IEC TR 63401-1:2022

IEC TR 63401-1 ®
Edition 1.0 2022-11
TECHNICAL
REPORT
colour
inside
Dynamic characteristics of inverter-based resources in bulk power systems –
Part 1: Interconnecting inverter-based resources to low short circuit ratio AC
networks
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IEC TR 63401-1 ®
Edition 1.0 2022-11
TECHNICAL
REPORT
colour
inside
Dynamic characteristics of inverter-based resources in bulk power systems –

Part 1: Interconnecting inverter-based resources to low short circuit ratio AC

networks
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.020 ISBN 978-2-8322-6143-9

– 2 – IEC TR 63401-1:2022  IEC 2022
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 10
3 Terms and definitions . 10
4 Characteristics of low short circuit ratio AC networks . 12
4.1 Definition of low short circuit ratio . 12
4.1.1 General . 12
4.1.2 Low SCR in IEEE Std 1204-1997 . 13
4.1.3 Low SCR in CIGRE B4.62 TB671 . 13
4.2 Stability issues posed by inverter-based resources . 15
4.2.1 General . 15
4.2.2 Static voltage control . 16
4.2.3 Fault ride-through . 16
4.2.4 Multi-frequency oscillation . 16
4.3 Summary . 17
5 Identification of low short circuit ratio AC networks . 17
5.1 Problem statement . 17
5.2 Short circuit ratio for a single-connected REPP system . 18
5.2.1 SCR calculation with fault current . 18
5.2.2 SCR calculation with equivalent circuit . 19
5.3 Short circuit ratio for multi grid-connected WPP system . 26
5.3.1 General . 26
5.3.2 Modal decoupling method . 27
5.3.3 Circuit aggregation method . 38
5.4 Summary . 45
6 Steady state voltage stability issue for low short circuit ratio AC networks . 47
6.1 Problem statements . 47
6.2 Steady state stability analysis method . 47
6.2.1 P-V curve . 47
6.2.2 Q-V curve . 48
6.2.3 Voltage sensitivity analysis . 49
6.2.4 Relation to short circuit ratio . 54
6.3 Control strategy for inverter-based resource . 56
6.3.1 Active power and reactive power control . 56
6.3.2 Voltage control . 58
6.4 Case study . 59
6.4.1 Steady state voltage stability problem – China . 59
6.4.2 Low SCR interconnection experience – Vestas . 62
6.5 Summary . 63
7 Transient issue for low short circuit ratio AC networks . 64
7.1 Problem statement . 64
7.2 Transient characteristic modelling and analysis . 65
7.2.1 Transient stability analysis tools and limitations . 65
7.2.2 Electromagnetic transient (EMT) type models . 66
7.2.3 Transient stability analysis model requirements . 67

7.3 Fault ride-through protection and control issue. 67
7.3.1 General . 67
7.3.2 Hardware protection of inverter-based resource during fault . 68
7.3.3 Unbalancing-voltage ride-through issue . 71
7.3.4 Overvoltage ride-through control strategy . 73
7.3.5 Multiple fault ride-through . 75
7.3.6 Under and over -voltage ride-through in time sequence . 78
7.3.7 Active/reactive current support of inverter-based resource during fault . 79
7.4 Operating experiences . 80
7.4.1 Operating experience – China . 80
7.4.2 Operating experience . 81
7.5 Summary . 83
8 Oscillatory instability issue for low short circuit ratio AC networks. 83
8.1 Problem statement . 83
8.2 Modelling and stability analysis . 86
8.2.1 Analysis and modelling of the inverter in the time-domain . 86
8.2.2 Analysis and modelling of the inverter in the frequency-domain . 86
8.3 Mitigation of the oscillation issues by active damping control . 93
8.4 Cases study based on the benchmark model . 94
8.5 Summary . 99
9 Conclusions . 100
Bibliography . 101

Figure 1 – Measured voltage and current curves of sub-synchronous oscillation . 15
Figure 2 – Schematic diagram of a WPP with no static or dynamic reactive support . 19
Figure 3 – Equivalent circuit representation of the WPP shown in Figure 2 . 20
Figure 4 – A typical SIPES . 24
Figure 5 – Changes of system eigenvalues, and the weakest system eigenvalue’s
damping ratio with SCR in a SIPES. 24
Figure 6 – Schematic diagram of a WPP with static reactive support plant (capacitor
banks) . 25
Figure 7 – Equivalent circuit representation of the WPP shown in Figure 6 . 25
Figure 8 – Schematic diagram of a WPP with dynamic reactive support plant
(synchronous condensers) . 26
Figure 9 – Equivalent circuit representation of the WPP shown in Figure 8 . 26
Figure 10 – Mechanism illustration of decoupling a MIPES into a set of equivalent
SIPESs . 28
Figure 11 – A typical MIPES . 29
Figure 12 – A test wind farm system that contains nine wind turbines . 33
Figure 13 – One-line diagram of 5-infeed PES . 35
Figure 14 – Eigenvalue comparison of 5-infeed PES and its 5 equivalent SIPESs . 36
Figure 15 – The 9-converter heterogeneous system with a IEEE 39-bus network
topology . 37
Figure 16 – The dominant eigenvalues and the damping ratios . 38
Figure 17 – Nearby WPP connected to the same region in a power system. 39
Figure 18 – Equivalent representation of multiple windfarms connecting to a power
system with its Z matrix . 40

– 4 – IEC TR 63401-1:2022  IEC 2022
Figure 19 – Equivalent circuit representation of two WPPs connected to the same
connection point-configuration 2 . 41
Figure 20 – Four WPPs integrated into the system with weak connections . 42
Figure 21 – Multiple WPPs connecting to the same HV bus or HV buses in close
proximity . 43
Figure 22 – Equivalent circuit representation of WPPs connecting to the same HV bus . 43
Figure 23 – Approximate equivalent representation assumed for CSCR method . 43
Figure 24 – System topology .
...