IEC 62891:2020

Maximum power point tracking efficiency of grid connected photovoltaic inverters

IEC 62891:2020 provides a procedure for the measurement of the efficiency of the maximum power point tracking (MPPT) of inverters used in grid-connected photovoltaic (PV) systems. Both the static and dynamic MPPT efficiency are considered. Based on the static MPPT efficiency calculated in this document and steady state conversion efficiency determined in IEC 61683 the overall efficiency can be calculated. The dynamic MPPT efficiency is indicated separately.

General Information

• Status: Published
• Publication Date: 14-Jul-2020
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• 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: 03-Jul-2020
• Completion Date: 15-Jul-2020

Standards Content (Sample)

IEC 62891 ®
Edition 1.0 2020-07
INTERNATIONAL
STANDARD
colour
inside
Maximum power point tracking efficiency of grid connected photovoltaic
inverters
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IEC 62891 ®
Edition 1.0 2020-07
INTERNATIONAL
STANDARD
colour
inside
Maximum power point tracking efficiency of grid connected photovoltaic

inverters
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-8470-4

– 2 – IEC 62891:2020 © IEC 2020
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
3.1 Inverter input (PV generator) . 6
3.2 Inverter output (grid) . 7
3.3 Measured quantities . 7
3.4 Calculated quantities . 8
4 MPPT efficiencies . 9
4.1 General description . 9
4.2 Test set-up . 10
4.3 Static MPPT efficiency . 11
4.3.1 Test conditions . 11
4.3.2 Measurement procedure . 12
4.3.3 Evaluation – Calculation of static MPPT efficiency . 13
4.4 Test conditions for dynamic MPPT efficiency . 13
4.4.1 Dynamic MPPT efficiency . 13
4.4.2 Measurement procedure . 14
4.4.3 Evaluation – Calculation of the dynamic MPPT efficiency . 14
5 Calculation of the overall efficiency . 15
Annex A (normative) Requirements on the measuring apparatus . 16
A.1 PV generator simulator . 16
A.1.1 General . 16
A.1.2 Requirements on the static characteristic . 16
A.1.3 Requirement on the transient stability . 17
A.1.4 Requirements on the dynamic characteristic . 17
A.1.5 Requirements on electrical characteristic . 17
A.1.6 Calibration – Uncertainty . 17
A.2 AC power supply . 17
Annex B (normative) Test conditions for dynamic MPPT efficiency . 18
B.1 Test profiles . 18
B.2 Test sequence with ramps 10 % – 50 % G (See Table B.1) . 20
STC
B.3 Test sequence with ramps 30 % – 100 % G (See Table B.2) . 21
STC
B.4 Start-up and shut-down test with slow ramps (See Table B.3 and Figure B.3) . 21
B.5 Total test duration . 22
Annex C (normative) Models of current/voltage characteristic of PV generator . 23
C.1 PV generator model for MPPT performance tests . 23
C.2 Alternative PV generator model for MPPT performance tests . 27
Annex D (normative) Efficiency weighting factors . 29
D.1 European efficiency . 29
D.2 CEC efficiency . 29
Annex E (normative) Specification of the static MPPT and conversion efficiency in
terms of normalised rated AC power . 30
E.1 General . 30
E.2 Re-normalisation of output power P to the rated output power P . 30
AC AC,r
E.3 Representation of the conversion efficiency in terms of normalised rated
output power . 30
E.4 Interpolation on normative nodes . 31
E.5 Result . 33
Bibliography . 34

Figure 1 – Example test set-up for MPPT efficiency measurements . 11
Figure B.1 – Test sequence for fluctuations between small and medium irradiation
intensities . 18
Figure B.2 – Test sequence for fluctuations between medium and high irradiation
intensities . 19
Figure B.3 – Test sequence for the start-up and shut-down test of grid connected
inverters . 22
Figure C.1 – Irradiation-dependent V-I- and V-P characteristic of a c-Si PV generator . 25
Figure C.2 – Irradiation-dependent V-I- and V-P characteristic of a thin-film PV
generator . 26

Table 1 – Test specifications for static MPPT efficiency . 12
Table A.1 – General requirements on the simulated I/V characteristic of the PV
generator . 16
Table B.1 – Dynamic MPPT-Test 10 %  50 % G (valid for the evaluation of
STC
η ) . 20
MPPTdyn
Table B.2 – Dynamic MPPT-Test 30 %  100 % G (valid for the evaluation of
STC
) . 21
η
MPPTdyn
Table B.3 – Dynamic MPPT- Slow Ramp 1 %  10 % G (valid for the evaluation of
STC
η ) . 21
MPPTdyn
Table C.1 – Technology-dependent parameters . 24
Table C.2 – MPP-values obtained with the cSi PV model . 25
Table C.3 – MPP-values obtained with the TF-PV mode . 27
Table D.1 – Weighting factors and partial MPP power levels for the calculation of the
European efficiency . 29
Table D.2 – Weighting factors and partial MPP power levels for the calculation of the
CEC efficiency (California Energy Commission) . 29
Table E.1 – Measured quantities at the conversion efficiency test . 30
Table E.2 – Conversion efficiency in term of rated AC power . 31
Table E.3 – Allowed limits for the nodes of the normalised AC power . 31
Table E.4 – Sought values by means of interpolation . 32
Table E.5 – Interpolated conversion efficiencies . 33

– 4 – IEC 62891:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAXIMUM POWER POINT TRACKING EFFICIENCY
OF GRID CONNECTED PHOTOVOLTAIC INVERTERS

FOREWORD
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