Ljubljana, 2013/14 18
6
Detuned filter
• frequency impedance characteristics
– calculation of parameters of detuned filter
• detuned filter
Rf =
1
( R / X ) fC + 2 ⋅ π ⋅ 50 ⋅ C f ( R / X ) fL
2 ⋅ π ⋅ 50 ⋅ C f
R f (141 Hz ) = 15 mΩ;
R f (225 Hz ) = 10 mΩ
Z f ( j 2π f ) = R f + j 2π f Lf +
1
j 2π f C f
Power Quality, Ljubljana, 2013/14 19
Detuned filter
• frequency impedance characteristics
– voltage harmonic source is on the network side
Power Quality, Ljubljana, 2013/14 20
Detuned filter
• frequency impedance characteristics
– harmonic source is on the network side
• impedance from the network side
• series resonance
Z1 ( jω ) = Z SC ( jω ) + ZTR ( jω ) +
1
1
1
+
Z L ( jω ) Z f ( jω )
absolute value → Z1 ( jω ) = Z1 ( j 2π f )
Power Quality, Ljubljana, 2013/14 21
7
Detuned filter – frequency response
• frequency impedance characteristics
– harmonic source
is on the network
side
• impedance
characteristics
as a function
of frequency
• filter resonance
frequency is
141 Hz
100
10
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 22
Detuned filter – frequency response
• frequency impedance characteristics
– harmonic source
is on the network
side
• impedance
characteristics
as a function
of frequency
• filter resonance
frequency is
225 Hz
100
10
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 23
Detuned filter – frequency response
• frequency impedance characteristics
– harmonic source
is on the network
side
• impedance
characteristics
as a function
of frequency
• filter resonance
frequency is
225 Hz
• one supply
transformer
100
10
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 24
8
Detuned filter – frequency response
• frequency impedance characteristics
– harmonic source
is on the network
side
• impedance
characteristics
as a function
of frequency
• comparison with
classical
compensator
100
10
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 25
Detuned filter
• frequency impedance characteristics
– current harmonic source is on the load side
Power Quality, Ljubljana, 2013/14 26
Detuned filter
• frequency impedance characteristics
– harmonic source is on the load side
• impedance from the load side
• parallel resonance
Z 2 ( jω ) =
1
1
1
1
+
+
Z L ( jω ) Z f ( jω ) Z SC ( jω ) + ZTR ( jω )
absolute value → Z 2 ( jω ) = Z 2 ( j 2π f )
Power Quality, Ljubljana, 2013/14 27
9
Detuned filter – frequency response
• frequency impedance characteristics
– harmonic source
is on the load
side
• impedance
characteristics
as a function
of frequency
• filter resonance
frequency is
141 Hz
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 28
Detuned filter – frequency response
• frequency impedance characteristics
– harmonic source
is on the load
side
• impedance
characteristics
as a function
of frequency
• filter resonance
frequency is
225 Hz
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 29
Detuned filter – frequency response
• frequency impedance characteristics
– harmonic source
is on the load
side
• impedance
characteristics
as a function
of frequency
• filter resonance
frequency is
225 Hz
• one supply
transformer
1
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 30
10
Detuned filter – frequency response
• frequency impedance characteristics
– harmonic source
is on the load
side
1
• impedance
characteristics
as a function
of frequency
• comparison with
classical
compensator
0.1
0.01
1 .10
3
0
100
200
300
400
500
600
700
800
900
1000
Power Quality, Ljubljana, 2013/14 31
Flicker - basic terms
Content
1st day
2nd day
3rd day
Session 1
Introduction to
Power Quality
• what is PQ
• economic value
• responsibilities
Harmonics –
definitions
• calculations
• non-linear loads
• harmonic
sequences
Harmonics - design
of power factor
correction devices
• resonance points
• filter design
Session 2
Basic terms and
definitions
• voltage quality
• continuity of
supply
• commercial
quality
Propagation of
harmonics
• sources
• consequences
• cancellation
Flicker - basic
terms
• voltage variation
• flicker frequency
• sources
• flickermeter
Session 3
PQ standards
• EN 50 160
• other standards
• limit values
Harmonics resonances in
network
• parallel
resonance
• series resonance
Flicker spreading
• radial network
• mashed network
• simulation
• examples
Session 4
PQ monitoring
• measurements
• PQ analyzers
• data analyses
Harmonics case
study
• calculation of
frequency
impedance
characteristics
Flicker mitigation
• system solutions
– network
enforcement
• compensation
4th day
Flicker case study
• calculation of
flicker spreading
in radial network
• variation of
network
parameters
Voltage sags –
definitions
• characteristics
• types
• causes
Propagation of
voltage sags
• transformer
connections
• equipment
sensitivity
• mitigation
Other voltage
variations
• unbalance
• voltage
transients
• overvoltages
5th day
Interruptions
• definitions
• reliability indices
• improving
reliability
Consequences of
inadequate power
quality
• voltage quality
• interruptions
• costs
Modern
compensation
devices
• active and hybrid
compensators
• series and shunt
compensators
Conclusions
• PQ improvement
and costs
• definition of
optimal solutions
Power Quality, Ljubljana, 2013/14 33
11
Flicker – basic terms
•
•
•
•
•
•
•
Voltage fluctuation
What is flicker?
Flicker frequency
Causes of flicker
Flicker evaluation
Flicker meter
Compatibility and planning levels
Power Quality, Ljubljana, 2013/14 34
Voltage fluctuation
•
voltage fluctuation – a series of voltage changes or a cyclic
variation of the voltage envelope
•
voltage fluctuations (rms value) can cause perceptible (low
frequency) light flicker depending on the magnitude and
frequency of the variation
Power Quality, Ljubljana, 2013/14 35
What is flicker?
•
•
•
•
flicker – impression of unsteadiness of visual sensation
induced by a light stimulus whose luminance or spectral
distribution fluctuates with time
the range of modulation frequency that causes noticeable
flicker is in the 0.5-25 Hz band, voltage variations are less
than 10 %
the most annoying flicker occurs at the voltage fluctuation
with the frequency 8.8 Hz.
flicker represents one of the largest problems related to
power quality in the power system of Slovenia
Power Quality, Ljubljana, 2013/14 36
12
What is flicker?
Power Quality, Ljubljana, 2013/14 37
Flicker frequency – case 1
• What is the frequency of flicker?
– assume sinusoidal modulation
– what signal does represent flicker with frequency 3 Hz
Power Quality, Ljubljana, 2013/14 38
Flicker frequency – case 2
– or
Power Quality, Ljubljana, 2013/14 39
13
What is the frequency of flicker
– case 1
v (t ) = V cosω 0t + m cosω f t
f 0 = 50 Hz
f f = 3 Hz
– case 2
v (t ) = V (1 + m cosω f t ) cosω 0t
m
m
⎡
⎤
v (t ) = V ⎢cosω0t + cos(ω0 + ω f )t + cos(ω 0 − ω f )t ⎥
2
2
⎣
⎦
f 0 = 50 Hz
f 0 + f f = 53 Hz
f 0 − f f = 47 Hz
Power Quality, Ljubljana, 2013/14 40
Causes of flicker
– loads drawing
large and highly
variable currents
– arc furnaces
installations
• voltage 20 kV
time (s)
Power Quality, Ljubljana, 2013/14 41
Causes of flicker
Voltage (%)
– steel rolling mils
– induction motors
starting
Power Quality, Ljubljana, 2013/14 42
14
Causes of flicker
– welding machines
– motor drives with cycloconverters
• simulation results (interharmonics)
time
Power Quality, Ljubljana, 2013/14 43
Causes of flicker
– wind farms in distributed production
– switching of capacitor banks
– households
• pumps, refrigerators, air conditioning, washing
machines, drills
• devices with heavy-start motors
–…
Power Quality, Ljubljana, 2013/14 44
Flicker evaluation
• flicker meter
– IEC 61000-4-15: Electromagnetic compatibility (EMC) Part 4: Testing and measurements techniques - Section
15: Flickermeter - Functional and design specifications
– flicker severity – intensity of flicker annoyance defined
by the UIE-IEC flicker measuring method and evaluated
by short and long term severity
Power Quality, Ljubljana, 2013/14 45
15
Flicker evaluation
• flicker meter
– short term severity Pst – measured over a period of 10
minutes
– long term severity Plt – calculated from a sequence of
12 Pst values over a two hour interval, according to the
following expression:
12
Plt =
3
∑P
i =1
3
sti
12
Power Quality, Ljubljana, 2013/14 46
Flicker evaluation
– comparison between Plt and Pst
Power Quality, Ljubljana, 2013/14 47
Scheme of a flicker meter
simulation of lamp-eye-brain response
BLOCK 1
BLOCK 2
BLOCK 3
BLOCK 4
dB
0
-3
1
∆U / U
(%)
-60
0,05
input
voltage
adaptor
35
0
Hz
8,8
demodulator
weighting filter
voltage
mesurement
BLOCK 5
range
selector
calculation
of
Pst
X2
and
Plt
Hz
statistical
evaluation
squaring
and
smoothing
P
Pst
and
Plt
Power Quality, Ljubljana, 2013/14 48
16
Scheme of a flicker meter
•
Block 1 – Input voltage adaptor and calibration checking
circuit
– signal generator for calibration and checking
– voltage adapting circuit that scales the input signal to a
reference per-unit level
•
Block 2 – Square law demodulator
– the input to the flicker meter is the relative voltage variation
– the modulated wave must be extracted from carrier (50 or 69
Hz)
– quadratic demodulator simulates the behavior of a lamp
Power Quality, Ljubljana, 2013/14 49
Scheme of a flickermeter
•
Block 3 and 4 – Weighting filters, squaring and smoothing
– block 3 is composed of a cascade of two filters and a measuring
range selector
– first filter eliminates the dc and double mains frequency ripple
components of the demodulator
– second filter is weighting filter block that simulates the
frequency response of a coiled filament gas-filled lamp (60 W,
230 V) combined with a human visual system
– block 4 is composed of a squaring multiplier and a first order
low-pass filter
– the human flicker sensation via lamp, eye and brain is
simulated by the combined non-linear response of blocks
2, 3 and 4
Power Quality, Ljubljana, 2013/14 50
Scheme of a flickermeter
•
Block 5 – On-line statistical analysis
– the statistical classifier models human irritability in the presence
of flicker stimulation
– it provides the statistical information required to calculate shortterm flicker severity Pst (observation period is 10 minutes)
Pst = 0,0314 ⋅ P0,1 + 0,0525 ⋅ P1s + 0,0657 ⋅ P3s + 0,28 ⋅ P10 s + 0,08 ⋅ P50 s
– smoothed percentil values
– i.e. P0.1 – the level exceeded by only 0.1 % of the observation
period (10 minutes)
Power Quality, Ljubljana, 2013/14 51
17
Flicker value
•
•
required magnitude of voltage fluctuation for sinusoidal and
rectangular modulation to get the flicker vale P = 1
the response function
is based on perceptibility
threshold found at each
frequency by 50 % of
the persons tested
Power Quality, Ljubljana, 2013/14 52
Flicker value
•
•
multiple fluctuating loads may be impacting the same
network
aggregate Pst value calculation from N loads
N
Pst = m ∑ Pstmi
i =1
–
–
–
–
m = 4 coordinated loads to avoid coincident fluctuations
m = 3 likelihood of coincident fluctuations is small
m = 2 likelihood of coincident stochastic noise is likely
m = 1 likelihood of coincident fluctuations is small
Power Quality, Ljubljana, 2013/14 53
Compatibility and planning levels
• graphical representation of flicker levels
– planning level is usualy less than planning level
– compatibility level may be exceed 5% of the evaluation
period
Power Quality, Ljubljana, 2013/14 54
18
Compatibility and planning levels
– compatibility levels
– EN 50160 gives
higher value for Plt
(1.0, 95 % value)
quantity
compatibility levels for
MV and LV networks
(IEC/TR3 61000-3-7)
Pst
1.0
Plt
0.8
quantity
planning levels
(IEC/TR3 61000-3-7)
– planning levels
MV
HV
Pst
0.9
0.8
Plt
0.7
0.6
Power Quality, Ljubljana, 2013/14 55
Compatibility and planning levels
• required short-circuit power in the point of
common coupling PCC
– primarily depends on nominal power of a supply
transformer of disturbing load
– Ssc = (90÷160)·Str [MVA]
– empirical and statistical evaluation
Power Quality, Ljubljana, 2013/14 56
Flicker spreading
19
Content
1st day
2nd day
3rd day
Session 1
Introduction to
Power Quality
• what is PQ
• economic value
• responsibilities
Harmonics –
definitions
• calculations
• non-linear loads
• harmonic
sequences
Harmonics - design
of power factor
correction devices
• resonance points
• filter design
Session 2
Basic terms and
definitions
• voltage quality
• continuity of
supply
• commercial
quality
Propagation of
harmonics
• sources
• consequences
• cancellation
Flicker - basic
terms
• voltage variation
• flicker frequency
• sources
• flickermeter
Session 3
PQ standards
• EN 50 160
• other standards
• limit values
Harmonics resonances in
network
• parallel
resonance
• series resonance
Flicker spreading
• radial network
• mashed network
• simulation
• examples
Session 4
PQ monitoring
• measurements
• PQ analyzers
• data analyses
Harmonics case
study
• calculation of
frequency
impedance
characteristics
Flicker mitigation
• system solutions
– network
enforcement
• compensation
4th day
Flicker case study
• calculation of
flicker spreading
in radial network
• variation of
network
parameters
Voltage sags –
definitions
• characteristics
• types
• causes
Propagation of
voltage sags
• transformer
connections
• equipment
sensitivity
• mitigation
Other voltage
variations
• unbalance
• voltage
transients
• overvoltages
5th day
Interruptions
• definitions
• reliability indices
• improving
reliability
Consequences of
inadequate power
quality
• voltage quality
• interruptions
• costs
Modern
compensation
devices
• active and hybrid
compensators
• series and shunt
compensators
Conclusions
• PQ improvement
and costs
• definition of
optimal solutions
Power Quality, Ljubljana, 2013/14 58
Flicker spreading
• calculation of voltage variation
– dynamic load
U1
R, X
I
X·I
U1
U2
θ
P, Q
φ
U2
R·I
I
U1 ⋅ cosΘ = U 2 + R ⋅ I ⋅ cosϕ + X ⋅ I ⋅ sinϕ
cosΘ ≈ 1
U1 − U 2 = R ⋅ I ⋅ cosϕ + X ⋅ I ⋅ sinϕ
Power Quality, Ljubljana, 2013/14 59
Flicker spreading
• relative voltage variation
U 1 − U 2 R ⋅ U 2 ⋅ I ⋅ cosϕ + X ⋅ U 2 ⋅ I ⋅ sinϕ
=
U2
U 22
ΔU R ⋅ P + X ⋅ Q
=
Un
U n2
ΔU X ⋅ Q Q
≈
=
Un
U n2
S sc
Power Quality, Ljubljana, 2013/14 60
20
Flicker spreading
• relative voltage variation
– active and reactive power variations of an arc furnace
Power Quality, Ljubljana, 2013/14 61
Flicker spreading
• flicker level decreases in the direction from the
disturbing load towards supply source
• flicker level practically does not change in a radial
direction from the disturbing load where are no
supply sources
• flicker reduction on transformers
Power Quality, Ljubljana, 2013/14 62
Flicker spreading
• transfer coefficient of flicker in a radial network
between point A and P (disturbing load)
TC AP =
Pst (A )
Pst (P )
A
P
P
• calculation in a mashed network is more complex
– use of simulation tools
Power Quality, Ljubljana, 2013/14 63
21
Flicker spreading
• flicker spreading in a radial network
– case A
A
P
P
ZA
A
P
ZAP
P
Pst (A ) = Pst (P ) ⋅ TC AP = Pst (P ) ⋅
ZA
Z A + Z AP
Power Quality, Ljubljana, 2013/14 64
Flicker spreading
• flicker spreading in radial network
– case B
A
P
B
P
Pst (B) = Pst (P ) ⋅ TC BP = Pst (P ) ⋅1 = Pst (P )
Power Quality, Ljubljana, 2013/14 65
Flicker spreading
• flicker spreading in radial network
– case C
A
B
P
P
Pst (B) = Pst (P ) ⋅ TC BP = Pst (P ) ⋅
Z A + Z AB
Z A + Z AB + Z BP
Power Quality, Ljubljana, 2013/14 66
22
Flicker spreading
• flicker spreading in radial network
– case D
A
P
P
B
Pst (B) = Pst (P ) ⋅ TC BP = Pst (P ) ⋅ TC AP ⋅ TC BA =
= Pst (P ) ⋅ TC AP ⋅1 = Pst (P ) ⋅ TCAP
Power Quality, Ljubljana, 2013/14 67
Simulation of flicker spreading
•
steady-state calculation
–
–
–
–
•
dynamic simulations
–
–
–
–
–
•
•
model of transmission system
switch on/off of the load
change of voltage magnitudes
injection of load current
model of transmission system
model of arc furnace
model of flicker meter
Influence of generator voltage controllers
models of compensation devices
calibration of simulation model wit measurements results
calculation of flicker levels for all buses
Power Quality, Ljubljana, 2013/14 68
Flicker spreading
• flicker spreading in mashed network
–
–
–
–
load flow method
two states of s disturbing load (0,1)
calculation of relative voltage drops
calculation of transfer coefficients
Δv x =
ΔVx V 0, x − V 1, x
=
V 0, x + V 1, x
Vx
kvij =
Δvi
Δv j
2
Power Quality, Ljubljana, 2013/14 69
23
Flicker spreading
• flicker spreading
in mashed
network
– load flow method
– comparison with
measurements
– variation of load
Power Quality, Ljubljana, 2013/14 70
Flicker spreading
• flicker spreading in mashed network
– current injection method
⎡ 0 ⎤ ⎡ Y11
⎢M ⎥ ⎢ .
⎢ ⎥ ⎢
⎢0⎥ ⎢ .
⎢ ⎥ ⎢
⎢I A ⎥ = ⎢ .
⎢0⎥ ⎢ .
⎢ ⎥ ⎢
⎢M ⎥ ⎢ .
⎢ ⎥ ⎢
⎣ 0 ⎦ ⎣ Y N1
.
.
.
.
.
.
.
.
.
Y AA
.
.
.
.
.
.
.
.
.
Y1N ⎤ ⎡ V 1 ⎤
. ⎥⎥ ⎢⎢ V 2 ⎥⎥
. ⎥ ⎢ M ⎥
⎥ ⎢
⎥
. ⎥ ⋅ ⎢V A ⎥
. ⎥ ⎢ M ⎥
⎥ ⎢
⎥
. ⎥ ⎢VN-1 ⎥
Y NN ⎦⎥ ⎣⎢ V N ⎦⎥
V = Y −1I
kvij =
ℜ(V i )
ℜ(V j )
Power Quality, Ljubljana, 2013/14 71
Flicker spreading
• flicker spreading
in mashed
network
– current injection
method
– comparison with
measurements
– variation of
injected current
Power Quality, Ljubljana, 2013/14 72
24
Flicker spreading
• flicker spreading through transformers
– in a radial direction from the disturbing load towards
lower voltage levels (first approximation is value 1)
– transfer coefficient of flicker from EHV to HV level is
approximately 0.8
– transfer coefficient of flicker from HV to MV level is
approximately 0.9 (worst case)
– transfer coefficient of flicker from MV to LV level is
approximately 1
Power Quality, Ljubljana, 2013/14 73
Example of flicker spreading analysis
• measurement campaign in Slovenian transmission
network
– 31 locations
– analysis of measurement results
• simulation of flicker spreading
–
–
–
–
–
–
network model
calibration of the model wit measurement results
simulation of flicker spreading in all nodes
present situation
future situation (2020)
analysis of compensation measures
Power Quality, Ljubljana, 2013/14 74
Flicker measurement locations
Power Quality, Ljubljana, 2013/14 75
25
Flicker measurement results (SIST EN 50160)
flicker level (Plt)
95 % values
location
RTP Jeklarna Jesenice
RTP Železarna Ravne
RTP Lipa
RTP Okroglo
RTP Zlato polje
RTP Kleče
RTP Beričevo
RTP Lj Center
RTP Šiška
RTP Logatec
RTP Slovenj Gradec
RTP Podlog
RTP Pekre
RTP Maribor
RTP Ljutomer
voltage
level (kV)
110
110
110
110
110
110
110
110
110
110
110
110
110
110
110
L1
L2
L3
7,41
2,87
1,62
1,256
1,25
7,50
2,80
1,48
1,331
1,33
7,85
2,68
1,57
1,415
1,41
0,85
0,74
0,79
0,92
0,90
0,87
0,69
0,80
0,95
0,94
0,92
0,80
0,85
1,02
1,00
1,47
0,82
0,60
1,44
0,76
0,62
1,33
0,79
0,56
0,50
0,50
0,51
0,52
0,48
0,53
Power Quality, Ljubljana, 2013/14 76
Flicker measurement results (SIST EN 50160)
flicker level (Plt)
95 % values
location
RTP Ljutomer
RTP Rače
RTP Laško
RTP Hudo
RTP Kočevje
RTP Divača
RTP Vrtojba
RTP Tolmin
RTP Koper
RTP Beričevo
RTP Podlog
RTP Kleče
RTP Beričevo
RTP Podlog
RTP Okroglo
RTP Krško
voltage
level (kV)
110
110
110
110
110
110
110
110
110
220
220
220
400
400
400
400
L1
L2
L3
0,50
0,60
0,81
0,72
0,81
0,39
0,30
0,40
0,63
0,56
0,52
0,52
0,75
0,88
1,98
0,40
0,31
0,37
0,61
0,58
0,53
0,51
0,78
0,75
0,87
0,56
0,44
0,41
0,65
0,60
0,34
0,56
0,35
0,58
0,41
0,60
0,59
0,41
0,74
0,27
0,59
0,42
0,74
0,23
0,60
0,46
0,74
0,59
Power Quality, Ljubljana, 2013/14 77
Flicker measurement results (SIST EN 50160)
•
•
arc furnace 40 MVA
short and long term flicker level at 110 kV
Power Quality, Ljubljana, 2013/14 78
26
Flicker measurement results (SIST EN 50160)
•
•
arc furnace 40 MVA
long term flicker level and current at 110 kV - correlation
Power Quality, Ljubljana, 2013/14 79
Flicker measurement results (SIST EN 50160)
•
•
network node – different configurations
cumulative flicker levels – determination of 95 % value
Power Quality, Ljubljana, 2013/14 80
Measurement results at 110 kV level
voltage (kV)
time (s)
current (A)
time (s)
Power Quality, Ljubljana, 2013/14 81
27
Measurement results at 20 kV level
voltage (kV)
time (s)
current (A)
time (s)
Power Quality, Ljubljana, 2013/14 82
Measurement results
•
•
•
•
arc furnace 40
MVA
voltage at 110 kV
voltage at 20 kV
current at 20 kV
Power Quality, Ljubljana, 2013/14 83
Measurement results
•
•
•
•
arc furnace 40
MVA
voltage at 110 kV
voltage at 20 kV
current at 20 kV
Power Quality, Ljubljana, 2013/14 84
28
Measurement results
•
•
arc furnace 40 MVA
correlation between the flicker level at 110 kV and 20 kV
Pst Jeklarna Ravne 110 kV
6
5
4
3
2
1
0
0
5
10
15
20
25
Pst Jeklarna Ravne UHP 20 kV
Power Quality, Ljubljana, 2013/14 85
Flicker spreading simulation
• analysis of flicker spreading in the Slovenian
power system (three arc furnaces)
– present situation – summation law m = 2.7
0%
12%
0%
29%
33%
17%
51%
67%
71%
20%
Plt>1,5
1<Plt<1,5
110 kV
0,6<Plt<1
Plt<0,6
Plt>1,5
1<Plt<1,5
0,6<Plt<1
Plt>0,6
220 kV
Plt>1,5
1<Plt<1,5
0,6<Plt<1
Plt>0,6
400 kV
percentage of nodes
Power Quality, Ljubljana, 2013/14 86
Flicker spreading simulation in 110 kV
network (m = 2.7)
Power Quality, Ljubljana, 2013/14 87
29
Flicker spreading simulation for the year
2020
• analysis of flicker spreading in the Slovenian
power system (three arc furnaces)
– results for the year 2020
5%
0%
0%
19%
49%
27%
Plt>1,5
1<Plt<1,5
110 kV
0,6<Plt<1
Plt>0,6
Plt>1,5
100%
1<Plt<1,5
0,6<Plt<1
Plt>0,6
220 kV
Plt>1,5
100% 0,6<Plt<1
1<Plt<1,5
Plt>0,6
400 kV
percentage of nodes
Power Quality, Ljubljana, 2013/14 88
Flicker spreading simulation in 110 kV
network for the year 2020
Power Quality, Ljubljana, 2013/14 89
Flicker mitigation
30
Content
1st day
2nd day
3rd day
Session 1
Introduction to
Power Quality
• what is PQ
• economic value
• responsibilities
Harmonics –
definitions
• calculations
• non-linear loads
• harmonic
sequences
Harmonics - design
of power factor
correction devices
• resonance points
• filter design
Session 2
Basic terms and
definitions
• voltage quality
• continuity of
supply
• commercial
quality
Propagation of
harmonics
• sources
• consequences
• cancellation
Flicker - basic
terms
• voltage variation
• flicker frequency
• sources
• flickermeter
Session 3
PQ standards
• EN 50 160
• other standards
• limit values
Harmonics resonances in
network
• parallel
resonance
• series resonance
Flicker spreading
• radial network
• mashed network
• simulation
• examples
Session 4
PQ monitoring
• measurements
• PQ analyzers
• data analyses
Harmonics case
study
• calculation of
frequency
impedance
characteristics
Flicker mitigation
• system solutions
– network
enforcement
• compensation
4th day
Flicker case study
• calculation of
flicker spreading
in radial network
• variation of
network
parameters
Voltage sags –
definitions
• characteristics
• types
• causes
Propagation of
voltage sags
• transformer
connections
• equipment
sensitivity
• mitigation
Other voltage
variations
• unbalance
• voltage
transients
• overvoltages
5th day
Interruptions
• definitions
• reliability indices
• improving
reliability
Consequences of
inadequate power
quality
• voltage quality
• interruptions
• costs
Modern
compensation
devices
• active and hybrid
compensators
• series and shunt
compensators
Conclusions
• PQ improvement
and costs
• definition of
optimal solutions
Power Quality, Ljubljana, 2013/14 91
Flicker mitigation
•
•
•
system enforcement – increased short-circuit power
electrical separation of disturbing loads – disconnected
substation busbars
compensation measures
– series reactor
– Static Var Compensator – SVC
– Static Compensator - StatCom
•
•
elimination of flicker sources – power reduction of disturbing
loads (if possible)
lighting technology
– fluorescent lamps are considered to be less sensitive to voltage
flicker than incandescent lamps
– ban of incandescent lamps due to energy savings reasons
Power Quality, Ljubljana, 2013/14 92
System enforcement
•
increased shortcircuit power will
reduce flicker
level
– new parallel
lines
– additional
transformers
– connection to
the higher
voltage level
line disconnection
Power Quality, Ljubljana, 2013/14 93
31
Separation of disturbing loads
•
electrical separation of disturbing loads – disconnected
substation busbars
Plt = 5,31
Okroglo 110 kV
»sunkovit«
Okroglo 110 kV
»ostali«
TR 412
400/110 kV
Plt = 1,13
Okroglo 110 kV
TR 412
400/110 kV
TR 411
400/110 kV
Okroglo 400 kV
Plt = 0,71
RTP Jeklarna
sunkovit odjem
Plt = 1,13
Plt = 3,03
Plt = 0,47
Plt = 3,44
RTP Jeklarna
sunkovit odjem
TR 411
400/110 kV
Okroglo 400 kV
Plt = 0,52
Plt = 0,71
Power Quality, Ljubljana, 2013/14 94
Separation of disturbing loads
•
electrical separation of
disturbing loads
– connected substation
busbars
– arc furnace is supplied
by two transformers in
parallel
Power Quality, Ljubljana, 2013/14 95
Separation of disturbing loads
•
electrical separation of
disturbing loads
– disconnected substation
busbars
– arc furnace is supplied
by one transformers
Power Quality, Ljubljana, 2013/14 96
32
Compensation measures
• series reactor
– for minor flicker level reduction
in the point of common coupling
– redistribution of flicker level
– influences the operation of arc
furnace
series
reactors
arc
Power Quality, Ljubljana, 2013/14 97
Compensation measures
• Static Var Compensator – SVC
– flicker and reactive power
compensation
– controllable shunt connected reactance
– TCR – Thyristor Controlled Reactor is
the main element
– reactive compensation current is a
function of voltage
– flicker reduction factor is up to 2
– reliable – good operational
experiences
– small operational losses
Power Quality, Ljubljana, 2013/14 98
Compensation measures
• Static Var Compensator – SVC
– single-line diagram
– TCR
– fixed capacitors
filters
and
Power Quality, Ljubljana, 2013/14 99
33
Compensation measures
• Static Var Compensator – SVC
– voltage profile improvement with SVC
Power Quality, Ljubljana, 2013/14 100
Compensation measures
• Static Var Compensator – SVC
– arc furnace performance improvement with SVC
Power Quality, Ljubljana, 2013/14 101
Compensation measures
• Static Var Compensator SVC
– practical applications
Power Quality, Ljubljana, 2013/14 102
34
Compensation measures
• Static Compensator - StatCom
– flicker and reactive power
compensation
– controllable source of reactive
current
– Voltage Sources Converter - VSC
is the main element
– employs GTO thyristors or IGBTs
– flicker reduction factor is up to 5
– not a lot of operational
experiences
– higher operational losses
compared to SVC
Power Quality, Ljubljana, 2013/14 103
Compensation measures
• Static Compensator StatCom
– single-line diagram
– VSC
– fixed capacitors
(tuned filters)
Power Quality, Ljubljana, 2013/14 104
Compensation measures
• Static Compensator – StatCom
– voltage profile improvement with StatCom
– increased power of arc furnace
Power Quality, Ljubljana, 2013/14 105
35
Compensation measures
• Static Compensator – StatCom
– substantial flicker level reduction
Power Quality, Ljubljana, 2013/14 106
Compensation measures
• Static Compensator – StatCom
– comparison of the arc furnace currents with the
compensated grid currents
Power Quality, Ljubljana, 2013/14 107
Compensation measures
• Static Compensator – StatCom
– first StatCom application for flicker mitigation – Hagfors,
Sweden (ABB commercial name SVC Light)
Power Quality, Ljubljana, 2013/14 108
36
Analysis of compensation measures
• analysis of flicker spreading in the Slovenian
power system (three arc furnaces)
– present situation – no compensation measures
12%
0%
0%
29%
33%
17%
51%
67%
71%
20%
Plt>1,5
1<Plt<1,5
0,6<Plt<1
Plt<0,6
110 kV
Plt>1,5
1<Plt<1,5
0,6<Plt<1
Plt>0,6
Plt>1,5
1<Plt<1,5
220 kV
0,6<Plt<1
Plt>0,6
400 kV
percentage of nodes
Power Quality, Ljubljana, 2013/14 109
Analysis of compensation measures
• analysis of flicker spreading in the Slovenian
power system (three arc furnaces)
– only arc furnace A is compensated (SVC)
6%
4%
0%
0%
24%
66%
Plt>1,5
1<Plt<1,5
0,6<Plt<1
Plt>1,5
Plt<0,6
110 kV
100%
1<Plt<1,5
0,6<Plt<1
Plt>0,6
Plt>1,5
100% 0,6<Plt<1
1<Plt<1,5
220 kV
Plt>0,6
400 kV
percentage of nodes
Power Quality, Ljubljana, 2013/14 110
Analysis of compensation measures
• analysis of flicker spreading in the Slovenian
power system (three arc furnaces)
– only arc furnace B is compensated (StatCom)
6%
0%
0%
16%
29%
33%
61%
17%
67%
71%
Plt>1,5
1<Plt<1,5
110 kV
0,6<Plt<1
Plt<0,6
Plt>1,5
1<Plt<1,5
0,6<Plt<1
220 kV
Plt<0,6
percentage of nodes
Plt>1,5
1<Plt<1,5
0,6<Plt<1
Plt<0,6
400 kV
Power Quality, Ljubljana, 2013/14 111
37
Analysis of compensation measures
• analysis of flicker spreading in the Slovenian
power system (three arc furnaces)
– only arc furnace C is compensated (series reactor)
12%
0%
0%
29%
33%
14%
53%
21%
Plt>1,5
1<Plt<1,5
0,6<Plt<1
Plt<0,6
67%
71%
Plt>1,5
110 kV
1<Plt<1,5
0,6<Plt<1
Plt<0,6
Plt>1,5
220 kV
1<Plt<1,5
0,6<Plt<1
Plt<0,6
400 kV
percentage of nodes
Power Quality, Ljubljana, 2013/14 112
Analysis of compensation measures
• analysis of flicker spreading in the Slovenian
power system (three arc furnaces)
– all three arc furnaces are compensated
1%
0%
0%
17%
82%
Plt>1,5
1<Plt<1,5
110 kV
0,6<Plt<1
Plt<0,6
Plt>1,5
100% 0,6<Plt<1
1<Plt<1,5
220 kV
Plt<0,6
percentage of nodes
Plt>1,5
100% 0,6<Plt<1
1<Plt<1,5
Plt<0,6
400 kV
Power Quality, Ljubljana, 2013/14 113
38