SIST EN 60891:2011

SLOVENSKI STANDARD
SIST EN 60891:2011
01-marec-2011
1DGRPHãþD
SIST EN 60891:2001
Postopki za temperaturno in sevalno korekcijo izmerjenih karakteristik I-U
fotonapetostnih naprav (IEC 60891:2009 (EQV))
Procedures for temperature and irradiance corrections to measured I-V characteristics of
photovoltaic devices
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SKRWRYROWDLVFKHQ%DXHOHPHQWHQDXIDQGHUH7HPSHUDWXUHQXQG%HVWUDKOXQJVVWlUNHQ
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Procédures pour les corrections en fonction de la température et de l'éclairement à
appliquer aux caractéristiques I-V mesurées des dispositifs photovoltaïques
Ta slovenski standard je istoveten z: EN 60891:2010
ICS:
27.160 6RQþQDHQHUJLMD Solar energy engineering
SIST EN 60891:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60891:2011

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SIST EN 60891:2011

EUROPEAN STANDARD
EN 60891

NORME EUROPÉENNE
March 2010
EUROPÄISCHE NORM

ICS 27.160 Supersedes EN 60891:1994


English version


Photovoltaic devices -
Procedures for temperature and irradiance corrections
to measured I-V characteristics
(IEC 60891:2009)


Dispositifs photovoltaïques -  Verfahren zur Umrechung
Procédures pour les corrections von gemessenen Strom-Spannungs-
en fonction de la température Kennlinien von photovoltaischen
et de l'éclairement à appliquer Bauelementen auf andere Temperaturen
aux caractéristiques I-V mesurées und Bestrahlungsstärken
(CEI 60891:2009) (IEC 60891:2009)




This European Standard was approved by CENELEC on 2010-03-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: Avenue Marnix 17, B - 1000 Brussels


© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60891:2010 E

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SIST EN 60891:2011
EN 60891:2010 - 2 -
Foreword
The text of document 82/581/FDIS, future edition 2 of IEC 60891, prepared by IEC TC 82, Solar
photovoltaic energy systems, was submitted to the IEC-CENELEC parallel vote and was approved by
CENELEC as EN 60891 on 2010-03-01.
This European Standard supersedes EN 60891:1994.
The main technical changes with regard to the EN 60891:1994 are as follows:
– extends existing translation procedure to irradiance change during I-V measurement;
– adds 2 new translation procedures;
– revises procedure for determination of temperature coefficients to include PV modules;
– defines new procedure for determination of internal series resistance;
– defines new procedure for determination of curve correction factor.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2010-12-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2013-03-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60891:2009 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60904-5 NOTE  Harmonized as EN 60904-5.
__________

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SIST EN 60891:2011
- 3 - EN 60891:2010
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

IEC 60904-1 - Photovoltaic devices - EN 60904-1 -
Part 1: Measurement of photovoltaic
current-voltage characteristics


IEC 60904-2 - Photovoltaic devices - EN 60904-2 -
Part 2: Requirements for reference solar
devices


IEC 60904-7 - Photovoltaic devices - EN 60904-7 -
Part 7: Computation of the spectral mismatch
correction for measurements of photovoltaic
devices


IEC 60904-9 - Photovoltaic devices - EN 60904-9 -
Part 9: Solar simulator performance
requirements


IEC 60904-10 - Photovoltaic devices - EN 60904-10 -
Part 10: Methods of linearity measurement

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SIST EN 60891:2011

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SIST EN 60891:2011
IEC 60891
®
Edition 2.0 2009-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Photovoltaic devices – Procedures for temperature and irradiance corrections to
measured I-V characteristics

Dispositifs photovoltaïques – Procédures pour les corrections en fonction de la
température et de l’éclairement à appliquer aux caractéristiques I-V mesurées

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
R
CODE PRIX
ICS 27.160 ISBN 978-2-88910-316-4
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 60891:2011
– 2 – 60891 © IEC:2009
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Correction procedures .5
3.1 General .5
3.2 Correction procedure 1.6
3.3 Correction procedure 2.7
3.4 Correction procedure 3.8
4 Determination of temperature coefficients.13
4.1 General .13
4.2 Apparatus.13
4.3 Procedure in natural sunlight.14
4.4 Procedure with a solar simulator .15
4.5 Calculation of temperature coefficients.15
5 Determination of internal series resistance R and R′ .15
S S
5.1 General .15
5.2 Correction procedure 1.16
5.3 Correction procedure 2.17
6 Determination of the curve correction factor κ and κ′ .18
6.1 General .18
6.2 Procedure .18
7 Reporting .19
Bibliography.21

Figure 1 – Example of the correction of the I-V characteristics by Equations (6) and (7) .10
Figure 2 – Schematic diagram of the relation of G and T which can be chosen in the
3 3
simultaneous correction for irradiance and temperature, for a fixed set of T , G , T ,
1 1 2
by Equations (8) and (9).11
and G
2
Figure 3 – Schematic diagram of the processes for correcting the I-V characteristics to
various ranges of irradiance and temperature based on three measured
characteristics .12
Figure 4 – Schematic diagram of the processes for correcting the I-V characteristics to
various ranges of irradiance and temperature based on four measured characteristics .13
Figure 5 – Positions for measuring the temperature of the test module behind the cells .14
Figure 6 – Determination of internal series resistance.16
Figure 7 – Determination of V irradiance correction factor and internal series
OC
resistance .18
Figure 8 – Determination of curve correction factor.19

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SIST EN 60891:2011
60891 © IEC:2009 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

PHOTOVOLTAIC DEVICES – PROCEDURES FOR TEMPERATURE AND
IRRADIANCE CORRECTIONS TO MEASURED I-V CHARACTERISTICS


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60891 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
This second edition cancels and replaces the first edition issued in 1987 and its Amendment 1
(1992) and constitutes a technical revision.
The main technical changes with regard the previous edition are as follows:
– extends edition 1 translation procedure to irradiance change during I-V measurement;
– adds 2 new translation procedures;
– revises procedure for determination of temperature coefficients to include PV modules;
– defines new procedure for determination of internal series resistance;
– defines new procedure for determination of curve correction factor.

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SIST EN 60891:2011
– 4 – 60891 © IEC:2009
The text of this standard is based on the following documents:
FDIS Report on voting
82/581/FDIS 82/588/RVD

Full information on the voting for the approval of this standard 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.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.

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SIST EN 60891:2011
60891 © IEC:2009 – 5 –
PHOTOVOLTAIC DEVICES – PROCEDURES FOR TEMPERATURE AND
IRRADIANCE CORRECTIONS TO MEASURED I-V CHARACTERISTICS



1 Scope
This standard defines procedures to be followed for temperature and irradiance corrections to
the measured I-V (current-voltage) characteristics of photovoltaic devices. It also defines the
procedures used to determine factors relevant for these corrections. Requirements for I-V
measurement of photovoltaic devices are laid down in IEC 60904-1.
NOTE 1 The photovoltaic devices include a single solar cell with or without a protective cover, a sub-assembly of
solar cells, or a module. A different set of relevant parameters for I-V correction applies for each type of device.
Although the determination of temperature coefficients for a module (or sub-assembly of cells) may be calculated
from single cell measurements, it should be noted that the internal series resistance and curve correction factor
should be separately measured for a module or subassembly of cells.
NOTE 2 The term “test specimen” is used to denote any of these devices.
NOTE 3 Care should be taken regarding the use of I-V correction parameters. The parameters are valid for the
PV device for which they have been measured. Variations may occur within a production lot or the type class.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60904-1, Photovoltaic devices – Part 1: Measurements of photovoltaic current-voltage
characteristics
IEC 60904-2, Photovoltaic devices – Part 2: Requirements for reference solar devices
IEC 60904-7, Photovoltaic devices – Part 7: Computation of the spectral mismatch correction
for measurements of photovoltaic devices
IEC 60904-9, Photovoltaic devices – Part 9: Solar simulator performance requirements
IEC 60904-10, Photovoltaic devices – Part 10: Methods of linearity measurement
3 Correction procedures
3.1 General
Three procedures for correcting measured current-voltage characteristics to other conditions
of temperature and irradiance (such as STC) can be applied. The first is identical to the
procedure given in Edition 1 of this standard, but the equation has been rewritten for easier
understanding. The second procedure is an alternative algebraic correction method which
yields better results for large irradiance corrections (>20 %). Both procedures require that
correction parameters of the PV device are known. If not known they need to be determined
prior to performing the correction. The third procedure is an interpolation method which does
not require correction parameters as input: It can be applied when a minimum of three
current-voltage curves have been measured for the test device. These three current-voltage
curves span the temperature and irradiance range for which the correction method is
applicable.

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SIST EN 60891:2011
– 6 – 60891 © IEC:2009
All methods are applicable to linear devices as defined in IEC 60904-10.
NOTE 1 An estimate on the translation accuracy is required (see Clause 7).
NOTE 2 All PV devices should be linear within a limited range of irradiances and device temperature. Details are
described in IEC 61853-1.
Common to all procedures is that I-V characteristics of the PV device are to be measured in
accordance with IEC 60904-1.
Usually irradiance G shall be calculated from the measured short circuit current (I ) of the

RC
PV reference device as defined in IEC 60904-2, and its calibration value at STC (I ). A
RC,STC
correction should be applied to account for the temperature of the reference device T using
RC
the specified relative temperature coefficient of the reference device (1/°C) which is given at
2
25 °C and 1 000 W/m .
−2
1 000 Wm ⋅I
RC

G = ⋅[]1− α ⋅()T − 25 °C
RC RC
I
RC,STC
The PV reference device shall either be spectrally matched to the test specimen, or a spectral
mismatch correction shall be performed in conformance with IEC 60904-7. The reference
device shall be linear in short-circuit current, as defined in IEC 60904-10 over the irradiance
range of interest.
3.2 Correction procedure 1
The measured current-voltage characteristic shall be corrected to standard test conditions or
other selected temperature and irradiance values by applying the following equations:
⎛ ⎞
G
2
⎜ ⎟
I = I + I ⋅ −1 + α ⋅()T − T (1)
2 1 SC 2 1
⎜ ⎟
G
⎝ 1 ⎠
V = V − R ⋅()I − I − κ ⋅ I ⋅(T − T) + β ⋅(T − T) (2)
2 1 S 2 1 2 2 1 2 1
where:
I , V are coordinates of points on the measured characteristics;
1 1
I , V are coordinates of the corresponding points on the corrected characteristic;
2 2
G is the irradiance measured with the reference device;
1
G is the irradiance at the standard or other desired irradiance;
2
T is the measured temperature of the test specimen;
1
T is the standard or other desired temperature;
2
I is the measured short-circuit current of the test specimen at G and T ;
SC 1 1
α and β are the current and voltage temperature coefficients of the test specimen in the
standard or target irradiance for correction and within the temperature range of
interest;
R is the internal series resistance of the test specimen;
S
κ is a curve correction factor.

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SIST EN 60891:2011
60891 © IEC:2009 – 7 –
NOTE 1 As the data point V will be shifted off the current axis when translating from lower to higher irradiance,
oc1
the translated V has to be determined by linear extrapolation from at least 3 data points near and below V or
oc2 oc1
the original IV curve has to be measured sufficiently far beyond V .
oc1
NOTE 2 The units of all correction parameters should be consistent.
NOTE 3 If the test specimen is a module the cell I-V correction parameters can be derived from the
interconnection circuit. These cell parameters may be used to calculate the module I-V correction parameters for
other module types using the same cells.
NOTE 4 For crystalline silicon PV devices α is normally positive and β negative.
Procedures for determination of the I-V correction parameters of the test specimen are
described in sections 4 to 6.
Equation (1) is only applicable for I-V curves measured at irradiances which are constant
during the acquisition of the entire I-V curve. For pulsed solar simulators with decaying
irradiance or any other kind of irradiance fluctuations during I-V measurement Equation (1) is
not applicable as such. In this case, each measured I-V curve has to be corrected to an
equivalent I-V curve at constant irradiance which requires an additional scaling factor in front
of I . For practical reasons this scaling factor is related to the irradiance corresponding to
SC
measured I . For non-constant irradiance Equation (1) will become the following translation
SC
equation.
′ ⎛ ⎞
G G
1 2
⎜ ⎟
I = I + ⋅ I ⋅ −1 + α ⋅()T − T (3)
2 1 SC 2 1
⎜ ⎟
G G '
SC ⎝ 1 ⎠
′
where G is the irradiance value at the time of I measurement and G is the irradiance
1
SC SC
measured at time of data acquisition of individual I-V data points.
3.3 Correction procedure 2
This procedure is based on the simplified one-diode model of PV devices. The semi-empirical
translation equations contain 5 I-V correction parameters which can be determined by
measurement of I-V curves at different temperature and irradiance conditions. Besides the
temperature coefficients for short circuit current (α) and open circuit voltage (β) an additional
temperature coefficient (κ′) is commonly used which accounts for changes of the internal
series resistance (and fill factor) with temperature.
The correction procedure is defined by the following equations for current and voltage:
G
2
I = I ⋅()1+ α ⋅()T − T ⋅ (4)
2 1 rel 2 1
G
1
⎛ ⎞
⎛ ⎞
G
2
⎜ ⎟
⎜ ⎟ ′ ′
V = V + V ⋅ β ⋅()T − T + a ⋅ln − R ⋅()I − I − κ ⋅ I ⋅(T − T) (5)
2 1 OC1 rel 2 1 S 2 1 2 2 1
⎜ ⎟
⎜ ⎟
G
⎝ 1⎠
⎝ ⎠
where:
I , V are coordinates of points on the measured I-V characteristic;
1 1
I , V are coordinates of the corresponding points on the corrected I-V curve;
2 2
G is the irradiance as measured with the reference device;
1
G is the target irradiance for the corrected I-V characteristic;
2
T is the measured temperature of the test specimen;
1

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SIST EN 60891:2011
– 8 – 60891 © IEC:2009
T is the target temperature of the test specimen;
2
V the open circuit voltage at test conditions;
OC1
α and β are the relative current and voltage temperature coefficients of the test specimen
rel rel
2
measured at 1 000 W/m . They are related to short circuit current and open circuit
voltage at STC;
a is the irradiance correction factor for open circuit voltage which is linked with the diode
thermal voltage D of the pn junction and the number of cells n serially connected in
S
the module;
R′ is the internal series resistance of the test specimen;
S
κ′ is interpreted as temperature coefficient of the internal series resistance R′
S.
NOTE 1 A typical value for the irradiance correction factor a is 0,06.
NOTE 2 Care should be taken that the numerical values for ′ for procedure 2 may be different to ′ of
R R
S S
correction procedure 1.
3.4 Correction procedure 3
3.4.1 General
This procedure is based on the linear interpolation or extrapolation of two measured I-V
characteristics. It uses a minimum of two I-V characteristics, and requires no correction
parameters or fitting parameters. The measured current-voltage characteristics shall be
corrected to standard test conditions or other selected temperature and irradiance values by
applying the following equations:
V = V + a ⋅()V −V (6)
3 1 2 1
I = I + a ⋅()I − I (7)
3 1 2 1
The pair of (I ,V ) and (I , V ) should be chosen so that I – I = I – I :
1 1 2 2 2 1 SC2 SC1
where:
I , V are coordinates of points on the measured characteristics at an irradiance G and
1 1 1
temperature T .
1
I , V are coordinates of points on the measured characteristics at an irradiance G and
2 2 2
temperature T .
2
I , V are coordinates of the corresponding points on the corrected characteristics at an
3 3
irradiance G and temperature T .
3 3
I , I are the measured short-circuit current of the test specimen.
SC1 SC2
a is a constant for the interpolation, which has the relation with the irradiance and
temperature as follows.
G = G + a ⋅ (G − G )
 (8)
3 1 2 1
T = T + a ⋅ (T − T )
. (9)
3 1 2 1

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SIST EN 60891:2011
60891 © IEC:2009 – 9 –
This method should be applicable to most PV technologies. Equations (6) to (9) can be used
for the irradiance correction, temperature correction, and simultaneous correction of
irradiance and temperature.
3.4.2 Correction for the irradiance and temperature from two measured I-V
characteristics
The procedure to correct the I-V characteristics to the irradiance and temperature (G , T )
3 3
from two I-V characteristics measured at the irradiances and temperatures of (G , T ) and (G ,
1 1 2
T ) is as follows (Figures 1(a) and 1(b)).
2
a) Measure the two I-V characteristics at the irradiances and temperatures of G , T and G ,
1 1 2
T , respectively (solid lines in Figure 1(a)). Find the values of I and I .
2 SC1 SC2
b) Calculate a by Equation (8) or (9). For example, when the two measured I-V curves were
made at:
2
G = 1 000 W/m and T = 50 °C
1 1
2
G = 500 W/m and T = 40 °C.
2 2
2
And the irradiance of interest is G = 800 W/m :
3
Then using Equation (8) a = 0,4.
And using Equation (9) T = 46 °C.
3
c) Choose a point (V , I ) on the I-V characteristic 1. Find a point (V , I ) on the I-V
1 1 2 2
– I = I – I is satisfied (Figure 1(b)).
characteristic 2, so that the relation I
2 1 SC2 SC1
d) Calculate V and I by Equations (6) and (7).
3 3
e) Select multiple sets of data points (V , I ) on the I-V characteristics 1, and calculate (V , I )
1 1 3 3
for each by the procedures (c) and (d).
f) The I-V characteristics 3 at the irradiance G and temperature T are given by the set of
3 3
data points (V , I ) (broken line in Figure 1(b)).
3 3
Figures 1(a) and 1(b) show an example of an irradiance correction. Figures 1(c) shows an
example of a temperature correction. Figure 1(d) shows a simultaneous correction of
irradiance and temperature. When 0 < a < 1, the procedure is interpolation. Otherwise, the
procedure is extrapolation.
It should be noted that when G , G , T and T are fixed, G and T cannot be chosen
1 2 1 2 3 3
independently, because they have the relationships given in Equations (8) and (9) (Figure 2).
2
2
For example, when G = 1 000 W/m , T = 20 °C, G = 0 W/m , T = 60 °C (dark I-V curve at
1 1 2 2
2
60°C), and you wish to have the new curve at G = 750 W/m , a is calculated to be 0,25 by
3
Equation (8). Therefore, T should be 30 °C from Equation (9).
3

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SIST EN 60891:2011
– 10 – 60891 © IEC:2009

a) b)
G , T G , T
1 1 1 1
I I
sc1 sc1
(V , I )
1 1
I –I
sc1 sc2
I –I
sc1 sc2
G , T
3 3
I –I
sc1 sc2
G , T G , T
2 2 2 2
I I
sc2 sc2
(V , I )
2 2
Voltage Voltage
IEC  2414/09 IEC  2415/09
G , T
I –I
1 1
sc1 sc2
c) I d)
sc1
I
sc1
G , T
2 2
I –I
sc1 sc2
I
sc2
G , T
1 1
I –I
G , T sc1 sc2
3 3
G ,
...