IEC 62891:2020

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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