Overview
IEC TR 63401-1:2022 is a Technical Report from the IEC that addresses the dynamic behavior and interconnection challenges of inverter-based resources (IBRs)-such as wind and solar plants-when connected to low short circuit ratio (SCR) AC networks in bulk power systems. Part 1 focuses on identifying low-SCR networks, characterizing stability risks, and describing potential technical solutions, methods and practices to support reliable operation, control and protection of modern grids with high inverter penetration.
Key topics
- Definition and identification of low SCR: methods for calculating SCR (fault-current and equivalent-circuit approaches), and approaches for single and multi-point grid connections.
- Stability issues:
- Steady-state voltage stability (P–V and Q–V analysis, voltage sensitivity, relation to SCR)
- Transient stability and fault ride-through (modelling requirements, EMT vs transient models, protection strategies, unbalanced faults, multiple fault sequences)
- Oscillatory stability (multi-frequency oscillations, frequency-domain/time-domain modelling, damping requirements)
- Modeling and analysis methods: modal decoupling, circuit aggregation, eigenvalue and sensitivity analyses, and benchmark/EMT modelling considerations.
- Control and protection strategies: voltage control, active/reactive power strategies, hardware protection, ride-through control flows, and active damping techniques (e.g., virtual resistance, PLL/current-loop impacts).
- Operational experience and case studies: practical examples, grid incidents and mitigation measures, and lessons for planning and operations.
- Guidance for further standardization: recommended areas for technology, methods and practices to increase system flexibility and efficiency.
Applications
IEC TR 63401-1:2022 is practical for:
- Grid planners and transmission system operators performing interconnection studies and assessing system strength.
- Renewable plant designers and inverter manufacturers developing control, protection and ride-through functions for low-SCR connection points.
- Protection engineers and system analysts modeling transient and oscillatory behaviors in weak-grid conditions.
- Policy makers and regulators drafting grid codes or technical requirements for large-scale inverter deployments.
- Standardization bodies seeking harmonized approaches for high-renewable bulk power systems.
Who should use this standard
- Transmission system operators (TSOs) and distribution network operators (DNOs)
- Renewable energy developers and EPC firms
- IBR/inverter manufacturers and power-electronics designers
- Protection and control engineers, consultants and researchers
- Standards developers and regulatory authorities
Related standards
- IEEE Std 1204-1997 (referenced approaches to SCR)
- CIGRE B4.62 / TB671 (low-SCR guidance referenced)
- IEC TR 63401-1:2022 complements other IEC grid-interconnection and power-quality publications
IEC TR 63401-1:2022 provides a structured, practical reference for understanding and mitigating stability risks when interconnecting inverter-based resources to weak grids-helping stakeholders implement robust solutions for reliable, high-renewable bulk power systems.