Harmonic levels in LV networks and methodology for assessing the impact

of new equipment

Panel on New Harmonic Sources in Modern Buildings: Characterization and Modeling

14PESGM1020

1

Jan Meyer Ana Maria Blanco

Max Domagk Technische Universitaet Dresden, Germany

2

Agenda

• Background

• Characterization and impact of new equipment

− Compact fluorescent lamps (CFL)

− Electrical vehicle chargers (EVC)

− Impact of circuit topopolgy changes

• Survey of harmonic levels in public LV grids

− Framework of the survey

− Some analysis results (3rd harmonic, 5th harmonic)

− Historical trend

3

Below 2 kHz Harmonics

(Linked to power frequency)

Above 2 kHz (up to 150 kHz) HF emission/supraharmonics

(Independent of power frequency)

● Devices with nonlinear i/u characteristic

● Simple electronic devices (line-commutated, e.g. no PFC)

● Mains signalling

Compact fluorescent lamp (P < 25 W) Compact fluorescent lamp (P > 25 W)

● Energyefficient circuit topologies, like active PFC

● Narrowband Power Line Communication

0 30 60 90 120 150 180-100

0

100

200

300

400

500

i(t) /

mA

angle / °

i(t)

t 20 22 24 26 28 30-50

0

50

100

150

200

250

i(t) /

mA

t / ms

i(t)

t

Types of Distortion

4

0 2.5 5 7.5 10-0.5

0

0.5

1

1.5

2

2.5

3

3.5

t / ms

i(t)

/ A

-0.2 -0.1 0 0.1 0.2-0.2

-0.1

0

0.1

0.2

Re(I5)/A

Im(I

5)/

A

(5) (5)

1 2(5)

p (5) (5)

1 2

I Ik 1

I I

0,131A1 0,57

0,307 A

Time domain (Halfwave)

Frequency domain (5. Harmonics)

Phase diversity index:

Computer power supply (P > 75 W) and notebook charger (P < 75 W)

Different circuit topologies have different behavior (passive power factor correction pPFC, no power factor correction nPFC)

(5)1I 0,172 A(5)gesI 0,131A

(5)2I 0,135 A

Cancellation effect:

(5)

1I

(5)

2I

(5)

gesI

Harmonic phase angle and phase diversity

Do prevailing phase angles exist for electronic mass-market equipment ?

5

Agenda

• Background

• Characterization and impact of new equipment

− Compact fluorescent lamps (CFL)

− Electrical vehicle chargers (EVC)

− Impact of circuit topopolgy changes

• Survey of harmonic levels in public LV grids

− Framework of the survey

− Some analysis results (3rd harmonic, 5th harmonic)

− Historical trend

100

200

300

400

30

210

60

240

90

270

120

300

150

330

180 0

5th Harmonic Current mA

CFL nPFC

pPFC

6

Characterisation of equipment

• Manufacturers prefer specific circuit topologies as consequence of given standards (e.g. 61000-3-2)

• Different topologies have different prevailing harmonic phase angles

• Effective cancellation for 5th harmonic, but less efficient for 3rd harmonic)

• Efficiency of cancellation depends on mix of equipment (circuit topologies)

5th current harmonic

228 electronic mass-market devices

Is it possible to identify dominating technologies by grid measurments ?

(5)p

k 0,78

Lighting 25 W Lighting > 25 W Other equipment 25 W Other equipment > 75 W

(3)p

k 0,44

7

Equipment Harmonic Database

Web-based platform for exchanging measurements of harmonic emission of single phase equipment

http://panda.et.tu-dresden.de

More than 10 labs from all over the world

More than 500 different devices

8

Field study - customer terminal (CFL)

• ON/OFF comparison for switching CFLs and ISLs (incandescent lamps): Similar magnitudes (210mA), but different phase angles (-40°-> 148°)

• Identification of connected equipment based on harmonic phase angle seems to be possible

-300 -150 0 150 300-300

-150

0

150

300

Ireal

/ mA

I ima

g /

mA

o – OFF¡ - ON

ISLCFL

Preferential phase angle for CFL

5th harmonic current

0 45 90 135 180-2

0

2

4

6

8

Winkel / °

i(t)

/ A

Waveform

CFLs OFF CFLs ON

9

Field study - LV feeder (EV charging)

• 10 single family houses

• 10 electrical vehicles (EV) of 4 different brands

• Coordinated ON/OFF switching of all EVs in one phase

Measurement up to 150 kHz

Measurement up to 2.5 kHz

Transformer

Junction box

Feeder end

10

LV feeder study – Individual current harmonics

• Low emission of households in 4th quadrant

• Similar 5th harmonic phase angle for different EV types in the 3rd quadrant (About 90°phase difference to typical household emission)

5th harmonic

Electrical vehicles

5th harmonic

Sum of households

Type A

Type B

Type C

Type D

Phase angle change from 4th to 3rd quadrant is expected, when cars are connected

11

LV feeder study – Total harmonic current

1

2

3

4

5

30

210

60

240

90

270

120

300

150

330

180 0

5th Harmonic Current (A) at D 5th Harmonic Voltage (V) at D

5

10

30

210

60

240

90

270

120

300

150

330

180 0

Switch On

Switch Off

2

4

6

8

10

30

210

60

240

90

270

120

300

150

330

180 0

3rd Harmonic Current (A) at D 3rd Harmonic Voltage (V) in D

2

4

30

210

60

240

90

270

120

300

150

330

180 0

Switch On

Switch Off

5th harmonic

at junction box

3rd harmonic

at junction box

Switching ON Switching OFF

• 5th harmonic current shifts phase (considerable diversity between households and EVs)

• 3rd harmonic current does not shift phase (almost no diversity between households and EVs)

-350 -175 0 175 350-350

-175

0

175

350

Ireal / mA

I im

ag /

mA CFL

• Most effective cancellation for CFLs in combination with passive PFC equipment

• Virtually no cancellation effect for 5th harmonic by active PFC equipment

5th harmonic current

No PFC (past) Passive PFC (today) Active PFC (future)

Cancellation effect

0 5 10 15 20 25

0.4

0.5

0.6

0.7

0.8

0.9

1

number CFL k

p(5)

Impact of technology changes

13

Agenda

• Background

• Characterization and impact of new equipment

− Compact fluorescent lamps (CFL)

− Electrical vehicle chargers (EVC)

• Survey of harmonic levels in public LV grids

− Framework of the survey

− Some analysis results (3rd harmonic, 5th harmonic)

14

Total harmonic emission of a LV grid

• Distinctive clouds represent a non-random behavior with a prevailing direction

• Location of prevailing direction may indicate dominating equipment mix (this case: nPFC and pPFC devices)

• Increasing number of CFLs or EVs could slightly reduce the 5th current harmonic

• „Balance“ between the different types of equipment is essential

5th current harmonic of a residential grid

Is this result representative for other LV grids ?

-30 -15 0 15 30-30

-15

0

15

30

Ireal

/ A

I ima

g /

A

-10 -5 0 5 10-10

-5

0

5

10

Ireal

/ A

I ima

g /

A

nPFC

pPFC

CFL

L1 L2 L3

15

Improvement of vizualisation

• Color-dependent density charts (2-D histogram)

• Improvement for explorative analysis (more information is revealed)

• BUT, processing of many sites requires further reduction of data amount and respective assessment indizes

3th current harmonic of a residential grid

16

Assessment indices (2 stage procedure)

2

( )

( ) 1

nh

ih i

V

I

In

( ) ( ) ( ) ( )

1

nh h h h

VEC VECVEC i

i

I I I

( )

1( )

( )

1

1

nh

i

ih

nh

i

i

I

VR

I

(B) Prevailing vector IV (only useful in case of low diversity):

(A) Variation ratio (diversity index) :

( ) ( )h h

V VEC

Magnitude

Angle

• Calculation of vector sum

• Measure for level of diversity (significance of prevailance)

• Opposite to prevailing ratio

• High value -> no prevailing direction

• Low value -> prevailing direction

17

Range of diversity index

5

10

15

30°

210°

60°

240°

90°

270°

120°

300°

150°

330°

180° 0°

5

10

15

30°

210°

60°

240°

90°

270°

120°

300°

150°

330°

180° 0°

5

10

15

30°

210°

60°

240°

90°

270°

120°

300°

150°

330°

180° 0°

Low diversity Medium diversity High diversity

10.20

43

0.022

V

V

I A

VF

10.20

84

0.3

V

V

I A

VF

10.20

19

0.8

V

V

I A

VF

Very low diversity (VL) VF 0,05

Low diversity (L) 0,05 < VF 0,11

Medium diversity (M) 0,11 < VF 0,2

High diversity (H) VF > 0,2

Prevailing vector meaningful

18

Headoffice of network operators

Systematic survey in Germany

More than 30 network operators

More than 150 sites

Comparability

Duration: 14 days

Interval: 1 minute

Location: MS/NS-substation (LV busbar)

Same type of monitors

Classification of sites acc. to:

Consumer topology (4 classes)

Generation topology (4 classes)

Grid topology (3 classes)

Survey on harmonic behavior of public LV grids

19

• Classification based on topology classes and priorisation according to the expected impact on harmonic levels

High priority: Consumer topology A1: Single family houses (small, medium, large) A2: Multi family houses (small, medium, large) A3: Shopping A4: Office A5: Special consumer

Medium priority: Generation topology E1: No generation E2: Generation smaller than 10% Sr E3: Generation between 10% Sr and 50% Sr E4: Generation larger than 50% Sr

Low priority: Network topology N1: Total length of lines smaller 800m N2: Total length of lines between 800m and 1600m N3: Total length of lines larger than 1600m

• 96 possible combinations

• Preference on grids with „pure“ consumer topologies A1 to A4

Network classification schema

20

c.d

.f.

Number

Coverage of consumer topologies

• Major focus on grids with residential customers

• Good representation of different grid sizes

Distribution of customer number per grid for SFH

Distribution of sites for consumer topology

A1: SFH A2: MFH A3: Shopping A4: Office

21

0%

20%

40%

60%

80%

100%

A1 A2 A3 A4

H

W

L

VL

0%

20%

40%

60%

80%

100%

A1 A2 A3 A4

H

W

L

VL

Variation ratio of all sites

• Most residential grids show clear prevailing phase angles.

• Higher probability of larger variations for shopping and office

3rd harmonic

5th harmonic

M

M

22

3rd harmonic (SFH)

3rd harmonic (Offices)

3rd harmonic (Shopping)

Prevailing 3rd harmonic vectors

• Residential: Small variation

• Office and Shopping: Higher variation between sites

• Virtually no impact of generation and network topology observed

• No prevailing phase angles in 1st quadrant

23

Prevailing 5th harmonic vector

• Residential: Small variation; no dominance of CFLs

• Office and Shopping: Higher variation; Dominating number of measurements in 2nd quadrant

• Virtually no impact of generation and network topology observed

5th harmonic (SFH)

5th harmonic (Offices)

5th harmonic (Shopping)

25

0 5 10 15 20 25 30 35 40 450

10

20

30

40

50

60

70

IV

3 in A

I S3

in

A

0 5 10 15 20 25 30 350

5

10

15

20

25

30

35

40

IV

5 in A

I S5

in

A

Some further data analytics (2)

Span vs. average current 95-%-percentile vs. average current

0 5 10 15 20 25 30 35 40 450

10

20

30

40

50

60

70

IV

3 in A

I 95

3

in

A

0 5 10 15 20 25 30 350

5

10

15

20

25

30

35

40

IV

5 in A I 9

5

5

in

A

A1 A2 A3 A4

• Span vs. average significantly higher for shopping (1,5) compared to residential topologies (0,3 .. 0,6)

• No distinctive evening peak for 5th harmonic current in many residential grids (95-%-perc./average ratio about 1,2)

26

• Measurement on Saturdays in 1999 and 2010 for 2 loading states:

No changes in consumer or network topology (350 residential customers in multi family houses)

Magnitude: Decrease of 5th harmonic, but increase of 3rd harmonic

Phase angle: Shift indicates possible increase of passive PFC equipment (technology change)

3rd harmonic current 5th harmonic current

-20 -10 0 10 20-20

-10

0

10

20

Ireal

/ A

I ima

g /

A

o - 1999¡ - 2010MorningEvening

passive PFC

no

PFC

CFL

-10 -5 0 5 10-10

-5

0

5

10

Ireal

/ A

I ima

g /

A

o - 1999

¡ - 2010

Morning

Evening

passive PFC

no

PFC

CFL

Historical data

27

• Present management for 5th harmonic seems to be more effective than for 3rd harmonic

• Different circuit topologies and their share have to be considered in modelling studies

• Emission of equipment considerably changes with changing voltage distortion, especially for active PFC equipment and inverters

• Every participation in PANDA project is highly appreciated (check out the website and send us an email)

• Measurements of prevailing harmonic phase angle in other countries are very welcome (contribution to IEC SC77A WG1)

Conclusions

28

Thank you for your attention !

Contact details:

Jan Meyer Technische Universität Dresden Institute of Electrical Power Systems and High Voltage Engenieering 01062 Dresden

tel. +49-351-463 35102 fax. +49-351-463 37036

email: jan.meyer@tu-dresden.de

Sometimes also aesthetic aspects should be considered

in terms of compatibility