Supraharmonics, a new field within power quality

Sarah Rönnberg Annual General meeting of the IEEE Chapter of Power & Energy Society

and Power Electronics 2019-03-04

A little bit about myself

• I have two grown daughters. • I enjoy outdoor activates, ice

hockey, reading books, videogames and handicraft.

• Volunteering at a women's shelter.

• Associate Professor in Electrical Engineering – I work mainly with power quality

• Serve at the board of PES Women in Power • Active in Cigree and IEEE working groups

Step 1: Setting Up the Webinar in WebEx

WiP’s Mission

Diversity is essential for any workforce or community. In 2012, we formed the IEEE Power & Energy Society Women in Power.

PES Women in Power’s mission is to advance the world through the creativity and innovation of diverse leadership, and to foster the careers,

connections, and talent of women in the Power Industry to achieve their full potential to become the leaders of the future.

WiP’s Objectives

Promote the community of women in the power industry. Develop early- to mid-career candidates for leadership positions

through recognition and leadership education. Develop support amongst institutions to provide opportunities for

qualified candidates to ascend to leadership positions. Provide networking opportunities and resources to help women in

power engineering to advance their careers. Provide inspiration and education through mentors, role models, and

success stories.

Member Benefits

career advancement Wanda Reder Pioneer in Power Award PES e-newsletters

networking PES conferences Regional Events Social media

education of women in the energy industry Webinars PES e-newsletters Conference participation

2018 IEEE PES Wanda Reder Pioneer in Power

Bhuvaneswari: For outstanding research in power quality converters and for educating new engineers.

Mondello: For leadership, and for serving as an inspiring role model and mentor to young women in the power industry.

The IEEE PES Wanda Reder Pioneer in Power Award seeks to recognize a deserving female in the field of electric power and energy engineering. The Award is intended

to provide visibility to the awardee’s pioneering efforts, accomplishments and future potential, while empowering her to be an inspiration and role model for other

women in the industry.

Diversity Efforts

WiP’s first annual conference in New Delhi,

India. The conference in March 2017 honored

Region 10 members, opening with a traditional

Indian ceremony, remarks from the Delhi

planning committee, and an interactive

session on Defining your Impact as a Leader.

WiP participated in IEEE PES PowerAfrica in

Accra, Ghana, inspiring female high school

students in Region 8, through the story of a

girl who loved reading maps and loves being

an engineer.

Visit our website to learn more

• http://www.pes-women-in-power.org/

Supraharmonics, a new field within power quality

The classical power quality issues

• Harmonics • Voltage dips • Light flicker due to fast voltage fluctuations

• Short and long interruptions • Slow voltage variations • Switching transients • Transient overvoltages

Supraharmonics

• Definitions • Sources of supraharmonics • Propagation of supraharmonics • Interference due to supraharmonics • Supraharmonics – research subject

12

Supraharmonics: Frequencies above 2 kHz and below 150 kHz

– Is not related to the power system frequency so e.g. 42 kHz is not referred to as the 840 harmonic

– Can be any frequency component e.g. 3500 Hz, 6223 Hz – There can be harmonics of a supraharmonic frequency as well, e.g.

n*42kHz, n=1,2,3 and so on

– Supraharmonics are not a subclass of harmonics, just like interharmonics are not

– … and, yes, a classification based on origin and character would of course be better,

… but we’re not there yet

13

Terminology

• Supra = beyond (c.f. interharmonics (in between) and subharmonics (below)

• Also referred to as: ”high frequency harmonics”, ”high frequency distortion”, ”low frequency EMC” or ”power conversion harmonics”

• The term Supraharmonics are not adopted by any standard but is used more and more – 1 publication in 2013, 85 publications 2018 (in total 264 since

2013, Google scholar). Term is also used in Cigre TB C4.24 and C4.29

14

• Borders at 2 kHz and 150 kHz are somewhat arbitrary; – up to 2 kHz covered by power quality standards – above 150 kHz is protected to prevent radio disturbances

• There is no sudden change in behavior at those frequencies

15

• IEC 61000-2-2 Annex D – Basis for the definition of the compatibility levels for voltage distortion in differential mode from 30 kHz to 150

kHz

• CISPR 16 – a series of 16 publications specifying equipment and methods for measuring disturbances and immunity to

them at frequencies above 9 kHz.

• IEC 61000-3-8 – Signalling on low-voltage electrical installations - Emission levels, frequency bands and electromagnetic

disturbance levels, from 3 kHz

• IEC 61000-4-19 – Test for immunity to conducted, differential mode disturbances and signalling in the frequency range 2 kHz to

150 kHz at a.c. power ports

• EN 55011 – Industrial, scientific and medical equipment - Radio-frequency disturbance characteristics - Limits and

methods of measurement, from 9 kHz

• EN 50160, CISPR 14, CISPR 15, EN 50065 all cover parts or all of the frequency range

16

Standards

Examples of sources

• PWM converters (around 3 kHz) • Industrial size converters (9 to 150 kHz) • Oscillations around commutation notches (up to

10 kHz) • Street lamps (up to 20 kHz) • EV chargers (15 kHz to 100 kHz) • PV inverters (3 kHz to 20 kHz) • Household devices (2 to 150 kHz) • Power line communication, AMR (9 to 95 kHz)

17

So what do these supraharmonics look like?

18

Time domain

19

Frequency domain

20

Time and frequency domain 21

Each domain give some information and all three are needed

22

What does the emission from one type of device look like?

Example: LED lamp

23

24 What does the emission from one type of device look like?

Example: LED lamp

There is a large diversity in emission from devices and it would be difficult to predict what the emission looks like at a certain moment in time or in a certain installation

25

Characteristic of emission (within fundamental cycle)

Constant emission: No significant change in magnitude and/or frequency within one fundamental cycle Varying emission (cyclostationary): Noticeable changes in magnitude and/or frequency within one fundamental cycle Transient emission: “Event”-like emission for a fraction of the fundamental cycle

26

• Levels in the the grid?

• Supraharmonic levels are not monitored in the grids in a similar way as e.g. harmonics are – Instrument – Method – Index/limits

27

Some examples

Data from http://map.pqube.com/

50, 95 and 99 percentiles of supraharmonic emission for 246 consecutive days, at a US site

50, 95 and 99 percentiles of supraharmonic emission for 122 consecutive days at a Korean site.

Propagation of Supraharmonics

29

Primary Emission • The part of the harmonic current driven by sources inside of the

device

Secondary Emission • The part of the harmonic current at the device terminals that is

driven by sources outside of the device.

Interaction • Relates to the non-linearity of the grid due to the connection of non-

linear devices.

More terminology 30

Primary emission from one single device or installation

•The primary emission depends on the grid impedance and is thus not the same at all locations. •The primary emission is not the same as the emission measured during a standardized test. The latter is (intended to be) reproducible, i.e. independent of time and location; the primary emission is not independent of time and location. •Both source impedance and terminal voltage impact the primary emission

Primary emission is effected by neighboring devices

Emission increases 2 times

Emission increases 5 times

Secondary emission

• The part of the supraharmonic current at the device terminals that is driven by sources outside of the device.

• Primary and secondary emission are relative terms, what is considered as primary emission seen from one device can be seen as secondary emission for another

Primary emission Secondary emission

The magnitude of the secondary emission can be many times greater than the primary emission

Device A Device B Device C

Power meter

Device N

Installation Grid

Power line communication Emission originating from Device A Emission originating from Device B Emission originating from Device C

Primary emission originating from Device C

Secondary emission measured at Device C

Example of how supraharmonics propagate

• By adding more devices the emission at the PCC sometimes decreases • By adding more devices the emission measured at device A sometimes increases

Reported cases of interference • Reduced quality of the output of a copy machine due to frequencies in the

lower kHz range • Interference with light dimmers, medical equipment, electricity meters, and

earth leakage current breakers • An 8-kHz voltage, due to a CNC mill, resulted in a range of complaints:

malfunction of a fully automated coffeemaker; a hair dryer randomly turning on an off; malfunctions of the control of the CNC drive itself.

• Unwanted tripping of earth leakage current breakers in Japan • Audible noise coming from a television • Failure of varistors due to repetitive activation by recurrent oscillations in

voltage • Voltage distortion around 12 kHz was shown to cause mechanical

oscillations and audible noise • Clocks running to fast • …. These are just examples and not all cases are reported

• S. Rönnberg et al. ”On waveform distortion in the frequency range of 2 kHz–150 kHz—Review and research challenges” Electric Power System Research 150 (2017): 1-10.

Interference

1. A device is occasionally not operating as intended or with reduced functionality.

2. Failed operation or damage of a device. 3. Interference with or due to power line

communication. 4. Audible noise from a device or installation.

0 20 40 60 80 100 120 140 160 180 200

-0.4

-0.2

0

0.2

0.4

0.6

time (ms)

power meter

0 20 40 60 80 100 120 140 160 180 200

-0.4

-0.2

0

0.2

0.4

0.6

time (ms)

energy saving lamp

0 20 40 60 80 100 120 140 160 180 200

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

time (ms)

concentrator

Cable Distribution Cabinet concentrator Energy meter

end-user equipment

Power line communication, should not disturb or be disturbed

Transmitted signal Received signal Signal shunted by a device connected in a neighboring house.

EV chargers, audible noise • Measurements of about 80% of the different chargers available on the

German market • Diversity between magnitudes and frequencies (50% switch within the

audible range)

60

70

80

90

100

110

120

130

0 20 40 60 80 100 120

Mag

nitu

de in

dB µ

A

Switching frequency / kHzHörbart område

J. Meyer, Technical University of Dresden. 2017

39

Supraharmonics – a research subject What we know today • Supraharmonics are generated by a large portion of devices

available on the market • They propagate mainly between neighboring devices but sometimes

over longer distances. • Resonances play an important part in the way they propagate • There is interference due to supraharmonics • There is interaction between devices • They can be found in the neutral conductor and the PE

• … More research is needed to fully understand this and to reduce

the risk of interference

40

Conclusions

• Supraharmonics exist – Emission has been confirmed by many studies

• They spread through the grid – Spread to and from MV and HV?

• They are able to cause interference – Again too many reported cases to just neglect

• Research is needed – Input to standardization – Base for spreading of knowledge – To assess the severity of the problem

Thank you

42