Ac harmonic filters -...

38
Ac harmonic filters

Transcript of Ac harmonic filters -...

Ac harmonic filters

FILTER

FILTER

HVDC Main Components

T8396

AC Harmonic Filters

� 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

Idealised Current Waveforms….

T8397

Combined Waveform…..

T8399

12 Pulse

Practical Harmonic Currents….

T8402

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

100

10

1.0

0.1

0.01

0.00110 20 30 40 50

Harmonic Number

In

I1%

Typical Spectrum…

T8409

� 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

Filter

Zfn

System

ZSnIcn

Ifn

VSn

ISn

T8378

Rmin

X(O

hm

s)

R(Ohms)

400kV System Harmonic Impedance

T8381

Rmax

2

Sasaram Filters

T8379

400kV

Double Damped

Filter

400kV

Double Tuned Filter

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.

AC Filter Layouts Double Damped Filter

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

f1 f0 f2 Frequency

High Q

Low Q

Y

Effect of De-tuning

T8414

� 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

Tuned / Damped Filters

f1 f0 f2 Frequency

Damped filter

Tuned filter

Filter admittance

T8417

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

Double Tuned Double Tuned

Double Tuned Filters

T8423

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

Main Capacitor

Corona Rings

Base Insulators

Horizontal Mounted

Cans

LV Terminal

HV Terminal

Auxiliary Capacitor

Base Insulators

Steel Frames

HV terminal

LV terminal

Reactors

Spiders

Terminal

Coil

Base

Insulators

Pedestals

Resistors

Roof

Base

Insulators

Bushings

Thank You