Post-Fault Power Flow Control for Multi-Terminal Bipolar HVDC Systems Connecting Offshore Wind Farms

IEEE Annual Southern Power Electronics Conference, pp. 1–6

Abstract

With increasing transport capacities required for offshore wind integration, bipolar HVDC systems are expected to replace state-of-the-art monopolar systems. Bipolar systems with a dedicated metallic return offer a 50% redundancy after single-pole DC faults and might therefore shorten outage times of offshore wind farms. To further extend this redundancy, and increase interconnection capacities, these bipolar links might to evolve towards multi-terminal HVDC networks. However, to utilize the full redundancy of bipolar systems, an adapted post-fault load flow control is required according to conceptual analyses in recent literature. AC-side coupling of the P- and N-pole offshore wind farms would allow to distribute power among the poles, but poses a challenge on the offshore wind farm control. Therefore, in this paper, a control concept is developed to redistribute power after faults in multi-terminal HVDC systems and avoid overload situations. A droop-based grid-forming control is adapted for the AC-side coupled offshore HVDC converters and validated via EMT simulations. It is shown for a 4-terminal network that the developed control concept allows to fully utilize the remaining transmission capacity up to a wind infeed of 75%without curtailment of the offshore wind power. Without the developed concept, curtailment is required starting at 50%.

Authors 3

1. Christopher Klein Aachen Institute for High Voltage Equipment and Grids

   RWTH Aachen University

   Affiliation as printed

   Institute for High Voltage Equipment and Grids, Digitalization and Energy Economics (IAEW) RWTH Aachen University,Aachen,Germany

2. Patrick Düllmann Aachen Institute for High Voltage Equipment and Grids

   RWTH Aachen University

   Affiliation as printed

   Institute for High Voltage Equipment and Grids, Digitalization and Energy Economics (IAEW) RWTH Aachen University,Aachen,Germany

3. Albert Moser Aachen Institute for High Voltage Equipment and Grids

   RWTH Aachen University

   Affiliation as printed

   Institute for High Voltage Equipment and Grids, Digitalization and Energy Economics (IAEW) RWTH Aachen University,Aachen,Germany