IEC TS 63156:2021

Photovoltaic systems - Power conversion equipment performance - Energy evaluation method

IEC TS 63156:2021 describes the procedure for evaluating the energy conversion performance of stand-alone or grid-connected power conversion equipment (PCE) used in PV systems. This procedure includes the calculation of inverter performance to anticipate the energy yield of PV systems. This evaluation method is based on standard power efficiency calculation procedures for PCE found in IEC 61683 and IEC 62891, but provides additional methods for evaluating the expected overall energy efficiency for a particular location given solar load profiles. This document can be used as the energy evaluation method for PCE in IEC TS 61724-3, which defines a procedure for evaluating a PV system’s actual energy production relative to its modeled or expected performance.

General Information

• Status: Published
• Publication Date: 03-Feb-2021
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 6 - TC 82/WG 6
• Current Stage: PPUB - Publication issued
• Start Date: 04-Feb-2021
• Completion Date: 17-Feb-2021

Overview

IEC TS 63156:2021 - "Photovoltaic systems - Power conversion equipment performance - Energy evaluation method" provides a procedure for evaluating the energy conversion performance of power conversion equipment (PCE) used in photovoltaic (PV) systems. The Technical Specification covers both stand‑alone and grid‑connected converters (inverters) and defines how to calculate expected energy yield from inverter performance using site‑specific solar load profiles. It extends standard efficiency test procedures to account for real‑world dynamic conditions and can be used as the PCE energy evaluation method referenced in IEC TS 61724‑3.

Key topics and requirements

• Energy conversion efficiency: Defines the ratio of AC energy delivered to DC energy received over a measurement period (ηCONV) and provides a framework for measuring and calculating it.
• MPPT efficiency: Includes definitions and methods for evaluating maximum power point tracking performance under changing conditions.
• Static and dynamic evaluation: Specifies separate test sequences and measurement conditions for static (steady‑state) and dynamic (time‑varying irradiance) performance of PCE.
• Weighted efficiency calculation: Describes how to compute an overall (site‑weighted) energy conversion efficiency using solar load profiles and weighting factors to reflect local irradiance distributions.
• Irradiance characterization: Addresses analysis of irradiance profiles and the rate of change of irradiance (R) to capture transient behavior relevant to converter performance.
• Test circuits and conditions: Specifies energy efficiency test circuit arrangements and required measurement conditions for repeatable evaluation.
• Workflow and calculation flowcharts: Provides procedural flowcharts for test execution and energy conversion efficiency calculation.

Practical applications and users

Who uses IEC TS 63156:2021:

• Inverter and PCE manufacturers for performance claims, R&D and product benchmarking under realistic irradiance profiles.
• Test laboratories and certification bodies performing energy‑based efficiency testing beyond steady‑state methods.
• PV system designers and integrators who need site‑specific energy yield predictions incorporating converter dynamics.
• Performance analysts and O&M teams comparing actual system output to modeled expectations (for use with IEC TS 61724‑3).
• Project developers and asset owners evaluating vendor equipment for long‑term energy yield and warranty assessments.

Typical applications:

• Predicting annual or seasonal energy yield accounting for dynamic converter response.
• Evaluating MPPT and transient behavior under fluctuating irradiance (clouds, shading).
• Comparative testing of PCE models for procurement and specification.
• Supporting performance modeling used in monitoring, loss analysis and contractual performance guarantees.

Related standards

• IEC 61683 - Procedure for measuring PCE efficiency (static tests)
• IEC 62891 - MPPT efficiency of grid‑connected inverters
• IEC TS 61724‑3 - PV system energy performance monitoring (uses IEC TS 63156 for PCE energy evaluation)

Keywords: IEC TS 63156:2021, photovoltaic systems, power conversion equipment, energy evaluation method, inverter performance, energy conversion efficiency, MPPT, dynamic efficiency, irradiance, PV energy yield.

Standards Content (Sample)

IEC TS 63156 ®
Edition 1.0 2021-02
TECHNICAL
SPECIFICATION
Photovoltaic systems – Power conversion equipment performance – Energy
evaluation method
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IEC TS 63156 ®
Edition 1.0 2021-02
TECHNICAL
SPECIFICATION
Photovoltaic systems – Power conversion equipment performance – Energy

evaluation method
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-9303-4

– 2 – IEC TS 63156:2021 © IEC 2021
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Workflow of energy conversion efficiency evaluation method . 10
4.1 General . 10
4.2 Flow of energy conversion efficiency evaluation test . 11
4.3 Flow of energy conversion efficiency calculation . 12
5 Energy efficiency measurement conditions . 13
5.1 Energy efficiency test circuit . 13
5.2 Test conditions . 14
6 Static energy conversion efficiency evaluation . 14
7 Dynamic energy conversion efficiency evaluation . 14
8 Weighted energy conversion efficiency calculation . 14
Annex A (informative) Rate of change of irradiance . 15
A.1 Analysis of irradiance profile . 15
A.2 Rate of change of irradiance . 18
Annex B (informative) Static energy conversion efficiency test sequence . 19
Annex C (informative) Dynamic energy conversion efficiency test sequence . 20
Annex D (informative) Weighted energy conversion efficiency . 22
Bibliography . 23

Figure 1 – Flowchart of energy conversion efficiency evaluation test . 11
Figure 2 – Flowchart of energy conversion efficiency calculation . 12
Figure 3 – Power conversion equipment test circuits . 13
Figure A.1 – Example of irradiance profile . 17
−2 −1
Figure A.2 – Histogram of the irradiance in Figure A.1 (< 2 W•m •s ) . 17
−2 −1
Figure A.3 – Histogram of rate of change of irradiance (>2 W•m •s ) . 18
Figure C.1 – Test sequence for fluctuations between medium and high irradiation
intensities . 20

Table 1 – Weighted energy conversion efficiency . 14
Table A.1 – Weighted factor ratios for F . 18
n=1 to 7
Table A.2 – Weighted factor ratios for J , J , etc. . 18
1 2
Table B.1 – Static energy efficiency . 19
Table C.1 – Dynamic energy efficiency test with input power from 30 % to 100 % . 21
Table C.2 – Dynamic energy efficiency data . 21
Table D.1 – Static energy conversion efficiency . 22
Table D.2 – Dynamic energy conversion efficiency . 22
Table D.3 – Weighted total conversion efficiency . 22

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC SYSTEMS –
POWER CONVERSION EQUIPMENT PERFORMANCE –
ENERGY EVALUATION METHOD
FOREWORD
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The main task of IEC technical committees is to prepare International Standards. In exceptional
circumstances, a technical committee may propose the publication of a Technical Specification
when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical Specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 63156, which is a Technical Specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.

– 4 – IEC TS 63156:2021 © IEC 2021
The text of this Technical Specification is based on the following documents:
Draft TS Report on voting
82/1755/DTS 82/1801A/RVDTS
Full information on the voting for the approval of this Technical Specification can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
INTRODUCTION
The performance of a photovoltaic power generation system is influenced by various factors,
such as meteorological conditions, installation environment (e.g. shade sources, soiling),
design, and so on. The performance of a power conversion equipment is one of the significant
indices for evaluating the performance of a PV system. IEC 61683 and IEC 62891 describe
procedures for measuring the static (constant) conversion efficiency of power conversion
equipment and MPPT efficiency, respectively. However, the standards do not define conversion
efficiency under dynamic changes in factors such as meteorological changes, installation
environment changes or temporal changes.
The CEC efficiency test protocol and EN 50530 define dynamic performance tests and
procedures partially, but do not define a calculation procedure for evaluating the quantity of
energy produced by a PV system. IEC TS 61724-3 describes a procedure for measuring and
analysing the energy production of a specific photovoltaic system relative to the production
expected for the same system from actual weather conditions for a certain period, but does not
define the procedure for measuring the performance of power conversion equipment under
actual environments.
Since there are areas where meteorological conditions, especially irradiance, change greatly
and could affect the performance of power conversion equipment, a performance evaluation
method under dynamic conditions needs to be defined. This document describes the procedure
for evaluating the dynamic performance and energy production efficiency of power conversion
equipment in a particular location using site-specific solar profiles.

– 6 – IEC TS 63156:2021 © IEC 2021
PHOTOVOLTAIC SYSTEMS –
POWER CONVERSION EQUIPMENT PERFORMANCE –
ENERGY EVALUATION METHOD
1 Scope
This document describes the procedure for evaluating the energy conversion performance of
stand-alone or grid-connected power conversion equipment (PCE) used in PV systems. This
procedure includes the calculation of inverter performance to anticipate the energy yield of PV
systems. This evaluation method is based on standard power efficiency calculation procedures
for PCE found in IEC 61683 and IEC 62891, but provides additional methods for evaluating the
expected overall energy efficiency for a particular location given solar load profiles. This
document can be used as the energy evaluation method for PCE in IEC TS 61724-3, which
defines a procedure for evaluating a PV system’s actual energy production relative to its
modeled or expected performance.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 61683, Photovoltaic systems – Power conditioners – Procedure for measuring efficiency
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
IEC 62891, Maximum power point tracking efficiency of grid connected photovoltaic inverters
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61836 as well as
the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
irradiance
G
electromagnetic radiated power per unit area
−2.
Note 1 to entry: Unit: W•m
3.2
in-plane irradiance
G
I
total irradiance on the plane of a PV cell or module
−2.
Note 1 to entry: Unit: W•m
3.3
rate of change of irradiance
R
change in irradiance amount during 1 s
−2 −1.
Note 1 to entry: Unit: W•m •s
3.4
rated input voltage
V
DC,r
rated input voltage specified by the manufacturer, to which other data sheet information refers
Note 1 to entry: Unit: V.
3.5
rated input power
P
DC,r
rated input power of the power conversion equipment, which can be converted under continuous
operating conditions
Note 1 to entry: Unit: W.
3.6
rated output voltage
V
AC,r
utility grid voltage to which other data sheet information refers
Note 1 to entry: Unit: V.
3.7
rated output power
P
AC,r
active power that the power conversion equipment can output during continuous operation
Note 1 to entry: Unit: W.
3.8
PV simulator MPP-Power
P
MPP,PVS
MPP power provided by the PV simulator
Note 1 to entry: Unit: W.
3.9
input power
P
DC
measured input power of the device under test
Note 1 to entry: Unit: W.
3.10
PV simulator MPP voltage
V
MPP,PVS
MPP voltage provided by the PV simulator
Note 1 to entry: Unit: V.
– 8 – IEC TS 63156:2021 © IEC 2021
3.11
input voltage
V
DC
measured input voltage of the device under test
Note 1 to entry: Unit: V.
3.12
PV simulator MPP current
I
MPP,PVS
MPP current provided by the PV simulator
Note 1 to entry: Unit: A.
3.13
input current
I
DC
measured input current of the device under test
Note 1 to entry: Unit: A.
3.14
output power
P
AC
measured AC output power of the device under test
Note 1 to entry: Unit: W.
3.15
output voltage
V
AC
measured AC voltage of the device under test
Note 1 to entry: Unit: V.
3.16
output current
I
AC
measured AC output current of the device under test
Note 1 to entry: Unit: A.
3.17
MPPT efficiency
η
MPPT
ratio of the energy drawn by the device under test within a defined measuring period T to the
M
energy provided theoretically by the PV simulator at the maximum power point (MPP):
T
M
P ( t )dt
DC
∫
η = (1)
MPPT
T
M
P ( t )dt
MPP
∫
where
η is MPPT efficiency;
MPPT
P (t) is the instantaneous value of the power drawn by the device under test, in kW;
DC
P (t) is the instantaneous value of the MPP power provided theoretically by the PV
MPP
simulator, in kW.
Note 1 to entry: Unit: dimension
...