Electromagnetic compatibility (EMC) - Part 3-15: Limits - Assessment of low frequency electromagnetic immunity and emission requirements for dispersed generation systems in LV network

IEC/TR 61000-3-15:2011(E) is concerned with the critical assessment of existing and emerging national and international standards for single and multi-phase dispersed generation systems up to 75 A per phase, particularly converters connected to the public supply low voltage network. This Technical Report intends to serve as a starting point and to ultimately pave the way for the definition of appropriate EMC requirements and test conditions. This Technical Report is limited to EMC issues (immunity and emission) up to 9 kHz and does not include other aspects of connection of generators to the grid. This Technical Report focuses on emission caused by distributed generation (mainly harmonics and inter-harmonics, DC emissions flicker, rapid voltage changes and fluctuations), as well as immunity aspects to normally occurring events in the public supply network (voltage dips and short interruptions, frequency variations, harmonics and interharmonics). Every effort has been made to utilize already existing emission and immunity standards, including the test set-up and existing test equipment in use.

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Publication Date
12-Sep-2011
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IEC/TR 61000-3-15
Edition 1.0 2011-09
TECHNICAL
REPORT
colour
inside
Electromagnetic compatibility (EMC) –
Part 3-15: Limits – Assessment of low frequency electromagnetic immunity and
emission requirements for dispersed generation systems in LV network
IEC/TR 61000-3-15:2011(E)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC/TR 61000-3-15
Edition 1.0 2011-09
TECHNICAL
REPORT
colour
inside
Electromagnetic compatibility (EMC) –
Part 3-15: Limits – Assessment of low frequency electromagnetic immunity and
emission requirements for dispersed generation systems in LV network
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
ICS 33.100.10 ISBN 978-2-88912-636-1
® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – TR 61000-3-15  IEC:2011(E)
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope ............................................................................................................................... 7

2 Terms and definitions ....................................................................................................... 7

3 General .......................................................................................................................... 10

4 Classification of DG generators ...................................................................................... 11

4.1 General ................................................................................................................. 11

4.2 Induction (asynchronous) generators ..................................................................... 11

4.3 Synchronous generators ........................................................................................ 12

4.4 Static power converters ......................................................................................... 12

5 Survey of EMC requirements for DG ............................................................................... 12

6 Proposed EMC requirements and tests ........................................................................... 15

6.1 General test requirements ..................................................................................... 15

6.2 Proposed tests ...................................................................................................... 17

7 Emission ........................................................................................................................ 18

7.1 General ................................................................................................................. 18

7.2 Harmonics ............................................................................................................. 18

7.2.1 Mechanisms of harmonic current emissions ............................................... 18

7.2.2 Proposed limits and tests for harmonic current emissions .......................... 19

7.2.3 Summary of harmonic current emission tests ............................................. 21

7.2.4 Product test procedure for harmonic current emissions .............................. 21

7.2.5 System test procedure for harmonic current emissions .............................. 23

7.3 Unbalance ............................................................................................................. 23

7.4 Voltage fluctuation and flicker ............................................................................... 24

7.4.1 General ..................................................................................................... 24

7.4.2 Flicker test conditions for DG equipment exporting power to the

public supply ............................................................................................. 25

7.5 DC injection........................................................................................................... 26

7.6 Short duration over voltages .................................................................................. 26

7.6.1 General ..................................................................................................... 26

7.6.2 Short duration over voltage test procedure ................................................ 28

7.7 Switching frequencies ........................................................................................... 29

8 Immunity ........................................................................................................................ 30

8.1 General ................................................................................................................. 30

8.2 Voltage dips and short interruptions ...................................................................... 31

8.2.1 General ..................................................................................................... 31

8.2.2 Short duration voltage dips test procedure ................................................. 36

8.2.3 Longer duration voltage dips test procedure .............................................. 37

8.3 Frequency variations ............................................................................................. 37

8.4 Harmonics and interharmonics .............................................................................. 39

Annex A (informative) Examples of harmonic measurements and analysis on DG

equipment connected to low voltage networks ...................................................................... 41

Bibliography .......................................................................................................................... 46

---------------------- Page: 4 ----------------------
TR 61000-3-15  IEC:2011(E) – 3 –

Figure 1 – General test setup for combined emission/immunity tests .................................... 16

Figure 2 – Over voltages produced during DG quick disconnection ....................................... 27

Figure 3 – Over voltages produced during DG slow disconnection (greater than 10 ms) ....... 27

Figure 4 – CBEMA curve (IEC 61000-2-14) ........................................................................... 28

Figure 5 – Distortion due to high power PV inverter .............................................................. 30

Figure 6 – Voltage dips and short interruption test levels from different standards ................ 32

Figure 7 – Voltage tolerance curves for DG immunity requirements ...................................... 33

Figure 8 – DG immunity test for short dips/interruptions: an example .................................... 36

Figure 9 – Test pattern for a DG voltage dip tolerance curve ................................................ 36

Figure 10 – DG frequency variation (increment) immunity test: an example .......................... 39

Figure A.1 – Total current distortion due the network and the connected inverter .................. 41

Figure A.2 – Harmonic distortions at different input power of a 5 kW inverter ........................ 42

Figure A.3 – DG equipment with LCL filter ............................................................................ 42

Figure A.4 – Impedance model for DG equipment with LCL filter ........................................... 43

Figure A.5 – Voltage spectrum: four AICs connected ............................................................ 44

Figure A.6 – Current harmonics: four AICs at 10 A r.m.s. (0,11 / ) ........................................ 44

Table 1 – DG specifications and emission requirements applied in different countries ......... 13

Table 2 – Proposed EMC requirements and tests for DG equipment ..................................... 17

Table 3 – Different suggested product and system tests for harmonic emissions ................. 21

Table 4 – Voltage distortion of simulated public supply (IEC 61000-3-2) ............................... 22

Table 5 – Voltage distortion of simulated public supply (IEC 61000-3-12) ............................. 22

Table 6 – Limits for DG up to 75 A/phase (in percent of I ) ................................................. 23

rms

Table 7 – Distortion values for a flat top and peaky voltage distortion V-THD of 4,0 % ......... 23

Table 8 – Protection requirements for PV inverters under voltage disturbances .................... 34

Table 9 – Protection requirements for PV inverters under frequency disturbances ............... 38

Table 10 – Harmonic voltage disturbance levels for odd harmonics (IEC 61000-4-13) .......... 40

Table A.1 – THD of increasing numbers of AICs with LCL filters connected to the

network ................................................................................................................................. 43

---------------------- Page: 5 ----------------------
– 4 – TR 61000-3-15  IEC:2011(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 3-15: Limits –
Assessment of low frequency electromagnetic immunity and emission
requirements for dispersed generation systems in LV network
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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The main task of IEC technical committees is to prepare International Standards. However, a

technical committee may propose the publication of a Technical Report when it has collected

data of a different kind from that which is normally published as an International Standard, for

example "state of the art".

IEC 61000-3-15, which is a technical report, has been prepared by subcommittee 77A: Low

frequency phenomena, of IEC technical committee 77: Electromagnetic compatibility.

---------------------- Page: 6 ----------------------
TR 61000-3-15  IEC:2011(E) – 5 –
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
77A/744/DTR 77A/759/RVC

Full information on the voting for the approval of this technical report can be found in the

report on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all the parts in the IEC 61000 series, published under the general title Electro-

magnetic compatibility can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct understanding

of its contents. Users should therefore print this document using a colour printer.

A bilingual version of this publication may be issued at a later date.
---------------------- Page: 7 ----------------------
– 6 – TR 61000-3-15  IEC:2011(E)
INTRODUCTION
IEC 61000 is published in separate parts according to the following structure:
Part 1: General
General considerations (introduction, fundamental principles)
Definitions, terminology
Part 2: Environment
Description of the environment
Classification of the environment
Compatibility levels
Part 3: Limits
Emission limits

Immunity limits (in so far as they do not fall under the responsibility of product committees)

Part 4: Testing and measurement techniques
Measurement techniques
Testing techniques
Part 5: Installation and mitigation guidelines
Installation guidelines
Mitigation methods and devices
Part 6: Generic standards
Part 9: Miscellaneous

Each part is further subdivided into several parts published either as International Standards

or as technical specifications or technical reports, some of which have already been published

as sections. Others are published with the part number followed by a dash and a second

number identifying the subdivision (example: IEC 61000-6-1).
---------------------- Page: 8 ----------------------
TR 61000-3-15  IEC:2011(E) – 7 –
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 3-15: Limits –
Assessment of low frequency electromagnetic immunity and emission
requirements for dispersed generation systems in LV network
1 Scope

This part of IEC 61000 is concerned with the critical assessment of existing and emerging

national and international standards for single and multi-phase dispersed generation systems

up to 75 A per phase, particularly converters connected to the public supply low voltage

network, to serve as a starting point and to ultimately pave the way for the definition of

appropriate EMC requirements and test conditions. This Technical Report is limited to EMC

issues (immunity and emission) up to 9 kHz and does not include other aspects of connection

of generators to the grid.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
electromagnetic compatibility
EMC

ability of an equipment or system to function satisfactorily in its electromagnetic environment

without introducing intolerable electromagnetic disturbances to anything in that environment

[IEC 60050-161:1990, 161-01-07]
2.2
distributed generation, embedded generation, dispersed generation

generation of electric energy by multiple sources which are connected to the power

distribution system
[IEC 60050-617:2009, 617-04-09]
2.3
current source inverter

stiff current source inverter (inverter operating as an impressed current source)

2.4
voltage source inverter

stiff voltage source inverter with current control (inverter operating as an impressed voltage

source)
2.5
low voltage

set of voltage levels used for the distribution of electricity and whose upper limit is generally

accepted to be 1 000 V a.c.
[IEC 60050-601:1985, 601-01-26]
---------------------- Page: 9 ----------------------
– 8 – TR 61000-3-15  IEC:2011(E)
2.6
(electromagnetic) emission
phenomenon by which electromagnetic energy emanates from a source
[IEC 60050-161:1990, 161-01-08]

NOTE For the purpose of this report, emission refers to phenomena such as conducted electromagnetic

disturbances that can cause distortions, fluctuations or unbalance on the supply voltage.

2.7
emission level (of a disturbing source)

level of a given electromagnetic disturbance emitted from a particular device, equipment,

system or disturbing installation as a whole, assessed and measured in a specified manner

2.8
power quality

characteristics of the electric current, voltage and frequencies at a given point in an electric

power system, evaluated against a set of reference technical parameters

NOTE These parameters might, in some cases, relate to the compatibility between electricity supplied in an

electric power system and the loads connected to that electric power system.
[IEC 60050-617:2009, 617-01-05]
2.9
point of common coupling
PCC

point of a power supply network, electrically nearest to a particular load, at which other loads

are, or may be, connected

NOTE 1 These loads can be either devices, equipment or systems, or distinct customer's installations.

NOTE 2 In some applications, the term “point of common coupling” is restricted to public networks.

2.10
emission limit (allowed from a disturbing source)

specified maximum emission level of a source of electromagnetic disturbance (e.g. device,

equipment, system or disturbing installation as a whole)
2.11
immunity (to a disturbance)

ability of a device, equipment or system to perform without degradation in the presence of an

electromagnetic disturbance
[IEC 60050-161:1990, 161-01-20]
2.12
immunity level

maximum level of a given electromagnetic disturbance on a particular device, equipment or

system for which it remains capable of operating with a declared degree of performance

2.13
fundamental component

sinusoidal component of the Fourier series of a periodic quantity having the frequency of the

quantity itself
2.14
harmonic frequency
frequency which is an integer multiple of the fundamental frequency

NOTE The ratio of the harmonic frequency to the fundamental frequency is the harmonic order (recommended

notation: “h”).
---------------------- Page: 10 ----------------------
TR 61000-3-15  IEC:2011(E) – 9 –
2.15
interharmonic frequency
frequency which is a non-integer multiple of the reference fundamental frequency

NOTE 1 By extension from harmonic order, the inter-harmonic order is the ratio of an inter-harmonic frequency to

the fundamental frequency. This ratio is not an integer. (Recommended notation “m”).

NOTE 2 In the case where m < 1, the term sub-harmonic frequency may be used.
2.16
total harmonic distortion
THD

ratio of the r.m.s. value of the harmonic content of an alternating quantity to the r.m.s. value

of the fundamental component of the quantity
2.17
voltage unbalance

in a poly-phase system, a condition in which the magnitudes of the phase voltages or the

phase angles between consecutive phases are not all equal (fundamental component)

2.18
flicker

impression of unsteadiness of visual sensation induced by a light stimulus whose luminance

or spectral distribution fluctuates with time
2.19
short-term flicker indicator

measure of flicker evaluated over a specified time interval of a relatively short duration

NOTE The duration is typically 10 min, in accordance with IEC 61000-4-15.
2.20
long term flicker indicator

measure of flicker evaluated over a specified time interval of a relatively long duration, using

successive values of the short-term flicker indicator

NOTE The duration is typically 2 h, using 12 successive values of P , in accordance with IEC 61000-4-15.

2.21
voltage fluctuation

series of voltage changes or a continuous variation of the r.m.s. or peak value of the voltage

2.22
voltage dip (voltage sag)

sudden reduction of the voltage at a point in an electrical system followed by voltage recovery

after a short period of time from a few cycles to a few seconds
2.23
short interruption (of supply voltage)

disappearance of the supply voltage for a time interval whose duration is between two

specified limits
2.24
distribution system operator, distribution network operator
DSO
party operating a distribution system
---------------------- Page: 11 ----------------------
– 10 – TR 61000-3-15  IEC:2011(E)
2.25
product test
test which assesses the DG current emissions in worst case conditions

NOTE This test method is based on the test circuits specified in IEC 61000-3-2 (up to 16 A), and IEC 61000-3-12

(up to 75 A).
2.26
system test
test which emulates the DG actual condition in the public supply network

NOTE This test method is based on the test circuits specified in IEC 61000-3-3 (up to 16 A), and IEC 61000-3-11

(up to 75 A), including the impedance, with the addition of a defined load and specified pre-distortion levels.

2.27
islanding protection

protection against the continuous operation of the inverter and part of the utility load once

isolated from the remainder of the electric utility system
2.28
active infeed converter
AIC

self commutated electronic power converter of all technologies, topologies, voltages and sizes

which are connected between the electrical a.c. power supply system (lines) and a d.c. side

(current source or voltage source) and which can convert electrical power in both directions

(generative or regenerative) and control the power factor of an applied voltage or current

NOTE Some of them can additionally control the harmonic distortion of an applied voltage or current. Basic

topologies may be realized as a Voltage Source Converter (VSC) or a Current Source Converter (CSC).

3 General

This Technical Report applies to DG and primarily concerns the critical assessment of several

common low frequency electromagnetic emission and immunity requirements.

It can be considered an initial proposal in order to gain experience toward the definition of

appropriate EMC limits and test conditions for the connection of potentially disturbing

installations to LV power systems.

This Technical Report focuses on emission caused by DG (mainly harmonics and inter-

harmonics, DC emissions flicker, rapid voltage changes and fluctuations), as well as immunity

aspects to normally occurring events in the public supply network (voltage dips and short

interruptions, frequency variations, harmonics and interharmonics).

In addition, every effort has been made to utilize already existing emission and immunity

standards, including the test set-up and existing test equipment in use.

The existing standards, in combination with the requirements of DG equipment, lend

themselves to the definition of two types of emission tests:
• the “product test”;
• the “system test”.

The application of these two test methods is believed to meet the demands from both DSO

and DG manufacturers and should result in reliable operation of DG equipment up to 75 A

when connected under typical network conditions. It should be noted that these tests,

although being primarily emission tests, also deal to some extent with the immunity of the DG

against normally occurring events in the public supply.
---------------------- Page: 12 ----------------------
TR 61000-3-15  IEC:2011(E) – 11 –

At this time, DG equipment is generally not designed to compensate for current or voltage

distortions but this possibility may be evaluated for future developments. For such

developments no requirements are included in this Technical Report, but the method of the

system test introduced in this report could be used to evaluate compensating behaviour.

The suggested emissions and immunity tests are devised to assure that DG equipment

connected to the network may be expected to function acceptably in the EMC environment.

4 Classification of DG generators
4.1 General

The aim of the following short description of different generation systems is to highlight the

behavior of static power supplies connected to the electrical network compared with other

types of generators.

There are three main types of generation systems that interface to the power system. These

include:
• induction (asynchronous) generators;
• synchronous generators;
• static power converters.

Each type has its own specific characteristic regarding synchronization equipment, protective

functions, starting practices, and electrical operating behavior. The primary energy source of

generating plant can be internal or external combustion, wind, fuel cells, electrochemical

accumulators flywheel storage systems, small scale hydro and photovoltaic cells.

In this Technical Report both current and voltage source inverters are addressed. Although,

most DG inverters might be considered as voltage source inverters based on their topology,

they behave with a current source control strategy when viewed from the network integration

perspective.

This means that it is generally assumed that the line voltage at the point of DG connection

can be regarded as constant, so the desired power injection is achieved by controlling the

current injected by the inverter.
4.2 Induction (asynchronous) generators

An induction generator, “asynchronous” generator, operates on the principles of an AC

induction motor, except that in normal operation it has a speed of rotation slightly greater than

the synchronous speed of the power system. Induction generators, however, are commonly

used in power plants that only need to operate in parallel with another source (such as the

utility system).
Induction generators take their excitation current via their stators. Thus, they
...

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