high frequency waveform distortiongrouper.ieee.org/groups/harmonic/simulate/panel...
TRANSCRIPT
1
A. Testa, Fellow Member IEEE
R. Langella, Senior Member IEEE
Second University of Naples, Italy
High Frequency Waveform Distortion:
theoretical and modeling considerations
Panel Session Harmonics from 2 kHz to 150 kHz: Immunity, Emission, Assessment and
Compatibility Denver GM2015
QUESTIONS
• Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
– Q1.1 - How do fluctuate vs time waveform RMS values at HF?
– Q1.2 - How do vary (H and IH) waveforms PEAK values with phase angles and how do fluctuate waveform PEAK values (only IH) vs time at HF?
2
QUESTIONS
• Q2 - Is it still possible to utilize simplified line models (RL, Pigrec…) at HF?
– Q2.1 - Is it needed to account for parameter (r, l, c,…) variability versus frequency at HF?
– Q2.2 - How to model lines at HF?
• Q3 - Do classical transformer models still work accurately or acceptably at HF?
3
Q1 - DOES IT MAKE SENSE TO DISTINGUISH AMONG HARMONICS AND INTERHARMONICS AT HF?
4
Q1.1 - How do fluctuate vs time waveform RMS values at HF?
5
RMS20ms: max fluctuations vs fn
6
Hz,...,,f,tfcos.tcos nnn 15000021 with 2010250212 1
1001
1
A
AAmax
n
Q1.1 - How do fluctuate vs time waveform RMS values at HF?
Q1.2 - How do vary (H and IH) waveforms PEAK values with phase angles and how do fluctuate waveform PEAK values (only IH) vs time at HF?
7
Peak values vs fn (An=1%)
8
20msT and 921 with 2010250212 w1 kHz,...,,f,tfcos.tcos nnn
Q1.2 - How do vary waveforms PEAK values…
1001
1
A
AAmax
n
1001
1
A
AAmin
n
Peak effects on Useful Life of Components
pn
pnnp kLkL
,
][
1][np
pn kEL
LE
kp time varing -> random variable
Normalized
Expected Life
Nominal
Operating
Temperature
1A
Ak p
9
Q1.2 - How do vary waveforms PEAK values…
pndepends on
component
insulation
L Values for Component Parameter np
Component np value L/Ln
0.99-np
L/Ln
1.01-np
L/Ln U~(0.99-np-
1.01-np)
film capacitors 6 1.06 0.94 1.0002
asynchronous motors
9
1.09 0.91 1.0007
transformers 11 1.12 0.90 1.0012
cables 15 1.16 0.86 1.0025
HF LF
Q1.2 - How do vary waveforms PEAK values…
Go to Case Study Q1.2
Q2 - IS IT STILL POSSIBLE TO UTILIZE SIMPLIFIED LINE MODELS (RL, PIGREC…) AT HF?
11
12
Cable and Over-Head Lines Distributed and Concentrated Parameters
Distributed Parameters model
of a finite x length line Concentrated Parameters
model of a finite x length line
short line
The resonance frequencies, fr, are located at frequencies:
Q2 – Is it still possible…
13
from
50Hz to 2.5kHz
from
2.5kHz to 9kHz
from
9kHz to 100kHz
10-2
10-1
100
101
102
10-1
100
101
102
103
104
Frequency [kHz]
/4
[km
]
2.5 kHz50 Hz9 kHz 100 kHz
1000km
30km
10km
0.75km
Cable and Over-Head Lines What does mean “short line”?
Q2 – Is it still possible…
Go to Case Study Q2
0.50km at 150kHz
Q2.1 - IS IT NEEDED TO ACCOUNT FOR PARAMETER (R, L, C,…) VARIABILITY VERSUS FREQUENCY AT HF?
14
15
0 10 20 30 40 50 60 70 80 90 1000.5
1
1.5
2
2.5
3
3.5
4
Frequency [kHz]
resis
tance [
]
0 10 20 30 40 50 60 70 80 90 1001.1
1.105
1.11
1.115
1.12
1.125
1.13
1.135
1.14
1.145
1.15x 10
-3
Frequency [kHz]
Inducta
nce [
H]
Cable and Over-Head Lines
Q2.1 – Is it needed to account for parameter (r, l, c, …)…
Go to Case Study Q2.1
Q2.2 - HOW TO MODEL LINES AT HF?
16
17
DP and P Models vs frequency
1. Coincidence of the
behaviour in the
frequency range from 0 to
2.5 kHz;
2. Difference of series
resonance frequency
values in the frequency
range from 2.5 to 9 kHz;
3. Entity of the damping
effects and the little shift
in the resonance
frequencies due to the
skin effect.
0 10 20 30 40 50 60 70 80 90 100
100
101
102
103
104
105
Frequency [kHz]
Impedence M
agnitude [
]
DP
P
DPno skin
Pno skin
Impedance Magnitude[0-100kHz]
Q2.2 – How to model lines at HF?
Positive sequence - 1 Equivalent
Q3 - DO CLASSICAL TRANSFORMER MODELS STILL WORK ACCURATELY OR ACCEPTABLY AT HF?
18
19
HF Power Transformers Model [1]
• ZH and ZL are the longitudinal impedances of high-voltage side and low-voltage side;
• Rm and Lm are the core losses;
• The capacitances CH, CL, and CHL take into account the capacitive coupling among high
frequency windings which values increase with transformer size .
[1] …….
Q3 – Do classical transformer…
20
Capacitive and Inductive Reactances vs frequency for a power Transformers (1MVA | 20/0.4kV)
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E+05
1.00E+06
1.00E+07
1.00E+08
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000 140000 150000 160000
XHL XCH Xcc
Q3 – Do classical transformer…
Go to Case Study Q3
CONCLUSION: ANSWERS (1)
• Q1 - Does it make sense to distinguish among harmonics and interharmonics at HF?
– NO! DIFFERENCES QUICKLY REDUCE INCREASING FREQUENCIES
• Q1.1 - How do fluctuate vs time waveform RMS values at HF?
– FLUCTUATIONS REACH NEGLIGIBLE VALUE BEFORE FEW kHz
21
CONCLUSION: ANSWERS (2) • Q1.2 - How do vary (H and IH) waveforms PEAK values with
phase angles and how do fluctuate waveform PEAK values (only IH) vs time at HF?
– NEGLIGIBLE VARIATIONS STARTING FROM FEW kHz (VALUES DEPEND ON H OR IH AMPLITUDE). ALWAYS MAX PEAK VALUES TO BE EXPECTED!
– LIMITS FOR HF COMPONENTS SHOULD TAKE CARE OF PEAK RELATED EFFECTS
22
– THEY STILL FLUCTUATE. AT FREQUENSIES THAT CAN BE VERY LOW (99990 Hz GIVES THE SAME FLUCTUATION FREQUENCY (10 HZ) OF 90 Hz). FLUCTUATION AMPLITUDES ARE NEGLIGIBLE STARTING FROM FEW kHz.
CONCLUSION: ANSWERS
• Q2 - Is it still possible to utilize simplified line models (RL, Pigrec…) at HF?
– NO!
• Q2.1 - Is it needed to account for parameter (r, l, c,…) variability versus frequency at HF?
– YES, IT IS!
• Q2.2 - How to model lines at HF?
– BY MEANS OF DISTRIBUTED PARAMETER OR MULTIPLE-P MODELS
23
CONCLUSION: ANSWERS
• Q3 - Do classical transformer models still work accurately or acceptably at HF?
– NO! MODELS ACCOUNTING FOR CAPACITIVE COUPLING ARE STRICTLY NEEDED: HF PROPAGATION TROUGH TRANSFORMERS CANNOT BE EXCLUDED!
24
25
Thank you for your attention!
Alfredo Testa: [email protected]
Roberto Langella: [email protected]
26
Q1 - DOES IT MAKE SENSE TO DISTINGUISH AMONG HARMONICS AND INTERHARMONICS AT HF?
27
H and IH: Nomenclature (1)
28
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
H and IH: Nomenclature: RMS (2)
29
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
H and IH: Nomenclature: Peak (3)
30
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
H and IH: Nomenclature: Peak (4)
31
nAAAmaxn
1
ˆˆ with HFfor ˆˆ
ˆˆ with MFfor ˆcosˆ
ˆˆ with LFfor ˆˆ
ˆmin
11
11
1
11
nn
nn
n
nn
AAAA
AAAA
AAAA
An
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
Go to Case Study Q1
Definitions
• Frequency ranges
– From 0 to 2 kHz (IEC)
– From 2 to 9 kHz (IEC Annex)
– From 9 to 150 kHz (?????)
• DC
• Subharmonics
• Harmonics
• Interharmonics
32
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
1/10 Go to Q1.1
Effects
• Thermal stress (RMS)
• Electric stress (PEAK)
• Components and Equipment Sensitivity
– Thermal stress depends on time constant
• Lamps t ~ 10 ms
• …….
• Cables t ~ hours
33
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
2/10 Go to Q1.1
Time window Tw
• Tw=TF = Fourier fundamental period
• Tw=10 ms
• Tw=20 ms
• Tw=200 ms
34
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
3/10 Go to Q1.1
RMS variability with frequency • ATF
(f)= const.
• ATW (f,phi,t,TW)=> oscillates between MIN and
MAX
– For harmonics RMS_TW = const.
– For interharmonics
• RMS_TW (f,phi,t,TW) for lower frequencies with a reducing sensitivity for higher TW (eg 200ms)
• RMS_TW = const. for higher frequencies
35
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
4/10 Go to Q1.1
PEAK variability with frequency • ÂTF
(f,phi)
– PEAK_TW (f,phi) for lower frequencies
– PEAK_TW =const. for higher frequencies
• PEAK_TW (f,phi,t)=> oscillates between MIN and MAX
– For harmonics and interharmonics PEAK_TW =const. for lower frequencies (in a range function of An)
– For harmonics and interharmonics PEAK_TW = const. for higher frequencies
36
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
5/10 Go to Q1.1
37
Time fluctuations 0402102050212 tcos.tcos
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
6/10 Go to Q1.1
38
Time fluctuations: Rms
0402102050212 tcos.tcos
20ms
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
8/10 Go to Q1.1
39
Time fluctuations: Peak
0402102050212 tcos.tcos
maxÂ
minÂ
40
Time fluctuations: Rms
0402102050212 tcos.tcos
20ms
0402102050212 tcos.tcos
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
9/10 Go to Q1.1
41
0402102050212 tcos.tcos
A20ms(k20ms)
maxA20ms
minA20ms
A20ms(t)
A
Q1 - does it make sense to distinguish among harmonics and interharmonics at HF?
Time fluctuations: Rms
10/10 Go to Q1.1
Q1.1 - How do fluctuate vs time waveform RMS values at HF?
42
RMSTF: max fluctuations vs fn
43
Hz,...,,f,tfcos.tcos nnn 15000021 with 2010250212 1
1001
1
A
AAmax
n
Q1.1 - How do fluctuate vs time waveform RMS values at HF?
RMS200ms: max fluctuations vs fn
44
Hz,...,,f,tfcos.tcos nnn 15000021 with 2010250212 1
1001
1
A
AAmax
n
Q1.1 - How do fluctuate vs time waveform RMS values at HF?
Go to Case Study Q1.1
RMS10ms: max fluctuations vs fn
45
Hz,...,,f,tfcos.tcos nnn 15000021 with 2010250212 1
1001
1
A
AAmax
n
Q1.1 - How do fluctuate vs time waveform RMS values at HF?
1/3 Go to Q1.2
46
Hz,...,,f,tfcos.tcos nnn 15000021 with 2010250212 1
RMS20ms: max fluctuations vs fn
1001
1
A
AAmax
n
Q1.1 - How do fluctuate vs time waveform RMS values at HF?
2/3 Go to Q1.2
47
Hz,...,,f,tfcos.tcos nnn 15000021 with 2010250212 1
RMS200ms: max fluctuations vs fn
1001
1
A
AAmax
n
Q1.1 - How do fluctuate vs time waveform RMS values at HF?
3/3 Go to Q1.2
Q1.2 - How do vary (H and IH) waveforms PEAK values with phase angles and how do fluctuate waveform PEAK values (only IH) vs time at HF?
48
49
20msT and 921 with 20010250212 w1 kHz,...,,f,tfcos.tcos nnn
Peak fluctuations vs fn (An=1o/oo)
1001
1
A
AAmax
n
1001
1
A
AAmin
n
Q1.2 - How do vary waveforms PEAK values…
Peak fluctuations vs fn (An=1%)
50
20msT and 921 with 2010250212 w1 kHz,...,,f,tfcos.tcos nnn
1001
1
A
AAmax
n
1001
1
A
AAmin
n
Q1.2 - How do vary waveforms PEAK values…
51
20msT and 921 with 210250212 w1 kHz,...,,f,tfcos.tcos nnn
Peak fluctuations vs fn (An=10%)
1001
1
A
AAmax
n
1001
1
A
AAmin
n
Q1.2 - How do vary waveforms PEAK values…
Peak fluctuations
52
0402102050212 tcos.tcos
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 -1.5
-1
-0.5
0
0.5
1
1.5
time [s]
sig
na
l
Amaxn
Aminn
Q1.2 - How do vary waveforms PEAK values…
1/7 Go to Q2
Peak fluctuations
53
089402102050212 tcos.tcos
AmaxAmin
Q1.2 - How do vary waveforms PEAK values…
2/7 Go to Q2
Peak fluctuations vs n (LF)
54
tcos.tcos 30020102050212 030020102050212 tcos.tcos
Q1.2 - How do vary waveforms PEAK values…
3/7 Go to Q2
55
Approximated Min Peak
(pu)009510105000
50001 ..cos.
tcos.tcos 500020102050212
ih
ih
Af
fcosA 22 1
1
Peak fluctuations vs n (HF) Q1.2 - How do vary waveforms PEAK values…
4/7 Go to Q2
56
Approximated Min Peak
ih
ih
Af
fcosA 22 1
1
tcos.tcos 900020102050212
(pu)0110109000
50001 ..cos.
Corresponds to Algebric
Max Peak
Peak fluctuations (HF) Q1.2 - How do vary waveforms PEAK values…
5/7 Go to Q2
57
20msT and 921 with 025022010250212 w1 kHz,...,,f,tcostfcos.tcos nnn
Peak fluctuations vs fn (An=1% mod)
Q1.2 - How do vary waveforms PEAK values…
6/7 Go to Q2
Peak fluctuations
58
tcos.tcos 900020102050212
,tcostcos.
tcos
2502900020102
050212
Q1.2 - How do vary waveforms PEAK values…
7/7 Go to Q2
Q2 - IS IT STILL POSSIBLE TO UTILIZE SIMPLIFIED LINE MODELS (RL, PIGREC…) AT HF?
59
60
1. Coincidence of the
behaviour of the two
different models in the
frequency range from 0 to
2.5 kHz;
2. Difference of series
resonance frequency
values for the two models
in the frequency range
from 2.5 to 9 kHz;
3. Entity of the damping
effects and the little shift
in the resonance
frequencies due to the
skin effect.
DP and P Models vs frequency
Impedance Magnitude[0-9kHz]
0 1 2 3 4 5 6 7 8 910
0
101
102
103
104
105
Frequency [kHz]
Impedence M
agnitude [
]
DP
P
DPno skin
Pno skin
2.5:9kHz
Positive sequence - 1 Equivalent
Q2.2 – How to model lines at HF?
2/4 Go to Q2.1 Go to Q2.2 Go to Q3
61
0 10 20 30 40 50 60 70 80 90 10010
1
102
103
104
105
Frequency [kHz]
Impedence M
agnitude [
]
DP
P
More resonances (18)
in respect to positive
sequence (13) from 0 to
100 kHz due to the LC
product which value
increases in zero
sequence.
More sensible damping
effects.
The zoom evidencies
once again the
criticality of one P over
2.5kHz
DP and P Models vs frequency Impedance Magnitude[0-100kHz]
Q2.2 – How to model lines at HF?
Zero sequence - 1 Equivalent
62
More resonances (18)
in respect to positive
sequence (13) from 0 to
100 kHz due to the LC
product which value
increases in zero
sequence.
More sensible damping
effects.
0 1 2 3 4 5 6 7 8 910
1
102
103
104
105
Frequency [kHz]
Impedence M
agnitude [
]
DP
P
The zoom evidencies
once again the
criticality of one P over
2.5kHz
DP and P Models vs frequency Impedance Magnitude[0-9kHz]
Zero sequence - 1 Equivalent
Q2.2 – How to model lines at HF?
Go to Case Study Q2.2
63
1. It is well known that under the hypotheses of
transposed lines disposed in a simmetrical
manner, a three-phase line can be represented
by a single-phase equivalent circuit.
2. For a finite length x line a succession of series
and parallel resonances of impedance equally
spaced in the frequency appears.
3. Tipically, for short lines, with length x less than
/4, reference is made to concentrated
parameter models.
Distributed Parameters Model of a
infinitesimal length dx line element
Model of a line based on a single P
equivalent
1/4 Go to Q2.1 Go to Q2.2 Go to Q3
Q2 – Is it still possible…
Q2.2 – How to model lines at HF?
Q2.1 – Is it needed…
64
CASE-STUDY
Wind turbine of 100 kW rated power connected to the MV network (20 kV) by
means of a 10 km length over-head line.
Full-power static converter with a switching frequency of 22.6 kHz
Simulations have been performed using either P and Distributed
Parameter models, both built-in in the EMTP-RV library.
2/4 Go to Q2.1 Go to Q2.2 Go to Q3
Q2 – Is it still possible…
Q2.2 – How to model lines at HF?
Q2.1 – Is it needed…
65
CASE-STUDY(2)
Using P equivalent,
the single harmonic
components around
the switching
frequency of 22.6 kHz,
appear lower than the
compatibility levels
(0.27 %) for harmonic
voltages.
Voltage measured at wind turbine terminals using P equivalent
(a1, b1), 50 P equivalents in cascade (a2, b2) and Distributed
Parameter (a3, b3) models not considering the skin effect: a) time
waveforms; b) spectra.
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02-20
0
20
time [s]V
oltage [
kV
]
a1
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02-20
0
20
time [s]
Voltage [
kV
]
a2
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02-20
0
20
time [s]
Voltage [
kV
]
a3
22 22.2 22.4 22.6 22.8 23 23.20
1
2
frequency [kHz]
Voltage [
%]
b1
22 22.2 22.4 22.6 22.8 23 23.20
1
2
frequency [kHz]
Voltage [
%]
b2
22 22.2 22.4 22.6 22.8 23 23.20
1
2
frequency [kHz]
Voltage [
%]
b3
P
DP
P50
P
DP
P50
3/4 Go to Q2.1 Go to Q2.2 Go to Q3
Q2 – Is it still possible…
Q2.2 – How to model lines at HF?
Q2.1 – Is it needed…
66
22 22.2 22.4 22.6 22.8 23 23.20
0.1
0.2
frequency [kHz]
Curr
ent
[%]
b1
22 22.2 22.4 22.6 22.8 23 23.20
0.1
0.2
frequency [kHz]
Curr
ent
[%]
b2
22 22.2 22.4 22.6 22.8 23 23.20
0.1
0.2
frequency [kHz]
Curr
ent
[%]
b3
22 22.2 22.4 22.6 22.8 23 23.20
1
2
frequency [kHz]
Voltage [
%]
b1
22 22.2 22.4 22.6 22.8 23 23.20
1
2
frequency [kHz]
Voltage [
%]
b2
22 22.2 22.4 22.6 22.8 23 23.20
1
2
frequency [kHz]
Voltage [
%]
b3
P
DP
P50
P
DP
P50
Voltage Distortion Current Distortion
CASE-STUDY(3)
4/4 Go to Q2.1 Go to Q2.2 Go to Q3
Q2 – Is it still possible…
Q2.2 – How to model lines at HF?
Q2.1 – Is it needed…
Q3 - DO CLASSICAL TRANSFORMER MODELS STILL WORK ACCURATELY OR ACCEPTABLY AT HF?
67
68
Power Transformers Calculation Parameters
This informations is usually available for any
transformer:
• Power rating (S); Voltage ratings (Vp, Vs); Excitation
current (Iexc); Excitation voltage (Vexc);Excitation losses
(Pexc); Short-circuit current (Ish); Short-circuit voltage
(Vsh); Short-circuit losses (Psh).
a is the percentage of the
resistance to be placed at the high-
voltage (HV) side and is the turn
ratio.
Resistances Total leakage reactance
Q3 – Do classical transformer…
1/5 Go to Conclusion
69
Power Transformers Calculation Parameters: Inductance
- For concentric winding designs, the inner winding has smaller reactance
than the outer winding, and most often, the inner winding is the lower-
voltage winding.
- When the core saturates, the division between primary and secondary inductance,
can provide wrong results. The following default assumptions can be made for
leakage split: 1. Assumes concentric winding with HV side as outer;
2. Put most leakage impedance on the HV side, 75%–90% of total
inductance as LH:
3. Adjust the slope of the saturation curve, so that (LM + LH)
became a reasonable estimate of (0.3 to 0.8 pu. on self-cooled
base for large, high BIL transformers; 0.05 to 0.15 pu. for
distribution transformers).
Q3 – Do classical transformer…
2/5 Go to Conclusion
70
Power Transformers Calculation Parameters: magnetizing components
Saturation can be incorporated into the magnetizing inductance of a power
transformer model using test data/manufacturer’s curves. In this case several
factors are to be taken into account:
1. The exciting current includes core loss and magnetizing
components;
2. Manufacturers usually provide root-mean-square (rms)
currents, not crest. Winding capacitance can significantly affect
low current data;
3. Hysteresis biases saturation curve . CORE LOSSES
Q3 – Do classical transformer…
3/5 Go to Conclusion
71
Power Transformers Calculation Parameters: Capacitances
Disk windings Helical windings
e0 dielectric permittivity of vacuum;
et relative dielectric permittivity of the insulating material that
covers the conductor;
ed relative dielectric permittivity of the insulating
material between disks;
D average diameter of the winding;
h height of the conductor strip;
dt thickness of the insulation covering the conductor;
dd thickness of the insulation between the discs;
N winding sections;
n number of turns per section;
r thickness of the disk.
d distance between turns;
d0'=d0+d with d0 the outer diameter;
di'= di+d with di the inner diameter;
nt numbers of turns.
Q3 – Do classical transformer…
4/5 Go to Conclusion
72
Power Transformers Calculation Parameters: Capacitances
e relative dielectric permittivity of the intervening
medium;
re internal radius of the external coil;
ri internal radius of the inner coil;
b axial distance between coils;
d diameter of the coil.
Concentric windings Different windings
Q3 – Do classical transformer…
5/5 Go to Conclusion
RMS and Peak Fluctuation frequency
fn=149990 Hz gives fF=10 Hz as fn=90 Hz
73
90 Hz
149990 Hz