B Zero Sequence Filters N A B C For Harmonic Mitigation C ...apic/uploads/Forum/poster3.pdf · Zero Sequence Filters For Harmonic Mitigation Tyrone Ding, Pooya Bagheri [email protected],

Zero Sequence Filters For Harmonic Mitigation

Tyrone Ding, Pooya Bagheri [email protected], [email protected]

The proliferation of the energy-efficient consumer electronic

appliances in modern households has resulted in significant voltage

and current waveform distortions in residential distribution systems.

Although each of the consumer electronic appliance is not individually

a big source of harmonics, the collective effect will be considerable and

can become a serious concern of utility companies.

Due to the fact that most of residential loads are single-phase, Zero-

Sequence (ZS) harmonics are expected to be created at the three phase

distribution feeders feeding them. High levels of ZS harmonics could

lead to neutral voltage/current raise and interference problems with the

adjacent telephone lines. Therefore, the ZS harmonics must be

considered when researching the harmonic mitigation solutions for

modern residential feeders.

Introduction

Traditional ZS Filters

Power and Energy Innovation Forum ♦ University of Alberta ♦ November 2013

Zero Sequence Frequency Scan of Designed Filters

A B C

A B C A B C

(a) Star-type (b) Star-type including a

three-phase inductor

(c) Zig-zag

transformer-based

The main drawbacks of traditional ZS filters are:

• The star-type (a) and (b) can affect the fundamental power flow and

may lead to positive or negative sequence resonances at other

frequencies.

• The zig-zag transformer-based type needs a nonstandard

transformer.

Transformer-based ZS Filters

Here the transformer-based ZS filters is developed from the concept

of grounding transformer. Such filters behave as an open circuit at

positive and negative sequences so it has no impact on normal power

system operation and non-zero-sequence harmonics.

C

A

B

C

N

A

B

C

N

(a) Single-tuned

Expanding the filter

configuration to trap two

harmonic orders with

just one transformer

(b) Double-tuned

Expanding the filter

configuration to trap

three harmonic orders

with just one transformer

A

B

C

N

(c) Three-tuned

C3

L1

C1

C2 L2

C2 L2

C1

Telephone Interference Mitigation Case Study

The 240/25 kV

Substation

Downstream

loads

Upstream

loads

Filter Location

Telephone line

sections Monitoring

Location

F

Transformer Size 75 kVA

Single-tuned

version C 10.29kVar

Double-tuned

version

C1 7.00kVar

C2 24.60kVar

L2 40.60µH

Three-tuned

version

C1 16.46kVar

C2 11.57kVar

C3 10.29kVar

L1 206.35µH

L2 293.35µH

3rd 5th 7th 9th 11th 13th 15th0

2

4

6

8

IDD

(%)

Simulation Results

No Filter

Single-tuned filter

Double-tuned filter

Three-tuned filter

The single-tuned filter is tuned to filter 9th harmonic, double-tuned filter

is tuned to filter 9th and 15th harmonics and three-tuned filter is tuned to

filter 3rd, 9th and 15th harmonics.

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 300

1000

2000

3000

4000

5000

Harmonic Order

Zero

Seq

uen

ce I

mp

ed

an

ce (

)

Single-tuned

Double-tuned

Three-tuned

Key Design Procedures

Substation

A block of residential loads

(e.g. a neighbourhood)

Filt

er

Normal Harmonic flow

New harmonic flows

after the filter is installed

• Determine ZS filter installation location.

• Assess transformer loading level.

Both of these two key design procedures are based on the harmonic

flow study of the problematic feeder.