IEC TS 62257-9-7:2019

IEC TS 62257-9-7 ®
Edition 1.0 2019-10
TECHNICAL
SPECIFICATION
Renewable energy and hybrid systems for rural electrification –
Part 9-7: Recommendations for selection of inverters
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IEC TS 62257-9-7 ®
Edition 1.0 2019-10
TECHNICAL
SPECIFICATION
Renewable energy and hybrid systems for rural electrification –

Part 9-7: Recommendations for selection of inverters

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-7397-5

– 2 – IEC TS 62257-9-7:2019 © IEC 2019
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Overview . 7
5 System architecture and inverter selection . 8
6 General considerations . 8
6.1 Overview. 8
6.2 IP rating . 8
6.3 Ambient temperature. 8
6.4 Altitude . 9
6.5 Direct sunlight . 9
6.6 Efficiency . 9
6.7 No-load and stand-by power requirements . 9
6.8 Ventilation requirements . 9
6.9 Earthing arrangements . 9
6.10 Waveform quality . 9
6.11 Compatibility with loads that produce significant harmonics . 9
6.12 Electromagnetic interference. 10
6.13 Load growth . 10
6.14 Protection . 10
7 Variable speed drives and T1I-c systems – REN systems operating with no
storage, DC source to AC application . 10
7.1 General . 10
7.2 Characteristics of the inverter . 11
7.2.1 Frequency control . 11
7.2.2 MPPT . 11
7.3 Sizing of the inverter . 11
7.3.1 General . 11
7.3.2 AC voltage . 12
7.3.3 AC current . 12
7.3.4 DC voltage . 12
7.3.5 DC current . 12
7.4 VFD standards . 12
7.5 Variations on the architecture . 12
8 Uni-directional grid creating inverters that work with batteries – Type T2I systems
– REN production with energy storage . 12
8.1 General . 12
8.2 Characteristics of the inverter . 13
8.2.1 Grid creation . 13
8.3 Sizing of the inverter . 14
8.3.1 Input DC voltage . 14
8.3.2 Input DC current . 14
8.3.3 AC current and power . 14
8.3.4 AC voltage . 14
8.3.5 Power factor handling range . 14
8.4 Variations on the architecture . 14

9 Uni-directional inverters that synchronize to the grid – Type T3I systems – REN
and diesel production without energy storage . 15
9.1 General . 15
9.2 Characteristics of the inverter . 16
9.2.1 General . 16
9.2.2 Grid synchronizing . 16
9.2.3 MPPT tracking . 16
9.2.4 Active power control . 16
9.2.5 Grid support . 16
9.3 Sizing of the inverter . 16
9.3.1 Input DC voltage . 16
9.3.2 Input DC current . 17
9.3.3 Output AC current and power . 17
9.4 Variations on the architecture . 17
10 Bi-directional grid creating inverters that work with batteries – Type T4I systems,
RE and diesel with energy storage . 17
10.1 General . 17
10.2 Characteristics of the inverter . 18
10.2.1 Grid creation . 18
10.2.2 Battery management . 18
10.2.3 Frequency modulation . 18
10.2.4 Master-slave . 19
10.2.5 Reactive power control . 19
10.3 Sizing the inverter . 19
10.3.1 General . 19
10.3.2 Input DC voltage . 19
10.3.3 Input DC current . 19
10.3.4 Output AC voltage . 19
10.3.5 Output AC current . 19
10.4 Variations on the architecture . 20

Figure 1 – Type T1I-c system – DC to AC with no batteries . 11
Figure 2 – Type T2I system – DC to AC with batteries . 13
Figure 3 – Type T3I system – DC to AC with diesel but no batteries . 15
Figure 4 – Type T4I system – DC to AC with diesel and batteries . 18

Table 1 – Types of inverter and system architecture it is applicable to . 8

– 4 – IEC TS 62257-9-7:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RENEWABLE ENERGY AND HYBRID SYSTEMS
FOR RURAL ELECTRIFICATION –
Part 9-7: Recommendations for selection of inverters

FOREWORD
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