ac harmonic filters -...
Post on 23-May-2018
235 Views
Preview:
TRANSCRIPT
� Idealised harmonic currents
� Practical harmonic currents
� Characteristic harmonics
� Theoretically cancelled harmonics
� Non-characteristic harmonics
Types of Harmonic
T8395
Filter Design Objectives
�Limit voltage distortion
�Minimise reactive power imbalance
�Minimise losses
�Improve system performance
� Idealised harmonic currents
� Practical harmonic currents
� Characteristic harmonics
� Theoretically cancelled harmonics
� Non-characteristic harmonics
Types of Harmonic
T8395
λ λ
πω ω ω ω ω
λ
πω ω ω ω ω
/
(cos cos cos cos cos ...
/
(cos cos cos cos cos ...
I ID
t t t t t
I ID
t t t t t
= − + − +
= + − + −
2 3 1
55
1
77
1
1111
1
1313
2 3 1
55
1
77
1
1111
1
1313
∆
Fourier Analysis
T8398
I ID
t t t
t t
= − +
− +
4 3 1
1 11 1
1
1 31 3
1
2 32 3
1
2 52 5
πω ω ω
ω ω
( c o s c o s c o s
c o s c o s . . .
Fourier Analysis
T8400
9
8
7
6
5
4
3
2
1
10 3020 40Overlap angle (degrees)
I11
I1
11th Harmonic as a Percentage of Fundamental
T8404
0.2 0.4 0.6 0.8 1.0
1
2
3
4
5
Harm
onic
lin
e c
urr
ent %
of
rate
d fundam
enta
l
Transmitted power (PU)
11th
13th
Characteristic Harmonic Generation
T8405
0.5
0.4
0.3
0.2
0.1
0.2 0.4 0.6 0.8 1.0
5th
7th
Transmitted Power(PU)
Harm
onic
lin
e c
urr
ent %
of
rate
d fundam
enta
l
Theoretically Cancelled Harmonic Generation
T8407
� Orders n = 1, 2, 3, 4 etc.
� AC system unbalance (NPS)
� Transformer reactance phase unbalance
� Pre-existing distortion
� firing angle jitter
Non - Characteristic Harmonics
T8408
AC Filter Layouts…
� Components mounted on the ground
� Insulation and magnetic clearances
� Two types of harmonic filter
� Double damped filter
� Double tuned filter
� Key Interlocking System for safety - to permit access only when filter is de-energised and earthed.
Admittance vs frequency for 400kV 112Mvar 3/13 double frequency filter
0.0000
0.0050
0.0100
0.0150
0.0200
0.0250
0.0300
0.0350
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54
Harm onic
Adm
itance
3/13th Double-Frequency Filter
Admittance vs frequency for 400kV 112Mvar 11/25 double frequency filter
0.0000
0.0050
0.0100
0.0150
0.0200
0.0250
0.0300
0.0350
0.0400
0.0450
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54
Harm onic
Adm
itance
11/25th Double-Frequency Filter
Single frequencytuned filter
2nd Order broadband
damped filter
3rd Order broadband
damped filter
‘C’ Type broadband
damped filter
Types of Filter
T8412
� Advantages
� Maximum attenuation at single harmonic
� Low loss
� Disadvantages
� May be de-tuned
� Off-circuit adjustment
Single Tuned
T8413
� Advantages
� Attenuation over a spectrum of harmonics
� Less sensitive to de-tuning
� Disadvantages
� Needs higher Mvar to achieve same performance as single tuned
� Additional losses in resistor
2nd Order Damped
T8416
Single frequency
tuned filter
2nd Order
broadband
damped filter
3rd Order
broadband
damped filter
‘C’ Type
broadband
damped filter
Types of Filter
T8418
� Advantages
� Lower losses in resistor
� Disadvantages
� Poorer performance than 2nd order
� Additional cost of capacitor
3rd Order Damped
T8419
� Advantages
� lower losses in resistor
� Better performance than 3rd order
� Disadvantages
� Poorer performance than 2nd order
� Additional cost of capacitor
� May require off-circuit adjustment
C - Type
T8421
� Advantages
� Only one HV capacitor bank
� Only one reactor subject to HV tests
� Reduced number of filter arms
� No minimum size
� Improved redundancy
� Low fundamental losses (double tuned)
Multiple Tuned Filters
T8422
0.03
0.02
0.01
0
-0.01
0 10 20 30 40 50
Harmonic
Adm
itta
nce (m
hos)
G
B
Admittance Characteristic(G= conductance, B= susceptance)
T1774
top related