IEC TR 63401-2:2022

Dynamic characteristics of inverter-based resources in bulk power systems - Part 2: Sub- and Super-synchronous control Interactions

IEC TR 63401-2:2022, which is a technical report, covers the "control interactions" in converter interfaced generators e.g, wind and PV with the frequency of the resulting oscillation below twice the system frequency. SSCI can be categorized into:
1) SSCI in DFIG is caused by the interaction between DFIG wind turbine converter controls and the series compensated network.
2) SSCI involving FSC (both type-4 wind turbine or PV generators) is caused by the interaction between wind turbine or solar PV's FSC controls and weak AC grid.
This technical report is organized into nine clauses. Clause 1 gives a brief introduction and highlights the scope of this document. Clause 4 presents the historical background of various types of subsynchronous oscillation (SSO) and revisits the terminologies, definitions, and classification in the context of classical SSR and emerging SSCI issues to better understand and classify the emerging interaction phenomena. Clause 5 provides the description, mechanism, and characteristics of the SSCI phenomenon in the framework of real-world incidents, including the SSCI events in the ERCOT, Guyuan, and Hami wind power systems. Clause 6 proposes two benchmark models to study the SSCI DFIG and FSC-based wind turbines or PV generators. Clause 7 gives an overview of existing and emerging modeling and stability analysis approaches to investigate the SSCI phenomenon. Clause 8 outlines various techniques to mitigate the SSCI. It discusses various SSCI mitigation schemes, such as bypassing the series capacitor, selective tripping of WTGs, generator, and plant-level damping control schemes. Clause 9 highlights the need for future works towards standardization of terms, definitions, classification, analysis methods, benchmark models, and mitigation methods.

General Information

• Status: Published
• Publication Date: 26-Jun-2022
• ICS: 27.160 - Solar energy engineering
• ICS: 27.180 - Wind turbine energy systems
• ICS: 29.020 - Electrical engineering in general
• Technical Committee: SC 8A - Grid Integration of Renewable Energy Generation
• Drafting Committee: JWG 5 - TC 8/SC 8A/JWG 5
• Current Stage: PPUB - Publication issued
• Start Date: 21-Jul-2022
• Completion Date: 27-Jun-2022

Standards Content (Sample)

IEC TR 63401-2 ®
Edition 1.0 2022-06
TECHNICAL
REPORT
colour
inside
Dynamic characteristics of inverter-based resources in bulk power systems –
Part 2: Sub- and super-synchronous control interactions
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IEC TR 63401-2 ®
Edition 1.0 2022-06
TECHNICAL
REPORT
colour
inside
Dynamic characteristics of inverter-based resources in bulk power systems –

Part 2: Sub- and super-synchronous control interactions

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160, 27.180, 29.020 ISBN 978-2-8322-3929-2

– 2 – IEC TR 63401-2:2022  IEC 2022
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 10
2 Normative references . 10
3 Terms and definitions . 10
4 Terms, definitions and classification . 11
4.1 Existing terms, definitions and historical background . 11
4.1.1 General . 11
4.1.2 Subsynchronous resonance (SSR) . 12
4.1.3 Device dependent SSO (DDSSO) . 13
4.2 Necessity to revisit the terms and classification . 13
4.3 Revisiting the terms and classification . 13
4.3.1 General . 13
4.3.2 Torsional interaction . 14
4.3.3 Network resonance . 15
4.3.4 Control interaction . 15
4.4 Clause summary . 16
5 SSCI incidents in real-world wind power systems . 16
5.1 General . 16
5.2 SSCI in DFIGs connected to series-compensated networks . 17
5.2.1 ERCOT SSCI incident in 2009 . 17
5.2.2 ERCOT SSCI events in 2017 . 18
5.2.3 SSCI events in Guyuan wind power system . 20
5.3 SSCI in FSC-based generators connected to weak AC network . 24
5.3.1 SSCI event in Hami wind power system . 24
5.4 Clause summary . 27
6 Modeling and analysis approaches . 28
6.1 Preview . 28
6.2 Time-domain modeling and analysis approaches . 28
6.2.1 General . 28
6.2.2 Nonlinear time-domain EMT simulation . 28
6.2.3 Controller hardware-in-the-loop simulation . 28
6.2.4 Linearized state-space modeling and modal analysis . 29
6.2.5 Discussions on time-domain approaches for SSCI studies . 30
6.3 Frequency-domain modeling and analysis approaches . 30
6.3.1 Frequency scanning . 30
6.3.2 Complex torque coefficient method . 31
6.3.3 Impedance-based modeling and analysis . 33
6.4 Guidelines on the approaches to SSCI studies . 39
6.5 Clause summary . 40
7 Proposed benchmark models . 40
7.1 Overview. 40
7.2 Benchmark model based on Guyuan wind power system . 40
7.2.1 General . 40
7.2.2 Configuration and parameters of the WTGs and Guyuan substation . 41
7.2.3 Parameters of the DFIG's converter control . 41

7.2.4 Series-compensated electrical network . 41
7.2.5 Case study . 41
7.3 Benchmark model based on Hami wind power system . 42
7.3.1 General . 42
7.3.2 Configuration and parameters of FSCs . 43
7.3.3 Configuration and parameters of LCC-HVDC . 43
7.3.4 Synchronous generators . 45
7.3.5 Electrical network . 45
7.3.6 Case studies . 45
7.4 Clause summary . 46
8 Mitigation methods . 46
8.1 General . 46
8.2 Bypassing the series capacitor . 47
8.3 Selective tripping of WTGs . 47
8.4 Network/Grid-side subsynchronous damping controller (GSDC) . 48
8.5 Generation-side subsynchronous mitigation schemes . 50
8.5.1 Adjusting the wind turbine converter control parameters . 50
8.5.2 Adding an SSDC in the RSC control loop . 51
8.5.3 Adding an SSDC in the GSC control loop . 53
8.6 Protection schemes . 54
8.7 Clause summary . 54
9 Future work . 54
Annex A (Informative) . 56
Bibliography . 60

Figure 1 – Multi-frequency oscillations in the modern power system with high-share of
renewables and power electronic converters . 10
Figure 2 – Timeline of the historical developments of SSO terms, definitions and
classification [12] . 11
Figure 3 – Terms and classification of SSR by IEEE [13] . 12
Figure 4 – Classification of subsynchronous interaction based on the origin [12]. 14
Figure 5 – Reclassification of subsynchronous interactions based on the interaction
mechanism . 14
Figure 6 – Timeline of SSCI events reported around the world . 16
Figure 7 – Structure of the ERCOT wind power system in 2009 [16]. 17
Figure 8 – Oscilloscope record of the 2009 SSCI event in the ERCOT system [19] . 18
Figure 9 – Structure of the ERCOT wind power system in 2017 [24]. 18
Figure 10 – Event#1 August 24, 2017: current, voltage and frequency spectrum of the
current during the SSCI event and after bypassing the series capacitor [24] . 19
Figure 11 – Event#2 September 27, 2017: current, voltage and frequency spectrum of
the current during the SSCI event [24] . 20
Figure 12 – Event#3 October 27, 2017: current, voltage and frequency spectrum of the
current during the SSCI event [24] . 20
Figure 13 – Geographical layout of the Guyuan wind power system, Hebei Province,
China . 21
Figure 14 – Power flow measured at the 200 kV side of the Guyuan step-up
transformer . 22
Figure 15 – Field recorded line current and frequency spectrum . 22

– 4 – IEC TR 63401-2:2022  IEC 2022
Figure 16 – Field recorded voltage and frequency spectrum . 23
Figure 17 – Hami wind power system, Xinjiang, China [27] . 24
Figure 18 – Current (upper plot) and active power (lower plot) . 25
Figure 19 – Frequency spectrum of the current (upper plot) and active power (lower
plot) . 25
Figure 20 – Field measured active power of a wind farm (a) From 09:46 to 09:47 (b)
From 11:52 to 11:53. 26
Figure 21 – Torsional modes and frequency variati
...