Challenges with Multi-Terminal UHVDC Transmissions

HVDC Circuit Breakers: A Review Identifying Future Research Needs

“…In case of a non-sustained fault, the stations and the line can be re-energized. This operation sequence takes at least a few 100ms [23], [31], [32] up to a few seconds [33], but is well suited for point-to-point connections. De-energizing the entire HVDC networks has also been suggested [24], [34], [35], but it is surely limited to small systems with only three or four terminals [36].…”

Impact of delays on a consensus-based primary frequency control scheme for AC systems connected by a multi-terminal HVDC grid

“…This may in turn lead to an effective variation of P dc i that is delayed with respect to the one predicted by (8).…”

“…Conventionally, in an MT-HVDC system, only one of the converters (indexed by k) regulates the DC voltage, while all the others control the real power exchanged between the AC and the DC sides [8]- [10]. In fact, converter k plays the role of the slack bus that maintains the power balance within the DC grid, and the DC grid can be considered as a real power exchange center between different AC areas.…”

Making VSC-HVDC control robust to geomagnetically induced current

“…This is partially due to the fact that VSC-HVDC is a relatively new technology, the total installed capacity of VSC-HVDC is substantially lower than LCC-HVDC and there has not yet been any reported major VSC-HVDC disruption caused by GIC. In fact, VSC-HVDC is considered to be immune to GIC events in certain research [18], since the converters operate at much higher voltage levels than the induced potential. However, the effects of abnormal harmonics generated by saturated converter transformers were not discussed in [18].…”

“…In fact, VSC-HVDC is considered to be immune to GIC events in certain research [18], since the converters operate at much higher voltage levels than the induced potential. However, the effects of abnormal harmonics generated by saturated converter transformers were not discussed in [18]. This paper addresses this issue.…”