Event

Moderator: Daniel EICHHOFF, Amprion GmbH

Multiterminal-system overview (by Jochen Haude, Amprion GmbH )
This B4 CIGRE 2026 workshop session provides insights into a bipolar multiterminal HVDC concept based on full-bridge VSC technology with hybrid overhead line (OHL) and cable, combining system architecture, performance requirements, converter design considerations, and operational experience. The contributions cover the multiterminal system overview and selective DC fault clearing, key grid-support functions and control strategies under events and faults, full-bridge converter design trade-offs versus half-bridge implementations (footprint, cost, and losses), and in-service STATCOM-mode experience including dynamic behaviour during unbalanced AC faults and validation against simulation.
- Introduction
- Multilevel VSC operation principle with half-bridge- and full-bridge-modules
- Operation modes in bipole configurations
- Multiterminal-hub and bipole-dc-switchyard for selective fault clearing and high system availability
- Switching circuit of the Ultranet multiterminal system
- DC-switchgear and converter station arrangement

System requirements and performance (by Klaus Vennemann, Amprion GmbH)
- Multiterminal operation without the need for explicit communication
- Managing of DC side faults while maintaining full converter controllability
- Strategy to manage AC-DC intersystem faults
- Support of AC-voltage (positive & negative sequence) in case of system events / faults
- Frequency Control in case of system split events
- Emergency Power Control
- Grid Forming Control
- Damping of power system oscillations (POD)
- System Recovery and Ancillary Services (SRAS)

Full-bridge converters (by Steffen Weghorn, Siemens Energy AG)
- Design comparison between Half-Bridge (HB) and Full-Bridge (FB) converter : difference in voltage control capability, difference in the converter hardware, component requirements
- Full Bridge converter design aspects: losses comparison with Half-Bridge design, losses optimized designs, HVDC station footprint, HVDC station costs compared with Half-Bridge design, HVDC station losses

In-service operating experiences in STATCOM-Mode (by Jiahua Weng, TransnetBW GmbH)
- Operational performance : operational system control configuration, analysis of reactive power performance, voltage stability and grid interaction, active power balance and efficiency
- Dynamic performance during unbalanced AC faults : results validation with reproduced simulation

Speakers

Daniel
EICHHOFF

Klaus
VENNEMANN

Eugen
STARSCHICH

Jiahua
WENG